Science.gov

Sample records for aircraft landing dynamics

  1. Langley Aircraft Landing Dynamics Facility

    NASA Technical Reports Server (NTRS)

    Davis, Pamela A.; Stubbs, Sandy M.; Tanner, John A.

    1987-01-01

    The Langley Research Center has recently upgraded the Landing Loads Track (LLT) to improve the capability of low-cost testing of conventional and advanced landing gear systems. The unique feature of the Langley Aircraft Landing Dynamics Facility (ALDF) is the ability to test aircraft landing gear systems on actual runway surfaces at operational ground speeds and loading conditions. A historical overview of the original LLT is given, followed by a detailed description of the new ALDF systems and operational capabilities.

  2. NASA Langley's Aircraft Landing Dynamics Facility

    NASA Technical Reports Server (NTRS)

    Davis, Pamela A.

    1993-01-01

    The Aircraft Landing Dynamics Facility (ALDF) is a unique facility with the ability to test aircraft landing gear systems on actual runway surfaces at operational ground speeds and loading conditions. A brief historical overview of the original Landing Loads Track (LLT) is given, followed by a detailed description of the new ALDF systems and operational capabilities.

  3. Aircraft Landing Dynamics Facility (ALDF)

    NASA Technical Reports Server (NTRS)

    1964-01-01

    Original Test Carriage: A carriage catapulted by a hydraulic jet at speeds up to 150 mph for studies of ground loads on high-speed aircraft is in operation at the Langley Research Center of the National Aeronautics and Space Administration. A drop test rig is installed on the carriage, which is catapulted 400 feet in 3.5 seconds. The carriage travels along a track and special instruments record loads data as an aircraft landing gear or other test specimen is dropped on a concrete strip. Five cables attached to a battery of 20 Navy Mark IV arresting gears, stretched across the 2,200-foot track, bring the carriage to a halt after the test run. The carriage, when loaded to its capacity of 20,000 pounds, represents a 50-ton load. The hydraulic catapult consists of a single water jet, which roars from a nozzle at the front end of the L-shaped pressure vessel (center) and is forced into a specially-shaped bucket on the carriage. The water jet, traveling at 660 feet per second, undergoes a 180 degree change of direction and floods out of another opening in the bucket below the incoming jet stream. The momentum change produces a thrust on the carriage of 400,00 pounds.

  4. Aircraft Landing Dynamics Facility - A unique facility with new capabilities

    NASA Technical Reports Server (NTRS)

    Davis, P. A.; Stubbs, S. M.; Tanner, J. A.

    1985-01-01

    The Aircraft Landing Dynamics Facility (ALDF), formerly called the Landing Loads Track, is described. The paper gives a historical overview of the original NASA Langley Research Center Landing Loads Track and discusses the unique features of this national test facility. Comparisons are made between the original track characteristics and the new capabilities of the Aircraft Landing Dynamics Facility following the recently completed facility update. Details of the new propulsion and arresting gear systems are presented along with the novel features of the new high-speed carriage. The data acquisition system is described and the paper concludes with a review of future test programs.

  5. Application of tire dynamics to aircraft landing gear design analysis

    NASA Technical Reports Server (NTRS)

    Black, R. J.

    1983-01-01

    The tire plays a key part in many analyses used for design of aircraft landing gear. Examples include structural design of wheels, landing gear shimmy, brake whirl, chatter and squeal, complex combination of chatter and shimmy on main landing gear (MLG) systems, anti-skid performance, gear walk, and rough terrain loads and performance. Tire parameters needed in the various analyses are discussed. Two tire models are discussed for shimmy analysis, the modified Moreland approach and the von Schlippe-Dietrich approach. It is shown that the Moreland model can be derived from the Von Schlippe-Dietrich model by certain approximations. The remaining analysis areas are discussed in general terms and the tire parameters needed for each are identified. Accurate tire data allows more accurate design analysis and the correct prediction of dynamic performance of aircraft landing gear.

  6. Aircraft landing gear systems

    NASA Technical Reports Server (NTRS)

    Tanner, John A. (Editor)

    1990-01-01

    Topics presented include the laboratory simulation of landing gear pitch-plane dynamics, a summary of recent aircraft/ground vehicle friction measurement tests, some recent aircraft tire thermal studies, and an evaluation of critical speeds in high-speed aircraft. Also presented are a review of NASA antiskid braking research, titanium matrix composite landing gear development, the current methods and perspective of aircraft flotation analysis, the flow rate and trajectory of water spray produced by an aircraft tire, and spin-up studies of the Space Shuttle Orbiter main gear tire.

  7. Dynamics of aircraft antiskid braking systems. [conducted at the Langley aircraft landing loads and traction facility

    NASA Technical Reports Server (NTRS)

    Tanner, J. A.; Stubbs, S. M.; Dreher, R. C.; Smith, E. G.

    1982-01-01

    A computer study was performed to assess the accuracy of three brake pressure-torque mathematical models. The investigation utilized one main gear wheel, brake, and tire assembly of a McDonnell Douglas DC-9 series 10 airplane. The investigation indicates that the performance of aircraft antiskid braking systems is strongly influenced by tire characteristics, dynamic response of the antiskid control valve, and pressure-torque response of the brake. The computer study employed an average torque error criterion to assess the accuracy of the models. The results indicate that a variable nonlinear spring with hysteresis memory function models the pressure-torque response of the brake more accurately than currently used models.

  8. Simulation of Aircraft Landing Gears with a Nonlinear Dynamic Finite Element Code

    NASA Technical Reports Server (NTRS)

    Lyle, Karen H.; Jackson, Karen E.; Fasanella, Edwin L.

    2000-01-01

    Recent advances in computational speed have made aircraft and spacecraft crash simulations using an explicit, nonlinear, transient-dynamic, finite element analysis code more feasible. This paper describes the development of a simple landing gear model, which accurately simulates the energy absorbed by the gear without adding substantial complexity to the model. For a crash model, the landing gear response is approximated with a spring where the force applied to the fuselage is computed in a user-written subroutine. Helicopter crash simulations using this approach are compared with previously acquired experimental data from a full-scale crash test of a composite helicopter.

  9. Assessment of dynamic effects on aircraft design loads: The landing impact case

    NASA Astrophysics Data System (ADS)

    Bronstein, Michael; Feldman, Esther; Vescovini, Riccardo; Bisagni, Chiara

    2015-10-01

    This paper addresses the potential benefits due to a fully dynamic approach to determine the design loads of a mid-size business jet. The study is conducted by considering the fuselage midsection of the DAEDALOS aircraft model with landing impact conditions. The comparison is presented in terms of stress levels between the novel dynamic approach and the standard design practice based on the use of equivalent static loads. The results illustrate that a slight reduction of the load levels can be achieved, but careful modeling of the damping level is needed. Guidelines for an improved load definition are discussed, and suggestions for future research activities are provided.

  10. Design considerations for attaining 250-knot test velocities at the aircraft landing dynamics facility

    NASA Technical Reports Server (NTRS)

    Gray, C. E., Jr.; Snyder, R. E.; Taylor, J. T.; Cires, A.; Fitzgerald, A. L.; Armistead, M. F.

    1980-01-01

    Preliminary design studies are presented which consider the important parameters in providing 250 knot test velocities at the Aircraft Landing Dynamics Facility. Four major components of this facility are: the hydraulic jet catapult, the test carriage structure, the reaction turning bucket, and the wheels. Using the hydraulic-jet catapult characteristics, a target design point was selected and a carriage structure was sized to meet the required strength requirements. The preliminary design results indicate that to attain 250 knot test velocities for a given hydraulic jet catapult system, a carriage mass of 25,424 kg (56,000 lbm.) cannot be exceeded.

  11. Improved aircraft dynamic response and fatigue life during ground operations using an active control landing gear system

    NASA Technical Reports Server (NTRS)

    Mcgehee, J. R.; Carden, H. D.; Edson, R.

    1978-01-01

    A three-degree-of-freedom aircraft landing analysis incorporating a series-hydraulic active control main landing gear has been developed and verified using preliminary experimental data from drop tests of a modified main landing gear from a 2722 kg (6000 lbm) class of airplane. The verified analysis was also employed to predict the landing dynamics of a supersonic research airplane with an active control main landing gear system. The results of this investigation have shown that this type of active gear is feasible and indicate a potential for improving airplane dynamic response and reducing structural fatigue damage during ground operations by approximately 90% relative to that incurred with the passive gear.

  12. An Experimental Investigation of Damaged Arresting Gear Tapes for the Langley Aircraft Landing Dynamics Facility

    NASA Technical Reports Server (NTRS)

    Mason, Angela J.

    1999-01-01

    An experimental investigation was performed on damaged arresting gear tapes at the Langley Aircraft Landing Dynamics Facility. The arrestment system uses five pairs of tapes to bring the test carriage to a halt. The procedure used to determine when to replace the tapes consists of a close evaluation of each of the 10 tapes after each run. During this evaluation, each tape is examined thoroughly and any damage observed on the tape is recorded. If the damaged tape does not pass the inspection, the tape is replaced with a new one. For the past 13 years, the most commonly seen damage types are edge fray damage and transverse damage. Tests were conducted to determine the maximum tensile strength of a damaged arresting gear tape specimen. The data indicate that tapes exhibiting transverse damage can withstand higher loads than tapes with edge fray damage.

  13. Aircraft landing using GPS

    NASA Astrophysics Data System (ADS)

    Lawrence, David Gary

    The advent of the Global Positioning System (GPS) is revolutionizing the field of navigation. Commercial aviation has been particularly influenced by this worldwide navigation system. From ground vehicle guidance to aircraft landing applications, GPS has the potential to impact many areas of aviation. GPS is already being used for non-precision approach guidance; current research focuses on its application to more critical regimes of flight. To this end, the following contributions were made: (1) Development of algorithms and a flexible software architecture capable of providing real-time position solutions accurate to the centimeter level with high integrity. This architecture was used to demonstrate 110 automatic landings of a Boeing 737. (2) Assessment of the navigation performance provided by two GPS-based landing systems developed at Stanford, the Integrity Beacon Landing System, and the Wide Area Augmentation System. (3) Preliminary evaluation of proposed enhancements to traditional techniques for GPS positioning, specifically, dual antenna positioning and pseudolite augmentation. (4) Introduction of a new concept for positioning using airport pseudolites. The results of this research are promising, showing that GPS-based systems can potentially meet even the stringent requirements of a Category III (zero visibility) landing system. Although technical and logistical hurdles still exist, it is likely that GPS will soon provide aircraft guidance in all phases of flight, including automatic landing, roll-out, and taxi.

  14. Experimental and analytical determination of characteristics affecting light aircraft landing-gear dynamics

    NASA Technical Reports Server (NTRS)

    Fasanella, E. L.; Mcgehee, J. R.; Pappas, M. S.

    1977-01-01

    An experimental and analytical investigation was conducted to determine which characteristics of a light aircraft landing gear influence gear dynamic behavior significantly. The investigation focused particularly on possible modification for load control. Pseudostatic tests were conducted to determine the gear fore-and-aft spring constant, axial friction as a function of drag load, brake pressure-torque characteristics, and tire force-deflection characteristics. To study dynamic tire response, vertical drops were conducted at impact velocities of 1.2, 1.5, and 1.8 m/s onto a level surface; to determine axial-friction effects, a second series of vertical drops were made at 1.5 m/s onto surfaces inclined 5 deg and 10 deg to the horizontal. An average dynamic axial-friction coefficient of 0.15 was obtained by comparing analytical data with inclined surface drop test data. Dynamic strut bending and associated axial friction were found to be severe for the drop tests on the 10 deg surface.

  15. Numerical simulation of the actuation system for the ALDF's propulsion control valve. [Aircraft Landing Dynamics Facility

    NASA Technical Reports Server (NTRS)

    Korte, John J.

    1990-01-01

    A numerical simulation of the actuation system for the propulsion control valve (PCV) of the NASA Langley Aircraft Landing Dynamics Facility was developed during the preliminary design of the PCV and used throughout the entire project. The simulation is based on a predictive model of the PCV which is used to evaluate and design the actuation system. The PCV controls a 1.7 million-pound thrust water jet used in propelling a 108,000-pound test carriage. The PCV can open and close in 0.300 second and deliver over 9,000 gallons of water per sec at pressures up to 3150 psi. The numerical simulation results are used to predict transient performance and valve opening characteristics, specify the hydraulic control system, define transient loadings on components, and evaluate failure modes. The mathematical model used for numerically simulating the mechanical fluid power system is described, and numerical results are demonstrated for a typical opening and closing cycle of the PCV. A summary is then given on how the model is used in the design process.

  16. Scheduling Aircraft Landings under Constrained Position Shifting

    NASA Technical Reports Server (NTRS)

    Balakrishnan, Hamsa; Chandran, Bala

    2006-01-01

    Optimal scheduling of airport runway operations can play an important role in improving the safety and efficiency of the National Airspace System (NAS). Methods that compute the optimal landing sequence and landing times of aircraft must accommodate practical issues that affect the implementation of the schedule. One such practical consideration, known as Constrained Position Shifting (CPS), is the restriction that each aircraft must land within a pre-specified number of positions of its place in the First-Come-First-Served (FCFS) sequence. We consider the problem of scheduling landings of aircraft in a CPS environment in order to maximize runway throughput (minimize the completion time of the landing sequence), subject to operational constraints such as FAA-specified minimum inter-arrival spacing restrictions, precedence relationships among aircraft that arise either from airline preferences or air traffic control procedures that prevent overtaking, and time windows (representing possible control actions) during which each aircraft landing can occur. We present a Dynamic Programming-based approach that scales linearly in the number of aircraft, and describe our computational experience with a prototype implementation on realistic data for Denver International Airport.

  17. Transport aircraft accident dynamics

    NASA Technical Reports Server (NTRS)

    Cominsky, A.

    1982-01-01

    A study was carried out of 112 impact survivable jet transport aircraft accidents (world wide) of 27,700 kg (60,000 lb.) aircraft and up extending over the last 20 years. This study centered on the effect of impact and the follow-on events on aircraft structures and was confined to the approach, landing and takeoff segments of the flight. The significant characteristics, frequency of occurrence and the effect on the occupants of the above data base were studied and categorized with a view to establishing typical impact scenarios for use as a basis of verifying the effectiveness of potential safety concepts. Studies were also carried out of related subjects such as: (1) assessment of advanced materials; (2) human tolerance to impact; (3) merit functions for safety concepts; and (4) impact analysis and test methods.

  18. 19 CFR 122.32 - Aircraft required to land.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 1 2013-04-01 2013-04-01 false Aircraft required to land. 122.32 Section 122.32... TREASURY AIR COMMERCE REGULATIONS Landing Requirements § 122.32 Aircraft required to land. (a) Any aircraft... where aircraft entering the U.S. from a foreign area may land. As such, aircraft must land at...

  19. 19 CFR 122.32 - Aircraft required to land.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Aircraft required to land. 122.32 Section 122.32... TREASURY AIR COMMERCE REGULATIONS Landing Requirements § 122.32 Aircraft required to land. (a) Any aircraft... where aircraft entering the U.S. from a foreign area may land. As such, aircraft must land at...

  20. 19 CFR 122.32 - Aircraft required to land.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Aircraft required to land. 122.32 Section 122.32... TREASURY AIR COMMERCE REGULATIONS Landing Requirements § 122.32 Aircraft required to land. (a) Any aircraft... where aircraft entering the U.S. from a foreign area may land. As such, aircraft must land at...

  1. 19 CFR 122.32 - Aircraft required to land.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Aircraft required to land. 122.32 Section 122.32... TREASURY AIR COMMERCE REGULATIONS Landing Requirements § 122.32 Aircraft required to land. (a) Any aircraft... where aircraft entering the U.S. from a foreign area may land. As such, aircraft must land at...

  2. 19 CFR 122.32 - Aircraft required to land.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 1 2014-04-01 2014-04-01 false Aircraft required to land. 122.32 Section 122.32... TREASURY AIR COMMERCE REGULATIONS Landing Requirements § 122.32 Aircraft required to land. (a) Any aircraft... where aircraft entering the U.S. from a foreign area may land. As such, aircraft must land at...

  3. Experimental investigation of active loads control for aircraft landing gear

    NASA Technical Reports Server (NTRS)

    Mcgehee, J. R.; Dreher, R. C.

    1982-01-01

    Aircraft dynamic loads and vibrations resulting from landing impact and from runway and taxiway unevenness are recognized as significant in causing fatigue damage, dynamic stress on the airframe, crew and passenger discomfort, and reduction of the pilot's ability to control the aircraft during ground operations. One potential method for improving operational characteistics of aircraft on the ground is the application of active control technology to the landing gears to reduce ground loads applied to the airframe. An experimental investigation was conducted which simulated the landing dynamics of a light airplane to determine the feasibility and potential of a series hydraulic active control main landing gear. The experiments involved a passive gear and an active control gear. Results of this investigation show that a series hydraulically controlled gear is feasible and that such a gear is very effective in reducing the loads transmitted by the gear to the airframe during ground operations.

  4. Emergency Landing Planning for Damaged Aircraft

    NASA Technical Reports Server (NTRS)

    Meuleau, Nicolas; Plaunt, Christian John; Smith, David E.

    2008-01-01

    Considerable progress has been made over the last 15 years on building adaptive control systems to assist pilots in flying damaged aircraft. Once a pilot has regained control of a damaged aircraft, the next problem is to determine the best site for an emergency landing. In general, the decision depends on many factors including the actual control envelope of the aircraft, distance to the site, weather en route, characteristics of the approach path, characteristics of the runway or landing site, and emergency facilities at the site. All of these influence the risk to the aircraft, to the passengers and crew, and to people and property on the ground. We describe an ongoing project to build and demonstrate an emergency landing planner that takes these various factors into consideration and proposes possible routes and landing sites to the pilot, ordering them according to estimated risk. We give an overview of the system architecture and input data, describe our preliminary modeling of risk, and describe how we search the space of landing sites and routes.

  5. AGFATL- ACTIVE GEAR FLEXIBLE AIRCRAFT TAKEOFF AND LANDING ANALYSIS

    NASA Technical Reports Server (NTRS)

    Mcgehee, J. R.

    1994-01-01

    The Active Gear, Flexible Aircraft Takeoff and Landing Analysis program, AGFATL, was developed to provide a complete simulation of the aircraft takeoff and landing dynamics problem. AGFATL can represent an airplane either as a rigid body with six degrees of freedom or as a flexible body with multiple degrees of freedom. The airframe flexibility is represented by the superposition of up to twenty free vibration modes on the rigid-body motions. The analysis includes maneuver logic and autopilots programmed to control the aircraft during glide slope, flare, landing, and takeoff. The program is modular so that performance of the aircraft in flight and during landing and ground maneuvers can be studied separately or in combination. A program restart capability is included in AGFATL. Effects simulated in the AGFATL program include: (1) flexible aircraft control and performance during glide slope, flare, landing roll, and takeoff roll under conditions of changing winds, engine failures, brake failures, control system failures, strut failures, restrictions due to runway length, and control variable limits and time lags; (2) landing gear loads and dynamics for up to five gears; (3) single and multiple engines (maximum of four) including selective engine reversing and failure; (4) drag chute and spoiler effects; (5) wheel braking (including skid-control) and selective brake failure; (6) aerodynamic ground effects; (7) aircraft carrier operations; (8) inclined runways and runway perturbations; (9) flexible or rigid airframes; 10) rudder and nose gear steering; and 11) actively controlled landing gear shock struts. Input to the AGFATL program includes data which describe runway roughness; vehicle geometry, flexibility and aerodynamic characteristics; landing gear(s); propulsion; and initial conditions such as attitude, attitude change rates, and velocities. AGFATL performs a time integration of the equations of motion and outputs comprehensive information on the airframe

  6. Aircraft Dynamic Modeling in Turbulence

    NASA Technical Reports Server (NTRS)

    Morelli, Eugene A.; Cunninham, Kevin

    2012-01-01

    A method for accurately identifying aircraft dynamic models in turbulence was developed and demonstrated. The method uses orthogonal optimized multisine excitation inputs and an analytic method for enhancing signal-to-noise ratio for dynamic modeling in turbulence. A turbulence metric was developed to accurately characterize the turbulence level using flight measurements. The modeling technique was demonstrated in simulation, then applied to a subscale twin-engine jet transport aircraft in flight. Comparisons of modeling results obtained in turbulent air to results obtained in smooth air were used to demonstrate the effectiveness of the approach.

  7. Empirical Prediction of Aircraft Landing Gear Noise

    NASA Technical Reports Server (NTRS)

    Golub, Robert A. (Technical Monitor); Guo, Yue-Ping

    2005-01-01

    This report documents a semi-empirical/semi-analytical method for landing gear noise prediction. The method is based on scaling laws of the theory of aerodynamic noise generation and correlation of these scaling laws with current available test data. The former gives the method a sound theoretical foundation and the latter quantitatively determines the relations between the parameters of the landing gear assembly and the far field noise, enabling practical predictions of aircraft landing gear noise, both for parametric trends and for absolute noise levels. The prediction model is validated by wind tunnel test data for an isolated Boeing 737 landing gear and by flight data for the Boeing 777 airplane. In both cases, the predictions agree well with data, both in parametric trends and in absolute noise levels.

  8. V/STOL aircraft and fluid dynamic

    NASA Astrophysics Data System (ADS)

    Roberts, L.; Anderson, S. B.

    1982-01-01

    The impact of military applications on rotorcraft and V/STOL aircraft design with respect to fixed wing aircraft is discussed. The influence of the mission needs on the configurational design of V/STOL aircraft, the implications regarding some problems in fluid dynamics relating to propulsive flows, and their interaction with the aircraft and the ground plane, are summarized.

  9. Dynamic response of aircraft structure

    NASA Technical Reports Server (NTRS)

    1975-01-01

    The physical and mathematical problems associated with the response of elastic structures to random excitations such as occurs during buffeting and other transonic phenomena were discussed. The following subjects were covered: (1) general dynamic system consisting of the aircraft structure, the aerodynamic driving forces due to separated flow, and the aerodynamic forces due to aircraft structural motion, (2) structural and aerodynamic quantities of the dynamic system with special emphasis given to the description of the aerodynamic forces, and including a treatment of similarity laws, scaling effects, and wind tunnel testing, and (3) methods for data processing of fluctuating pressure recordings and techniques for response analysis for random excitation. A general buffeting flutter model, which takes into account the interactions between the separated and motion induced flows was presented. Relaxations of this model leading to the forced vibration model were explained.

  10. Validation of a Flexible Aircraft TakeOff and Landing Analysis /FATOLA/ computer program using flight landing data

    NASA Technical Reports Server (NTRS)

    Carden, H. D.; Mcgehee, J. R.

    1977-01-01

    A multiple-degree-of-freedom takeoff and landing analysis, Flexible Aircraft TakeOff and Landing Analysis computer program (FATOLA), was used to predict the landing behavior of a rigid-body X-24B reentry research vehicle and of a flexible-body modified-delta-wing supersonic YF-12 research aircraft. The analytical predictions were compared with flight test data for both research vehicles. Predicted time histories of vehicle motion and attitude, landing-gear strut stroke, and axial force transmitted from the landing gear to the airframe during the landing impact and rollout compared well with the actual time histories. Based on the comparisons presented, the versatility and validity of the FATOLA program for predicting landing dynamics of aircraft has been demonstrated.

  11. Flightworthy active control landing gear for a supersonic aircraft

    NASA Technical Reports Server (NTRS)

    Ross, I.

    1980-01-01

    A flightworthy active control landing gear system for a supersonic aircraft was designed to minimize aircraft loads during takeoff, impact, rollout, and taxi. The design consists of hydromechanical modifications to the existing gear and the development of a fail-safe electronic controller. analytical RESULTS INDICATE that for an aircraft sink rate of 0.914 m/sec (3 ft/sec) the system achieves a peak load reduction of 36% during landing impact.

  12. Wet runways. [aircraft landing and directional control

    NASA Technical Reports Server (NTRS)

    Horne, W. B.

    1975-01-01

    Aircraft stopping and directional control performance on wet runways is discussed. The major elements affecting tire/ground traction developed by jet transport aircraft are identified and described in terms of atmospheric, pavement, tire, aircraft system and pilot performance factors or parameters. Research results are summarized, and means for improving or restoring tire traction/aircraft performance on wet runways are discussed.

  13. X-1 research aircraft landing on lakebed

    NASA Technical Reports Server (NTRS)

    1947-01-01

    The first of the rocket-powered research aircraft, the X-1 (originally designated the XS-1), was a bullet-shaped airplane that was built by the Bell Aircraft Company for the US Air Force and the National Advisory Committee on Aeronautics (NACA). The mission of the X-1 was to investigate the transonic speed range (speeds from just below to just above the speed of sound) and, if possible, to break the 'sound barrier'. The first of the three X-1s was glide-tested at Pinecastle Air Force Base, FL, in early 1946. The first powered flight of the X-1 was made on Dec. 9, 1946, at Edwards Air Force Base with Chalmers Goodlin, a Bell test pilot, at the controls. On Oct. 14, 1947, with USAF Captain Charles 'Chuck' Yeager as pilot, the aircraft flew faster than the speed of sound for the first time. Captain Yeager ignited the four-chambered XLR-11 rocket engines after being air-launched from under the bomb bay of a B-29 at 21,000 ft. The 6,000-lbthrust ethyl alcohol/liquid oxygen burning rockets, built by Reaction Motors, Inc., pushed him up to a speed of 700 mph in level flight. Captain Yeager was also the pilot when the X-1 reached its maximum speed of 957 mph. Another USAF pilot. Lt. Col. Frank Everest, Jr., was credited with taking the X-1 to its maximum altitude of 71,902 ft. Eighteen pilots in all flew the X-1s. The number three plane was destroyed in a fire before ever making any powered flights. A single-place monoplane, the X-1 was 31 ft long, 10 ft high, and had a wingspan of 29 ft. It weighed 4,900 lb and carried 8,200 lb of fuel. It had a flush cockpit with a side entrance and no ejection seat. This roughly 30-second video clip shows the X-1 landing on Rogers Dry Lakebed followed by the safety chase aircraft.

  14. X-38 research aircraft landing - computer animation

    NASA Technical Reports Server (NTRS)

    1997-01-01

    In the mid-1990's researchers at the NASA Dryden Flight Research Center, Edwards, California, and Johnson Space Center in Houston, Texas, began working actively with the sub-scale X-38 prototype crew return vehicle (CRV). This was an unpiloted lifting body designed at 80 percent of the size of a projected emergency crew return vehicle for the International Space Station. The X-38 and the actual CRV are patterned after a lifting-body shape first employed in the Air Force X-23 (SV-5) program in the mid-1960's and the Air Force-NASA X-24A lifting-body project in the early to mid-1970's. Built by Scaled Composites, Inc., in Mojave, California, and outfitted with avionics, computer systems, and other hardware at Johnson Space Center, two X-38 aircraft were involved in flight research at Dryden beginning in July of 1997. Before that, however, Dryden conducted some 13 flights at a drop zone near California City, California. These tests were done with a 1/6-scale model of the X-38 aircraft to test the parafoil concept that would be employed on the X-38 aircraft and the actual CRV. The basic concept is that the actual CRV will use an inertial navigation system together with the Global Positioning System of satellites to guide it from the International Space Station into the earth's atmosphere. A deorbit engine module will redirect the vehicle from orbit into the atmosphere where a series of parachutes and a parafoil will deploy in sequence to bring the vehicle to a landing, possibly in a field next to a hospital. Flight research at NASA Dryden for the X-38 began with an unpiloted captive carry flight in which the vehicle remained attached to its future launch vehicle, the Dryden B-52 008. There were four captive flights in 1997 and three in 1998, plus the first drop test on March 12, 1998, using the parachutes and parafoil. Further captive and drop tests occurred in 1999. Although the X-38 landed safely on the lakebed at Edwards after the March 1998 drop test, there had

  15. Composition of smoke generated by landing aircraft.

    PubMed

    Bennett, Michael; Christie, Simon M; Graham, Angus; Thomas, Bryony S; Vishnyakov, Vladimir; Morris, Kevin; Peters, Daniel M; Jones, Rhys; Ansell, Cathy

    2011-04-15

    A combination of techniques has been used to examine the composition of smoke generated by landing aircraft. A sample of dust from the undercarriage from several commercial airliners was examined with SEM/EDX (Scanning Electron Microscope/Energy Dispersive X-ray) to determine its elemental composition and also with an aerosizer/aerodisperser in order to measure the particle size spectrum. The observed size spectrum was bimodal with equal numbers of particles at peaks of aerodynamic diameter ∼10 μm and ∼50 μm. The EDX analysis suggested that the former peak is carbonaceous, while the latter consists of elements typical of an asphalt concrete runway. In the field, a scanning Lidar, in combination with optical and condensation particle counters, was deployed to obtain limits to the number concentration and size of such particles. Most of the (strong) Lidar signal probably arose from the coarser 50 μm aerosol, while respirable aerosol was too sparse to be detected by the optical particle counters.

  16. Composition of smoke generated by landing aircraft.

    PubMed

    Bennett, Michael; Christie, Simon M; Graham, Angus; Thomas, Bryony S; Vishnyakov, Vladimir; Morris, Kevin; Peters, Daniel M; Jones, Rhys; Ansell, Cathy

    2011-04-15

    A combination of techniques has been used to examine the composition of smoke generated by landing aircraft. A sample of dust from the undercarriage from several commercial airliners was examined with SEM/EDX (Scanning Electron Microscope/Energy Dispersive X-ray) to determine its elemental composition and also with an aerosizer/aerodisperser in order to measure the particle size spectrum. The observed size spectrum was bimodal with equal numbers of particles at peaks of aerodynamic diameter ∼10 μm and ∼50 μm. The EDX analysis suggested that the former peak is carbonaceous, while the latter consists of elements typical of an asphalt concrete runway. In the field, a scanning Lidar, in combination with optical and condensation particle counters, was deployed to obtain limits to the number concentration and size of such particles. Most of the (strong) Lidar signal probably arose from the coarser 50 μm aerosol, while respirable aerosol was too sparse to be detected by the optical particle counters. PMID:21434600

  17. Decentralized aircraft landing scheduling at single runway non-controlled airports

    NASA Astrophysics Data System (ADS)

    Ding, Yuanyuan

    The existing air transportation system is approaching a bottleneck because its dominant hub-and-spoke model results in a concentration of a large percentage of the air traffic at a few hub airports. Advanced technologies are greatly needed to enhance the transportation capabilities of the small airports in the U.S.A., and distribute the high volume of air traffic at the hub airports to those small airports, which are mostly non-controlled airports. Currently, two major focus areas of research are being pursued to achieve this objective. One focus concentrates on the development of tools to improve operations in the current Air Traffic Management system. A more long-term research effort focuses on the development of decentralized Air Traffic Management techniques. This dissertation takes the latter approach and seeks to analyze the degree of decentralization for scheduling aircraft landings in the dynamic operational environment at single runway non-controlled airports. Moreover, it explores the feasibility and capability of scheduling aircraft landings within uninterrupted free-flight environment in which there is no existence of Air Traffic Control (ATC). First, it addresses the approach of developing static optimization algorithms for scheduling aircraft landings and, thus, analyzes the capability of automated aircraft landing scheduling at single runway non-controlled airports. Then, it provides detailed description of the implementation of a distributed Air Traffic Management (ATM) system that achieves decentralized aircraft landing scheduling with acceptable performance whereas a solution to the distributed coordination issues is presented. Finally real-time Monte Carlo flight simulations of multi-aircraft landing scenarios are conducted to evaluate the static and dynamic performance of the aircraft landing scheduling algorithms and operation concepts introduced. Results presented in the dissertation demonstrate that decentralized aircraft landing scheduling

  18. Coupling Dynamics in Aircraft: A Historical Perspective

    NASA Technical Reports Server (NTRS)

    Day, Richard E.

    1997-01-01

    Coupling dynamics can produce either adverse or beneficial stability and controllability, depending on the characteristics of the aircraft. This report presents archival anecdotes and analyses of coupling problems experienced by the X-series, Century series, and Space Shuttle aircraft. The three catastrophic sequential coupling modes of the X-2 airplane and the two simultaneous unstable modes of the X-15 and Space Shuttle aircraft are discussed. In addition, the most complex of the coupling interactions, inertia roll coupling, is discussed for the X-2, X-3, F-100A, and YF-102 aircraft. The mechanics of gyroscopics, centrifugal effect, and resonance in coupling dynamics are described. The coupling modes discussed are interacting multiple degrees of freedom of inertial and aerodynamic forces and moments. The aircraft are assumed to be rigid bodies. Structural couplings are not addressed. Various solutions for coupling instabilities are discussed.

  19. An Overview of Landing Gear Dynamics

    NASA Technical Reports Server (NTRS)

    Pritchard, Jocelyn I.

    1999-01-01

    One of the problems facing the aircraft community is landing gear dynamics, especially shimmy and brake-induced vibration. Although neither shimmy nor brake-induced vibrations are usually catastrophic, they can lead to accidents due to excessive wear and shortened life of gear parts and contribute to pilot and passenger discomfort. Recently, NASA has initiated an effort to increase the safety of air travel by reducing the number of accidents by a factor of five in ten years. This safety initiative has spurred an increased interest in improving landing gear design to minimize shimmy and brake-induced vibration that are still largely misunderstood phenomena. In order to increase the understanding of these problems, a literature survey was performed. The major focus of the paper is to summarize work documented from the last ten years to highlight the latest efforts in solving these vibration problems. Older publications are included to understand the longevity of the problem and the findings from earlier researchers. The literature survey revealed a variety of analyses, testing, modeling, and simulation of aircraft landing gear. Experimental validation and characterization of shimmy and brake-induced vibration of aircraft landing gear are also reported. This paper presents an overview of the problem documented in the references together with a history of landing gear dynamic problems and solutions. Based on the assessment of this survey, recommendations of the most critically needed enhancements to the state of the art are given.

  20. Realistic localizer courses for aircraft instrument landing simulators

    NASA Technical Reports Server (NTRS)

    Murphy, T. A.

    1984-01-01

    The realistic instrument landing simulator (ILS) course structures for use in aircraft simulators are described. Software developed for data conversion and translation of ILS course structure measurements and calcomp plots of the courses provided are described. A method of implementing the ILS course structure data in existing aircraft simulators is outlined. A cockpit used in the lab to review the digitized ILS course structures is displayed.

  1. Aircraft landing response in a discrete multipath environment

    NASA Technical Reports Server (NTRS)

    Guarino, C. R.

    1975-01-01

    This paper considers the problem of discrete multipath reflections upon an aircraft in the landing phase. A model is developed for the communication channel for a typical receiver. Simulation studies are presented showing the effects of discrete multipath upon the aircraft's ability to follow a specified flight path. A development is presented for the analytical determination of the probability density function of the angular errors.

  2. Influence of landing gear flexibility on aircraft performance during ground roll

    NASA Technical Reports Server (NTRS)

    Sivaramakrishnan, M. M.

    1981-01-01

    An analysis is made of the influence of landing gear deflection characteristics on aircraft performance on the ground up to rotation. A quasi-steady dynamic equilibrium state is assumed, including other simplifying assumptions such as calm air conditions and normal aircraft lift and drag. Ground incidence is defined as the angle made by the mean aerodynamic chord of the wing with respect to the ground plane, and equations are given for force and balance which determine the quasi-equilibrium conditions for the aircraft during ground roll. Results indicate that the landing gear deflections lead to a substantial increase in the angle of attack, and the variation in the ground incidence due to landing gear flexibility could be as much as + or - 50%, and the reduction in tail load requirements almost 25%.

  3. Aerodynamic penalties of heavy rain on a landing aircraft

    NASA Technical Reports Server (NTRS)

    Haines, P. A.; Luers, J. K.

    1982-01-01

    The aerodynamic penalties of very heavy rain on landing aircraft were investigated. Based on severity and frequency of occurrence, the rainfall rates of 100 mm/hr, 500 mm/hr, and 2000 mm/hr were designated, respectively, as heavy, severe, and incredible. The overall and local collection efficiencies of an aircraft encountering these rains were calculated. The analysis was based on raindrop trajectories in potential flow about an aircraft. All raindrops impinging on the aircraft are assumed to take on its speed. The momentum loss from the rain impact was later used in a landing simulation program. The local collection efficiency was used in estimating the aerodynamic roughness of an aircraft in heavy rain. The drag increase from this roughness was calculated. A number of landing simulations under a fixed stick assumption were done. Serious landing shortfalls were found for either momentum or drag penalties and especially large shortfalls for the combination of both. The latter shortfalls are comparable to those found for severe wind shear conditions.

  4. An Overview of Landing Gear Dynamics

    NASA Technical Reports Server (NTRS)

    Pritchard, Jocelyn I.

    1999-01-01

    One of the problems facing the aircraft community is landing gear dynamics, especially shimmy and brake-induced vibration. Shimmy and brake-induced vibrations can lead to accidents due to excessive wear and shortened life of gear parts and contribute to pilot and passenger discomfort. To increase understanding of these problems, a literature survey was performed. The major focus is on work from the last ten years. Some older publications are included to understand the longevity of the problem and the background from earlier researchers. The literature survey includes analyses, testing, modeling, and simulation of aircraft landing gear; and experimental validation and characterization of shimmy and brake-induced vibration of aircraft landing gear. The paper presents an overview of the problem, background information, and a history of landing gear dynamics problems and solutions. Based on the survey an assessment and recommendations of the most critically needed enhancements to the state of the art will be presented. The status of Langley work contributing to this activity will be given.

  5. Automatic carrier landing system for V/STOL aircraft using L1 adaptive and optimal control

    NASA Astrophysics Data System (ADS)

    Hariharapura Ramesh, Shashank

    This thesis presents a framework for developing automatic carrier landing systems for aircraft with vertical or short take-off and landing capability using two different control strategies---gain-scheduled linear optimal control, and L1 adaptive control. The carrier landing sequence of V/STOL aircraft involves large variations in dynamic pressure and aerodynamic coefficients arising because of the transition from aerodynamic-supported to jet-borne flight, descent to the touchdown altitude, and turns performed to align with the runway. Consequently, the dynamics of the aircraft exhibit a highly non-linear dynamical behavior with variations in flight conditions prior to touchdown. Therefore, the implication is the need for non-linear control techniques to achieve automatic landing. Gain-scheduling has been one of the most widely employed techniques for control of aircraft, which involves designing linear controllers for numerous trimmed flight conditions, and interpolating them to achieve a global non-linear control. Adaptive control technique, on the other hand, eliminates the need to schedule the controller parameters as they adapt to changing flight conditions.

  6. TAKEOFF AND LANDING PERFORMANCE CAPABILITIES OF TRANSPORT CATEGORY AIRCRAFT

    NASA Technical Reports Server (NTRS)

    Foss, W. E.

    1994-01-01

    One of the most important considerations in the design of a commercial transport aircraft is the aircraft's performance during takeoff and landing operations. The aircraft must be designed to meet field length constraints in accordance with airworthiness standards specified in the Federal Aviation Regulations. In addition, the noise levels generated during these operations must be within acceptable limits. This computer program provides for the detailed analysis of the takeoff and landing performance capabilities of transport category aircraft. The program calculates aircraft performance in accordance with the airworthiness standards of the Federal Aviation Regulations. The aircraft and flight constraints are represented in sufficient detail to permit realistic sensitivity studies in terms of either configuration modifications or changes in operational procedures. This program provides for the detailed performance analysis of the takeoff and landing capabilities of specific aircraft designs and allows for sensitivity studies. The program is not designed to synthesize configurations or to generate aerodynamic, propulsion, or structural characteristics. This type of information must be generated externally to the program and then input as data. The program's representation of the aircraft data is extensive and includes realistic limits on engine and aircraft operational boundaries and maximum attainable lift coefficients. The takeoff and climbout flight-path is generated by a stepwise integration of the equation of motion. Special features include options for nonstandard-day operation, for balanced field length, for derated throttle to meet a given field length for off-loaded aircraft, and for throttle cutback during climbout for community noise alleviation. Advanced takeoff procedures for noise alleviation such as programmed throttle and control flaps may be investigated with the program. Approach profiles may incorporate advanced procedures such as two segment

  7. Metallurgical analysis of fractured F-27 aircraft landing gear

    SciTech Connect

    Witherell, C.E.

    1987-12-15

    The Materials Division of LLNL's Chemistry and Materials Science Department was asked to conduct a study of a fractured component of the main (starboard) landing gear on the F-27 aircraft (N768RL). The purpose of the study was to determine from metallurgical evidence the probable failure mode, its cause, and contribution to the recent landing incident at Livermore. 21 refs., 15 figs., 1 tab.

  8. Concentric circles based simple optical landing aid for vertical takeoff and landing aircrafts

    NASA Astrophysics Data System (ADS)

    Murshid, Syed H.; Enaya, Rayan; Lovell, Gregory L.

    2014-09-01

    Vertical takeoff and landing (VTOL) aircrafts such as helicopters and drones, add a flexible degree of operation to airborne vehicles. In order to operate these devices in low light situations, where it is difficult to determine slope of the landing surface, a lightweight and standalone device is proposed here. This small optical device can be easily integrated into current VTOL systems. An optical projector consisting of low power, light weight, solid state laser along with minimal optics is utilized to illuminate the landing surface with donut shaped circles and coaxial centralized dot. This device can placed anywhere on the aircraft and a properly placed fiber system can be used to illuminate the surface beneath the bottom of the VTOL aircraft in a fashion that during operation, when the aircraft is parallel to the landing surface, the radius between the central dot and outer ring(s) are equidistant for the entire circumference; however, when there the landing surface of the VTOL aircraft is not parallel to the landing strip, the radial distance between two opposite sides of the circle and central dot will be unequal. The larger this distortion, the greater the difference will be between the opposite sides of the circle. Visual confirmation or other optical devices can be used to determine relative alignment of the projector output allowing the pilot to make proper adjustments as they approach the landing surface to ensure safe landings. Simulated and experimental results from a prototype optical projector are presented here.

  9. Improving Student Naval Aviator Aircraft Carrier Landing Performance

    ERIC Educational Resources Information Center

    Sheppard, Thomas H.; Foster, T. Chris

    2008-01-01

    This article discusses the use of human performance technology (HPT) to improve qualification rates for learning to land onboard aircraft carriers. This project started as a request for a business case analysis and evolved into a full-fledged performance improvement project, from mission analysis through evaluation. The result was a significant…

  10. Enhanced vision for adverse weather aircraft landing

    NASA Astrophysics Data System (ADS)

    Sadjadi, Firooz; Helgeson, Mike; Radke, Jeff; Stein, Gunter

    1996-01-01

    Landing in poor weather is a crucial problem for the air transportation system of the future. To aid the pilots for these conditions several solutions have been suggested and/or implemented including instrument landing system(ILS) and microwave landing system(MLS) that put the responsibility of the landing to a large extent in the hands of the airport facilities. These systems even though useful are not available due to their high costs except in few major metropolitan airports. This shortcoming has generated interest in providing all weather capabilities not on the landing facility but on the vehicle itself. The Synthetic Vision System Technology Demonstration sponsored by the United States Federal Aviation Administration(FAA) and the US Air Force represents an effort to respond to the above needs[1,2]. In this paper we present a summary of a typical synthetic vision system. This system consists of a scanning 35GHz radar a scanning antenna, a signal/image processor and a head up display(HUD). The pilot is presented a final perspective image of the scene sensed by the radar with associated flight guidance symbology. This systems is implemented in real time hardware and has been under going tower and flight testing under a variety of weather conditions since early 1992.

  11. Method and device for landing aircraft dependent on runway occupancy time

    NASA Technical Reports Server (NTRS)

    Ghalebsaz Jeddi, Babak (Inventor)

    2012-01-01

    A technique for landing aircraft using an aircraft landing accident avoidance device is disclosed. The technique includes determining at least two probability distribution functions; determining a safe lower limit on a separation between a lead aircraft and a trail aircraft on a glide slope to the runway; determining a maximum sustainable safe attempt-to-land rate on the runway based on the safe lower limit and the probability distribution functions; directing the trail aircraft to enter the glide slope with a target separation from the lead aircraft corresponding to the maximum sustainable safe attempt-to-land rate; while the trail aircraft is in the glide slope, determining an actual separation between the lead aircraft and the trail aircraft; and directing the trail aircraft to execute a go-around maneuver if the actual separation approaches the safe lower limit. Probability distribution functions include runway occupancy time, and landing time interval and/or inter-arrival distance.

  12. Actively Controlled Landing Gear for Aircraft Vibration Reduction

    NASA Technical Reports Server (NTRS)

    Horta, Lucas G.; Daugherty, Robert H.; Martinson, Veloria J.

    1999-01-01

    Concepts for long-range air travel are characterized by airframe designs with long, slender, relatively flexible fuselages. One aspect often overlooked is ground induced vibration of these aircraft. This paper presents an analytical and experimental study of reducing ground-induced aircraft vibration loads using actively controlled landing gears. A facility has been developed to test various active landing gear control concepts and their performance. The facility uses a NAVY A6-intruder landing gear fitted with an auxiliary hydraulic supply electronically controlled by servo valves. An analytical model of the gear is presented including modifications to actuate the gear externally and test data is used to validate the model. The control design is described and closed-loop test and analysis comparisons are presented.

  13. Impact of aircraft plume dynamics on airport local air quality

    NASA Astrophysics Data System (ADS)

    Barrett, Steven R. H.; Britter, Rex E.; Waitz, Ian A.

    2013-08-01

    Air quality degradation in the locality of airports poses a public health hazard. The ability to quantitatively predict the air quality impacts of airport operations is of importance for assessing the air quality and public health impacts of airports today, of future developments, and for evaluating approaches for mitigating these impacts. However, studies such as the Project for the Sustainable Development of Heathrow have highlighted shortcomings in understanding of aircraft plume dispersion. Further, if national or international aviation environmental policies are to be assessed, a computationally efficient method of modeling aircraft plume dispersion is needed. To address these needs, we describe the formulation and validation of a three-dimensional integral plume model appropriate for modeling aircraft exhaust plumes at airports. We also develop a simplified concentration correction factor approach to efficiently account for dispersion processes particular to aircraft plumes. The model is used to explain monitoring station results in the London Heathrow area showing that pollutant concentrations are approximately constant over wind speeds of 3-12 m s-1, and is applied to reproduce empirically derived relationships between engine types and peak NOx concentrations at Heathrow. We calculated that not accounting for aircraft plume dynamics would result in a factor of 1.36-2.3 over-prediction of the mean NOx concentration (depending on location), consistent with empirical evidence of a factor of 1.7 over-prediction. Concentration correction factors are also calculated for aircraft takeoff, landing and taxi emissions, providing an efficient way to account for aircraft plume effects in atmospheric dispersion models.

  14. CV-990 Landing Systems Research Aircraft (LSRA) during final Space Shuttle tire test

    NASA Technical Reports Server (NTRS)

    1995-01-01

    A Convair 990 (CV-990) was used as a Landing Systems Research Aircraft (LSRA) at NASA's Dryden Flight Research Center, Edwards, California, to test space shuttle landing gear and braking systems as part of NASA's effort to upgrade and improve space shuttle capabilities. The first flight at Dryden of the CV-990 with shuttle test components occurred in April 1993, and tests continued into August 1995, when this photo shows a test of the shuttle tires. The purpose of this series of tests was to determine the performance parameters and failure limits of the tires. This particular landing was on the dry lakebed at Edwards, but other tests occurred on the main runway there. The CV-990, built in 1962 by the Convair Division of General Dynamics Corp., Ft. Worth, Texas, served as a research aircraft at Ames Research Center, Moffett Field, California, before it came to Dryden.

  15. Comparison of Predictive Modeling Methods of Aircraft Landing Speed

    NASA Technical Reports Server (NTRS)

    Diallo, Ousmane H.

    2012-01-01

    Expected increases in air traffic demand have stimulated the development of air traffic control tools intended to assist the air traffic controller in accurately and precisely spacing aircraft landing at congested airports. Such tools will require an accurate landing-speed prediction to increase throughput while decreasing necessary controller interventions for avoiding separation violations. There are many practical challenges to developing an accurate landing-speed model that has acceptable prediction errors. This paper discusses the development of a near-term implementation, using readily available information, to estimate/model final approach speed from the top of the descent phase of flight to the landing runway. As a first approach, all variables found to contribute directly to the landing-speed prediction model are used to build a multi-regression technique of the response surface equation (RSE). Data obtained from operations of a major airlines for a passenger transport aircraft type to the Dallas/Fort Worth International Airport are used to predict the landing speed. The approach was promising because it decreased the standard deviation of the landing-speed error prediction by at least 18% from the standard deviation of the baseline error, depending on the gust condition at the airport. However, when the number of variables is reduced to the most likely obtainable at other major airports, the RSE model shows little improvement over the existing methods. Consequently, a neural network that relies on a nonlinear regression technique is utilized as an alternative modeling approach. For the reduced number of variables cases, the standard deviation of the neural network models errors represent over 5% reduction compared to the RSE model errors, and at least 10% reduction over the baseline predicted landing-speed error standard deviation. Overall, the constructed models predict the landing-speed more accurately and precisely than the current state-of-the-art.

  16. Potential for Landing Gear Noise Reduction on Advanced Aircraft Configurations

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Nickol, Craig L.; Burley, Casey L.; Guo, Yueping

    2016-01-01

    The potential of significantly reducing aircraft landing gear noise is explored for aircraft configurations with engines installed above the wings or the fuselage. An innovative concept is studied that does not alter the main gear assembly itself but does shorten the main strut and integrates the gear in pods whose interior surfaces are treated with acoustic liner. The concept is meant to achieve maximum noise reduction so that main landing gears can be eliminated as a major source of airframe noise. By applying this concept to an aircraft configuration with 2025 entry-into-service technology levels, it is shown that compared to noise levels of current technology, the main gear noise can be reduced by 10 EPNL dB, bringing the main gear noise close to a floor established by other components such as the nose gear. The assessment of the noise reduction potential accounts for design features for the advanced aircraft configuration and includes the effects of local flow velocity in and around the pods, gear noise reflection from the airframe, and reflection and attenuation from acoustic liner treatment on pod surfaces and doors. A technical roadmap for maturing this concept is discussed, and the possible drag increase at cruise due to the addition of the pods is identified as a challenge, which needs to be quantified and minimized possibly with the combination of detailed design and application of drag reduction technologies.

  17. Lockheed ER-2 #806 high altitude research aircraft during landing

    NASA Technical Reports Server (NTRS)

    1998-01-01

    ER-2 tail number 806, is one of two Airborne Science ER-2s used as science platforms by Dryden. The aircraft are platforms for a variety of high-altitude science missions flown over various parts of the world. They are also used for earth science and atmospheric sensor research and development, satellite calibration and data validation. The ER-2s are capable of carrying a maximum payload of 2,600 pounds of experiments in a nose bay, the main equipment bay behind the cockpit, two wing-mounted superpods and small underbody and trailing edges. Most ER-2 missions last about six hours with ranges of about 2,200 nautical miles. The aircraft typically fly at altitudes above 65,000 feet. On November 19, 1998, the ER-2 set a world record for medium weight aircraft reaching an altitude of 68,700 feet. The aircraft is 63 feet long, with a wingspan of 104 feet. The top of the vertical tail is 16 feet above ground when the aircraft is on the bicycle-type landing gear. Cruising speeds are 410 knots, or 467 miles per hour, at altitude. A single General Electric F-118 turbofan engine rated at 17,000 pounds thrust powers the ER-2.

  18. Landing flying qualities evaluation criteria for augmented aircraft

    NASA Technical Reports Server (NTRS)

    Radford, R. C.; Smith, R.; Bailey, R.

    1980-01-01

    The criteria evaluated were: Calspan Neal-Smith; Onstott (Northrop Time Domain); McDonnell-Douglas Equivalent System Approach; R. H. Smith Criterion. Each criterion was applied to the same set of longitudinal approach and landing flying qualities data. A revised version of the Neal-Smith criterion which is applicable to the landing task was developed and tested against other landing flying qualities data. Results indicated that both the revised Neal-Smith criterion and the Equivalent System Approach are good discriminators of pitch landing flying qualities; Neal-Smith has particular merit as a design guide, while the Equivalent System Approach is well suited for development of appropriate military specification requirements applicable to highly augmented aircraft.

  19. Flight dynamics research for highly agile aircraft

    NASA Technical Reports Server (NTRS)

    Nguyen, Luat T.

    1989-01-01

    This paper highlights recent results of research conducted at the NASA Langley Research Center as part of a broad flight dynamics program aimed at developing technology that will enable future combat aircraft to achieve greatly enhanced agility capability at subsonic combat conditions. Studies of advanced control concepts encompassing both propulsive and aerodynamic approaches are reviewed. Dynamic stall phenomena and their potential impact on maneuvering performance and stability are summarized. Finally, issues of mathematical modeling of complex aerodynamics occurring during rapid, large amplitude maneuvers are discussed.

  20. An engineering optimization method with application to STOL-aircraft approach and landing trajectories

    NASA Technical Reports Server (NTRS)

    Jacob, H. G.

    1972-01-01

    An optimization method has been developed that computes the optimal open loop inputs for a dynamical system by observing only its output. The method reduces to static optimization by expressing the inputs as series of functions with parameters to be optimized. Since the method is not concerned with the details of the dynamical system to be optimized, it works for both linear and nonlinear systems. The method and the application to optimizing longitudinal landing paths for a STOL aircraft with an augmented wing are discussed. Noise, fuel, time, and path deviation minimizations are considered with and without angle of attack, acceleration excursion, flight path, endpoint, and other constraints.

  1. Videopanorama Frame Rate Requirements Derived from Visual Discrimination of Deceleration During Simulated Aircraft Landing

    NASA Technical Reports Server (NTRS)

    Furnstenau, Norbert; Ellis, Stephen R.

    2015-01-01

    In order to determine the required visual frame rate (FR) for minimizing prediction errors with out-the-window video displays at remote/virtual airport towers, thirteen active air traffic controllers viewed high dynamic fidelity simulations of landing aircraft and decided whether aircraft would stop as if to be able to make a turnoff or whether a runway excursion would be expected. The viewing conditions and simulation dynamics replicated visual rates and environments of transport aircraft landing at small commercial airports. The required frame rate was estimated using Bayes inference on prediction errors by linear FRextrapolation of event probabilities conditional on predictions (stop, no-stop). Furthermore estimates were obtained from exponential model fits to the parametric and non-parametric perceptual discriminabilities d' and A (average area under ROC-curves) as dependent on FR. Decision errors are biased towards preference of overshoot and appear due to illusionary increase in speed at low frames rates. Both Bayes and A - extrapolations yield a framerate requirement of 35 < FRmin < 40 Hz. When comparing with published results [12] on shooter game scores the model based d'(FR)-extrapolation exhibits the best agreement and indicates even higher FRmin > 40 Hz for minimizing decision errors. Definitive recommendations require further experiments with FR > 30 Hz.

  2. Status report on the land processes aircraft science management operations working group

    NASA Technical Reports Server (NTRS)

    Lawless, James G.; Mann, Lisa J.

    1991-01-01

    Since its inception three years ago, the Land Processes Aircraft Science Management Operations Working Group (MOWG) provided recommendations on the optimal use of the Agency's aircraft in support of the Land Processes Science Program. Recommendations covered topics such as aircraft and sensor usage, development of long-range plans, Multisensor Airborne Campaigns (MAC), program balance, aircraft sensor databases, new technology and sensor development, and increased University scientist participation in the program. Impacts of these recommendations improved the efficiency of various procedures including the flight request process, tracking of flight hours, and aircraft usage. The group also created a bibliography focused on publications produced by Land Processes scientists from the use of the aircraft program, surveyed NASA funded PI's on their participation in the aircraft program, and developed a planning template for multi-sensor airborne campaigns. Benefits from these activities are summarized.

  3. Multi-aircraft dynamics, navigation and operation

    NASA Astrophysics Data System (ADS)

    Houck, Sharon Wester

    Air traffic control stands on the brink of a revolution. Fifty years from now, we will look back and marvel that we ever flew by radio beacons and radar alone, much as we now marvel that early aviation pioneers flew by chronometer and compass alone. The microprocessor, satellite navigation systems, and air-to-air data links are the technical keys to this revolution. Many airports are near or at capacity now for at least portions of the day, making it clear that major increases in airport capacity will be required in order to support the projected growth in air traffic. This can be accomplished by adding airports, adding runways at existing airports, or increasing the capacity of the existing runways. Technology that allows use of ultra closely spaced (750 ft to 2500 ft) parallel approaches would greatly reduce the environmental impact of airport capacity increases. This research tackles the problem of multi aircraft dynamics, navigation, and operation, specifically in the terminal area, and presents new findings on how ultra closely spaced parallel approaches may be accomplished. The underlying approach considers how multiple aircraft are flown in visual conditions, where spacing criteria is much less stringent, and then uses this data to study the critical parameters for collision avoidance during an ultra closely spaced parallel approach. Also included is experimental and analytical investigations on advanced guidance systems that are critical components of precision approaches. Together, these investigations form a novel approach to the design and analysis of parallel approaches for runways spaced less than 2500 ft apart. This research has concluded that it is technically feasible to reduce the required runway spacing during simultaneous instrument approaches to less than the current minimum of 3400 ft with the use of advanced navigation systems while maintaining the currently accepted levels of safety. On a smooth day with both pilots flying a tunnel

  4. Full color hybrid display for aircraft simulators. [landing aids

    NASA Technical Reports Server (NTRS)

    Chase, W. D. (Inventor)

    1977-01-01

    A full spectrum color monitor, connected to the camera and lens system of a television camera supported by a gantry frame over a terrain model simulating an aircraft landing zone, projects the monitor image onto a lens or screen visually accessible to a trainee in the simulator. A digital computer produces a pattern corresponding to the lights associated with the landing strip onto a monochromatic display, and an optical system projects the calligraphic image onto the same lens so that it is superposed on the video representation of the landing field. The optical system includes a four-color wheel which is rotated between the calligraphic display and the lens, and an apparatus for synchronizing the generation of a calligraphic pattern with the color segments on the color wheel. A servo feedback system responsive to the servo motors on the gantry frame produces an input to the computer so that the calligraphically generated signal corresponds in shape, size and location to the video signal.

  5. Altus I aircraft in flight, retracting landing gear after takeoff

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The landing gear of the remotely piloted Altus I aircraft retracts into the fuselage after takeoff from Rogers Dry Lake adjacent to NASA's Dryden Flight Research Center, Edwards, Calif. The short series of test flights sponsored by the Naval Postgraduate School in early August, 1997, was designed to demonstrate the ability of the experimental craft to cruise at altitudes above 40,000 feet for sustained durations. On its final flight Aug. 15, the Altus I reached an altitude of 43,500 feet. The Altus I and its sister ship, the Altus II, are variants of the Predator surveillance drone built by General Atomics/Aeronautical Systems, Inc. They are designed for high-altitude, long-duration scientific sampling missions. The Altus I incorporates a single-stage turbocharger, while the Altus II, built for NASA's Environmental Research Aircraft and Sensor Technology project, sports a two-stage turbocharger to enable the craft to fly at altitudes above 55,000 feet.

  6. Unmanned Aircraft Systems for Monitoring Department of the Interior Lands

    NASA Astrophysics Data System (ADS)

    Hutt, M. E.; Quirk, B.

    2013-12-01

    Unmanned Aircraft Systems (UAS) technology is quickly evolving and will have a significant impact on Earth science research. The U.S. Geological Survey (USGS) is conducting an operational test and evaluation of UAS to see how this technology supports the mission of the Department of the Interior (DOI). Over the last 4 years, the USGS, working with many partners, has been actively conducting proof of concept UAS operations, which are designed to evaluate the potential of UAS technology to support the mandated DOI scientific, resource and land management missions. UAS technology is being made available to monitor environmental conditions, analyze the impacts of climate change, respond to natural hazards, understand landscape change rates and consequences, conduct wildlife inventories and support related land management and law enforcement missions. Using small UAS (sUAS), the USGS is able to tailor solutions to meet project requirements by obtaining very high resolution video data, acquiring thermal imagery, detecting chemical plumes, and generating digital terrain models at a fraction of the cost of conventional surveying methods. UAS technology is providing a mechanism to collect timely remote sensing data at a low cost and at low risk over DOI lands that can be difficult to monitor and consequently enhances our ability to provide unbiased scientific information to better enable decision makers to make informed decisions. This presentation describes the UAS technology and infrastructure being employed, the application projects already accomplished, lessons learned and future of UAS within the DOI. We fully expect that by 2020 UAS will emerge as a primary platform for all DOI remote sensing applications. Much like the use of Internet technology, Geographic Information Systems (GIS) and Global Positioning Systems (GPS), UAS have the potential of enabling the DOI to be better stewards of the land.

  7. Altus I aircraft landing on Edwards lakebed runway 23

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The remotely-piloted Altus I aircraft lands on Rogers Dry Lake adjacent to NASA's Dryden Flight Research Center, Edwards, Calif. The short series of test flights sponsored by the Naval Postgraduate School in early August, 1997, were designed to demonstrate the ability of the experimental craft to cruise at altitudes above 40,000 feet for sustained durations. On its final flight Aug. 15, the Altus I reached an altitude of 43,500 feet. The Altus I and its sister ship, the Altus II, are variants of the Predator surveillance drone built by General Atomics/Aeronautical Systems, Inc. They are designed for high-altitude, long-duration scientific sampling missions, and are powered by turbocharged piston engines. The Altus I incorporates a single-stage turbocharger, while the Altus II, built for NASA's Environmental Research Aircraft and Sensor Technology program, sports a two-stage turbocharger to enable the craft to fly at altitudes above 55,000 feet. The Altus II, the first of the two craft to be completed, made its first flight on May 1, 1996. With its engine augmented by a single-stage turbocharger, the Altus II reached an altitude of 37,000 ft during its first series of development flights at Dryden in Aug., 1996. In Oct. of that year, the Altus II was flown in an Atmospheric Radiation Measurement study for the Department of Energy's Sandia National Laboratory in Oklahoma. During the course of those flights, the Altus II set a single-flight endurance record for remotely-operated aircraft of more than 26 hours. The Altus I, completed in 1997, flew a series of development flights at Dryden that summer. Those test flights culminated with the craft reaching an altitude of 43,500 ft while carrying a simulated 300-lb payload, a record for an unmanned aircraft powered by a piston engine augmented with a single-stage turbocharger. The Altus II sustained an altitudeof 55,000 feet for four hours in 1999. A pilot in a control station on the ground flies the craft by radio

  8. Effects of higher order control systems on aircraft approach and landing longitudinal handling qualities

    NASA Technical Reports Server (NTRS)

    Pasha, M. A.; Dazzo, J. J.; Silverthorn, J. T.

    1982-01-01

    An investigation of approach and landing longitudinal flying qualities, based on data generated using a variable stability NT-33 aircraft combined with significant control system dynamics is described. An optimum pilot lead time for pitch tracking, flight path angle tracking, and combined pitch and flight path angle tracking tasks is determined from a closed loop simulation using integral squared error (ISE) as a performance measure. Pilot gain and lead time were varied in the closed loop simulation of the pilot and aircraft to obtain the best performance for different control system configurations. The results lead to the selection of an optimum lead time using ISE as a performance criterion. Using this value of optimum lead time, a correlation is then found between pilot rating and performance with changes in the control system and in the aircraft dynamics. It is also shown that pilot rating is closely related to pilot workload which, in turn, is related to the amount of lead which the pilot must generate to obtain satisfactory response. The results also indicate that the pilot may use pitch angle tracking for the approach task and then add flight path angle tracking for the flare and touchdown.

  9. Taxiing, Take-Off, and Landing Simulation of the High Speed Civil Transport Aircraft

    NASA Technical Reports Server (NTRS)

    Reaves, Mercedes C.; Horta, Lucas G.

    1999-01-01

    The aircraft industry jointly with NASA is studying enabling technologies for higher speed, longer range aircraft configurations. Higher speeds, higher temperatures, and aerodynamics are driving these newer aircraft configurations towards long, slender, flexible fuselages. Aircraft response during ground operations, although often overlooked, is a concern due to the increased fuselage flexibility. This paper discusses modeling and simulation of the High Speed Civil Transport aircraft during taxiing, take-off, and landing. Finite element models of the airframe for various configurations are used and combined with nonlinear landing gear models to provide a simulation tool to study responses to different ground input conditions. A commercial computer simulation program is used to numerically integrate the equations of motion and to compute estimates of the responses using an existing runway profile. Results show aircraft responses exceeding safe acceptable human response levels.

  10. 32 CFR 855.6 - Aircraft exempt from the requirement for a civil aircraft landing permit.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... includes aircraft owned by individuals but leased by Army or Navy aero clubs. (4) A US State, County... local Government has retained liability responsibilities. (7) Civil aircraft transporting critically...

  11. Landing Gear Integration in Aircraft Conceptual Design. Revision

    NASA Technical Reports Server (NTRS)

    Chai, Sonny T.; Mason, William H.

    1997-01-01

    The design of the landing gear is one of the more fundamental aspects of aircraft design. The design and integration process encompasses numerous engineering disciplines, e.g., structure, weights, runway design, and economics, and has become extremely sophisticated in the last few decades. Although the design process is well-documented, no attempt has been made until now in the development of a design methodology that can be used within an automated environment. As a result, the process remains to be a key responsibility for the configuration designer and is largely experience-based and graphically-oriented. However, as industry and government try to incorporate multidisciplinary design optimization (MDO) methods in the conceptual design phase, the need for a more systematic procedure has become apparent. The development of an MDO-capable design methodology as described in this work is focused on providing the conceptual designer with tools to help automate the disciplinary analyses, i.e., geometry, kinematics, flotation, and weight. Documented design procedures and analyses were examined to determine their applicability, and to ensure compliance with current practices and regulations. Using the latest information as obtained from industry during initial industry survey, the analyses were in terms modified and expanded to accommodate the design criteria associated with the advanced large subsonic transports. Algorithms were then developed based on the updated analysis procedures to be incorporated into existing MDO codes.

  12. A head-up display format for application to transport aircraft approach and landing

    NASA Technical Reports Server (NTRS)

    Bray, R. S.

    1980-01-01

    A head up display (HUD) format used in simulator studies of the application of HUD to the landing of civil transport aircraft is described in detail. The display features an indication of the aircraft's instantaneous flightpath that constitutes the primary controlled element. Discrete ILS error and altitude signals are scaled and positioned to provide precise guidance modes when tracked with the flightpath symbol. Consideration is given to both the availability and nonavailability of inertial velocity information in the aircraft.

  13. X-38 research aircraft - First drop flight and landing

    NASA Technical Reports Server (NTRS)

    1998-01-01

    In the mid-1990's researchers at the NASA Dryden Flight Research Center, Edwards, California, and Johnson Space Center in Houston, Texas, began working actively with the sub-scale X-38 prototype crew return vehicle (CRV). This was an unpiloted lifting body designed at 80 percent of the size of a projected emergency crew return vehicle for the International Space Station. The X-38 and the actual CRV are patterned after a lifting-body shape first employed in the Air Force X-23 (SV-5) program in the mid-1960's and the Air Force-NASA X-24A lifting-body project in the early to mid-1970's. Built by Scaled Composites, Inc., in Mojave, California, and outfitted with avionics, computer systems, and other hardware at Johnson Space Center, two X-38 aircraft were involved in flight research at Dryden beginning in July of 1997. Before that, however, Dryden conducted some 13 flights at a drop zone near California City, California. Those tests were done with a 1/6-scale model of the X-38 aircraft to test the parafoil concept that would be employed on the X-38 and the actual CRV. The basic concept is that the actual CRV will use an inertial navigation system together with the Global Positioning System of satellites to guide it from the International Space Station into the Earth's atmosphere. A deorbit engine module will redirect the vehicle from orbit into the atmosphere where a series of parachutes and a parafoil will deploy in sequence to bring the vehicle to a landing, possibly in a field next to a hospital. Flight research at NASA Dryden for the X-38 began with an unpiloted captive carry flight in which the vehicle remained attached to its future launch vehicle the Dryden B-52 008. There were four captive flights in 1997 and three in 1998, plus the first drop test on March 12, 1998, using the parachutes and parafoil. Further captive and drop tests occurred in 1999. Although the X-38 landed safely on the lakebed at Edwards after the March 1998 drop test, there had been some

  14. Stress-strain state of ice cover during aircraft takeoff and landing

    NASA Astrophysics Data System (ADS)

    Pogorelova, A. V.; Kozin, V. M.; Matyushina, A. A.

    2015-09-01

    We consider the linear unsteady motion of an IL-76TD aircraft on ice. Water is treated as an ideal incompressible liquid, and the liquid motion is considered potential. Ice cover is modeled by an initially unstressed uniform isotropic elastic plate, and the load exerted by the aircraft on the ice cover with consideration of the wing lift is modeled by regions of distributed pressure of variable intensity, arranged under the aircraft landing gear. The effect of the thickness and elastic modulus of the ice plate, takeoff and landing regimes on stress-strain state of the ice cover used as a runway.

  15. Microphysical Properties of Warm Clouds During The Aircraft Take-Off and Landing Over Bucharest, Romania

    NASA Astrophysics Data System (ADS)

    Stefan, Sabina; Nicolae Vajaiac, Sorin; Boscornea, Andreea

    2016-06-01

    This paper is focused on airborne measurements of microphysical parameters into warm clouds when the aircraft penetrates the cloud, both during take-off and landing. The experiment was conducted during the aircraft flight between Bucharest and Craiova, in the southern part of Romania. The duration of the experimental flight was 2 hours and 35 minutes in October 7th, 2014, but the present study is dealing solely with the analysis of cloud microphysical properties at the beginning of the experiment (during the aircraft take-off) and at the end, when it got finalized by the aircraft landing procedure. The processing and interpretation of the measurements showed the differences between microphysical parameters, emphasizing that the type of cloud over Bucharest changed, as it was expected. In addition, the results showed that it is important to take into account both the synoptic context and the cloud perturbation due to the velocity of the aircraft, in such cases.

  16. Effects of asymmetry on the dynamic stability of aircraft

    NASA Technical Reports Server (NTRS)

    Fantino, R. E.; Parsons, E. K.; Powell, J. D.; Shevell, R. S.

    1975-01-01

    The oblique wing concept for transonic aircraft was proposed to reduce drag. The dynamic stability of the aircraft was investigated by analytically determining the stability derivatives at angles of skew ranging from 0 and 45 deg and using these stability derivatives in a linear analysis of the coupled aircraft behavior. The stability derivatives were obtained using a lifting line aerodynamic theory and found to give reasonable agreement with derivatives developed in a previous study for the same aircraft. In the dynamic analysis, no instability or large changes occurred in the root locations for skew angles varying from 0 to 45 deg with the exception of roll convergence. The damping in roll, however, decreased by an order of magnitude. Rolling was a prominent feature of all the oscillatory mode shapes at high skew angles.

  17. A review of the analytical simulation of aircraft crash dynamics

    NASA Technical Reports Server (NTRS)

    Fasanella, Edwin L.; Carden, Huey D.; Boitnott, Richard L.; Hayduk, Robert J.

    1990-01-01

    A large number of full scale tests of general aviation aircraft, helicopters, and one unique air-to-ground controlled impact of a transport aircraft were performed. Additionally, research was also conducted on seat dynamic performance, load-limiting seats, load limiting subfloor designs, and emergency-locator-transmitters (ELTs). Computer programs were developed to provide designers with methods for predicting accelerations, velocities, and displacements of collapsing structure and for estimating the human response to crash loads. The results of full scale aircraft and component tests were used to verify and guide the development of analytical simulation tools and to demonstrate impact load attenuating concepts. Analytical simulation of metal and composite aircraft crash dynamics are addressed. Finite element models are examined to determine their degree of corroboration by experimental data and to reveal deficiencies requiring further development.

  18. Flight Dynamics Modeling and Simulation of a Damaged Transport Aircraft

    NASA Technical Reports Server (NTRS)

    Shah, Gautam H.; Hill, Melissa A.

    2012-01-01

    A study was undertaken at NASA Langley Research Center to establish, demonstrate, and apply methodology for modeling and implementing the aerodynamic effects of MANPADS damage to a transport aircraft into real-time flight simulation, and to demonstrate a preliminary capability of using such a simulation to conduct an assessment of aircraft survivability. Key findings from this study include: superpositioning of incremental aerodynamic characteristics to the baseline simulation aerodynamic model proved to be a simple and effective way of modeling damage effects; the primary effect of wing damage rolling moment asymmetry may limit minimum airspeed for adequate controllability, but this can be mitigated by the use of sideslip; combined effects of aerodynamics, control degradation, and thrust loss can result in significantly degraded controllability for a safe landing; and high landing speeds may be required to maintain adequate control if large excursions from the nominal approach path are allowed, but high-gain pilot control during landing can mitigate this risk.

  19. An electronic control for an electrohydraulic active control landing gear for the F-4 aircraft

    NASA Technical Reports Server (NTRS)

    Ross, I.

    1982-01-01

    A controller for an electrohydraulic active control landing gear was developed for the F-4 aircraft. A controller was modified for this application. Simulation results indicate that during landing and rollout over repaired bomb craters the active gear effects a force reduction, relative to the passive gear, or approximately 70%.

  20. Development and evaluation of automatic landing control laws for power lift STOL aircraft

    NASA Technical Reports Server (NTRS)

    Feinreich, B.; Gevaert, G.

    1981-01-01

    A series of investigations were conducted to generate and verify through ground bases simulation and flight research a data base to aid in the design and certification of advanced propulsive lift short takeoff and landing aircraft. Problems impacting the design of powered lift short haul aircraft that are to be landed automatically on STOL runways in adverse weather were examined. An understanding of the problems was gained by a limited coverage of important elements that are normally included in the certification process of a CAT 3 automatic landing system.

  1. Dynamic ground effects flight test of an F-15 aircraft

    NASA Technical Reports Server (NTRS)

    Corda, Stephen; Stephenson, Mark T.; Burcham, Frank W.; Curry, Robert E.

    1994-01-01

    Flight tests to determine the changes in the aerodynamic characteristics of an F-15 aircraft caused by dynamic ground effects are described. Data were obtained for low and high sink rates between 0.7 and 6.5 ft/sec and at two landing approach speeds and flap settings: 150 kn with the flaps down and 170 kn with the flaps up. Simple correlation curves are given for the change in aerodynamic coefficients because of ground effects as a function of sink rate. Ground effects generally caused an increase in the lift, drag, and nose-down pitching movement coefficients. The change in the lift coefficient increased from approximately 0.05 at the high-sink rate to approximately 0.10 at the low-sink rate. The change in the drag coefficient increased from approximately 0 to 0.03 over this decreasing sink rate range. No significant difference because of the approach configuration was evident for lift and drag; however, a significant difference in pitching movement was observed for the two approach speeds and flap settings. For the 170 kn with the flaps up configuration, the change in the nose-down pitching movement increased from approximately -0.008 to -0.016. For the 150 kn with the flaps down configuration, the change was approximately -0.008 to -0.038.

  2. Dynamic ground effects flight test of the NASA F-15 aircraft

    NASA Technical Reports Server (NTRS)

    Corda, Stephen

    1995-01-01

    Aerodynamic characteristics of an aircraft may significantly differ when flying close to the ground rather than when flying up and away. Recent research has also determined that dynamic effects (i.e., sink rate) influence ground effects (GE). A ground effects flight test program of the F-15 aircraft was conducted to support the propulsion controlled aircraft (PCA) program at the NASA Dryden Flight Research Center. Flight data was collected for 24 landings on seven test flights. Dynamic ground effects data were obtained for low- and high-sink rates, between 0.8 and 6.5 ft/sec, at two approach speed and flap combinations. These combinations consisted of 150 kt with the flaps down (30 deg deflection) and 170 kt with the flaps up (0 deg deflection), both with the inlet ramps in the full-up position. The aerodynamic coefficients caused by ground effects were estimated from the flight data. These ground effects data were correlated with the aircraft speed, flap setting, and sink rate. Results are compared to previous flight test and wind-tunnel ground effects data for various wings and for complete aircraft.

  3. Dynamics and Adaptive Control for Stability Recovery of Damaged Aircraft

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan; Krishnakumar, Kalmanje; Kaneshige, John; Nespeca, Pascal

    2006-01-01

    This paper presents a recent study of a damaged generic transport model as part of a NASA research project to investigate adaptive control methods for stability recovery of damaged aircraft operating in off-nominal flight conditions under damage and or failures. Aerodynamic modeling of damage effects is performed using an aerodynamic code to assess changes in the stability and control derivatives of a generic transport aircraft. Certain types of damage such as damage to one of the wings or horizontal stabilizers can cause the aircraft to become asymmetric, thus resulting in a coupling between the longitudinal and lateral motions. Flight dynamics for a general asymmetric aircraft is derived to account for changes in the center of gravity that can compromise the stability of the damaged aircraft. An iterative trim analysis for the translational motion is developed to refine the trim procedure by accounting for the effects of the control surface deflection. A hybrid direct-indirect neural network, adaptive flight control is proposed as an adaptive law for stabilizing the rotational motion of the damaged aircraft. The indirect adaptation is designed to estimate the plant dynamics of the damaged aircraft in conjunction with the direct adaptation that computes the control augmentation. Two approaches are presented 1) an adaptive law derived from the Lyapunov stability theory to ensure that the signals are bounded, and 2) a recursive least-square method for parameter identification. A hardware-in-the-loop simulation is conducted and demonstrates the effectiveness of the direct neural network adaptive flight control in the stability recovery of the damaged aircraft. A preliminary simulation of the hybrid adaptive flight control has been performed and initial data have shown the effectiveness of the proposed hybrid approach. Future work will include further investigations and high-fidelity simulations of the proposed hybrid adaptive Bight control approach.

  4. An electric control for an electrohydraulic active control aircraft landing gear

    NASA Technical Reports Server (NTRS)

    Ross, I.; Edson, R.

    1979-01-01

    An electronic controller for an electrohydraulic active control aircraft landing gear was developed. Drop tests of a modified gear from a 2722 Kg (6000 lbm) class of airplane were conducted to illustrate controller performance. The results indicate that the active gear effects a force reduction, relative to that of the passive gear, from 9 to 31 percent depending on the aircraft sink speed and the static gear pressure.

  5. Dynamics and control of robotic aircraft with articulated wings

    NASA Astrophysics Data System (ADS)

    Paranjape, Aditya Avinash

    There is a considerable interest in developing robotic aircraft, inspired by birds, for a variety of missions covering reconnaissance and surveillance. Flapping wing aircraft concepts have been put forth in light of the efficiency of flapping flight at small scales. These aircraft are naturally equipped with the ability to rotate their wings about the root, a form of wing articulation. This thesis covers some problems concerning the performance, stability and control of robotic aircraft with articulated wings in gliding flight. Specifically, we are interested in aircraft without a vertical tail, which would then use wing articulation for longitudinal as well as lateral-directional control. Although the dynamics and control of articulated wing aircraft share several common features with conventional fixed wing aircraft, the presence of wing articulation presents several unique benefits as well as limitations from the perspective of performance and control. One of the objective of this thesis is to understand these features using a combination of theoretical and numerical tools. The aircraft concept envisioned in this thesis uses the wing dihedral angles for longitudinal and lateral-directional control. Aircraft with flexible articulated wings are also investigated. We derive a complete nonlinear model of the flight dynamics incorporating dynamic CG location and the changing moment of inertia. We show that symmetric dihedral configuration, along with a conventional horizontal tail, can be used to control flight speed and flight path angle independently of each other. This characteristic is very useful for initiating an efficient perching maneuver. It is shown that wing dihedral angles alone can effectively regulate sideslip during rapid turns and generate a wide range of equilibrium turn rates while maintaining a constant flight speed and regulating sideslip. We compute the turning performance limitations that arise due to the use of wing dihedral for yaw control

  6. Dynamic tests of composite panels of an aircraft wing

    NASA Astrophysics Data System (ADS)

    Splichal, Jan; Pistek, Antonin; Hlinka, Jiri

    2015-10-01

    The paper describes the analysis of aerospace composite structures under dynamic loading. Today, it is common to use design procedures based on assumption of static loading only, and dynamic loading is rarely assumed and applied in design and certification of aerospace structures. The paper describes the application of dynamic loading for the design of aircraft structures, and the validation of the procedure on a selected structure. The goal is to verify the possibility of reducing the weight through improved design/modelling processes using dynamic loading instead of static loading. The research activity focuses on the modelling and testing of a composite panel representing a local segment of an aircraft wing section, investigating in particular the buckling behavior under dynamic loading. Finite Elements simulation tools are discussed, as well as the advantages of using a digital optical measurement system for the evaluation of the tests. The comparison of the finite element simulations with the results of the tests is presented.

  7. Design criteria for flightpath and airspeed control for the approach and landing of STOL aircraft

    NASA Technical Reports Server (NTRS)

    Franklin, J. A.; Innis, R. C.; Hardy, G. H.; Stephenson, J. D.

    1982-01-01

    A flight research program was conducted to assess requirements for flightpath and airspeed control for glide-slope tracking during a precision approach and for flare control, particularly as applied to powered-lift, short takeoff and landing (STOL) aircraft. Ames Research Center's Augmentor Wing Research Aircraft was used to fly approaches on a 7.5 deg glide slope to landings on a 30 X 518 m (100 X 1700 ft) STOL runway. The dominant aircraft response characteristics determined were flightpath overshoot, flightpath-airspeed coupling, and initial flightpath response time. The significant contribution to control of the landing flare using pitch attitude was the short-term flightpath response. The limiting condition for initial flightpath response time for flare control with thrust was also identified. It is possible to define flying-qualities design criteria for glide-slope and flare control based on the aforementioned response characteristics.

  8. Occupant injury and fatality in general aviation aircraft for which dynamic crash testing is certification-mandated.

    PubMed

    Boyd, Douglas D

    2015-06-01

    Towards further improving general aviation aircraft crashworthiness, multi-axis dynamic tests have been required for aircraft certification (14CFR23.562) since 1985. The objective of this study was to determine if occupants in aircraft certified to these higher crashworthiness standards show a mitigated fraction of fatal accidents and/or injury severity. The NTSB aviation database was queried for accidents occurring between 2002 and 2012 involving aircraft certified to, or immune from, dynamic crash testing and manufactured after 1999. Only operations conducted under 14CFR Part 91 were considered. Statistical analysis employed proportion tests and logistic regression. Off-airport landings are associated with high decelerative forces; however for off-airport landings, the fraction of fatal accidents for aircraft subject to, or exempt from, dynamic crash testing was similar (0.53 and 0.60, respectively). Unexpectedly, for on-airport landings a higher fraction of fatalities was evident for aircraft whose certification mandated dynamic crash testing. Improved crashworthiness standards would be expected to translate into a reduced severity of accident injuries. For all accidents, as well as for those deemed survivable, the fraction of minor and serious injuries was reduced for occupants in aircraft certified to the higher crashworthiness standards. Surprisingly, the fraction of occupants fatally injured was not decreased for aircraft subject to dynamic crash tests. To shed light on this unexpected finding flight history, airman demographics and post-impact fires for aircraft for which dynamic crash testing is mandatory or exempt was examined. For the former cohort the median distance of the accident flight was nearly 44% higher. Aircraft subject to dynamic crash testing were also involved in a greater fraction (0.25 versus 0.12, respectively) of post-impact fires. Our data suggest that while the more stringent crashworthiness standards have mitigated minor and serious

  9. Occupant injury and fatality in general aviation aircraft for which dynamic crash testing is certification-mandated.

    PubMed

    Boyd, Douglas D

    2015-06-01

    Towards further improving general aviation aircraft crashworthiness, multi-axis dynamic tests have been required for aircraft certification (14CFR23.562) since 1985. The objective of this study was to determine if occupants in aircraft certified to these higher crashworthiness standards show a mitigated fraction of fatal accidents and/or injury severity. The NTSB aviation database was queried for accidents occurring between 2002 and 2012 involving aircraft certified to, or immune from, dynamic crash testing and manufactured after 1999. Only operations conducted under 14CFR Part 91 were considered. Statistical analysis employed proportion tests and logistic regression. Off-airport landings are associated with high decelerative forces; however for off-airport landings, the fraction of fatal accidents for aircraft subject to, or exempt from, dynamic crash testing was similar (0.53 and 0.60, respectively). Unexpectedly, for on-airport landings a higher fraction of fatalities was evident for aircraft whose certification mandated dynamic crash testing. Improved crashworthiness standards would be expected to translate into a reduced severity of accident injuries. For all accidents, as well as for those deemed survivable, the fraction of minor and serious injuries was reduced for occupants in aircraft certified to the higher crashworthiness standards. Surprisingly, the fraction of occupants fatally injured was not decreased for aircraft subject to dynamic crash tests. To shed light on this unexpected finding flight history, airman demographics and post-impact fires for aircraft for which dynamic crash testing is mandatory or exempt was examined. For the former cohort the median distance of the accident flight was nearly 44% higher. Aircraft subject to dynamic crash testing were also involved in a greater fraction (0.25 versus 0.12, respectively) of post-impact fires. Our data suggest that while the more stringent crashworthiness standards have mitigated minor and serious

  10. 32 CFR 855.6 - Aircraft exempt from the requirement for a civil aircraft landing permit.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... individuals but leased by an Air Force aero club. (3) Aero clubs of other US military services. Note: This... pilot will always be in uniform and normally have a copy of a Coast Guard Auxiliary Patrol Order. If the aircraft is operating under “verbal orders of the commander,” the pilot can provide the telephone number...

  11. Runway Independent Aircraft Extremely Short Takeoff and Landing

    NASA Technical Reports Server (NTRS)

    Hall, David W.; Pasman, Renee

    2004-01-01

    This report Summarizes the work done is support of NASA/Ames Runway Independent Aircraft Research during the summer of 2003. This work centered on the tasks laid out by the Statement of Work, which was to: Identify and assess operational scenarios including airport air and ground operations and how RIA operations would interface; 2) Identify critical technologies and create a list of technologies that might be pushed to provide a quantum jump in operating economy, reliability, and safety should sufficient finding be available; 3) Create public domain powered high lift methodologies; and 4) Identify and assess vehicle concepts that provide innovative approaches to RIA operations. All these tasks were accomplished, with certain areas needing additional exploration in future grant work. Three designs were analyzed to provide strawman configurations for the RIA operations. All three aircraft carried 60 passengers, with a stage length of 1,000 nautical miles. They were capable of operating with a balanced field length of 2000 feet or less. Three different technology approaches were explored. The first, the Model 115, was a mid-wing USB design, developed as a near-term, low risk concept. The second aircraft, the EMAX, used a directed thrust system, was a far-term, high-risk approach. The third configuration was the Model 114, whose development began in summer 2002. In addition, further research was conducted on issues related to STOL operations, such as noise concerns, SNI operations, and other areas of interest.

  12. Automatic Dynamic Aircraft Modeler (ADAM) for the Computer Program NASTRAN

    NASA Technical Reports Server (NTRS)

    Griffis, H.

    1985-01-01

    Large general purpose finite element programs require users to develop large quantities of input data. General purpose pre-processors are used to decrease the effort required to develop structural models. Further reduction of effort can be achieved by specific application pre-processors. Automatic Dynamic Aircraft Modeler (ADAM) is one such application specific pre-processor. General purpose pre-processors use points, lines and surfaces to describe geometric shapes. Specifying that ADAM is used only for aircraft structures allows generic structural sections, wing boxes and bodies, to be pre-defined. Hence with only gross dimensions, thicknesses, material properties and pre-defined boundary conditions a complete model of an aircraft can be created.

  13. A Comparison of Risk Sensitive Path Planning Methods for Aircraft Emergency Landing

    NASA Technical Reports Server (NTRS)

    Meuleau, Nicolas; Plaunt, Christian; Smith, David E.; Smith, Tristan

    2009-01-01

    Determining the best site to land a damaged aircraft presents some interesting challenges for standard path planning techniques. There are multiple possible locations to consider, the space is 3-dimensional with dynamics, the criteria for a good path is determined by overall risk rather than distance or time, and optimization really matters, since an improved path corresponds to greater expected survival rate. We have investigated a number of different path planning methods for solving this problem, including cell decomposition, visibility graphs, probabilistic road maps (PRMs), and local search techniques. In their pure form, none of these techniques have proven to be entirely satisfactory - some are too slow or unpredictable, some produce highly non-optimal paths or do not find certain types of paths, and some do not cope well with the dynamic constraints when controllability is limited. In the end, we are converging towards a hybrid technique that involves seeding a roadmap with a layered visibility graph, using PRM to extend that roadmap, and using local search to further optimize the resulting paths. We describe the techniques we have investigated, report on our experiments with these techniques, and discuss when and why various techniques were unsatisfactory.

  14. Longitudinal handling qualities during approach and landing of a powered lift STOL aircraft

    NASA Technical Reports Server (NTRS)

    Franklin, J. A.; Innis, R. C.

    1972-01-01

    Longitudinal handling qualities evaluations were conducted on the Ames Research Center Flight Simulator for Advanced Aircraft (FSAA) for the approach and landing tasks of a powered lift STOL research aircraft. The test vehicle was a C-8A aircraft modified with a new wing incorporating internal blowing over an augmentor flap. The investigation included: (1) use of various flight path and airspeed control techniques for the basic vehicle; (2) assessment of stability and command augmentation schemes for pitch attitude and airspeed control; (3) determination of the influence of longitudinal and vertical force coupling for the power control; (4) determination of the influence of pitch axis coupling with the thrust vector control; and (5) evaluations of the contribution of stability and command augmentation to recovery from a single engine failure. Results are presented in the form of pilot ratings and commentary substantiated by landing approach time histories.

  15. 14 CFR 135.183 - Performance requirements: Land aircraft operated over water.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... operated over water. 135.183 Section 135.183 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... AND OPERATIONS OPERATING REQUIREMENTS: COMMUTER AND ON DEMAND OPERATIONS AND RULES GOVERNING PERSONS... operated over water. No person may operate a land aircraft carrying passengers over water unless— (a) It...

  16. Evaluating source area contributions from aircraft flux measurements over heterogeneous land cover by large eddy simulation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The estimation of spatial patterns in surface fluxes from aircraft observations poses several challenges in presence of heterogeneous land cover. In particular, the effects of turbulence on scalar transport and the different behavior of passive (e.g. moisture) versus active (e.g. temperature) scalar...

  17. 14 CFR 135.183 - Performance requirements: Land aircraft operated over water.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... operated over water. 135.183 Section 135.183 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... AND OPERATIONS OPERATING REQUIREMENTS: COMMUTER AND ON DEMAND OPERATIONS AND RULES GOVERNING PERSONS... operated over water. No person may operate a land aircraft carrying passengers over water unless— (a) It...

  18. Particle and gaseous emissions from commercial aircraft at each stage of the landing and takeoff cycle.

    PubMed

    Mazaheri, M; Johnson, G R; Morawska, L

    2009-01-15

    A novel technique was used to measure emission factors for commonly used commercial aircraft including a range of Boeing and Airbus airframes under real world conditions. Engine exhaust emission factors for particles in terms of particle number and mass (PM2.5), along with those for CO2 and NOx, were measured for over 280 individual aircraft during the various modes of landing/takeoff (LTO) cycle. Results from this study show that particle number, and NOx emission factors are dependent on aircraft engine thrust level. Minimum and maximum emissions factors for particle number, PM2.5, and NOx emissions were found to be in the range of 4.16 x 10(15)-5.42 x 10(16) kg(-1), 0.03-0.72 g.kg(-1), and 3.25-37.94 g.kg(-1), respectively, for all measured airframes and LTO cycle modes. Number size distributions of emitted particles for the naturally diluted aircraft plumes in each mode of LTO cycle showed that particles were predominantly in the range of 4-100 nm in diameter in all cases. In general, size distributions exhibit similar modality during all phases of the LTO cycle. A very distinct nucleation mode was observed in all particle size distributions, except for taxiing and landing of A320 aircraft. Accumulation modes were also observed in all particle size distributions. Analysis of aircraft engine emissions during LTO cycle showed that aircraft thrust level is considerably higher during taxiing than idling suggesting that International Civil Aviation Organization (ICAO) standards need to be modified as the thrust levels for taxi and idle are considered to be the same (7% of total thrust) (Environmental Protection, Annex 16, Vol. II, Aircraft Engine Emissions, 2nd ed.; ICAO--International Civil Aviation Organization: Montreal, 1993).

  19. Dynamic Forms. Part 2; Application to Aircraft Guidance

    NASA Technical Reports Server (NTRS)

    Meyer, George; Smith, G. Allan

    1997-01-01

    The paper describes a method for guiding a dynamic system through a given set of points. The paradigm is a fully automatic aircraft subject to air traffic control (ATC). The ATC provides a sequence of waypoints through which the aircraft trajectory must pass. The waypoints typically specify time, position, and velocity. The guidance problem is to synthesize a system state trajectory that satisfies both the ATC and aircraft constraints. Complications arise because the controlled process is multidimensional, multiaxis, nonlinear, highly coupled, and the state space is not flat. In addition, there is a multitude of operating modes, which may number in the hundreds. Each such mode defines a distinct state space model of the process by specifying the state space coordinatization, the partition of the controls into active controls and configuration controls, and the output map. Furthermore, mode transitions are required to be smooth. The proposed guidance algorithm is based on the inversion of the pure feedback approximation, followed by correction for the effects of zero dynamics. The paper describes the structure and major modules of the algorithm, and the performance is illustrated by several example aircraft maneuvers.

  20. Aircraft path planning for optimal imaging using dynamic cost functions

    NASA Astrophysics Data System (ADS)

    Christie, Gordon; Chaudhry, Haseeb; Kochersberger, Kevin

    2015-05-01

    Unmanned aircraft development has accelerated with recent technological improvements in sensing and communications, which has resulted in an "applications lag" for how these aircraft can best be utilized. The aircraft are becoming smaller, more maneuverable and have longer endurance to perform sensing and sampling missions, but operating them aggressively to exploit these capabilities has not been a primary focus in unmanned systems development. This paper addresses a means of aerial vehicle path planning to provide a realistic optimal path in acquiring imagery for structure from motion (SfM) reconstructions and performing radiation surveys. This method will allow SfM reconstructions to occur accurately and with minimal flight time so that the reconstructions can be executed efficiently. An assumption is made that we have 3D point cloud data available prior to the flight. A discrete set of scan lines are proposed for the given area that are scored based on visibility of the scene. Our approach finds a time-efficient path and calculates trajectories between scan lines and over obstacles encountered along those scan lines. Aircraft dynamics are incorporated into the path planning algorithm as dynamic cost functions to create optimal imaging paths in minimum time. Simulations of the path planning algorithm are shown for an urban environment. We also present our approach for image-based terrain mapping, which is able to efficiently perform a 3D reconstruction of a large area without the use of GPS data.

  1. Real-time radar signal processing for autonomous aircraft landing

    NASA Astrophysics Data System (ADS)

    Sadjadi, Firooz A.; Helgeson, Michael A.; Radke, Jeffrey D.; Stein, Gunter

    1993-11-01

    Landing in poor weather is a crucial problem for the air transportation system. To aid the pilots for these conditions several solutions have been suggested and/or implemented including instrument landing systems (ILS) and microwave landing systems (MLS) that put the responsibility of the landing to a large extent in the hands of the airport facilities. These systems even though useful are not available due to their high costs even in a few major metropolitan airports. This shortcoming has generated interest in providing all weather capabilities not on the landing facility but on the vehicle itself. The Synthetic Vision System Technology Demonstration sponsored by the United States Federal Aviation Administration (FAA) and the U.S. Air Force represents an effort to respond to the above needs. In this paper we present a summary of a typical synthetic vision system. This system consists of a scanning 35 GHz radar, a scanning antenna, a signal/image processor and a head up display (HUD). The pilot is presented a final perspective image of the scene sensed by the radar with associated flight guidance symbology. This system is implemented in real time hardware and has been undergoing tower and flight testing under a variety of weather conditions since early 1992.

  2. Cross-stream ejection in the inter-wheel region of aircraft landing gears

    NASA Astrophysics Data System (ADS)

    McCarthy, Philip; Ekmekci, Alis

    2014-11-01

    The reduction of aircraft noise is an important challenge currently faced by aircraft manufacturers. During approach and landing, the landing gears contribute a significant proportion of the aircraft generated noise. It is therefore critical that the key noise sources be identified and understood in order for effective mitigation methods to be developed. For a simplified two-wheel nose landing gear, a strong cross stream flow ejection phenomena has been observed to occur in the inter-wheel region in presence of wheel wells. The location and orientation of these flow ejections causes highly unsteady, three dimensional flow between the wheels that may impinge on other landing gear components, thereby potentially acting as a significant noise generator. The effects of changing the inter-wheel geometry (inter-wheel spacing, the wheel well depth and main strut geometry) upon the cross-stream ejection behaviour has been experimentally investigated using both qualitative flow visualisation and quantitative PIV techniques. A summary of the key results will be presented for the three main geometrical parameters under examination and the application of these findings to real life landing gears will be discussed. Thanks to Messier-Bugatti-Dowty and NSERC for their support for this project.

  3. Experimental and analytical investigation of active loads control for aircraft landing gear

    NASA Technical Reports Server (NTRS)

    Morris, D. L.; Mcgehee, J. R.

    1983-01-01

    A series hydraulic, active loads control main landing gear from a light, twin-engine civil aircraft was investigated. Tests included landing impact and traversal of simulated runway roughness. It is shown that the active gear is feasible and very effective in reducing the force transmitted to the airframe. Preliminary validation of a multidegree of freedom active gear flexible airframe takeoff and landing analysis computer program, which may be used as a design tool for active gear systems, is accomplished by comparing experimental and computed data for the passive and active gears.

  4. Feedback Linearized Aircraft Control Using Dynamic Cell Structure

    NASA Technical Reports Server (NTRS)

    Jorgensen, C. C.

    1998-01-01

    A Dynamic Cell Structure (DCS ) Neural Network was developed which learns a topology representing network (TRN) of F-15 aircraft aerodynamic stability and control derivatives. The network is combined with a feedback linearized tracking controller to produce a robust control architecture capable of handling multiple accident and off-nominal flight scenarios. This paper describes network and its performance for accident scenarios including differential stabilator lock, soft sensor failure, control, stability derivative variation, and turbulence.

  5. Magnetic levitation assisted aircraft take-off and landing (feasibility study - GABRIEL concept)

    NASA Astrophysics Data System (ADS)

    Rohacs, Daniel; Rohacs, Jozsef

    2016-08-01

    The Technology Roadmap 2013 developed by the International Air Transport Association envisions the option of flying without an undercarriage to be in operation by 2032. Preliminary investigations clearly indicate that magnetic levitation technology (MagLev) might be an appealing solution to assist the aircraft take-off and landing. The EU supported research project, abbreviated as GABRIEL, was dealing with (i) the concept development, (ii) the identification, evaluation and selection of the deployable magnetic levitation technology, (iii) the definition of the core system elements (including the required aircraft modifications, the ground-based system and airport elements, and the rendezvous control system), (iv) the analysis of the safety and security aspects, (v) the concept validation and (vi) the estimation of the proposed concept impact in terms of aircraft weight, noise, emission, cost-benefit). All results introduced here are compared to a medium size hypothetic passenger aircraft (identical with an Airbus A320). This paper gives a systematic overview of (i) the applied methods, (ii) the investigation of the possible use of magnetic levitation technology to assist the commercial aircraft take-off and landing processes and (iii) the demonstrations, validations showing the feasibility of the radically new concept. All major results are outlined.

  6. Experimental and Numerical Investigation of the Dynamic Seat Comfort in Aircrafts

    NASA Astrophysics Data System (ADS)

    Ciloglu, Hakan

    This research focuses on the dynamic seat comfort in aircrafts specifically during takeoff, landing and cruise through turbulence flight conditions. The experiments are performed using a multi axis shaker table in the Automotive Centre of Excellence (ACE) at the University of Ontario Institute of Technology subjected to sample takeoff, landing and cruise vibration recordings obtained onboard of an actual flight. The input vibrations introduced to the aircraft seats during actual flight conditions and during the experiments in the ACE are compared and it is concluded that the given flight conditions were successfully replicated for the interest of this thesis. The experiments are conducted with two different aircraft seats, economy class and business class. Furthermore, to investigate the importance of seat cushion characteristics in addition to economy and business class seat cushions, three laboratory made cushions were included in the investigation as well. Moreover, the effect of passenger weight is also discussed by conducting the experiments with 1 and 2 identical dummies. It is concluded that static seat properties play a significant role in the comfort perception level as well as flight conditions. Among the three flight condition, landing appeared to be the most uncomfortable case comparing to takeoff and cruise. In addition to experimental work, a numerical study to simulate the flight conditions is undertaken with the initial work of CAD modelling. The simulated responses of the seat is partially matching with experimental results due to unknown parameters of the cushion and the connections of the aircraft seat that cannot be created in the CAD model due to unknown manufacturing processes.

  7. Uncertain structural dynamics of aircraft panels and fuzzy structures analysis

    NASA Astrophysics Data System (ADS)

    Sparrow, Victor W.; Buehrle, Ralph D.

    2002-11-01

    Aircraft fuselage panels, seemingly simple structures, are actually complex because of the uncertainty of the attachments of the frame stiffeners and longitudinal stringers. It is clearly important to understand the dynamics of these panels because of the subsequent radiation into the passenger cabin, even when complete information is not available for all portions of the finite-element model. Over the last few years a fuzzy structures analysis (FSA) approach has been undertaken at Penn State and NASA Langley to quantify the uncertainty in modeling aircraft panels. A new MSC.Nastran [MSC.Software Corp. (Santa Ana, CA)] Direct Matrix Abstraction Program (DMAP) code was written and tested [AIAA paper 2001-1320, 42nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conf., Seattle, WA, 16 April 2001] and was applied to simple fuselage panel models [J. Acoust. Soc. Am. 109, 2410(A) (2001)]. Recently the work has focused on understanding the dynamics of a realistic aluminum fuselage panel, typical of today's aircraft construction. This presentation will provide an overview of the research and recent results will be given for the fuselage panel. Comparison between experiments and the FSA results will be shown for different fuzzy input parameters. [Work supported by NASA Research Cooperative Agreement NCC-1-382.

  8. Flexible body dynamic stability for high performance aircraft

    NASA Technical Reports Server (NTRS)

    Goforth, E. A.; Youssef, H. M.; Apelian, C. V.; Schroeder, S. C.

    1991-01-01

    Dynamic equations which include the effects of unsteady aerodynamic forces and a flexible body structure were developed for a free flying high performance fighter aircraft. The linear and angular deformations are assumed to be small in the body reference frame, allowing the equations to be linearized in the deformation variables. Equations for total body dynamics and flexible body dynamics are formulated using the hybrid coordinate method and integrated in a state space format. A detailed finite element model of a generic high performance fighter aircraft is used to generate the mass and stiffness matrices. Unsteady aerodynamics are represented by a rational function approximation of the doublet lattice matrices. The equations simplify for the case of constant angular rate of the body reference frame, allowing the effect of roll rate to be studied by computing the eigenvalues of the system. It is found that the rigid body modes of the aircraft are greatly affected by introducing a constant roll rate, while the effect on the flexible modes is minimal for this configuration.

  9. Dynamics and control of robotic aircraft with articulated wings

    NASA Astrophysics Data System (ADS)

    Paranjape, Aditya Avinash

    There is a considerable interest in developing robotic aircraft, inspired by birds, for a variety of missions covering reconnaissance and surveillance. Flapping wing aircraft concepts have been put forth in light of the efficiency of flapping flight at small scales. These aircraft are naturally equipped with the ability to rotate their wings about the root, a form of wing articulation. This thesis covers some problems concerning the performance, stability and control of robotic aircraft with articulated wings in gliding flight. Specifically, we are interested in aircraft without a vertical tail, which would then use wing articulation for longitudinal as well as lateral-directional control. Although the dynamics and control of articulated wing aircraft share several common features with conventional fixed wing aircraft, the presence of wing articulation presents several unique benefits as well as limitations from the perspective of performance and control. One of the objective of this thesis is to understand these features using a combination of theoretical and numerical tools. The aircraft concept envisioned in this thesis uses the wing dihedral angles for longitudinal and lateral-directional control. Aircraft with flexible articulated wings are also investigated. We derive a complete nonlinear model of the flight dynamics incorporating dynamic CG location and the changing moment of inertia. We show that symmetric dihedral configuration, along with a conventional horizontal tail, can be used to control flight speed and flight path angle independently of each other. This characteristic is very useful for initiating an efficient perching maneuver. It is shown that wing dihedral angles alone can effectively regulate sideslip during rapid turns and generate a wide range of equilibrium turn rates while maintaining a constant flight speed and regulating sideslip. We compute the turning performance limitations that arise due to the use of wing dihedral for yaw control

  10. Preliminary design of a supersonic Short Takeoff and Vertical Landing (STOVL) fighter aircraft

    NASA Technical Reports Server (NTRS)

    Cox, Brian; Borchers, Paul; Gomer, Charlie; Henderson, Dean; Jacobs, Tavis; Lawson, Todd; Peterson, Eric; Ross, Tweed, III; Bellmard, Larry

    1990-01-01

    The preliminary design study of a supersonic Short Takeoff and Vertical Landing (STOVL) fighter is presented. A brief historical survey of powered lift vehicles was presented, followed by a technology assessment of the latest supersonic STOVL engine cycles under consideration by industry and government in the U.S. and UK. A survey of operational fighter/attack aircraft and the modern battlefield scenario were completed to develop, respectively, the performance requirements and mission profiles for the study. Three configurations were initially investigated with the following engine cycles: a hybrid fan vectored thrust cycle, a lift+lift/cruise cycle, and a mixed flow vectored thrust cycle. The lift+lift/cruise aircraft configuration was selected for detailed design work which consisted of: (1) a material selection and structural layout, including engine removal considerations, (2) an aircraft systems layout, (3) a weapons integration model showing the internal weapons bay mechanism, (4) inlet and nozzle integration, (5) an aircraft suckdown prediction, (6) an aircraft stability and control analysis, including a takeoff, hover, and transition control analysis, (7) a performance and mission capability study, and (8) a life cycle cost analysis. A supersonic fighter aircraft with STOVL capability with the lift+lift/cruise engine cycle seems a viable option for the next generation fighter.

  11. High-order computational fluid dynamics tools for aircraft design.

    PubMed

    Wang, Z J

    2014-08-13

    Most forecasts predict an annual airline traffic growth rate between 4.5 and 5% in the foreseeable future. To sustain that growth, the environmental impact of aircraft cannot be ignored. Future aircraft must have much better fuel economy, dramatically less greenhouse gas emissions and noise, in addition to better performance. Many technical breakthroughs must take place to achieve the aggressive environmental goals set up by governments in North America and Europe. One of these breakthroughs will be physics-based, highly accurate and efficient computational fluid dynamics and aeroacoustics tools capable of predicting complex flows over the entire flight envelope and through an aircraft engine, and computing aircraft noise. Some of these flows are dominated by unsteady vortices of disparate scales, often highly turbulent, and they call for higher-order methods. As these tools will be integral components of a multi-disciplinary optimization environment, they must be efficient to impact design. Ultimately, the accuracy, efficiency, robustness, scalability and geometric flexibility will determine which methods will be adopted in the design process. This article explores these aspects and identifies pacing items. PMID:25024419

  12. High-order computational fluid dynamics tools for aircraft design.

    PubMed

    Wang, Z J

    2014-08-13

    Most forecasts predict an annual airline traffic growth rate between 4.5 and 5% in the foreseeable future. To sustain that growth, the environmental impact of aircraft cannot be ignored. Future aircraft must have much better fuel economy, dramatically less greenhouse gas emissions and noise, in addition to better performance. Many technical breakthroughs must take place to achieve the aggressive environmental goals set up by governments in North America and Europe. One of these breakthroughs will be physics-based, highly accurate and efficient computational fluid dynamics and aeroacoustics tools capable of predicting complex flows over the entire flight envelope and through an aircraft engine, and computing aircraft noise. Some of these flows are dominated by unsteady vortices of disparate scales, often highly turbulent, and they call for higher-order methods. As these tools will be integral components of a multi-disciplinary optimization environment, they must be efficient to impact design. Ultimately, the accuracy, efficiency, robustness, scalability and geometric flexibility will determine which methods will be adopted in the design process. This article explores these aspects and identifies pacing items.

  13. High-order computational fluid dynamics tools for aircraft design

    PubMed Central

    Wang, Z. J.

    2014-01-01

    Most forecasts predict an annual airline traffic growth rate between 4.5 and 5% in the foreseeable future. To sustain that growth, the environmental impact of aircraft cannot be ignored. Future aircraft must have much better fuel economy, dramatically less greenhouse gas emissions and noise, in addition to better performance. Many technical breakthroughs must take place to achieve the aggressive environmental goals set up by governments in North America and Europe. One of these breakthroughs will be physics-based, highly accurate and efficient computational fluid dynamics and aeroacoustics tools capable of predicting complex flows over the entire flight envelope and through an aircraft engine, and computing aircraft noise. Some of these flows are dominated by unsteady vortices of disparate scales, often highly turbulent, and they call for higher-order methods. As these tools will be integral components of a multi-disciplinary optimization environment, they must be efficient to impact design. Ultimately, the accuracy, efficiency, robustness, scalability and geometric flexibility will determine which methods will be adopted in the design process. This article explores these aspects and identifies pacing items. PMID:25024419

  14. Airborne antenna coverage requirements for the TCV B-737 aircraft. [for operation with microwave landing systems

    NASA Technical Reports Server (NTRS)

    Southall, W. A., Jr.; White, W. F.

    1978-01-01

    The airborne antenna line of sight look angle requirement for operation with a Microwave Landing System (MLS) was studied. The required azimuth and elevation line of sight look angles from an antenna located on an aircraft to three ground based antenna sites at the Wallops Flight Center (FPS-16 radar, MLS aximuth, and MLS elevation) as the aircraft follows specific approach paths selected as representative of MLS operations at the Denver, Colorado, terminal area are presented. These required azimuth and elevation look angles may be interpreted as basic design requirements for antenna of the TCV B-737 airplane for MLS operations along these selected approach paths.

  15. Application of an autonomous landing guidance system for civil and military aircraft

    NASA Astrophysics Data System (ADS)

    Franklin, Michael R.

    1995-06-01

    The ever increasing demand in the airline industry to reduce the costs associated with weather- related flight delays and cancellations has resulted in the need to be able to land an aircraft in low visibility. This has influenced research in recent years in the development of enhanced vision systems which allow all-weather operations, by providing both visual cues to the pilot and an independent integrity monitor. This research has focused on providing aircraft users with both enhanced performance and a cost effective landing solution with less dependence on ground systems, and has interested both the military and civil aircraft operator communities. The Autonomous Landing Guidance (ALG) system provides the capability to land in low visibility by displaying to the pilot an image of the real world without the need for an onboard Category II or III (CAT II/III) autoload system and without the associated ground facilities normally required. Besides the inherent advantage of saving the cost of expensive installations at airports, ALG also has the effect of inevitably solving the airport capacity problem, weather-related delays and diversions, and airport closures. Low visibility conditions typically cause the complete shutdown of smaller regional airports and reduces the availability of runways at major hubs, which creates a capacity problem to airlines.

  16. Crash Testing and Simulation of a Cessna 172 Aircraft: Hard Landing Onto Concrete

    NASA Technical Reports Server (NTRS)

    Jackson, Karen E.; Fasanella, Edwin L.

    2016-01-01

    A full-scale crash test of a Cessna 172 aircraft was conducted at the Landing and Impact Research Facility at NASA Langley Research Center during the summer of 2015. The purpose of the test was to evaluate the performance of Emergency Locator Transmitters (ELTs) that were mounted at various locations in the aircraft and to generate impact test data for model validation. A finite element model of the aircraft was developed for execution in LSDYNA to simulate the test. Measured impact conditions were 722.4-in/s forward velocity and 276-in/s vertical velocity with a 1.5deg pitch (nose up) attitude. These conditions were intended to represent a survivable hard landing. The impact surface was concrete. During the test, the nose gear tire impacted the concrete, followed closely by impact of the main gear tires. The main landing gear spread outward, as the nose gear stroked vertically. The only fuselage contact with the impact surface was a slight impact of the rearmost portion of the lower tail. Thus, capturing the behavior of the nose and main landing gear was essential to accurately predict the response. This paper describes the model development and presents test-analysis comparisons in three categories: inertial properties, time sequence of events, and acceleration and velocity time-histories.

  17. Stability of Castering Wheels for Aircraft Landing Gears, Special Report

    NASA Technical Reports Server (NTRS)

    Kantrowitz, Arthur

    1937-01-01

    In many installations of castering rubber-tired wheels there is a tendency for the wheel to oscillate violently about the spindle axis. This phenomenon, popularly called 'shimmy,' has occurred in some airplane tail wheels and has been corrected in two ways: first by the application of friction in the spindles of the tail wheels; and, second, by locking the wheels while taxiing at high speeds. Shimmy is common with the large wheels used as nose wheels in tricycle landing gears and, since it is impossible to lock the wheels, friction in the nose-wheel spindle has been the sole means of correction. Because the nose wheel is larger than the conventional tail wheel and usually carries a greater load, the larger amounts of spindle friction necessary to prevent shimmy are objectionable. the present paper presents a theoretical and experimental study of the problem of the stability of castering wheels for airplane landing gears. On the basis of simplified assumptions induced from experimental observations, a theoretical study has been made of the shimmy of castering wheels. The theory is based on the discovery of a phenomenon called 'kinematic shimmy' and is compared quantitatively with the results of model experiments. Experimental checks, using a model having low-pressure tires, are reported and the applicability of the results to full scale is discussed. Theoretical methods of estimating the spindle viscous damping and spindle solid friction necessary to avoid shimmy - lateral freedom - is introduced.

  18. Direct Adaptive Aircraft Control Using Dynamic Cell Structure Neural Networks

    NASA Technical Reports Server (NTRS)

    Jorgensen, Charles C.

    1997-01-01

    A Dynamic Cell Structure (DCS) Neural Network was developed which learns topology representing networks (TRNS) of F-15 aircraft aerodynamic stability and control derivatives. The network is integrated into a direct adaptive tracking controller. The combination produces a robust adaptive architecture capable of handling multiple accident and off- nominal flight scenarios. This paper describes the DCS network and modifications to the parameter estimation procedure. The work represents one step towards an integrated real-time reconfiguration control architecture for rapid prototyping of new aircraft designs. Performance was evaluated using three off-line benchmarks and on-line nonlinear Virtual Reality simulation. Flight control was evaluated under scenarios including differential stabilator lock, soft sensor failure, control and stability derivative variations, and air turbulence.

  19. Planar equations of rollout motion for an aircraft with free or steerable landing gears

    NASA Technical Reports Server (NTRS)

    Sleeper, R. K.; Smith, E. G.

    1982-01-01

    Equations were derived for an aircraft in a three-point attitude. Transient tire forces were simulated by delaying the application of forces derived from steady-state considerations. Predicted rollout trajectories were similar to those measured in tests of a small-scale landing-gear model equipped with pneumatic tires (where a laterally sloping runway was used to simulate a crosswind), both with and without nose-wheel steering.

  20. A head-up display format for transport aircraft approach and landing

    NASA Technical Reports Server (NTRS)

    Bray, R. S.; Scott, B. C.

    1981-01-01

    An electronic flight-guidance display format was designed for use in evaluations of the collimated head-up display concept applied to transport aircraft landing. In the design process of iterative evaluation and modification, some general principles, or guidelines, applicable to electronic flight displays were suggested. The usefulness of an indication of instantaneous inertial flightpath was clearly demonstrated. Evaluator pilot acceptance of the unfamiliar display concepts was very positive when careful attention was given to indoctrination and training.

  1. 19 CFR 122.24 - Landing requirements for certain aircraft arriving from areas south of U.S.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... aircraft which have not landed in foreign territory or are arriving directly from Puerto Rico, if the... directly from Puerto Rico or if the aircraft was inspected by Customs officers in the U.S. Virgin Islands.... West Palm Beach, Fla Palm Beach International Airport. Wilmington, NC New Hanover County Airport...

  2. 19 CFR 122.24 - Landing requirements for certain aircraft arriving from areas south of U.S.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... aircraft which have not landed in foreign territory or are arriving directly from Puerto Rico, if the... directly from Puerto Rico or if the aircraft was inspected by Customs officers in the U.S. Virgin Islands.... West Palm Beach, Fla Palm Beach International Airport. Wilmington, NC New Hanover County Airport...

  3. Validation of an Active Gear, Flexible Aircraft Take-off and Landing analysis (AGFATL)

    NASA Technical Reports Server (NTRS)

    Mcgehee, J. R.

    1984-01-01

    The results of an analytical investigation using a computer program for active gear, flexible aircraft take off and landing analysis (AGFATL) are compared with experimental data from shaker tests, drop tests, and simulated landing tests to validate the AGFATL computer program. Comparison of experimental and analytical responses for both passive and active gears indicates good agreement for shaker tests and drop tests. For the simulated landing tests, the passive and active gears were influenced by large strut binding friction forces. The inclusion of these undefined forces in the analytical simulations was difficult, and consequently only fair to good agreement was obtained. An assessment of the results from the investigation indicates that the AGFATL computer program is a valid tool for the study and initial design of series hydraulic active control landing gear systems.

  4. Automatic guidance and control of a transport aircraft during a helical landing approach

    NASA Technical Reports Server (NTRS)

    Crawford, D. J.

    1975-01-01

    A linear optimal regulator theory was applied to a nonlinear simulation of a transport aircraft performing a helical landing approach. A closed-form expression for the quasi-steady nominal flight path is presented along with the method for determining the corresponding constant nominal control inputs. The Jacobian matrices and the weighting matrices in the cost functional were time varying. A method of solving for the optimal feedback gains is reviewed. The control system was tested on several alternative landing approaches using both 3 deg and 6 deg flight path angles. On each landing approach, the aircraft was subjected to large random initial-state errors and to randomly directed crosswinds. The system was also tested for sensitivity to changes in the parameters of the aircraft and of the atmosphere. Results indicate that performance of the optimal controller on all the 3 deg approaches is very good. The control system proved to be reasonably insensitive to parametric uncertainties. Performance is not as good on the 6 deg approaches. A modification to the 6 deg flight path was proposed for the purpose of improving performance.

  5. Practical aspects of modeling aircraft dynamics from flight data

    NASA Technical Reports Server (NTRS)

    Iliff, K. W.; Maine, R. E.

    1984-01-01

    The purpose of parameter estimation, a subset of system identification, is to estimate the coefficients (such as stability and control derivatives) of the aircraft differential equations of motion from sampled measured dynamic responses. In the past, the primary reason for estimating stability and control derivatives from flight tests was to make comparisons with wind tunnel estimates. As aircraft became more complex, and as flight envelopes were expanded to include flight regimes that were not well understood, new requirements for the derivative estimates evolved. For many years, the flight determined derivatives were used in simulations to aid in flight planning and in pilot training. The simulations were particularly important in research flight test programs in which an envelope expansion into new flight regimes was required. Parameter estimation techniques for estimating stability and control derivatives from flight data became more sophisticated to support the flight test programs. As knowledge of these new flight regimes increased, more complex aircraft were flown. Much of this increased complexity was in sophisticated flight control systems. The design and refinement of the control system required higher fidelity simulations than were previously required.

  6. Application of Probabilistic Analysis to Aircraft Impact Dynamics

    NASA Technical Reports Server (NTRS)

    Lyle, Karen H.; Padula, Sharon L.; Stockwell, Alan E.

    2003-01-01

    Full-scale aircraft crash simulations performed with nonlinear, transient dynamic, finite element codes can incorporate structural complexities such as: geometrically accurate models; human occupant models; and advanced material models to include nonlinear stressstrain behaviors, laminated composites, and material failure. Validation of these crash simulations is difficult due to a lack of sufficient information to adequately determine the uncertainty in the experimental data and the appropriateness of modeling assumptions. This paper evaluates probabilistic approaches to quantify the uncertainty in the simulated responses. Several criteria are used to determine that a response surface method is the most appropriate probabilistic approach. The work is extended to compare optimization results with and without probabilistic constraints.

  7. Coupled nonlinear aeroelasticity and flight dynamics of fully flexible aircraft

    NASA Astrophysics Data System (ADS)

    Su, Weihua

    This dissertation introduces an approach to effectively model and analyze the coupled nonlinear aeroelasticity and flight dynamics of highly flexible aircraft. A reduced-order, nonlinear, strain-based finite element framework is used, which is capable of assessing the fundamental impact of structural nonlinear effects in preliminary vehicle design and control synthesis. The cross-sectional stiffness and inertia properties of the wings are calculated along the wing span, and then incorporated into the one-dimensional nonlinear beam formulation. Finite-state unsteady subsonic aerodynamics is used to compute airloads along lifting surfaces. Flight dynamic equations are then introduced to complete the aeroelastic/flight dynamic system equations of motion. Instead of merely considering the flexibility of the wings, the current work allows all members of the vehicle to be flexible. Due to their characteristics of being slender structures, the wings, tail, and fuselage of highly flexible aircraft can be modeled as beams undergoing three dimensional displacements and rotations. New kinematic relationships are developed to handle the split beam systems, such that fully flexible vehicles can be effectively modeled within the existing framework. Different aircraft configurations are modeled and studied, including Single-Wing, Joined-Wing, Blended-Wing-Body, and Flying-Wing configurations. The Lagrange Multiplier Method is applied to model the nodal displacement constraints at the joint locations. Based on the proposed models, roll response and stability studies are conducted on fully flexible and rigidized models. The impacts of the flexibility of different vehicle members on flutter with rigid body motion constraints, flutter in free flight condition, and roll maneuver performance are presented. Also, the static stability of the compressive member of the Joined-Wing configuration is studied. A spatially-distributed discrete gust model is incorporated into the time simulation

  8. Dynamic thermal tomography for nondestructive inspection of aging aircraft

    SciTech Connect

    Del Grande, N.K.; Dolan, K.W.; Durbin, P.F.; Gorvad, M.R.; Shapiro, A.B.

    1993-11-01

    The authors apply dual-band infrared (DBIR) imaging as a dynamic thermal tomography tool for wide area inspection of a Boeing 737 aircraft and several Boeing KC-135 aircraft panels. The analyses are discussed in this report. After flash-heating the aircraft skin, they record synchronized DBIR images every 40 ms, from onset to 8 seconds after the heat flash. They analyze selective DBIR image ratios which enhance surface temperature contrast and remove surface-emissivity clutter. The Boeing 737 and KC-135 aircraft fuselage panels have varying percent thickness losses from corrosion. They established the correlation of percent thickness loss with surface temperature rise (above ambient) for a partially corroded F-18 wing box structure and several aluminum plates which had 6 to 60% thickness losses at milled flat-bottom hole sites. Based on this correlation, lap splice temperatures rise 1C per 24 {plus_minus} 5% material loss at 0.4 s after the heat flash. They tabulate and map corrosion-related percent thickness loss effects for the riveted Boeing 737, and the riveted Boeing KKC-135. They map the fuselage composite thermal inertia, based on the (inverse) slope of the surface temperature versus inverse square root of time. Composite thermal inertia maps characterized shallow skin defects within the lap splice at early times (< 0.3 s) and deeper skin defects within the lap splice at late times (> 0.4 s). Late time composite thermal inertia maps depict where corrosion-related thickness losses occur (e.g., on the inside of the Boeing 737 lap splice, beneath the galley and the latrine). Lap splice sites on a typical Boeing KC-135 panel with low composite thermal inertia values had high skin-thickness losses from corrosion.

  9. Aircraft

    DOEpatents

    Hibbs, B.D.; Lissaman, P.B.S.; Morgan, W.R.; Radkey, R.L.

    1998-09-22

    This disclosure provides a solar rechargeable aircraft that is inexpensive to produce, is steerable, and can remain airborne almost indefinitely. The preferred aircraft is a span-loaded flying wing, having no fuselage or rudder. Travelling at relatively slow speeds, and having a two-hundred foot wingspan that mounts photovoltaic cells on most all of the wing`s top surface, the aircraft uses only differential thrust of its eight propellers to turn. Each of five sections of the wing has one or more engines and photovoltaic arrays, and produces its own lift independent of the other sections, to avoid loading them. Five two-sided photovoltaic arrays, in all, are mounted on the wing, and receive photovoltaic energy both incident on top of the wing, and which is incident also from below, through a bottom, transparent surface. The aircraft is capable of a top speed of about ninety miles per hour, which enables the aircraft to attain and can continuously maintain altitudes of up to sixty-five thousand feet. Regenerative fuel cells in the wing store excess electricity for use at night, such that the aircraft can sustain its elevation indefinitely. A main spar of the wing doubles as a pressure vessel that houses hydrogen and oxygen gases for use in the regenerative fuel cell. The aircraft has a wide variety of applications, which include weather monitoring and atmospheric testing, communications, surveillance, and other applications as well. 31 figs.

  10. Aircraft

    DOEpatents

    Hibbs, Bart D.; Lissaman, Peter B. S.; Morgan, Walter R.; Radkey, Robert L.

    1998-01-01

    This disclosure provides a solar rechargeable aircraft that is inexpensive to produce, is steerable, and can remain airborne almost indefinitely. The preferred aircraft is a span-loaded flying wing, having no fuselage or rudder. Travelling at relatively slow speeds, and having a two-hundred foot wingspan that mounts photovoltaic cells on most all of the wing's top surface, the aircraft uses only differential thrust of its eight propellers to turn. Each of five sections of the wing has one or more engines and photovoltaic arrays, and produces its own lift independent of the other sections, to avoid loading them. Five two-sided photovoltaic arrays, in all, are mounted on the wing, and receive photovoltaic energy both incident on top of the wing, and which is incident also from below, through a bottom, transparent surface. The aircraft is capable of a top speed of about ninety miles per hour, which enables the aircraft to attain and can continuously maintain altitudes of up to sixty-five thousand feet. Regenerative fuel cells in the wing store excess electricity for use at night, such that the aircraft can sustain its elevation indefinitely. A main spar of the wing doubles as a pressure vessel that houses hydrogen and oxygen gasses for use in the regenerative fuel cell. The aircraft has a wide variety of applications, which include weather monitoring and atmospheric testing, communications, surveillance, and other applications as well.

  11. Influence of friction forces on the motion of VTOL aircraft during landing operations on ships at sea

    NASA Technical Reports Server (NTRS)

    Howard, J. C.; Chin, D. O.

    1981-01-01

    Equations describing the friction forces generated during landing operations on ships at sea were formulated. These forces depend on the platform reaction and the coefficient of friction. The platform reaction depends on the relative sink rate and the shock absorbing capability of the landing gear. The friction coefficient varies with the surface condition of the landing platform and the angle of yaw of the aircraft relative to the landing platform. Landings by VTOL aircraft, equipped with conventional oleopneumatic landing gears are discussed. Simplifications are introduced to reduce the complexity of the mathematical description of the tire and shock strut characteristics. Approximating the actual complicated force deflection characteristic of the tire by linear relationship is adequate. The internal friction forces in the shock strut are included in the landing gear model. A set of relatively simple equations was obtained by including only those tire and shock strut characteristics that contribute significantly to the generation of landing gear forces.

  12. A mathematical model for Vertical Attitude Takeoff and Landing (VATOL) aircraft simulation. Volume 3: User's manual for VATOL simulation program

    NASA Technical Reports Server (NTRS)

    Fortenbaugh, R. L.

    1980-01-01

    Instructions for using Vertical Attitude Takeoff and Landing Aircraft Simulation (VATLAS), the digital simulation program for application to vertical attitude takeoff and landing (VATOL) aircraft developed for installation on the NASA Ames CDC 7600 computer system are described. The framework for VATLAS is the Off-Line Simulation (OLSIM) routine. The OLSIM routine provides a flexible framework and standardized modules which facilitate the development of off-line aircraft simulations. OLSIM runs under the control of VTOLTH, the main program, which calls the proper modules for executing user specified options. These options include trim, stability derivative calculation, time history generation, and various input-output options.

  13. A comparison of land-use determinations using data from ERTS-1 and high altitude aircraft

    NASA Technical Reports Server (NTRS)

    Lundelius, M. A.; Chestnutwood, C. M.; Garcia, J. G.; Erb, R. B.

    1973-01-01

    A manual interpretation of ERTS-1 MSS system corrected imagery has been performed on a study area within the Houston Area Test Site to classify land use using the Level 1 categories proposed by the Department of the Interior. The two types of imagery used included: (1) black and white transparencies of each band enlarged to a scale of approximately 1:250,000 and (2) color transparencies composited from the computer compatible tapes using the film recorder on a multispectral data analysis station. The results of this interpretation have been compared with the 1970 land use inventory of HATS which was compiled using color ektachrome imagery from high altitude aircraft (scale 1:120,000). Urban data from the same scene was also analyzed using a computer-aided (clustering) technique. The resulting clusters, representing areas of similar content, were compared with existing land use patterns in Houston. A technique was developed to correlate the spectral clusters to specific urban features on aircraft imagery by the location of specific, high contrast objects in particular resolution elements. It was concluded that ERTS-1 data could be used to develop Level 1 and many Level 2 land use categories for regional inventories and perhaps to some degree on a local level.

  14. Lumped mass modelling for the dynamic analysis of aircraft structures

    NASA Technical Reports Server (NTRS)

    Abu-Saba, Elias G.; Shen, Ji Yao; Mcginley, William M.; Montgomery, Raymond C.

    1992-01-01

    Aircraft structures may be modelled by lumping the masses at particular strategic points and the flexibility or stiffness of the structure is obtained with reference to these points. Equivalent moments of inertia for the section at these positions are determined. The lumped masses are calculated based on the assumption that each point will represent the mass spread on one half of the space on each side. Then these parameters are used in the differential equation of motion and the eigen characteristics are determined. A comparison is made with results obtained by other established methods. The lumped mass approach in the dynamic analysis of complicated structures provides an easier means of predicting the dynamic characteristics of these structures. It involves less computer time and avoids computational errors that are inherent in the numerical solution of complicated systems.

  15. Life and dynamic capacity modeling for aircraft transmissions

    NASA Technical Reports Server (NTRS)

    Savage, Michael

    1991-01-01

    A computer program to simulate the dynamic capacity and life of parallel shaft aircraft transmissions is presented. Five basic configurations can be analyzed: single mesh, compound, parallel, reverted, and single plane reductions. In execution, the program prompts the user for the data file prefix name, takes input from a ASCII file, and writes its output to a second ASCII file with the same prefix name. The input data file includes the transmission configuration, the input shaft torque and speed, and descriptions of the transmission geometry and the component gears and bearings. The program output file describes the transmission, its components, their capabilities, locations, and loads. It also lists the dynamic capability, ninety percent reliability, and mean life of each component and the transmission as a system. Here, the program, its input and output files, and the theory behind the operation of the program are described.

  16. Flight-path and airspeed control during landing approach for powered-lift aircraft

    NASA Technical Reports Server (NTRS)

    Franklin, J. A.; Innis, R. C.

    1974-01-01

    Manual control of flight path and airspeed during landing approach has been investigated for powered-lift transport aircraft. An analysis was conducted to identify the behavior of the aircraft which would be potentially significant to the pilot controlling flight path and airspeed during the approach. The response characteristics found to describe the aircraft behavior were (1) the initial flight-path response and flight-path overshoot for a step change in thrust, (2) the steady-state coupling of flight path and airspeed for a step change in thrust, and (3) the sensitivity of airspeed to changes in pitch attitude. The significance of these response characteristics was evaluated by pilots on a large-motion, ground-based simulator at Ames Research Center. Coupling between flight path and airspeed was considered by the pilot to be the dominant influence on handling qualities for the approach task. Results are compared with data obtained from flight tests of three existing powered-lift V/STOL aircraft.

  17. Flight study of on-board enhanced vision system for all-weather aircraft landing

    NASA Astrophysics Data System (ADS)

    Akopdjanan, Yuri A.; Machikhin, Alexander S.; Bilanchuk, Vyacheslav V.; Drynkin, Vladimir N.; Falkov, Eduard Y.; Tsareva, Tatiana I.; Fomenko, Anatoly I.

    2014-11-01

    On-board enhanced vision system for all-weather aircraft navigation and landing which is currently under development in State research institute of aviation systems is described. The system is based on combination of three imagers sensitive in visible, short wave infrared (SWIR) and long wave infrared (LWIR) spectral ranges and demonstrating to the pilot only the most informative images from the time-aligned multi-sensor data. The results of flight tests at glissade trajectories of the light aircraft OR-5 MO obtained at various weather conditions are presented. It is shown that each spectral range may be informative under certain conditions of observation. In adverse and poor-visibility conditions, such as fog, high humidity and low clouds, SWIR range has the biggest information content.

  18. A preliminary study of containment concepts for aircraft landing on elevated STOL-ports

    NASA Technical Reports Server (NTRS)

    Haviland, J. K.

    1971-01-01

    A preliminary study of containment systems for aircraft landing on elevated STOL-ports was conducted as part of an overall study of human acceptance problems associated with STOL operations. The study included a survey and feasibility study of different concepts and a computer analysis of four arrestment systems. The principal conclusion was that a system referred to as the FAA system appears to offer the greatest promise. In this system, standard arresting gear cables are stretched across the roof-top, at roughly 100-foot intervals, but are shielded over the 100-foot-wide primary landing strip. Thus a pilot can land with an arresting hook down, but will not contact the cable unless he swerves off the landing strip, either because he has made a bad landing, or because his landing gear has failed. It was also noted that a suitable curb or guard rail should be developed. Presently available arresting gears and nylon net barriers were considered satisfactory for the overshoot problem.

  19. Adaptive Data-based Predictive Control for Short Take-off and Landing (STOL) Aircraft

    NASA Technical Reports Server (NTRS)

    Barlow, Jonathan Spencer; Acosta, Diana Michelle; Phan, Minh Q.

    2010-01-01

    Data-based Predictive Control is an emerging control method that stems from Model Predictive Control (MPC). MPC computes current control action based on a prediction of the system output a number of time steps into the future and is generally derived from a known model of the system. Data-based predictive control has the advantage of deriving predictive models and controller gains from input-output data. Thus, a controller can be designed from the outputs of complex simulation code or a physical system where no explicit model exists. If the output data happens to be corrupted by periodic disturbances, the designed controller will also have the built-in ability to reject these disturbances without the need to know them. When data-based predictive control is implemented online, it becomes a version of adaptive control. The characteristics of adaptive data-based predictive control are particularly appropriate for the control of nonlinear and time-varying systems, such as Short Take-off and Landing (STOL) aircraft. STOL is a capability of interest to NASA because conceptual Cruise Efficient Short Take-off and Landing (CESTOL) transport aircraft offer the ability to reduce congestion in the terminal area by utilizing existing shorter runways at airports, as well as to lower community noise by flying steep approach and climb-out patterns that reduce the noise footprint of the aircraft. In this study, adaptive data-based predictive control is implemented as an integrated flight-propulsion controller for the outer-loop control of a CESTOL-type aircraft. Results show that the controller successfully tracks velocity while attempting to maintain a constant flight path angle, using longitudinal command, thrust and flap setting as the control inputs.

  20. CV-990 Landing Systems Research Aircraft (LSRA) flight #145 drilling of shuttle tire using Tire Assa

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Created from a 1/16th model of a German World War II tank, the TAV (Tire Assault Vehicle) was an important safety feature for the Convair 990 Landing System Research Aircraft, which tested space shuttle tires. It was imperative to know the extreme conditions the shuttle tires could tolerate at landing without putting the shuttle and its crew at risk. In addition, the CV990 was able to land repeatedly to test the tires. The TAV was built from a kit and modified into a radio controlled, video-equipped machine to drill holes in aircraft test tires that were in imminent danger of exploding because of one or more conditions: high air pressure, high temperatures, and cord wear. An exploding test tire releases energy equivalent to two and one-half sticks of dynamite and can cause severe injuries to anyone within 50 ft. of the explosion, as well as ear injury - possibly permanent hearing loss - to anyone within 100 ft. The degree of danger is also determined by the temperature pressure and cord wear of a test tire. The TAV was developed by David Carrott, a PRC employee under contract to NASA.

  1. Structural dynamics and vibrations of damped, aircraft-type structures

    NASA Technical Reports Server (NTRS)

    Young, Maurice I.

    1992-01-01

    Engineering preliminary design methods for approximating and predicting the effects of viscous or equivalent viscous-type damping treatments on the free and forced vibration of lightly damped aircraft-type structures are developed. Similar developments are presented for dynamic hysteresis viscoelastic-type damping treatments. It is shown by both engineering analysis and numerical illustrations that the intermodal coupling of the undamped modes arising from the introduction of damping may be neglected in applying these preliminary design methods, except when dissimilar modes of these lightly damped, complex aircraft-type structures have identical or nearly identical natural frequencies. In such cases, it is shown that a relatively simple, additional interaction calculation between pairs of modes exhibiting this 'modal response' phenomenon suffices in the prediction of interacting modal damping fractions. The accuracy of the methods is shown to be very good to excellent, depending on the normal natural frequency separation of the system modes, thereby permitting a relatively simple preliminary design approach. This approach is shown to be a natural precursor to elaborate finite element, digital computer design computations in evaluating the type, quantity, and location of damping treatment.

  2. Evaluation of Aircraft Platforms for SOFIA by Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Klotz, S. P.; Srinivasan, G. R.; VanDalsem, William (Technical Monitor)

    1995-01-01

    The selection of an airborne platform for the Stratospheric Observatory for Infrared Astronomy (SOFIA) is based not only on economic cost, but technical criteria, as well. Technical issues include aircraft fatigue, resonant characteristics of the cavity-port shear layer, aircraft stability, the drag penalty of the open telescope bay, and telescope performance. Recently, two versions of the Boeing 747 aircraft, viz., the -SP and -200 configurations, were evaluated by computational fluid dynamics (CFD) for their suitability as SOFIA platforms. In each configuration the telescope was mounted behind the wings in an open bay with nearly circular aperture. The geometry of the cavity, cavity aperture, and telescope was identical in both platforms. The aperture was located on the port side of the aircraft and the elevation angle of the telescope, measured with respect to the vertical axis, was 500. The unsteady, viscous, three-dimensional, aerodynamic and acoustic flow fields in the vicinity of SOFIA were simulated by an implicit, finite-difference Navier-Stokes flow solver (OVERFLOW) on a Chimera, overset grid system. The computational domain was discretized by structured grids. Computations were performed at wind-tunnel and flight Reynolds numbers corresponding to one free-stream flow condition (M = 0.85, angle of attack alpha = 2.50, and sideslip angle beta = 0 degrees). The computational domains consisted of twenty-nine(29) overset grids in the wind-tunnel simulations and forty-five(45) grids in the simulations run at cruise flight conditions. The maximum number of grid points in the simulations was approximately 4 x 10(exp 6). Issues considered in the evaluation study included analysis of the unsteady flow field in the cavity, the influence of the cavity on the flow across empennage surfaces, the drag penalty caused by the open telescope bay, and the noise radiating from cavity surfaces and the cavity-port shear layer. Wind-tunnel data were also available to compare

  3. Design of a Low Cost Short Takeoff-vertical Landing Export Fighter/attack Aircraft

    NASA Technical Reports Server (NTRS)

    Belcher, Anne; Bodeker, Dan, III; Miu, Steve; Petro, Laura; Senf, Cary Taylor; Woeltjen, Donald

    1990-01-01

    The design of a supersonic short takeoff and vertical landing (STOVL) aircraft is presented that is suitable for export. An advanced four poster, low bypass turbofan engine is to be used for propulsion. Preliminary aerodynamic analysis is presented covering a determination of CD versus CL, CD versus Mach number, as well as best cruise Mach number and altitude. Component locations are presented and center of gravity determined. Cost minimization is achieved through the use of developed subsystems and standard fabrication techniques using nonexotic materials. Conclusions regarding the viability of the STOVL design are presented.

  4. Dynamics of tilting proprotor aircraft in cruise flight

    NASA Technical Reports Server (NTRS)

    Johnson, W.

    1974-01-01

    A nine degree-of-freedom theoretical model is developed for investigations of the dynamics of a proprotor operating in high inflow axial flight on a cantilever wing. The basic characteristics of the rotor high inflow aerodynamics and the resulting rotor aeroelastic behavior are discussed. The problems of classical whirl flutter, the two-bladed rotor, and the influence of the proprotor on the stability derivatives of the aircraft are treated briefly. The influence of various elements of the theoretical model is discussed, including the modeling used for the blade and wing aerodynamics, and the influence of the rotor lag degree of freedom. The results from tests of two full-scale proprotors - a gimballed, stiff-inplane rotor and a hingeless, soft-inplane rotor - are presented; comparisons with the theoretical results show good correlation.

  5. Inferring Small Scale Dynamics from Aircraft Measurements of Tracers

    NASA Technical Reports Server (NTRS)

    Sparling, L. C.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    The millions of ER-2 and DC-8 aircraft measurements of long-lived tracers in the Upper Troposphere/Lower Stratosphere (UT/LS) hold enormous potential as a source of statistical information about subgrid scale dynamics. Extracting this information however can be extremely difficult because the measurements are made along a 1-D transect through fields that are highly anisotropic in all three dimensions. Some of the challenges and limitations posed by both the instrumentation and platform are illustrated within the context of the problem of using the data to obtain an estimate of the dissipation scale. This presentation will also include some tutorial remarks about the conditional and two-point statistics used in the analysis.

  6. In flight image processing on multi-rotor aircraft for autonomous landing

    NASA Astrophysics Data System (ADS)

    Henry, Richard, Jr.

    An estimated $6.4 billion was spent during the year 2013 on developing drone technology around the world and is expected to double in the next decade. However, drone applications typically require strong pilot skills, safety, responsibilities and adherence to regulations during flight. If the flight control process could be safer and more reliable in terms of landing, it would be possible to further develop a wider range of applications. The objective of this research effort is to describe the design and evaluation of a fully autonomous Unmanned Aerial system (UAS), specifically a four rotor aircraft, commonly known as quad copter for precise landing applications. The full landing autonomy is achieved by image processing capabilities during flight for target recognition by employing the open source library OpenCV. In addition, all imaging data is processed by a single embedded computer that estimates a relative position with respect to the target landing pad. Results shows a reduction on the average offset error by 67.88% in comparison to the current return to lunch (RTL) method which only relies on GPS positioning. The present work validates the need for relying on image processing for precise landing applications instead of the inexact method of a commercial low cost GPS dependency.

  7. Description of a landing site indicator (LASI) for light aircraft operation

    NASA Technical Reports Server (NTRS)

    Fuller, H. V.; Outlaw, B. K. E.

    1976-01-01

    An experimental cockpit mounted head-up type display system was developed and evaluated by LaRC pilots during the landing phase of light aircraft operations. The Landing Site Indicator (LASI) system display consists of angle of attack, angle of sideslip, and indicated airspeed images superimposed on the pilot's view through the windshield. The information is made visible to the pilot by means of a partially reflective viewing screen which is suspended directly in frot of the pilot's eyes. Synchro transmitters are operated by vanes, located at the left wing tip, which sense angle of attack and sideslip angle. Information is presented near the center of the display in the form of a moving index on a fixed grid. The airspeed is sensed by a pitot-static pressure transducer and is presented in numerical form at the top center of the display.

  8. Simulation comparison of aircraft landing performance in foggy conditions aided by different UV sensors.

    PubMed

    Lavigne, Claire; Durand, Gérard; Roblin, Antoine

    2009-04-20

    In the atmosphere pointlike sources are surrounded by an aureole due to molecular and aerosol scattering. UV phase functions of haze droplets have a very important forward peak that limits signal angular spreading in relation to the clear atmosphere case where Rayleigh scattering predominates. This specific property can be exploited using solar blind UV source detection as an aircraft landing aid under foggy conditions. Two methods have been used to compute UV light propagation, based on the Monte Carlo technique and a semi-empirical approach. Results obtained after addition of three types of sensor and UV runway light models show that an important improvement in landing conditions during foggy weather could be achieved by use of a solar blind UV intensified CCD camera with two stages of microchannel plates.

  9. Fuel conservative guidance for shipboard landing of powered-lift STOL aircraft

    NASA Technical Reports Server (NTRS)

    Warner, D. N., Jr.; Mcgee, L. A.; Mclean, J. D.; Schmidt, G. K.

    1985-01-01

    A computer-simulation study was undertaken to investigate the application of Fuel Conservative Guidance (FCG) techniques, developed at NASA Ames Research Center, to improve the fuel efficiency and minimize recovery time of powered-lift short-takeoff-and-landing (STOL) airplanes operating from aircraft carriers at sea. The FCG system consists of a set of algorithms whose coefficients and parameters limits match those of the Quiet Short-Haul Research Aircraft. When a flightpath is specified by a set of initial conditions for the aircraft and a set of positional waypoints with associated airspeeds, the FCG synthesizes the necessary guidance commands to capture the specified path at any specified waypoint and to optimize fuel consumption and time fo fly along the path. Closed-form expressions are developed for calculating the altitude profile synthesized by the algorithm. Results of this simulation study show that when restrictions on the approach flightpath imposed for manual operation are removed completely, fuel consumption during the approach was reduced by as much as 38 percent (434 lb of fuel) and the time required to fly the flightpath was reduced by as much as 28 percent (209 sec). Savings because of FCG were produced by: (1) shortening the total flight time and distance, and (2) keeping the airspeed high as long as possible to minimize time spent flying in a powered-lift mode.

  10. Composition and morphology of particle emissions from in-use aircraft during takeoff and landing.

    PubMed

    Mazaheri, Mandana; Bostrom, Thor E; Johnson, Graham R; Morawska, Lidia

    2013-05-21

    In order to provide realistic data for air pollution inventories and source apportionment at airports, the morphology and composition of ultrafine particles (UFP) in aircraft engine exhaust were measured and characterized. For this purpose, two independent measurement techniques were employed to collect emissions during normal takeoff and landing operations at Brisbane Airport, Australia. PM1 emissions in the airfield were collected on filters and analyzed using the particle-induced X-ray emission (PIXE) technique. Morphological and compositional analyses of individual ultrafine particles in aircraft plumes were performed on silicon nitride membrane grids using transmission electron microscopy (TEM) combined with energy-dispersive X-ray microanalysis (EDX). TEM results showed that the deposited particles were in the range of 5-100 nm in diameter, had semisolid spherical shapes and were dominant in the nucleation mode (18-20 nm). The EDX analysis showed the main elements in the nucleation particles were C, O, S, and Cl. The PIXE analysis of the airfield samples was generally in agreement with the EDX in detecting S, Cl, K, Fe, and Si in the particles. The results of this study provide important scientific information on the toxicity of aircraft exhaust and their impact on local air quality.

  11. Fuel conservative guidance concept for shipboard landing of powered-life aircraft

    NASA Technical Reports Server (NTRS)

    Warner, D. N., Jr.; Mcghee, L. A.; Mclean, J. D.; Schmidt, G. K.

    1984-01-01

    A simulation study was undertaken to investigate the application of energy conservative guidance (ECG) software, developed at NASA Ames Research Center, to improve the time and fuel efficiency of powered lift airplanes operating from aircraft carriers at sea. When a flightpath is indicated by a set of initial conditions for the aircraft and a set of positional waypoints with associated airspeeds, the ECG software synthesizes the necessary guidance commands to optimize fuel and time along the specified path. A major feature of the ECG system is the ability to synthesize a trajectory that will allow the aircraft to capture the specified path at any waypoint with the desired heading and airspeed from an arbitrary set of initial conditions. Five paths were identified and studied. These paths demonstrate the ECG system's ability to save flight time and fuel by more efficiently managing the aircraft's capabilities. Results of this simulation study show that when restrictions on the approach flightpath imposed for manual operation are removed completely, fuel consumption during the approach was reduced by as much as 49% (610 lb fuel) and the time required to fly the flightpath was reduced by as much as 41% (5 min). Savings due to ECG were produced by: (1) shortening the total flight time; (2) keeping the airspeed high as long as possible to minimize time spent flying in a regime in which more engine thrust is required for lift to aid the aerodynamic lift; (3) minimizing time spent flying at constant altitude at slow airspeeds; and (4) synthesizing a path from any location for a direct approach to landing without entering a holding pattern or other fixed approach path.

  12. In-Service Evaluation of HVOF Coated Main Landing Gear on Navy P-3 Aircraft

    NASA Technical Reports Server (NTRS)

    Devereaux, jon L.; Forrest, Clint

    2008-01-01

    Due to the environmental and health concerns with Electroplated Hard Chrome (EHC), the Hard Chrome Alternatives Team (HCAT) has been working to provide an alternative wear coating for EHC. The US Navy selected Tungsten-Carbide Cobalt (WC- 17Co) High Velocity Oxy-Fuel (HVOF) thermal spray coating for this purpose and completed service evaluations on select aircraft components to support the HCAT charter in identifying an alternative wear coating for chrome plating. Other benefits of WC-Co thermal spray coatings over EHC are enhanced corrosion resistance, improved durability, and exceptional wear properties. As part of the HCAT charter and to evaluate HVOF coatings on operational Navy components, the P-3 aircraft was selected for a service evaluation to determine the coating durability as compared to chrome plating. In April 1999, a VP-30 P-3 aircraft was outfitted with a right-hand Main Landing Gear (MLG) shock strut coated with WCCo HYOF thermal spray applied to the piston barrel and four axle journals. The HVOF coating on the piston barrel and axle journals was applied by Southwest United Industries, Inc. This HVOF coated strut assembly has since completed 6,378 landings. Teardown analysis .for this WC-Co HVOF coated MLG asset is significant in assessing the durability of this wear coating in service relative to EHC and to substantiate Life Cycle Cost (LCC) data to support a retrograde transition from EHC to HVOF thermal spray coatings. Findings from this teardown analysis may also benefit future transitions to HVOF thermal spray coatings by identifying enhancements to finishing techniques, mating bearing and liner material improvements, improved seal materials, and improvements in HVOF coating selection.

  13. Forward Looking Radar Imaging by Truncated Singular Value Decomposition and Its Application for Adverse Weather Aircraft Landing

    PubMed Central

    Huang, Yulin; Zha, Yuebo; Wang, Yue; Yang, Jianyu

    2015-01-01

    The forward looking radar imaging task is a practical and challenging problem for adverse weather aircraft landing industry. Deconvolution method can realize the forward looking imaging but it often leads to the noise amplification in the radar image. In this paper, a forward looking radar imaging based on deconvolution method is presented for adverse weather aircraft landing. We first present the theoretical background of forward looking radar imaging task and its application for aircraft landing. Then, we convert the forward looking radar imaging task into a corresponding deconvolution problem, which is solved in the framework of algebraic theory using truncated singular decomposition method. The key issue regarding the selecting of the truncated parameter is addressed using generalized cross validation approach. Simulation and experimental results demonstrate that the proposed method is effective in achieving angular resolution enhancement with suppressing the noise amplification in forward looking radar imaging. PMID:26094627

  14. Forward Looking Radar Imaging by Truncated Singular Value Decomposition and Its Application for Adverse Weather Aircraft Landing.

    PubMed

    Huang, Yulin; Zha, Yuebo; Wang, Yue; Yang, Jianyu

    2015-06-18

    The forward looking radar imaging task is a practical and challenging problem for adverse weather aircraft landing industry. Deconvolution method can realize the forward looking imaging but it often leads to the noise amplification in the radar image. In this paper, a forward looking radar imaging based on deconvolution method is presented for adverse weather aircraft landing. We first present the theoretical background of forward looking radar imaging task and its application for aircraft landing. Then, we convert the forward looking radar imaging task into a corresponding deconvolution problem, which is solved in the framework of algebraic theory using truncated singular decomposition method. The key issue regarding the selecting of the truncated parameter is addressed using generalized cross validation approach. Simulation and experimental results demonstrate that the proposed method is effective in achieving angular resolution enhancement with suppressing the noise amplification in forward looking radar imaging.

  15. Forward Looking Radar Imaging by Truncated Singular Value Decomposition and Its Application for Adverse Weather Aircraft Landing.

    PubMed

    Huang, Yulin; Zha, Yuebo; Wang, Yue; Yang, Jianyu

    2015-01-01

    The forward looking radar imaging task is a practical and challenging problem for adverse weather aircraft landing industry. Deconvolution method can realize the forward looking imaging but it often leads to the noise amplification in the radar image. In this paper, a forward looking radar imaging based on deconvolution method is presented for adverse weather aircraft landing. We first present the theoretical background of forward looking radar imaging task and its application for aircraft landing. Then, we convert the forward looking radar imaging task into a corresponding deconvolution problem, which is solved in the framework of algebraic theory using truncated singular decomposition method. The key issue regarding the selecting of the truncated parameter is addressed using generalized cross validation approach. Simulation and experimental results demonstrate that the proposed method is effective in achieving angular resolution enhancement with suppressing the noise amplification in forward looking radar imaging. PMID:26094627

  16. Development and evaluation of automatic landing control laws for light wing loading STOL aircraft

    NASA Technical Reports Server (NTRS)

    Feinreich, B.; Degani, O.; Gevaert, G.

    1981-01-01

    Automatic flare and decrab control laws were developed for NASA's experimental Twin Otter. This light wing loading STOL aircraft was equipped with direct lift control (DLC) wing spoilers to enhance flight path control. Automatic landing control laws that made use of the spoilers were developed, evaluated in a simulation and the results compared with these obtained for configurations that did not use DLC. The spoilers produced a significant improvement in performance. A simulation that could be operated faster than real time in order to provide statistical landing data for a large number of landings over a wide spectrum of disturbances in a short time was constructed and used in the evaluation and refinement of control law configurations. A longitudinal control law that had been previously developed and evaluated in flight was also simulated and its performance compared with that of the control laws developed. Runway alignment control laws were also defined, evaluated, and refined to result in a final recommended configuration. Good landing performance, compatible with Category 3 operation into STOL runways, was obtained.

  17. Decadal land cover change dynamics in Bhutan.

    PubMed

    Gilani, Hammad; Shrestha, Him Lal; Murthy, M S R; Phuntso, Phuntso; Pradhan, Sudip; Bajracharya, Birendra; Shrestha, Basanta

    2015-01-15

    Land cover (LC) is one of the most important and easily detectable indicators of change in ecosystem services and livelihood support systems. This paper describes the decadal dynamics in LC changes at national and sub-national level in Bhutan derived by applying object-based image analysis (OBIA) techniques to 1990, 2000, and 2010 Landsat (30 m spatial resolution) data. Ten LC classes were defined in order to give a harmonized legend land cover classification system (LCCS). An accuracy of 83% was achieved for LC-2010 as determined from spot analysis using very high resolution satellite data from Google Earth Pro and limited field verification. At the national level, overall forest increased from 25,558 to 26,732 km(2) between 1990 and 2010, equivalent to an average annual growth rate of 59 km(2)/year (0.22%). There was an overall reduction in grassland, shrubland, and barren area, but the observations were highly dependent on time of acquisition of the satellite data and climatic conditions. The greatest change from non-forest to forest (277 km(2)) was in Bumthang district, followed by Wangdue Phodrang and Trashigang, with the least (1 km(2)) in Tsirang. Forest and scrub forest covers close to 75% of the land area of Bhutan, and just over half of the total area (51%) has some form of conservation status. This study indicates that numerous applications and analyses can be carried out to support improved land cover and land use (LCLU) management. It will be possible to replicate this study in the future as comparable new satellite data is scheduled to become available.

  18. A recurrence matrix solution for the dynamic response of aircraft in gusts

    NASA Technical Reports Server (NTRS)

    Houbolt, John C

    1951-01-01

    A systematic procedure developed for the calculation of the structural response of aircraft flying through a gust by use of difference equations in the solution of dynamic problems is first illustrated by means of a simple-damped-oscillator example. A detailed analysis is then given which leads to a recurrence matrix equation for the determination of the response of an airplane in a gust. The method takes into account wing bending and twisting deformations, fuselage deflection, vertical and pitching motion of the airplane, and some tail forces. The method is based on aerodynamic strip theory, but compressibility and three-dimensional aerodynamic effects can be taken into account approximately by means of over-all corrections. Either a sharp-edge gust or a gust of arbitrary shape in the spanwise or flight directions may be treated. In order to aid in the application of the method to any specific case, a suggested computational procedure is included. The possibilities of applying the method to a variety of transient aircraft problems, such as landing, are brought out. A brief review of matrix algebra, covering the extent to which it is used in the analysis, is also included. (author)

  19. Non-linear controls influence functions in an aircraft dynamics simulator

    NASA Astrophysics Data System (ADS)

    Guerreiro, Nelson M.; Hubbard, James E., Jr.; Motter, Mark A.

    2006-03-01

    In the development and testing of novel structural and controls concepts, such as morphing aircraft wings, appropriate models are needed for proper system characterization. In most instances, available system models do not provide the required additional degrees of freedom for morphing structures but may be modified to some extent to achieve a compatible system. The objective of this study is to apply wind tunnel data collected for an Unmanned Air Vehicle (UAV), that implements trailing edge morphing, to create a non-linear dynamics simulator, using well defined rigid body equations of motion, where the aircraft stability derivatives change with control deflection. An analysis of this wind tunnel data, using data extraction algorithms, was performed to determine the reference aerodynamic force and moment coefficients for the aircraft. Further, non-linear influence functions were obtained for each of the aircraft's control surfaces, including the sixteen trailing edge flap segments. These non-linear controls influence functions are applied to the aircraft dynamics to produce deflection-dependent aircraft stability derivatives in a non-linear dynamics simulator. Time domain analysis of the aircraft motion, trajectory, and state histories can be performed using these nonlinear dynamics and may be visualized using a 3-dimensional aircraft model. Linear system models can be extracted to facilitate frequency domain analysis of the system and for control law development. The results of this study are useful in similar projects where trailing edge morphing is employed and will be instrumental in the University of Maryland's continuing study of active wing load control.

  20. Portable device to assess dynamic accuracy of global positioning systems (GPS) receivers used in agricultural aircraft

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A device was designed to test the dynamic accuracy of Global Positioning System (GPS) receivers used in aerial vehicles. The system works by directing a sun-reflected light beam from the ground to the aircraft using mirrors. A photodetector is placed pointing downward from the aircraft and circuitry...

  1. 31 CFR 585.208 - Prohibited overflights, takeoffs and landings of aircraft en route to or from the FRY (S&M).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., 14 CFR part 91. ... landings of aircraft en route to or from the FRY (S&M). 585.208 Section 585.208 Money and Finance: Treasury..., takeoffs and landings of aircraft en route to or from the FRY (S&M). Except as otherwise authorized,...

  2. Optimisation of shimmy suppression device in an aircraft main landing gear

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Jiang, Jason Zheng; Neild, Simon

    2016-09-01

    In earlier publications of landing gear shimmy analysis, efforts have concentrated on predicting the onset of shimmy instability and investigating how to stabilise shimmy-prone landing gears. Less attention has been given to the improvements of shimmy performance for a gear that is free from dynamic instability. This is the main interest of this work. We investigate the effectiveness of a linear passive mechanical device that consists of springs, dampers and inerters on suppressing landing gear shimmy oscillations. A linear model of a Fokker 100 main landing gear and two configurations of candidate shimmy suppression device have been presented. Considering the physical shimmy motions, time-domain optimisation of the parameters in the shimmy suppression devices, using a cost function of maximum amplitude of gear torsional-yaw motion, has been carried out. The performance advantage of a shimmy suppression device incorporating inerter has been presented.

  3. Downscaling of Aircraft-, Landsat-, and MODIS-based Land Surface Temperature Images with Support Vector Machines

    NASA Astrophysics Data System (ADS)

    Ha, W.; Gowda, P. H.; Oommen, T.; Howell, T. A.; Hernandez, J. E.

    2010-12-01

    High spatial resolution Land Surface Temperature (LST) images are required to estimate evapotranspiration (ET) at a field scale for irrigation scheduling purposes. Satellite sensors such as Landsat 5 Thematic Mapper (TM) and Moderate Resolution Imaging Spectroradiometer (MODIS) can offer images at several spectral bandwidths including visible, near-infrared (NIR), shortwave-infrared, and thermal-infrared (TIR). The TIR images usually have coarser spatial resolutions than those from non-thermal infrared bands. Due to this technical constraint of the satellite sensors on these platforms, image downscaling has been proposed in the field of ET remote sensing. This paper explores the potential of the Support Vector Machines (SVM) to perform downscaling of LST images derived from aircraft (4 m spatial resolution), TM (120 m), and MODIS (1000 m) using normalized difference vegetation index images derived from simultaneously acquired high resolution visible and NIR data (1 m for aircraft, 30 m for TM, and 250 m for MODIS). The SVM is a new generation machine learning algorithm that has found a wide application in the field of pattern recognition and time series analysis. The SVM would be ideally suited for downscaling problems due to its generalization ability in capturing non-linear regression relationship between the predictand and the multiple predictors. Remote sensing data acquired over the Texas High Plains during the 2008 summer growing season will be used in this study. Accuracy assessment of the downscaled 1, 30, and 250 m LST images will be made by comparing them with LST data measured with infrared thermometers at a small spatial scale, upscaled 30 m aircraft-based LST images, and upscaled 250 m TM-based LST images, respectively.

  4. Flight Dynamics of Flexible Aircraft with Aeroelastic and Inertial Force Interactions

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T.; Tuzcu, Ilhan

    2009-01-01

    This paper presents an integrated flight dynamic modeling method for flexible aircraft that captures coupled physics effects due to inertial forces, aeroelasticity, and propulsive forces that are normally present in flight. The present approach formulates the coupled flight dynamics using a structural dynamic modeling method that describes the elasticity of a flexible, twisted, swept wing using an equivalent beam-rod model. The structural dynamic model allows for three types of wing elastic motion: flapwise bending, chordwise bending, and torsion. Inertial force coupling with the wing elasticity is formulated to account for aircraft acceleration. The structural deflections create an effective aeroelastic angle of attack that affects the rigid-body motion of flexible aircraft. The aeroelastic effect contributes to aerodynamic damping forces that can influence aerodynamic stability. For wing-mounted engines, wing flexibility can cause the propulsive forces and moments to couple with the wing elastic motion. The integrated flight dynamics for a flexible aircraft are formulated by including generalized coordinate variables associated with the aeroelastic-propulsive forces and moments in the standard state-space form for six degree-of-freedom flight dynamics. A computational structural model for a generic transport aircraft has been created. The eigenvalue analysis is performed to compute aeroelastic frequencies and aerodynamic damping. The results will be used to construct an integrated flight dynamic model of a flexible generic transport aircraft.

  5. A head up display format for application to V/STOL aircraft approach and landing

    NASA Technical Reports Server (NTRS)

    Merrick, Vernon K.; Farris, Glenn G.; Vanags, Andrejs A.

    1990-01-01

    A head up display (HUD) format developed at NASA Ames Research Center to provide pilots of V/STOL aircraft with complete flight guidance and control information for category-3C terminal-area flight operations, is described in detail. These flight operations cover a large spectrum, from STOL operations on land-based runways to VTOL operations on small ships in high seas. Included in this description is a complete geometrical specification of the HUD elements and their drive laws. The principal features of this display format are the integration of the flightpath and pursuit guidance information into a narrow field of view, easily assimilated by the pilot with a single glance, and the superposition of vertical and horizontal situation information. The display is a derivative of a successful design developed for conventional transport aircraft. The design is the outcome of many piloted simulations conducted over a four-year period. Whereas the concepts on which the display format rests could not be fully exploited because of field-of-view restrictions, and some reservations remain about the acceptability of superimposing vertical and horizontal situation information, the design successfully fulfilled its intended objectives.

  6. Application of active control landing gear technology to the A-10 aircraft

    NASA Technical Reports Server (NTRS)

    Ross, I.; Edson, R.

    1983-01-01

    Two concepts which reduce the A-10 aircraft's wing/gear interface forces as a result of applying active control technology to the main landing gear are described. In the first concept, referred to as the alternate concept a servovalve in a closed pressure control loop configuration effectively varies the size of the third stage spool valve orifice which is embedded in the strut. This action allows the internal energy in the strut to shunt hydraulic flow around the metering orifice. The command signal to the loop is reference strut pressure which is compared to the measured strut pressure, the difference being the loop error. Thus, the loop effectively varies the spool valve orifice size to maintain the strut pressure, and therefore minimizes the wing/gear interface force referenced.

  7. The effects of aeroelastic deformation on the unaugmented stopped-rotor dynamics of an X-Wing aircraft

    NASA Technical Reports Server (NTRS)

    Gilbert, Michael G.; Silva, Walter A.

    1987-01-01

    A new design concept in the development of vertical takeoff and landing aircraft with high forward flight speed capability is that of the X-Wing. The X-Wing is a stiff, bearingless helicopter rotor system which can be stopped in flight and the blades used as two forward-swept wings and two aft-swept wings. Because of the unusual configuration in the fixed-wing mode, there is a high potential for aeroelastic divergence or flutter and coupling of blade vibration modes with rigid-body modes. An aeroelastic stability analysis of an X-Wing configuration aircraft was undertaken to determine if these problems could exist. This paper reports on the results of dynamic stability analyses in the lateral and longitudinal directions including the vehicle rigid-body and flexible modes. A static aeroelastic analysis using the normal vibration mode equations of motion was performed to determine the cause of a loss of longitudinal static margin with increasing airspeed. This loss of static margin was found to be due to aeroelastic 'washin' of the forward-swept blades and 'washout' of the aft-swept blades moving the aircraft aerodynamic center forward of the center of gravity. This phenomenon is likely to be generic to X-Wing aircraft.

  8. Aircraft Landing Gear, Ice and Rain Control Systems (Course Outline), Aviation Mechanics 3 (Air Frame):9067.02.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    This document presents an outline for a 135-hour course designed to familiarize the student with operation, inspection, troubleshooting, and repair of aircraft landing gear, ice and rain control systems. It is designed to help the trainee master the knowledge and skills necessary to become an aviation airframe mechanic. The aviation airframe…

  9. Study of dynamics of X-14B VTOL aircraft

    NASA Technical Reports Server (NTRS)

    Loscutoff, W. V.; Mitchiner, J. L.; Roesener, R. A.; Seevers, J. A.

    1973-01-01

    Research was initiated to investigate certain facets of modern control theory and their integration with a digital computer to provide a tractable flight control system for a VTOL aircraft. Since the hover mode is the most demanding phase in the operation of a VTOL aircraft, the research efforts were concentrated in this mode of aircraft operation. Research work on three different aspects of the operation of the X-14B VTOL aircraft is discussed. A general theory for optimal, prespecified, closed-loop control is developed. The ultimate goal was optimal decoupling of the modes of the VTOL aircraft to simplify the pilot's task of handling the aircraft. Modern control theory is used to design deterministic state estimators which provide state variables not measured directly, but which are needed for state variable feedback control. The effect of atmospheric turbulence on the X-14B is investigated. A maximum magnitude gust envelope within which the aircraft could operate stably with the available control power is determined.

  10. Dynamic Modeling Accuracy Dependence on Errors in Sensor Measurements, Mass Properties, and Aircraft Geometry

    NASA Technical Reports Server (NTRS)

    Grauer, Jared A.; Morelli, Eugene A.

    2013-01-01

    A nonlinear simulation of the NASA Generic Transport Model was used to investigate the effects of errors in sensor measurements, mass properties, and aircraft geometry on the accuracy of dynamic models identified from flight data. Measurements from a typical system identification maneuver were systematically and progressively deteriorated and then used to estimate stability and control derivatives within a Monte Carlo analysis. Based on the results, recommendations were provided for maximum allowable errors in sensor measurements, mass properties, and aircraft geometry to achieve desired levels of dynamic modeling accuracy. Results using other flight conditions, parameter estimation methods, and a full-scale F-16 nonlinear aircraft simulation were compared with these recommendations.

  11. A unique facility for V/STOL aircraft hover testing. [Langley Impact Dynamics Research Facility

    NASA Technical Reports Server (NTRS)

    Culpepper, R. G.; Murphy, R. D.; Gillespie, E. A.; Lane, A. G.

    1979-01-01

    The Langley Impact Dynamics Research Facility (IDRF) was modified to obtain static force and moment data and to allow assessment of aircraft handling qualities during dynamic tethered hover flight. Test probe procedures were also established. Static lift and control measurements obtained are presented along with results of limited dynamic tethered hover flight.

  12. Probabilistic Modeling of Aircraft Trajectories for Dynamic Separation Volumes

    NASA Technical Reports Server (NTRS)

    Lewis, Timothy A.

    2016-01-01

    With a proliferation of new and unconventional vehicles and operations expected in the future, the ab initio airspace design will require new approaches to trajectory prediction for separation assurance and other air traffic management functions. This paper presents an approach to probabilistic modeling of the trajectory of an aircraft when its intent is unknown. The approach uses a set of feature functions to constrain a maximum entropy probability distribution based on a set of observed aircraft trajectories. This model can be used to sample new aircraft trajectories to form an ensemble reflecting the variability in an aircraft's intent. The model learning process ensures that the variability in this ensemble reflects the behavior observed in the original data set. Computational examples are presented.

  13. The role of computational fluid dynamics (CFD) in aircraft design

    SciTech Connect

    Tinoco, E.N. )

    1990-01-01

    The application of CFD to aircraft design configurations and its influence on the aircraft development and support process is analyzed. Results indicate that combining CFD and the wind tunnel can achieve design solutions that otherwise would not be found, and can also significantly reduce the length of the design cycle. It is concluded that CFD provides for a better understanding of flow physics, achievement of design solutions that are otherwise unobtainable, and reduction of development flowtime.

  14. Creating a Test Validated Structural Dynamic Finite Element Model of the X-56A Aircraft

    NASA Technical Reports Server (NTRS)

    Pak, Chan-Gi; Truong, Samson

    2014-01-01

    Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of the Multi Utility Technology Test-bed, X-56A aircraft, is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of the X-56A aircraft. The ground vibration test-validated structural dynamic finite element model of the X-56A aircraft is created in this study. The structural dynamic finite element model of the X-56A aircraft is improved using a model tuning tool. In this study, two different weight configurations of the X-56A aircraft have been improved in a single optimization run. Frequency and the cross-orthogonality (mode shape) matrix were the primary focus for improvement, while other properties such as center of gravity location, total weight, and offdiagonal terms of the mass orthogonality matrix were used as constraints. The end result was a more improved and desirable structural dynamic finite element model configuration for the X-56A aircraft. Improved frequencies and mode shapes in this study increased average flutter speeds of the X-56A aircraft by 7.6% compared to the baseline model.

  15. Probabilistic model, analysis and computer code for take-off and landing related aircraft crashes into a structure

    SciTech Connect

    Glaser, R.

    1996-02-06

    A methodology is presented that allows the calculation of the probability that any of a particular collection of structures will be hit by an aircraft in a take-off or landing related accident during a specified window of time with a velocity exceeding a given critical value. A probabilistic model is developed that incorporates the location of each structure relative to airport runways in the vicinity; the size of the structure; the sizes, types, and frequency of use of commercial, military, and general aviation aircraft which take-off and land at these runways; the relative frequency of take-off and landing related accidents by aircraft type; the stochastic properties of off-runway crashes, namely impact location, impact angle, impact velocity, and the heading, deceleration, and skid distance after impact; and the stochastic properties of runway overruns and runoffs, namely the position at which the aircraft exits the runway, its exit velocity, and the heading and deceleration after exiting. Relevant probability distributions are fitted from extensive commercial, military, and general aviation accident report data bases. The computer source code for implementation of the calculation is provided.

  16. Flight evaluation of highly augmented controls and electronic displays for precision approach and landing of powered-lift aircraft

    NASA Technical Reports Server (NTRS)

    Franklin, J. A.; Hynes, C. S.

    1985-01-01

    Experiments were conducted on simulators and on the Quiet Short-Haul Research Aircraft to evaluate the effect of highly augmented control modes and electronic displays on the ability of pilots to execute precision approaches and landings on a short runway. It is found that the primary benefits of highly augmented flightpath and airspeed controls and electronic displays are realized when the pilot is required to execute precisely a complex transition and approach under instrument conditions and in the presence of a wide range of wind and turbulence conditions. A flightpath and airspeed command and stabilization system incorporating nonlinear, inverse system concepts produced fully satisfactory flightpath control throughout the aircraft's terminal operating envelope.

  17. The Impact of Land Use/Land Cover Changes on Land Degradation Dynamics: A Mediterranean Case Study

    NASA Astrophysics Data System (ADS)

    Bajocco, S.; De Angelis, A.; Perini, L.; Ferrara, A.; Salvati, L.

    2012-05-01

    In the last decades, due to climate changes, soil deterioration, and Land Use/Land Cover Changes (LULCCs), land degradation risk has become one of the most important ecological issues at the global level. Land degradation involves two interlocking systems: the natural ecosystem and the socio-economic system. The complexity of land degradation processes should be addressed using a multidisciplinary approach. Therefore, the aim of this work is to assess diachronically land degradation dynamics under changing land covers. This paper analyzes LULCCs and the parallel increase in the level of land sensitivity to degradation along the coastal belt of Sardinia (Italy), a typical Mediterranean region where human pressure affects the landscape characteristics through fires, intensive agricultural practices, land abandonment, urban sprawl, and tourism concentration. Results reveal that two factors mainly affect the level of land sensitivity to degradation in the study area: (i) land abandonment and (ii) unsustainable use of rural and peri-urban areas. Taken together, these factors represent the primary cause of the LULCCs observed in coastal Sardinia. By linking the structural features of the Mediterranean landscape with its functional land degradation dynamics over time, these results contribute to orienting policies for sustainable land management in Mediterranean coastal areas.

  18. The impact of land use/land cover changes on land degradation dynamics: a Mediterranean case study.

    PubMed

    Bajocco, S; De Angelis, A; Perini, L; Ferrara, A; Salvati, L

    2012-05-01

    In the last decades, due to climate changes, soil deterioration, and Land Use/Land Cover Changes (LULCCs), land degradation risk has become one of the most important ecological issues at the global level. Land degradation involves two interlocking systems: the natural ecosystem and the socio-economic system. The complexity of land degradation processes should be addressed using a multidisciplinary approach. Therefore, the aim of this work is to assess diachronically land degradation dynamics under changing land covers. This paper analyzes LULCCs and the parallel increase in the level of land sensitivity to degradation along the coastal belt of Sardinia (Italy), a typical Mediterranean region where human pressure affects the landscape characteristics through fires, intensive agricultural practices, land abandonment, urban sprawl, and tourism concentration. Results reveal that two factors mainly affect the level of land sensitivity to degradation in the study area: (i) land abandonment and (ii) unsustainable use of rural and peri-urban areas. Taken together, these factors represent the primary cause of the LULCCs observed in coastal Sardinia. By linking the structural features of the Mediterranean landscape with its functional land degradation dynamics over time, these results contribute to orienting policies for sustainable land management in Mediterranean coastal areas.

  19. The impact of land use/land cover changes on land degradation dynamics: a Mediterranean case study.

    PubMed

    Bajocco, S; De Angelis, A; Perini, L; Ferrara, A; Salvati, L

    2012-05-01

    In the last decades, due to climate changes, soil deterioration, and Land Use/Land Cover Changes (LULCCs), land degradation risk has become one of the most important ecological issues at the global level. Land degradation involves two interlocking systems: the natural ecosystem and the socio-economic system. The complexity of land degradation processes should be addressed using a multidisciplinary approach. Therefore, the aim of this work is to assess diachronically land degradation dynamics under changing land covers. This paper analyzes LULCCs and the parallel increase in the level of land sensitivity to degradation along the coastal belt of Sardinia (Italy), a typical Mediterranean region where human pressure affects the landscape characteristics through fires, intensive agricultural practices, land abandonment, urban sprawl, and tourism concentration. Results reveal that two factors mainly affect the level of land sensitivity to degradation in the study area: (i) land abandonment and (ii) unsustainable use of rural and peri-urban areas. Taken together, these factors represent the primary cause of the LULCCs observed in coastal Sardinia. By linking the structural features of the Mediterranean landscape with its functional land degradation dynamics over time, these results contribute to orienting policies for sustainable land management in Mediterranean coastal areas. PMID:22419398

  20. Enhanced Airport Capacity Through Safe, Dynamic Reductions in Aircraft Separation: NASA's Aircraft VOrtex Spacing System (AVOSS)

    NASA Technical Reports Server (NTRS)

    OConnor, Cornelius J.; Rutishauser, David K.

    2001-01-01

    An aspect of airport terminal operations that holds potential for efficiency improvements is the separation criteria applied to aircraft for wake vortex avoidance. These criteria evolved to represent safe spacing under weather conditions conducive to the longest wake hazards, and are consequently overly conservative during a significant portion of operations. Under many ambient conditions, such as moderate crosswinds or turbulence, wake hazard durations are substantially reduced. To realize this reduction NASA has developed a proof-of-concept Aircraft Vortex Spacing System (AVOSS). Successfully operated in a real-time field demonstration during July 2000 at the Dallas Ft. Worth International Airport, AVOSS is a novel integration of weather sensors, wake sensors, and analytical wake prediction algorithms. Gains in airport throughput using AVOSS spacing as compared to the current criteria averaged 6%, with peak values approaching the theoretical maximum of 16%. The average throughput gain translates to 15-40% reductions in delay when applied to realistic capacity ratios at major airports.

  1. Piloting Changes to Changing Aircraft Dynamics: What Do Pilots Need to Know?

    NASA Technical Reports Server (NTRS)

    Trujillo, Anna C.; Gregory, Irene M.

    2011-01-01

    An experiment was conducted to quantify the effects of changing dynamics on a subject s ability to track a signal in order to eventually model a pilot adapting to changing aircraft dynamics. The data will be used to identify primary aircraft dynamics variables that influence changes in pilot s response and produce a simplified pilot model that incorporates this relationship. Each run incorporated a different set of second-order aircraft dynamics representing short period transfer function pitch attitude response: damping ratio, frequency, gain, zero location, and time delay. The subject s ability to conduct the tracking task was the greatest source of root mean square error tracking variability. As for the aircraft dynamics, the factors that affected the subjects ability to conduct the tracking were the time delay, frequency, and zero location. In addition to creating a simplified pilot model, the results of the experiment can be utilized in an advisory capacity. A situation awareness/prediction aid based on the pilot behavior and aircraft dynamics may help tailor pilot s inputs more quickly so that PIO or an upset condition can be avoided.

  2. Design of an aircraft landing system using dual-frequency GNSS

    NASA Astrophysics Data System (ADS)

    Konno, Hiroyuki

    There is a strong demand for new all-weather navigation aids to support aircraft precision approach and landing. The Federal Aviation Administration's Local Area Augmentation System (LAAS) is one such navigation aid that uses the Global Positioning System (GPS) to estimate aircraft location. LAAS is required to provide very high levels of accuracy, integrity, continuity, and availability, and the integrity requirement of one undetected navigation failure in a billion approaches has been a critical challenge in the design of this system. Tremendous efforts have developed methods to guarantee integrity for various potential anomalies that might threaten LAAS-aided landing. Currently, almost all these risks are mitigated by existing methods. One issue that remains is the risk due to ionosphere anomalies. This dissertation introduces novel integrity algorithms for ionosphere anomalies that take advantage of GPS modernization---undergoing changes in the GPS system that enhance civil user capabilities. This modernization includes adding new GPS civil signals, and these signals make possible multiple-frequency techniques. This research focuses on two types of dual-frequency carrier-smoothing methods---Divergence-Free Smoothing and Ionosphere-Free Smoothing---and develops integrity algorithms for ionosphere anomalies using these methods. Simulations show that the first algorithm, using Ionosphere-Free Smoothing, can achieve 96% to 99.9% availability at best over a broad region of the Conterminous United States (CONUS). This level of availability is unacceptably low for practical use. However, a benefit is that the resulting availability is not a function of the ionosphere condition. The second algorithm, based on Divergence-Free Smoothing, is shown by simulations to achieve more than 99.9% availability over more than 70% of CONUS under nominal ionosphere conditions. However, it has the potential to completely lose availability under severe ionosphere conditions. Taking

  3. Non-linear controls influence functions in an aircraft dynamics simulator

    NASA Technical Reports Server (NTRS)

    Guerreiro, Nelson M.; Hubbard, James E., Jr.; Motter, Mark A.

    2006-01-01

    In the development and testing of novel structural and controls concepts, such as morphing aircraft wings, appropriate models are needed for proper system characterization. In most instances, available system models do not provide the required additional degrees of freedom for morphing structures but may be modified to some extent to achieve a compatible system. The objective of this study is to apply wind tunnel data collected for an Unmanned Air Vehicle (UAV), that implements trailing edge morphing, to create a non-linear dynamics simulator, using well defined rigid body equations of motion, where the aircraft stability derivatives change with control deflection. An analysis of this wind tunnel data, using data extraction algorithms, was performed to determine the reference aerodynamic force and moment coefficients for the aircraft. Further, non-linear influence functions were obtained for each of the aircraft s control surfaces, including the sixteen trailing edge flap segments. These non-linear controls influence functions are applied to the aircraft dynamics to produce deflection-dependent aircraft stability derivatives in a non-linear dynamics simulator. Time domain analysis of the aircraft motion, trajectory, and state histories can be performed using these nonlinear dynamics and may be visualized using a 3-dimensional aircraft model. Linear system models can be extracted to facilitate frequency domain analysis of the system and for control law development. The results of this study are useful in similar projects where trailing edge morphing is employed and will be instrumental in the University of Maryland s continuing study of active wing load control.

  4. Dynamic changes of sandy land in northwest of Beijing, China.

    PubMed

    Wang, Jing; He, Ting; Guo, Xudong; Liu, Aixia; Zhou, Qing

    2006-10-01

    The area northwest of Beijing is one of the most important regions where many organizations invest and pay most attention. The environmental problems in this region affect not only Beijing but also the surrounding area. Based on observation of the characteristics of the change in sandy land, this study classified four types of dynamic change of sandy land, including extended sandy land, the reversely changed sandy land, the potential sandy land and no change in sandy land. Then the process and the trend of changes in sandy land and their environmental impact on the area northwest of Beijing were analyzed. The results show that the area of sandy land has increased in this region in the period of 1991 to 2002. Change between sandy land and grassland was the dominant change. It is found that the monitoring zones of Hunshandake sandy land and north of Yin Shan are regions with high ratio of extended sandy land, and are connected with widespread potential change of sandy land. This implies that these two regions have a high probability of increase in sandy land in the future. On the other hand, in the monitoring zone of Horqin sandy land and Ba Shang Plateau and its surrounding area, desertification had been controlled and the area of sandy land is expected to decrease. This indicates that the direction of the sandstorm to Beijing is expected to gradually move to the northwest. Furthermore, the decreases in sandy land and the reversing change from arable land to grassland and forests in the study region will affect the land quality and atmosphere. And the logistic multiple regression (LMR) model was employed to better understand the complexity and processes of increases in sandy land. This model predicts that there is a high probability of increases in sandy land in north of Siziwang Banner, Zhengxiangbai Banner and Zhenglan Banner. Finally, suggestions to the ecological construction of the study area have been proposed. PMID:16758285

  5. Design and fabrication of an aeroelastic flap element for a Short TakeOff and Landing (STOL) aircraft model

    NASA Technical Reports Server (NTRS)

    Belleman, G. W.; June, R. R.

    1973-01-01

    A flap element typifying a third element in the flap system of a short takeoff and landing aircraft was designed, fabricated, and instrumented. It was delivered to NASA for flight-simulated testing. The flap element was aluminum skin-stringer-rib construction with adhesive laminated skins. The tests conducted were as follows: (1) sonic check, (2) thermal expansion, (3) end fitting stiffness, (4) material properties, (5) maximum bending stress in the skin, and (6) effective skin width and stringer spacing.

  6. Analysis of flexible aircraft longitudinal dynamics and handling qualities. Volume 2: Data

    NASA Technical Reports Server (NTRS)

    Waszak, M. R.; Schmidt, D. K.

    1985-01-01

    Two analysis methods are applied to a family of flexible aircraft in order to investigate how and when structural (especially dynamic aeroelastic) effects affect the dynamic characteristics of aircraft. The first type of analysis is an open loop modal analysis technique. This method considers the effect of modal residue magnitudes on determining vehicle handling qualities. The second method is a pilot in the loop analysis procedure that considers several closed loop system characteristics. Both analyses indicated that dynamic aeroelastic effects caused a degradation in vehicle tracking performance, based on the evaluation of some simulation results. Volume 2 consists of the presentation of the state variable models of the flexible aircraft configurations used in the analysis applications mode shape plots for the structural modes, numerical results from the modal analysis frequency response plots from the pilot in the loop analysis and a listing of the modal analysis computer program.

  7. Frequency-response identification of XV-15 tilt-rotor aircraft dynamics

    NASA Technical Reports Server (NTRS)

    Tischler, Mark B.

    1987-01-01

    The timely design and development of the next generation of tilt-rotor aircraft (JVX) depend heavily on the in-depth understanding of existing XV-15 dynamics and the availability of fully validated simulation models. Previous studies have considered aircraft and simulation trim characteristics, but analyses of basic flight vehicle dynamics were limited to qualitative pilot evaluation. The present study has the following objectives: documentation and evaluation of XV-15 bare-airframe dynamics; comparison of aircraft and simulation responses; and development of a validated transfer-function description of the XV-15 needed for future studies. A nonparametric frequency-response approach is used which does not depend on assumed model order or structure. Transfer-function representations are subsequently derived which fit the frequency responses in the bandwidth of greatest concern for piloted handling-qualities and control-system applications.

  8. Dependence of Dynamic Modeling Accuracy on Sensor Measurements, Mass Properties, and Aircraft Geometry

    NASA Technical Reports Server (NTRS)

    Grauer, Jared A.; Morelli, Eugene A.

    2013-01-01

    The NASA Generic Transport Model (GTM) nonlinear simulation was used to investigate the effects of errors in sensor measurements, mass properties, and aircraft geometry on the accuracy of identified parameters in mathematical models describing the flight dynamics and determined from flight data. Measurements from a typical flight condition and system identification maneuver were systematically and progressively deteriorated by introducing noise, resolution errors, and bias errors. The data were then used to estimate nondimensional stability and control derivatives within a Monte Carlo simulation. Based on these results, recommendations are provided for maximum allowable errors in sensor measurements, mass properties, and aircraft geometry to achieve desired levels of dynamic modeling accuracy. Results using additional flight conditions and parameter estimation methods, as well as a nonlinear flight simulation of the General Dynamics F-16 aircraft, were compared with these recommendations

  9. Effects of Inertial and Geometric Nonlinearities in the Simulation of Flexible Aircraft Dynamics

    NASA Astrophysics Data System (ADS)

    Bun Tse, Bosco Chun

    This thesis examines the relative importance of the inertial and geometric nonlinearities in modelling the dynamics of a flexible aircraft. Inertial nonlinearities are derived by employing an exact definition of the velocity distribution and lead to coupling between the rigid body and elastic motions. The geometric nonlinearities are obtained by applying nonlinear theory of elasticity to the deformations. Peters' finite state unsteady aerodynamic model is used to evaluate the aerodynamic forces. Three approximate models obtained by excluding certain combinations of nonlinear terms are compared with that of the complete dynamics equations to obtain an indication of which terms are required for an accurate representation of the flexible aircraft behavior. A generic business jet model is used for the analysis. The results indicate that the nonlinear terms have a significant effect for more flexible aircraft, especially the geometric nonlinearities which leads to increased damping in the dynamics.

  10. Identification and verification of frequency-domain models for XV-15 tilt-rotor aircraft dynamics

    NASA Technical Reports Server (NTRS)

    Tischler, M. B.; Leung, J. G. M.; Dugan, D. C.

    1984-01-01

    Frequency-domain methods are used to extract the open-loop dynamics of the XV-15 tilt-rotor aircraft from flight test data for the cruise condition (V = 170 knots). The frequency responses are numerically fitted with transfer-function forms to identify equivalent model characteristics. The associated handling quality parameters meet or exceed Level 2, Category A, requirements for fixed-wing military aircraft. Step response matching is used to verify the time-domain fidelity of the transfer-function models for the cruise and hover flight conditions. The transient responses of the model and aircraft are in close agreement in all cases, except for the normal acceleration response to elevator deflection in cruise. This discrepancy is probably due to the unmodeled rotor rpm dynamics. The utility of the frequency-domain approach for dynamics identification and analysis is clearly demonstrated.

  11. Crash Test of Three Cessna 172 Aircraft at NASA Langley Research Center's Landing and Impact Research Facility

    NASA Technical Reports Server (NTRS)

    Littell, Justin D.

    2015-01-01

    During the summer of 2015, three Cessna 172 aircraft were crash tested at the Landing and Impact Research Facility (LandIR) at NASA Langley Research Center (LaRC). The three tests simulated three different crash scenarios. The first simulated a flare-to-stall emergency or hard landing onto a rigid surface such as a road or runway, the second simulated a controlled flight into terrain with a nose down pitch on the aircraft, and the third simulated a controlled flight into terrain with an attempt to unsuccessfully recover the aircraft immediately prior to impact, resulting in a tail strike condition. An on-board data acquisition system captured 64 channels of airframe acceleration, along with acceleration and load in two onboard Hybrid II 50th percentile Anthropomorphic Test Devices, representing the pilot and co-pilot. Each test contained different airframe loading conditions and results show large differences in airframe performance. This paper presents test methods used to conduct the crash tests and will summarize the airframe results from the test series.

  12. Computational Fluid Dynamics of Whole-Body Aircraft

    NASA Astrophysics Data System (ADS)

    Agarwal, Ramesh

    1999-01-01

    The current state of the art in computational aerodynamics for whole-body aircraft flowfield simulations is described. Recent advances in geometry modeling, surface and volume grid generation, and flow simulation algorithms have led to accurate flowfield predictions for increasingly complex and realistic configurations. As a result, computational aerodynamics has emerged as a crucial enabling technology for the design and development of flight vehicles. Examples illustrating the current capability for the prediction of transport and fighter aircraft flowfields are presented. Unfortunately, accurate modeling of turbulence remains a major difficulty in the analysis of viscosity-dominated flows. In the future, inverse design methods, multidisciplinary design optimization methods, artificial intelligence technology, and massively parallel computer technology will be incorporated into computational aerodynamics, opening up greater opportunities for improved product design at substantially reduced costs.

  13. Aerodynamically controlled expansion (ACE) nozzle for short takeoff and vertical landing aircraft

    NASA Astrophysics Data System (ADS)

    Terrier, Douglas Anthony

    2000-10-01

    An Aerodynamically Controlled Expansion (ACE) propulsion nozzle that improves hover thrust performance by 2.5 percent in a short take off and vertical landing (STOVL) aircraft has been developed. The ACE concept employs a carefully defined step in the nozzle internal contour that interacts with the boundary layer to induce flow separation in the divergent section, thereby relieving over-expansion losses during hover. This study specifies design parameters for a passive boundary layer control step for application on the Joint Strike Fighter (JSF). In addition, parametric performance predictions presented herein provide a basic understanding of how the step concept can be applied to overcome undesirable over-expansion in generalized supersonic nozzle flows. The aerodynamic phenomena governing the interaction of the step with the nozzle flow were investigated in an extensive, parametric CFD analysis. The CFD analysis matrix consists of thirty-three axi-symmetric nozzle cases including expansion area ratios (A9/A 8) of 1.1, 1.3 and 1.5, slot area ratios (A s/A8) of 1.0 (baseline), 1.1 and 1.2, and covering the nozzle pressure ratio (NPR) range of 2.0 to 8.0. The CFD results define the NPR at which flow separation occurs as a function of A9/A8, and A s/A8, and the effect of the step on nozzle performance. Results indicate that the onset of separation occurs at higher NPR with increasing A9/A 8 and increasing As/A 8. For the case of the JSF nozzle with A9/ A8 = 1.3, the CFD analysis predicted that a nozzle having an As/A8 = 1.1 produces an improvement of approximately 2.5 percent in hover thrust relative to the baseline with a minimal adverse impact at other design conditions. Twelve percent scale models representing the baseline, and step sizes of 1.1 and 1.2 were tested in the Lockheed Martin Thrust Measurement Facility (TMF). Test results showed excellent agreement with CFD predictions and validated the step performance. Preliminary design integration studies support

  14. Optimal input design for aircraft parameter estimation using dynamic programming principles

    NASA Technical Reports Server (NTRS)

    Klein, Vladislav; Morelli, Eugene A.

    1990-01-01

    A new technique was developed for designing optimal flight test inputs for aircraft parameter estimation experiments. The principles of dynamic programming were used for the design in the time domain. This approach made it possible to include realistic practical constraints on the input and output variables. A description of the new approach is presented, followed by an example for a multiple input linear model describing the lateral dynamics of a fighter aircraft. The optimal input designs produced by the new technique demonstrated improved quality and expanded capability relative to the conventional multiple input design method.

  15. Optimal Input Design for Aircraft Parameter Estimation using Dynamic Programming Principles

    NASA Technical Reports Server (NTRS)

    Morelli, Eugene A.; Klein, Vladislav

    1990-01-01

    A new technique was developed for designing optimal flight test inputs for aircraft parameter estimation experiments. The principles of dynamic programming were used for the design in the time domain. This approach made it possible to include realistic practical constraints on the input and output variables. A description of the new approach is presented, followed by an example for a multiple input linear model describing the lateral dynamics of a fighter aircraft. The optimal input designs produced by the new technique demonstrated improved quality and expanded capability relative to the conventional multiple input design method.

  16. Flight dynamics simulation modeling and control of a large flexible tiltrotor aircraft

    NASA Astrophysics Data System (ADS)

    Juhasz, Ondrej

    A high order rotorcraft mathematical model is developed and validated against the XV-15 and a Large Civil Tiltrotor (LCTR) concept. The mathematical model is generic and allows for any rotorcraft configuration, from single main rotor helicopters to coaxial and tiltrotor aircraft. Rigid-body and inflow states, as well as flexible wing and blade states are used in the analysis. The separate modeling of each rotorcraft component allows for structural flexibility to be included, which is important when modeling large aircraft where structural modes affect the flight dynamics frequency ranges of interest, generally 1 to 20 rad/sec. Details of the formulation of the mathematical model are given, including derivations of structural, aerodynamic, and inertial loads. The linking of the components of the aircraft is developed using an approach similar to multibody analyses by exploiting a tree topology, but without equations of constraints. Assessments of the effects of wing flexibility are given. Flexibility effects are evaluated by looking at the nature of the couplings between rigid-body modes and wing structural modes and vice versa. The effects of various different forms of structural feedback on aircraft dynamics are analyzed. A proportional-integral feedback on the structural acceleration is deemed to be most effective at both improving the damping and reducing the overall excitation of a structural mode. A model following control architecture is then implemented on full order flexible LCTR models. For this aircraft, the four lowest frequency structural modes are below 20 rad/sec, and are thus needed for control law development and analysis. The impact of structural feedback on both Attitude-Command, Attitude-Hold (ACAH) and Translational Rate Command (TRC) response types are investigated. A rigid aircraft model has optimistic performance characteristics, and a control system designed for a rigid aircraft could potentially destabilize a flexible one. The various

  17. Longitudinal control of aircraft dynamics based on optimization of PID parameters

    NASA Astrophysics Data System (ADS)

    Deepa, S. N.; Sudha, G.

    2016-03-01

    Recent years many flight control systems and industries are employing PID controllers to improve the dynamic behavior of the characteristics. In this paper, PID controller is developed to improve the stability and performance of general aviation aircraft system. Designing the optimum PID controller parameters for a pitch control aircraft is important in expanding the flight safety envelope. Mathematical model is developed to describe the longitudinal pitch control of an aircraft. The PID controller is designed based on the dynamic modeling of an aircraft system. Different tuning methods namely Zeigler-Nichols method (ZN), Modified Zeigler-Nichols method, Tyreus-Luyben tuning, Astrom-Hagglund tuning methods are employed. The time domain specifications of different tuning methods are compared to obtain the optimum parameters value. The results prove that PID controller tuned by Zeigler-Nichols for aircraft pitch control dynamics is better in stability and performance in all conditions. Future research work of obtaining optimum PID controller parameters using artificial intelligence techniques should be carried out.

  18. Topics in landing gear dynamics research at NASA Langley

    NASA Technical Reports Server (NTRS)

    Mccomb, H. G., Jr.; Tanner, J. A.

    1986-01-01

    Four topics in landing gear dynamics are discussed. Three of these topics are subjects of recent research: tilt steering phenomenon, water spray ingestion on flooded runways, and actively controlled landing gear. The fourth topic is a description of a major facility recently enhanced in capability.

  19. Effect of mass variation on the dynamics of receiver aircraft during aerial refueling

    NASA Astrophysics Data System (ADS)

    Mao, Weixin

    This dissertation presents the results of a study of the dynamic behavior of two aircraft that are flying in formation while one of them (the receiver) is being refueled by the other (the tanker) in mid-flight. The current procedure for aerial refueling requires that the receiver aircraft fly below, behind, and in relatively close proximity of the tanker for refueling to be possible. This means that the receiver aircraft is subjected to the full impact of the tanker wake turbulence; and this can clearly have a major impact on the motion of the receiver craft. Another important fact about aerial refueling is that large quantity of fuel is transferred from one vehicle to the other in a relatively short time. The resulting change in mass and the attendant change in aircraft inertia properties can also affect the dynamics of the aircraft system during fuel transfer. The principal goal of this project is to investigate the importance of this latter effect. This work accomplishes two main objectives. First, it shows how mass variation can be effectively factored into an analytical study of in-flight refueling; and it does this while keeping the analyses involved manageable. In addition, a numerical study of the equations of motion is utilized to extract useful information on how mass variation and some changes in receiver aircraft parameters can affect the motion of the receiver relative to the tanker. Results obtained indicate that mass variation due to fuel transfer compounds the difficulties created by tanker wake turbulence. In order to keep the receiver aircraft at a fixed position relative to the tanker during aerial refueling, appreciable adjustments must be made to the receiver's angle of attack, throttle setting and elevator deflection. A larger refueling rate demands even larger adjustments. Changes in certain other parameters related to aerial refueling can also amplify the effects of mass variation on the receiver motion, or influence the system's dynamics in

  20. Conceptual Design Optimization of an Augmented Stability Aircraft Incorporating Dynamic Response and Actuator Constraints

    NASA Technical Reports Server (NTRS)

    Welstead, Jason; Crouse, Gilbert L., Jr.

    2014-01-01

    Empirical sizing guidelines such as tail volume coefficients have long been used in the early aircraft design phases for sizing stabilizers, resulting in conservatively stable aircraft. While successful, this results in increased empty weight, reduced performance, and greater procurement and operational cost relative to an aircraft with optimally sized surfaces. Including flight dynamics in the conceptual design process allows the design to move away from empirical methods while implementing modern control techniques. A challenge of flight dynamics and control is the numerous design variables, which are changing fluidly throughout the conceptual design process, required to evaluate the system response to some disturbance. This research focuses on addressing that challenge not by implementing higher order tools, such as computational fluid dynamics, but instead by linking the lower order tools typically used within the conceptual design process so each discipline feeds into the other. In thisresearch, flight dynamics and control was incorporated into the conceptual design process along with the traditional disciplines of vehicle sizing, weight estimation, aerodynamics, and performance. For the controller, a linear quadratic regulator structure with constant gains has been specified to reduce the user input. Coupling all the disciplines in the conceptual design phase allows the aircraft designer to explore larger design spaces where stabilizers are sized according to dynamic response constraints rather than historical static margin and volume coefficient guidelines.

  1. Coupled nonlinear flight dynamics, aeroelasticity, and control of very flexible aircraft

    NASA Astrophysics Data System (ADS)

    Shearer, Christopher M.

    Flight dynamics and control of rigid aircraft motion coupled with linearized structural dynamics has been studied for several decades. However, new requirements for very flexible aircraft are challenging the validity of most rigid body coupled linearized structural motion formulations, due to the presence of large elastic motions. This dissertation presents, the flight dynamics, integration, and control of the six degree-of-freedom equations of motion of a reference point on a very flexible aircraft coupled with the aeroelastic equations which govern the geometrically nonlinear structural response of the vehicle. A low-order strain-based nonlinear structural analysis coupled with unsteady finite-state potential flow aerodynamics form the basis for the aeroelastic formulation. The nonlinear beam structural model is based upon the finite strain approach. Kinematic differential equations are used to provide orientation and position of the fixed reference point. The resulting governing differential equations are non-linear, first- and second-order differential algebraic equations and provide a low-order complete nonlinear aircraft formulation. The resulting equations are integrated using an implicit Modified Newmark Method. The method incorporates both first- and second-order nonlinear equations without the necessity of transforming second-order equations to first-order form. The method also incorporates a Newton-Raphson sub-iteration scheme to reduce residual error. Due to the inherent flexibility of these aircraft, the low order structural modes couple directly with the rigid body modes. This creates a system which cannot be separated as in traditional control schemes. Trajectory control techniques are developed based upon a combination of linear and nonlinear inner-loop tracking and an outer-loop nonlinear transformation from desired trajectories to reference frame velocities. Numerical simulations are presented validating the proposed integration scheme and the

  2. Development of SCR Aircraft takeoff and landing procedures for community noise abatement and their impact on flight safety

    NASA Technical Reports Server (NTRS)

    Grantham, W. D.; Smith, P. M.

    1980-01-01

    Piloted simulator studies to determine takeoff and landing procedures for a supersonic cruise transport concept that result in predicted community noise levels which meet current Federal Aviation Administration (FAA) standards are discussed. The results indicate that with the use of advanced procedures, the subject simulated aircraft meets the FAA traded noise levels during takeoff and landing utilizing average flight crew skills. The advanced takeoff procedures developed involved violating three of the current Federal Aviation Regulations (FAR) noise test conditions. These were: (1) thrust cutbacks at altitudes below 214 meters (700 ft); (2) thrust cutback level below those presently allowed; and (3) configuration change, other than raising the landing gear. It was not necessary to violate any FAR noise test conditions during landing approach. It was determined that the advanced procedures developed do not compromise flight safety. Automation of some of the aircraft functions reduced pilot workload, and the development of a simple head-up display to assist in the takeoff flight mode proved to be adequate.

  3. Validation of Methodology for Estimating Aircraft Unsteady Aerodynamic Parameters from Dynamic Wind Tunnel Tests

    NASA Technical Reports Server (NTRS)

    Murphy, Patrick C.; Klein, Vladislav

    2003-01-01

    A basic problem in flight dynamics is the mathematical formulation of the aerodynamic model for aircraft. This study is part of an ongoing effort at NASA Langley to develop a more general formulation of the aerodynamic model for aircraft that includes nonlinear unsteady aerodynamics and to develop appropriate test techniques that facilitate identification of these models. A methodology for modeling and testing using wide-band inputs to estimate the unsteady form of the aircraft aerodynamic model was developed previously but advanced test facilities were not available at that time to allow complete validation of the methodology. The new model formulation retained the conventional static and rotary dynamic terms but replaced conventional acceleration terms with more general indicial functions. In this study advanced testing techniques were utilized to validate the new methodology for modeling. Results of static, conventional forced oscillation, wide-band forced oscillation, oscillatory coning, and ramp tests are presented.

  4. Analysis of flexible aircraft longitudinal dynamics and handling qualities. Volume 1: Analysis methods

    NASA Technical Reports Server (NTRS)

    Waszak, M. R.; Schmidt, D. S.

    1985-01-01

    As aircraft become larger and lighter due to design requirements for increased payload and improved fuel efficiency, they will also become more flexible. For highly flexible vehicles, the handling qualities may not be accurately predicted by conventional methods. This study applies two analysis methods to a family of flexible aircraft in order to investigate how and when structural (especially dynamic aeroelastic) effects affect the dynamic characteristics of aircraft. The first type of analysis is an open loop model analysis technique. This method considers the effects of modal residue magnitudes on determining vehicle handling qualities. The second method is a pilot in the loop analysis procedure that considers several closed loop system characteristics. Volume 1 consists of the development and application of the two analysis methods described above.

  5. Simulation of Aircraft Engine Blade-Out Structural Dynamics

    NASA Technical Reports Server (NTRS)

    Lawrence, Charles; Carney, Kelly; Gallardo, Vicente

    2001-01-01

    A primary concern of aircraft structure designers is the accurate simulation of the blade-out event and the subsequent windmilling of the engine. Reliable simulations of the blade-out event are required to insure structural integrity during flight as well as to guarantee successful blade-out certification testing. The system simulation includes the lost blade loadings and the interactions between the rotating turbomachinery and the remaining aircraft structural components. General-purpose finite element structural analysis codes such as MSC NASTRAN are typically used and special provisions are made to include transient effects from the blade loss and rotational effects resulting from the engine's turbomachinery. The present study provides the equations of motion for rotordynamic response including the effect of spooldown speed and rotor unbalance and examines the effects of these terms on a cantilevered rotor. The effect of spooldown speed is found to be greater with increasing spooldown rate. The parametric term resulting from the mass unbalance has a more significant effect on the rotordynamic response than does the spooldown term. The parametric term affects both the peak amplitudes as well as the resonant frequencies of the rotor.

  6. Simulation of Aircraft Engine Blade-Out Structural Dynamics. Revised

    NASA Technical Reports Server (NTRS)

    Lawrence, Charles; Carney, Kelly; Gallardo, Vicente

    2001-01-01

    A primary concern of aircraft structure designers is the accurate simulation of the blade-out event and the subsequent windmilling of the engine. Reliable simulations of the blade-out event are required to insure structural integrity during flight as well as to guarantee successful blade-out certification testing. The system simulation includes the lost blade loadings and the interactions between the rotating turbomachinery and the remaining aircraft structural components. General-purpose finite element structural analysis codes such as MSC NASTRAN are typically used and special provisions are made to include transient effects from the blade loss and rotational effects resulting from the engine's turbomachinery. The present study provides the equations of motion for rotordynamic response including the effect of spooldown speed and rotor unbalance and examines the effects of these terms on a cantilevered rotor. The effect of spooldown speed is found to be greater with increasing spooldown rate. The parametric term resulting from the mass unbalance has a more significant effect on the rotordynamic response than does the spooldown term. The parametric term affects both the peak amplitudes as well as the resonant frequencies of the rotor.

  7. Modelling land cover dynamics: integration of fine-scale land cover data with landscape attributes

    NASA Astrophysics Data System (ADS)

    Mertens, Benoît; Lambin, Eric

    Land cover change detection based on remote sensing data allows the identification of major processes of change and, by inference, the characterization of land use dynamics. Empirical diagnostic models of land use/cover change can be developed from these observations. To grasp the complexity of landscape mosaics and changes in land use, fine-scale land cover and socio-economic data are required. Case studies need to be representative of conditions at a broader scale, and selected where sufficient knowledge on social and ecological processes leading to land use changes exists. For this reason, collaboration between remote sensing specialists and human ecologists conducting long-term field-based land use studies is extremely productive. Continental-scale analysis of Africa was conducted to detect land cover change "hot spots". Fine-scale analyses were performed for validation purposes and to understand better the land cover change processes. Spatial statistical models of land cover change can be developed in order to anticipate where changes are more likely to occur next. Such predictive information is essential to support the implementation of appropriate policy responses to, for example, land degradation that would lead to the depletion of essential resources. Results of a spatial model of deforestation in southern Cameroon are discussed.

  8. Land Surface Microwave Emissivity Dynamics: Observations, Analysis and Modeling

    NASA Technical Reports Server (NTRS)

    Tian, Yudong; Peters-Lidard, Christa D.; Harrison, Kenneth W.; Kumar, Sujay; Ringerud, Sarah

    2014-01-01

    Land surface microwave emissivity affects remote sensing of both the atmosphere and the land surface. The dynamical behavior of microwave emissivity over a very diverse sample of land surface types is studied. With seven years of satellite measurements from AMSR-E, we identified various dynamical regimes of the land surface emission. In addition, we used two radiative transfer models (RTMs), the Community Radiative Transfer Model (CRTM) and the Community Microwave Emission Modeling Platform (CMEM), to simulate land surface emissivity dynamics. With both CRTM and CMEM coupled to NASA's Land Information System, global-scale land surface microwave emissivities were simulated for five years, and evaluated against AMSR-E observations. It is found that both models have successes and failures over various types of land surfaces. Among them, the desert shows the most consistent underestimates (by approx. 70-80%), due to limitations of the physical models used, and requires a revision in both systems. Other snow-free surface types exhibit various degrees of success and it is expected that parameter tuning can improve their performances.

  9. Using an ecoregion framework to analyze land-cover and land-use dynamics.

    USGS Publications Warehouse

    Gallant, A.L.; Loveland, T.R.; Sohl, T.L.; Napton, D.E.

    2004-01-01

    The United States has a highly varied landscape because of wide-ranging differences in combinations of climatic, geologic, edaphic, hydrologic, vegetative, and human management (land use) factors. Land uses are dynamic, with the types and rates of change dependent on a host of variables, including land accessibility, economic considerations, and the internal increase and movement of the human population. There is a convergence of evidence that ecoregions are very useful for organizing, interpreting, and reporting information about land-use dynamics. Ecoregion boundaries correspond well with patterns of land cover, urban settlement, agricultural variables, and resource-based industries. We implemented an ecoregion framework to document trends in contemporary land-cover and land-use dynamics over the conterminous United States from 1973 to 2000. Examples of results from six eastern ecoregions show that the relative abundance, grain of pattern, and human alteration of land-cover types organize well by ecoregion and that these characteristics of change, themselves, change through time.

  10. Method and System for Dynamic Automated Corrections to Weather Avoidance Routes for Aircraft in En Route Airspace

    NASA Technical Reports Server (NTRS)

    McNally, B. David (Inventor); Erzberger, Heinz (Inventor); Sheth, Kapil (Inventor)

    2015-01-01

    A dynamic weather route system automatically analyzes routes for in-flight aircraft flying in convective weather regions and attempts to find more time and fuel efficient reroutes around current and predicted weather cells. The dynamic weather route system continuously analyzes all flights and provides reroute advisories that are dynamically updated in real time while the aircraft are in flight. The dynamic weather route system includes a graphical user interface that allows users to visualize, evaluate, modify if necessary, and implement proposed reroutes.

  11. Integrated Approach to the Dynamics and Control of Maneuvering Flexible Aircraft

    NASA Technical Reports Server (NTRS)

    Waszak, Martin R. (Technical Monitor); Meirovitch, Leonard; Tuzcu, Ilhan

    2003-01-01

    This work uses a fundamental approach to the problem of simulating the flight of flexible aircraft. To this end, it integrates into a single formulation the pertinent disciplines, namely, analytical dynamics, structural dynamics, aerodynamics, and controls. It considers both the rigid body motions of the aircraft, three translations (forward motion, sideslip and plunge) and three rotations (roll, pitch and yaw), and the elastic deformations of every point of the aircraft, as well as the aerodynamic, propulsion, gravity and control forces. The equations of motion are expressed in a form ideally suited for computer processing. A perturbation approach yields a flight dynamics problem for the motions of a quasi-rigid aircraft and an 'extended aeroelasticity' problem for the elastic deformations and perturbations in the rigid body motions, with the solution of the first problem entering as an input into the second problem. The control forces for the flight dynamics problem are obtained by an 'inverse' process and the feedback controls for the extended aeroservoelasticity problem are determined by the LQG theory. A numerical example presents time simulations of rigid body perturbations and elastic deformations about 1) a steady level flight and 2) a level steady turn maneuver.

  12. The development of advanced automatic flare and decrab for powered lift short haul aircraft using a microwave landing system

    NASA Technical Reports Server (NTRS)

    Gevaert, G.; Feinreich, B.

    1977-01-01

    Advanced automatic flare and decrab control laws were developed for future powered lift STOL aircraft using the NASA-C-8A augmentor wing vehicle as the aircraft model. The longitudinal control laws utilize the throttle for flight path control and use the direct lift augmentor flap chokes for flight path augmentation. The elevator is used to control airspeed during the approach phase and to enhance path control during the flare. The forward slip maneuver was selected over the flat decrab technique for runway alignment because it can effectively handle the large crab angles obtained at STOL approach speeds. Performance evaluation of selected system configurations were obtained over the total landing environment. Limitations were defined and critical failure modes assessed. Pilot display concepts are discussed.

  13. Pitch attitude, flight path, and airspeed control during approach and landing of a powered lift STOL aircraft

    NASA Technical Reports Server (NTRS)

    Franklin, J. A.; Innis, R. C.

    1972-01-01

    Analytical investigations and piloted moving base simulator evaluations were conducted for manual control of pitch attitude, flight path, and airspeed for the approach and landing of a powered lift jet STOL aircraft. Flight path and speed response characteristics were described analytically and were evaluated for the simulation experiments which were carried out on a large motion simulator. The response characteristics were selected and evaluated for a specified path and speed control technique. These charcteristics were: (1) the initial pitch response and steady pitch rate sensitivity for control of attitude with a pitch rate command/ attitude hold system, (2) the initial flight path response, flight path overshoot, and flight path-airspeed coupling in response to a change in thrust, and (3) the sensitivity of airspeed to pitch attitude changes. Results are presented in the form of pilot opinion ratings and commentary, substantiated where appropriate by response time histories and aircraft states at the point of touchdown.

  14. Flight evaluation of advanced controls and displays for transition and landing on the NASA V/STOL systems research aircraft

    NASA Technical Reports Server (NTRS)

    Franklin, James A.; Stortz, Michael W.; Borchers, Paul F.; Moralez, Ernesto, III

    1996-01-01

    Flight experiments were conducted on Ames Research Center's V/STOL Systems Research Aircraft (VSRA) to assess the influence of advanced control modes and head-up displays (HUD's) on flying qualities for precision approach and landing operations. Evaluations were made for decelerating approaches to hover followed by a vertical landing and for slow landings for four control/display mode combinations: the basic YAV-8B stability augmentation system; attitude command for pitch, roll, and yaw; flightpath/acceleration command with translational rate command in the hover; and height-rate damping with translational-rate command. Head-up displays used in conjunction with these control modes provided flightpath tracking/pursuit guidance and deceleration commands for the decelerating approach and a mixed horizontal and vertical presentation for precision hover and landing. Flying qualities were established and control usage and bandwidth were documented for candidate control modes and displays for the approach and vertical landing. Minimally satisfactory bandwidths were determined for the translational-rate command system. Test pilot and engineer teams from the Naval Air Warfare Center, the Boeing Military Airplane Group, Lockheed Martin, McDonnell Douglas Aerospace, Northrop Grumman, Rolls-Royce, and the British Defense Research Agency participated in the program along with NASA research pilots from the Ames and Lewis Research Centers. The results, in conjunction with related ground-based simulation data, indicate that the flightpath/longitudinal acceleration command response type in conjunction with pursuit tracking and deceleration guidance on the HUD would be essential for operation to instrument minimums significantly lower than the minimums for the AV-8B. It would also be a superior mode for performing slow landings where precise control to an austere landing area such as a narrow road is demanded. The translational-rate command system would reduce pilot workload for

  15. Application of dynamic fracture mechanics to the investigation of catastrophic failure in aircraft structures

    NASA Astrophysics Data System (ADS)

    Chow, Benjamin Bin

    A dynamic fracture mechanics approach to the estimation of the residual strength of aircraft structures is presented. The dependence of the dynamic crack initiation toughness of aluminum 2024-T3 on loading rate is first studied experimentally. Based on the experimental results and on established dynamic fracture mechanic concepts, a fracture mechanics based failure model is established and is used to estimate the residual strength of aircraft structures. A methodology to determine residual strength of dynamically loaded structures based on global structural analysis coupled with local finite element analysis is introduced. Local finite element calculations were performed for different loading rates to simulate the conditions encountered in an explosively loaded aircraft fuselage. The results from the analyses were then used in conjunction with the experimental results for the dynamic fracture toughness of a 2024-T3 aluminum alloy as a function of loading rate, KdIC vs. K˙d(t), to determine the time to failure, tf, for a given loading rate. A failure envelope, sf vs. ṡ , based on the failure model and finite element analysis, is presented for the different cases and the implications for the residual strength of aircraft structures is discussed. Mixed mode dynamic crack initiation in aluminum 2024-T3 alloy is investigated by combining experiments with numerical simulations. The optical technique of coherent gradient sensing (CGS) and a strain gage method are employed to study the evolution of the mixed mode stress intensity factors. The dynamic mixed mode failure envelope is obtained using the crack initiation data from the experiments at a nominal loading rate of 7 x 105 MPam/s . Numerical simulations of the experiments are conducted to both help in designing the experiments and to validate the results of the experiments. The numerical simulations show good correlation with the experimental results.

  16. Modeling the Effects of Aircraft Emissions on Atmospheric Photochemistry Using Layered Plume Dynamics

    NASA Astrophysics Data System (ADS)

    Cameron, M. A.; Jacobson, M. Z.; Naiman, A. D.; Lele, S. K.

    2012-12-01

    Aviation is an expanding industry, experiencing continued growth and playing an increasingly noticed role in upper tropospheric/lower stratospheric composition. Nitrogen oxides and other gas-phase emissions from aircraft react to affect ozone photochemistry. This research investigates the effects of treating aircraft gas-phase chemistry within an expanding layered plume versus at the grid scale. SMVGEAR II, a sparse-matrix, vectorized Gear-type solver for ordinary differential equations, is used to solve chemical equations at both the grid scale and subgrid scale. A Subgrid Plume Model (SPM) is used to advance the expanding plume, accounting for wind shear and diffusion. Simulations suggest that using a layered plume approach results in noticeably different final NOx concentrations, demonstrating the importance of these plume dynamics in predicting the effects of aircraft on ozone concentrations. Results showing the effects of a layered plume, single plume, and no plume on ozone after several hours will be presented.

  17. Cost, accuracy, and consistency comparisons of land use maps made from high-altitutde aircraft photography and ERTS imagery

    USGS Publications Warehouse

    Fitzpatrick, Katherine A.

    1975-01-01

    Accuracy analyses for the land use maps of the Central Atlantic Regional Ecological Test Site were performed for a 1-percent sample of the area. Researchers compared Level II land use maps produced at three scales, 1:24,000, 1:100,000, and 1:250,000 from high-altitude photography, with each other and with point data obtained in the field. They employed the same procedures to determine the accuracy of the Level I land use maps produced at 1:250,000 from high-altitude photography and color composite ERTS imagery. The accuracy of the Level II maps was 84.9 percent at 1:24,000, 77.4 percent at 1:100,000, and 73.0 percent at 1:250,000. The accuracy of the Level I 1:250,000 maps produced from high-altitude aircraft photography was 76.5 percent and for those produced from ERTS imagery was 69.5 percent The cost of Level II land use mapping at 1:24,000 was found to be high ($11.93 per km2 ). The cost of mapping at 1:100,000 ($1.75) was about 2 times as expensive as mapping at 1:250,000 ($.88), and the accuracy increased by only 4.4 percent. Level I land use maps, when mapped from highaltitude photography, were about 4 times as expensive as the maps produced from ERTS imagery, although the accuracy is 7.0 percent greater. The Level I land use category that is least accurately mapped from ERTS imagery is urban and built-up land in the non-urban areas; in the urbanized areas, built-up land is more reliably mapped.

  18. Modal analysis of sailplane and transport aircraft wings using the dynamic stiffness method

    NASA Astrophysics Data System (ADS)

    Banerjee, J. R.

    2016-05-01

    The purpose of this paper is to provide theory, results, discussion and conclusions arising from an in-depth investigation on the modal behaviour of high aspect ratio aircraft wings. The illustrative examples chosen are representative of sailplane and transport airliner wings. To achieve this objective, the dynamic stiffness method of modal analysis is used. The wing is represented by a series of dynamic stiffness elements of bending-torsion coupled beams which are assembled to form the overall dynamic stiffness matrix of the complete wing. With cantilever boundary condition applied at the root, the eigenvalue problem is formulated and finally solved with the help of the Wittrick-Williams algorithm to yield the eigenvalues and eigenmodes which are essentially the natural frequencies and mode shapes of the wing. Results for wings of two sailplanes and four transport aircraft are discussed and finally some conclusions are drawn

  19. Effect of noise reducing components on nose landing gear stability for a mid-size aircraft coupled with vortex shedding and freeplay

    NASA Astrophysics Data System (ADS)

    Eret, Petr; Kennedy, John; Bennett, Gareth J.

    2015-10-01

    In the pursuit of quieter aircraft, significant effort has been dedicated to airframe noise identification and reduction. The landing gear is one of the main sources of airframe noise on approach. The addition of noise abatement technologies such as fairings or wheel hub caps is usually considered to be the simplest solution to reduce this noise. After touchdown, noise abatement components can potentially affect the inherently nonlinear and dynamically complex behaviour (shimmy) of landing gear. Moreover, fairings can influence the aerodynamic load on the system and interact with the mechanical freeplay in the torque link. This paper presents a numerical study of nose landing gear stability for a mid-size aircraft with low noise solutions, which are modelled by an increase of the relevant model structural parameters to address a hypothetical effect of additional fairings and wheel hub caps. The study shows that the wheel hub caps are not a threat to stability. A fairing has a destabilising effect due to the increased moment of inertia of the strut and a stabilising effect due to the increased torsional stiffness of the strut. As the torsional stiffness is dependent on the method of attachment, in situations where the fairing increases the torsional inertia with little increase to the torsional stiffness, a net destabilising effect can result. Alternatively, it is possible that for the case that if the fairing were to increase equally both the torsional stiffness and the moment of inertia of the strut, then their effects could be mutually negated. However, it has been found here that for small and simple fairings, typical of current landing gear noise abatement design, their implementation will not affect the dynamics and stability of the system in an operational range (Fz ≤ 50 000 N, V ≤ 100 m/s). This generalisation is strictly dependent on size and installation methods. The aerodynamic load, which would be influenced by the presence of fairings, was modelled

  20. Moving-base simulation evaluation of thrust margins for vertical landing for the NASA YAV-8B Harrier aircraft

    NASA Technical Reports Server (NTRS)

    Franklin, James A.; Stortz, Michael W.

    1993-01-01

    A simulation experiment was conducted on Ames Research Center's Vertical Motion Simulator to evaluate the thrust margin for vertical landing required for the YAV-8B Harrier. Two different levels of ground effect were employed, representing the aircraft with or without lift improvement devices installed. In addition, two different inlet temperature profiles were included to cover a wide range of hot gas ingestion. For each ground effect and hot gas ingestion variant, vertical landings were performed at successively heavier weights, with the pilot assessing the acceptability of the operation in each case. Results are presented as a function of hover weight ratio and a metric of the mean ground effect and ingestion that reflect the increase in thrust margin required to provide acceptable control of sink rate during the descent to touchdown with increasing suck down and hot gas ingestion.

  1. Continuation Methods for Qualitative Analysis of Aircraft Dynamics

    NASA Technical Reports Server (NTRS)

    Cummings, Peter A.

    2004-01-01

    A class of numerical methods for constructing bifurcation curves for systems of coupled, non-linear ordinary differential equations is presented. Foundations are discussed, and several variations are outlined along with their respective capabilities. Appropriate background material from dynamical systems theory is presented.

  2. Dynamic postural stability for double-leg drop landing.

    PubMed

    Niu, Wenxin; Zhang, Ming; Fan, Yubo; Zhao, Qinping

    2013-01-01

    Dynamic postural stability has been widely studied for single-leg landing, but seldom considered for double-leg landing. This study aimed to evaluate the dynamic postural stability and the influence mechanism of muscle activities during double-leg drop landing. Eight recreationally active males and eight recreationally active females participated in this study and dropped individually from three heights (0.32 m, 0.52 m, and 0.72 m). Ground reaction force was recorded to calculate the time to stabilisation. Electromyographic activities were recorded for selected lower-extremity muscles. A multivariate analysis of variance was carried out and no significant influence was found in time to stabilisation between genders or limb laterals (P > 0.05). With increasing drop height, time to stabilisation decreased significantly in two horizontal directions and the lower-extremity muscle activities were enhanced. Vertical time to stabilisation was not significantly influenced by drop height. Dynamic postural stability improved by neuromuscular change more than that required due to the increase of drop height. Double-leg landing on level ground is a stable movement, and the body would often be injured before dynamic postural stability is impaired. It is understandable to protect tissues from mechanical injuries by the sacrifice of certain dynamic postural stability in the design of protective devices or athlete training.

  3. Some aspects of aircraft dynamic loads due to flow separation

    NASA Astrophysics Data System (ADS)

    Mabey, D. G.

    Topics discussed in this paper include the need for consistent definitions of buffet and buffeting, the advantages of a consistent notation, buffeting due to wings and other components, the alleviation of buffeting, the special difficulties of flight tests and the special advantages of buffeting measurements in cryogenic wind-tunnels. Single degree of freedom flutter due to flow separation is not discussed, but may contribute significant dynamic loads.

  4. Combined dynamic inversion and QFT flight control of an unstable high performance aircraft

    NASA Astrophysics Data System (ADS)

    Stout, Perry Walter

    Quantitative Feedback Theory (QFT) is a control system synthesis, technique that directly considers system uncertainties and disturbance magnitudes when formulating closed-loop control algorithms. Dynamic Inversion is a nonlinear control system design technique that relies on accurate mathematical models to compute control inputs producing arbitrary system responses. Both techniques have been applied to unstable high performance aircraft flight control, and produced effective aircraft controllers. Both techniques have certain drawbacks: Nonlinear QFT controllers tend to be unnecessarily conservative (the computed controllers have excessive bandwidth) because known system properties are treated as "unknown" disturbances during loop synthesis. Meanwhile Dynamic Inversion control is sensitive to differences between assumed mathematical models and actual system dynamic properties. Combining the two control techniques provides the benefit of both while suffering the drawbacks of neither, as demonstrated by Single Input, Single Output (SISO) control of a constant airspeed, no roll, no yaw nonlinear model of the F-16 aircraft, and by Multi-Input, Multi-Output (MIMO) control of a full six-degree-of-freedom version. Design performance of the combined controllers is verified by reduced actuator efforts and by reduced sensor noise to actuator input (U( s)/n(s)) transfer function magnitudes compared to standard QFT versions.

  5. A Mathematical Model for Vertical Attitude Takeoff and Landing (VATOL) Aircraft Simulation. Volume 1; Model Description Application

    NASA Technical Reports Server (NTRS)

    Fortenbaugh, R. L.

    1980-01-01

    A mathematical model of a high performance airplane capable of vertical attitude takeoff and landing (VATOL) was developed. An off line digital simulation program incorporating this model was developed to provide trim conditions and dynamic check runs for the piloted simulation studies and support dynamic analyses of proposed VATOL configuration and flight control concepts. Development details for the various simulation component models and the application of the off line simulation program, Vertical Attitude Take-Off and Landing Simulation (VATLAS), to develop a baseline control system for the Vought SF-121 VATOL airplane concept are described.

  6. Design and evaluation of a robust dynamic neurocontroller for a multivariable aircraft control problem

    NASA Technical Reports Server (NTRS)

    Troudet, T.; Garg, S.; Merrill, W.

    1992-01-01

    The design of a dynamic neurocontroller with good robustness properties is presented for a multivariable aircraft control problem. The internal dynamics of the neurocontroller are synthesized by a state estimator feedback loop. The neurocontrol is generated by a multilayer feedforward neural network which is trained through backpropagation to minimize an objective function that is a weighted sum of tracking errors, and control input commands and rates. The neurocontroller exhibits good robustness through stability margins in phase and vehicle output gains. By maintaining performance and stability in the presence of sensor failures in the error loops, the structure of the neurocontroller is also consistent with the classical approach of flight control design.

  7. User's Manual for Computer Program ROTOR. [to calculate tilt-rotor aircraft dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Yasue, M.

    1974-01-01

    A detailed description of a computer program to calculate tilt-rotor aircraft dynamic characteristics is presented. This program consists of two parts: (1) the natural frequencies and corresponding mode shapes of the rotor blade and wing are developed from structural data (mass distribution and stiffness distribution); and (2) the frequency response (to gust and blade pitch control inputs) and eigenvalues of the tilt-rotor dynamic system, based on the natural frequencies and mode shapes, are derived. Sample problems are included to assist the user.

  8. Alaskan flight trials of a synthetic vision system for instrument landings of a piston twin aircraft

    NASA Astrophysics Data System (ADS)

    Barrows, Andrew K.; Alter, Keith W.; Jennings, Chad W.; Powell, J. D.

    1999-07-01

    Stanford University has developed a low-cost prototype synthetic vision system and flight tested it onboard general aviation aircraft. The display aids pilots by providing an 'out the window' view, making visualization of the desired flight path a simple task. Predictor symbology provides guidance on straight and curved paths presented in a 'tunnel- in-the-sky' format. Based on commodity PC hardware to achieve low cost, the Tunnel Display system uses differential GPS (typically from Stanford prototype Wide Area Augmentation System hardware) for positioning and GPS-aided inertial sensors for attitude determination. The display has been flown onboard Piper Dakota and Beechcraft Queen Air aircraft at several different locations. This paper describes the system, its development, and flight trials culminating with tests in Alaska during the summer of 1998. Operational experience demonstrated the Tunnel Display's ability to increase flight- path following accuracy and situational awareness while easing the task instrument flying.

  9. Interactions among bioenergy feedstock choices, landscape dynamics, and land use

    SciTech Connect

    Dale, Virginia H; Kline, Keith L; Wright, Lynn L; Perlack, Robert D; Downing, Mark; Graham, Robin Lambert

    2011-01-01

    Landscape implications of bioenergy feedstock choices are significant and depend on land-use practices and their environmental impacts. Although land-use changes and carbon emissions associated with bioenergy feedstock production are dynamic and complicated, lignocellulosic feedstocks may offer opportunities that enhance sustainability when compared to other transportation fuel alternatives. For bioenergy sustainability, major drivers and concerns revolve around energy security, food production, land productivity, soil carbon and erosion, greenhouse gas emissions, biodiversity, air quality, and water quantity and quality. The many implications of bioenergy feedstock choices require several indicators at multiple scales to provide a more complete accounting of effects. Ultimately, the long-term sustainability of bioenergy feedstock resources (as well as food supplies) throughout the world depends on land-use practices and landscape dynamics. Land-management decisions often invoke trade-offs among potential environmental effects and social and economic factors as well as future opportunities for resource use. The hypothesis being addressed in this paper is that sustainability of bioenergy feedstock production can be achieved via appropriately designed crop residue and perennial lignocellulosic systems. We find that decision makers need scientific advancements and adequate data that both provide quantitative and qualitative measures of the effects of bioenergy feedstock choices at different spatial and temporal scales and allow fair comparisons among available options for renewable liquid fuels.

  10. Evaluating the Handling Qualities of Flight Control Systems Including Nonlinear Aircraft and System Dynamics

    NASA Astrophysics Data System (ADS)

    Lin, Raymond Chao

    The handling qualities evaluation of nonlinear aircraft systems is an area of concern in loss-of-control (LOC) prevention. The Get Transfer Function (GetTF) method was demonstrated for evaluating the handling qualities of flight control systems and aircraft containing nonlinearities. NASA's Generic Transport Model (GTM), a nonlinear model of a civilian jet transport aircraft, was evaluated. Using classical techniques, the stability, control, and augmentation (SCAS) systems were designed to control pitch rate, roll rate, and airspeed. Hess's structural pilot model was used to model pilot dynamics in pitch and roll-attitude tracking. The simulated task was simultaneous tracking of, both, pitch and roll attitudes. Eight cases were evaluated: 1) gain increase of pitch-attitude command signal, 2) gain increase of roll-attitude command signal, 3) gain reduction of elevator command signal, 4) backlash in elevator actuator, 5) combination 3 and 4 in elevator actuator, 6) gain reduction of aileron command signal, 7) backlash in aileron actuator, and 8) combination of 6 and 7 in aileron actuator. The GetTF method was used to estimate the transfer function approximating a linear relationship between the proprioceptive signal of the pilot model and the command input. The transfer function was then used to predict the handling qualities ratings (HQR) and pilot-induced oscillation ratings (PIOR). The HQR is based on the Cooper-Harper rating scale. In pitch-attitude tracking, the nominal aircraft is predicted to have Level 2* HQRpitch and 2 < PIORpitch < 4. The GetTF method generally predicted degraded handling qualities for cases with impaired actuators. The results demonstrate GetTF's utility in evaluating the handling qualities during the design phase of flight control and aircraft systems. A limited human-in-the-loop pitch tracking exercise was also conducted to validate the structural pilot model.

  11. Applications of the unsteady vortex-lattice method in aircraft aeroelasticity and flight dynamics

    NASA Astrophysics Data System (ADS)

    Murua, Joseba; Palacios, Rafael; Graham, J. Michael R.

    2012-11-01

    The unsteady vortex-lattice method provides a medium-fidelity tool for the prediction of non-stationary aerodynamic loads in low-speed, but high-Reynolds-number, attached flow conditions. Despite a proven track record in applications where free-wake modelling is critical, other less-computationally expensive potential-flow models, such as the doublet-lattice method and strip theory, have long been favoured in fixed-wing aircraft aeroelasticity and flight dynamics. This paper presents how the unsteady vortex-lattice method can be implemented as an enhanced alternative to those techniques for diverse situations that arise in flexible-aircraft dynamics. A historical review of the methodology is included, with latest developments and practical applications. Different formulations of the aerodynamic equations are outlined, and they are integrated with a nonlinear beam model for the full description of the dynamics of a free-flying flexible vehicle. Nonlinear time-marching solutions capture large wing excursions and wake roll-up, and the linearisation of the equations lends itself to a seamless, monolithic state-space assembly, particularly convenient for stability analysis and flight control system design. The numerical studies emphasise scenarios where the unsteady vortex-lattice method can provide an advantage over other state-of-the-art approaches. Examples of this include unsteady aerodynamics in vehicles with coupled aeroelasticity and flight dynamics, and in lifting surfaces undergoing complex kinematics, large deformations, or in-plane motions. Geometric nonlinearities are shown to play an instrumental, and often counter-intuitive, role in the aircraft dynamics. The unsteady vortex-lattice method is unveiled as a remarkable tool that can successfully incorporate all those effects in the unsteady aerodynamics modelling.

  12. Modeling biofuel expansion effects on land use change dynamics

    NASA Astrophysics Data System (ADS)

    Warner, Ethan; Inman, Daniel; Kunstman, Benjamin; Bush, Brian; Vimmerstedt, Laura; Peterson, Steve; Macknick, Jordan; Zhang, Yimin

    2013-03-01

    Increasing demand for crop-based biofuels, in addition to other human drivers of land use, induces direct and indirect land use changes (LUC). Our system dynamics tool is intended to complement existing LUC modeling approaches and to improve the understanding of global LUC drivers and dynamics by allowing examination of global LUC under diverse scenarios and varying model assumptions. We report on a small subset of such analyses. This model provides insights into the drivers and dynamic interactions of LUC (e.g., dietary choices and biofuel policy) and is not intended to assert improvement in numerical results relative to other works. Demand for food commodities are mostly met in high food and high crop-based biofuel demand scenarios, but cropland must expand substantially. Meeting roughly 25% of global transportation fuel demand by 2050 with biofuels requires >2 times the land used to meet food demands under a presumed 40% increase in per capita food demand. In comparison, the high food demand scenario requires greater pastureland for meat production, leading to larger overall expansion into forest and grassland. Our results indicate that, in all scenarios, there is a potential for supply shortfalls, and associated upward pressure on prices, of food commodities requiring higher land use intensity (e.g., beef) which biofuels could exacerbate.

  13. Rosetta lander Philae: Flight Dynamics analyses for landing site selection and post-landing operations

    NASA Astrophysics Data System (ADS)

    Jurado, Eric; Martin, Thierry; Canalias, Elisabet; Blazquez, Alejandro; Garmier, Romain; Ceolin, Thierry; Gaudon, Philippe; Delmas, Cedric; Biele, Jens; Ulamec, Stephan; Remetean, Emile; Torres, Alex; Laurent-Varin, Julien; Dolives, Benoit; Herique, Alain; Rogez, Yves; Kofman, Wlodek; Jorda, Laurent; Zakharov, Vladimir; Crifo, Jean-François; Rodionov, Alexander; Heinish, P.; Vincent, Jean-Baptiste

    2016-08-01

    On the 12th of November 2014, The Rosetta Lander Philae became the first spacecraft to softly land on a comet nucleus. Due to the double failure of the cold gas hold-down thruster and the anchoring harpoons that should have fixed Philae to the surface, it spent approximately two hours bouncing over the comet surface to finally come at rest one km away from its target site. Nevertheless it was operated during the 57 h of its First Science Sequence. The FSS, performed with the two batteries, should have been followed by the Long Term Science Sequence but Philae was in a place not well illuminated and fell into hibernation. Yet, thanks to reducing distance to the Sun and to seasonal effect, it woke up at end of April and on 13th of June it contacted Rosetta again. To achieve this successful landing, an intense preparation work had been carried out mainly between August and November 2014 to select the targeted landing site and define the final landing trajectory. After the landing, the data collected during on-comet operations have been used to assess the final position and orientation of Philae, and to prepare the wake-up. This paper addresses the Flight Dynamics studies done in the scope of this landing preparation from Lander side, in close cooperation with the team at ESA, responsible for Rosetta, as well as for the reconstruction of the bouncing trajectory and orientation of the Lander after touchdown.

  14. Urban Dynamics: Analyzing Land Use Change in Urban Environments

    NASA Technical Reports Server (NTRS)

    Acevedo, William; Richards, Lora R.; Buchanan, Janis T.; Wegener, Whitney R.

    2000-01-01

    In FY99, the Earth Resource Observation System (EROS) staff at Ames continued managing the U.S. Geological Survey's (USGS) Urban Dynamics Research program, which has mapping and analysis activities at five USGS mapping centers. Historic land use reconstruction work continued while activities in geographic analysis and modeling were expanded. Retrospective geographic information system (GIS) development - the spatial reconstruction of a region's urban land-use history - focused on the Detroit River Corridor, California's Central Valley, and the city of Sioux Falls, South Dakota.

  15. An experimental study of pilots' control characteristics for flight of an STOL aircraft in backside of drag curve at approach and landing.

    PubMed

    Ema, T

    1992-01-01

    In general, most vehicles can be modelled by a multi-variable system which has interactive variables. It can be clearly shown that there is an interactive response in an aircraft's velocity and altitude obtained by stick control and/or throttle control. In particular, if the flight conditions fall to backside of drag curve in the flight of an STOL aircraft at approach and landing then the ratio of drag variation to velocity change has a negative value (delta D/delta u less than 0) and the system of motion presents a non-minimum phase. Therefore, the interaction between velocity and altitude response becomes so complicated that it affects to pilot's control actions and it may be difficult to control the STOL aircraft at approach and landing. In this paper, experimental results of a pilot's ability to control the STOL aircraft are presented for a multi-variable manual control system using a fixed ground base simulator and the pilot's control ability is discussed for the flight of an STOL aircraft at backside of drag curve at approach and landing.

  16. The space-developed dynamic vertical cutoff rigidity model and its applicability to aircraft radiation dose.

    PubMed

    Smart, D F; Shea, M A

    2003-01-01

    We have developed a dynamic geomagnetic vertical cutoff rigidity model that predicts the energetic charged particle transmission through the magnetosphere. Initially developed for space applications, we demonstrate the applicability of this library of cutoff rigidity models for computing aircraft radiation dose. The world grids of vertical cutoff rigidities were obtained by particle trajectory tracing in a magnetospheric model. This reference set of world grids of vertical cutoff rigidities calculated for satellite altitudes covers all magnetic activity levels from super quiet to extremely disturbed (i.e., Kp indices ranging from 0 to 9+) for every three hours in universal time. We utilize the McIlwain "L" parameter as the basis of the interpolation technique to reduce these initial satellite altitude vertical cutoff rigidities to cutoff rigidity values at aircraft altitudes.

  17. Flight evaluation of stabilization and command augmentation system concepts and cockpit displays during approach and landing of powered-lift STOL aircraft

    NASA Technical Reports Server (NTRS)

    Franklin, J. A.; Innis, R. C.; Hardy, G. H.

    1980-01-01

    A flight research program was conducted to assess the effectiveness of manual control concepts and various cockpit displays in improving altitude (pitch, roll, and yaw) and longitudinal path control during short takeoff aircraft approaches and landings. Satisfactory flying qualities were demonstrared to minimum decision heights of 30 m (100 ft) for selected stabilization and command augmentation systems and flight director combinations. Precise landings at low touchdown sink rates were achieved with a gentle flare maneuver.

  18. A Model for Space Shuttle Orbiter Tire Side Forces Based on NASA Landing Systems Research Aircraft Test Results

    NASA Technical Reports Server (NTRS)

    Carter, John F.; Nagy, Christopher J.; Barnicki, Joseph S.

    1997-01-01

    Forces generated by the Space Shuttle orbiter tire under varying vertical load, slip angle, speed, and surface conditions were measured using the Landing System Research Aircraft (LSRA). Resulting data were used to calculate a mathematical model for predicting tire forces in orbiter simulations. Tire side and drag forces experienced by an orbiter tire are cataloged as a function of vertical load and slip angle. The mathematical model is compared to existing tire force models for the Space Shuttle orbiter. This report describes the LSRA and a typical test sequence. Testing methods, data reduction, and error analysis are presented. The LSRA testing was conducted on concrete and lakebed runways at the Edwards Air Force Flight Test Center and on concrete runways at the Kennedy Space Center (KSC). Wet runway tire force tests were performed on test strips made at the KSC using different surfacing techniques. Data were corrected for ply steer forces and conicity.

  19. Predicting the effects of unmodeled dynamics on an aircraft flight control system design using eigenspace assignment

    NASA Technical Reports Server (NTRS)

    Johnson, Eric N.; Davidson, John B.; Murphy, Patrick C.

    1994-01-01

    When using eigenspace assignment to design an aircraft flight control system, one must first develop a model of the plant. Certain questions arise when creating this model as to which dynamics of the plant need to be included in the model and which dynamics can be left out or approximated. The answers to these questions are important because a poor choice can lead to closed-loop dynamics that are unpredicted by the design model. To alleviate this problem, a method has been developed for predicting the effect of not including certain dynamics in the design model on the final closed-loop eigenspace. This development provides insight as to which characteristics of unmodeled dynamics will ultimately affect the closed-loop rigid-body dynamics. What results from this insight is a guide for eigenstructure control law designers to aid them in determining which dynamics need or do not need to be included and a new way to include these dynamics in the flight control system design model to achieve a required accuracy in the closed-loop rigid-body dynamics. The method is illustrated for a lateral-directional flight control system design using eigenspace assignment for the NASA High Alpha Research Vehicle (HARV).

  20. Runway Independent Aircraft Extremely Short Takeoff and Landing Regional Airliner: The Model 110

    NASA Technical Reports Server (NTRS)

    Hall, David W.

    2003-01-01

    Airports throughout the United States are plagued with growing congestion. With the increase in air traffic predicted in the next few years, congestion will worsen. The accepted solution of building larger airplanes to carry more travelers is no longer a viable option, as airports are unable to accommodate larger aircraft without expensive infrastructure changes. Past NASA research has pointed to the need for a new approach, which can economically and safely utilize smaller airports. To study this option further, NASA requested the California Polytechnic State University at San Luis Obispo (Cal Poly/SLO) to design a baseline aircraft to be used for system studies. The requirements put forth by NASA are summarized. The design team was requested to create a demonstrator vehicle, which could be built without requiring enabling technology development. To this end, NASA requested that the tested and proven high-lift system of the Boeing C-17 Globemaster III be combined with the fuselage of the BAe-146. NASA also requested that Cal Poly determine the availability and usability of underutilized airports starting with California, then expanding if time and funds permitted to the U.S.

  1. Land Cover Applications, Landscape Dynamics, and Global Change

    USGS Publications Warehouse

    Tieszen, Larry L.

    2007-01-01

    The Land Cover Applications, Landscape Dynamics, and Global Change project at U.S. Geological Survey (USGS) Center for Earth Resources Observation and Science (EROS) seeks to integrate remote sensing and simulation models to better understand and seek solutions to national and global issues. Modeling processes related to population impacts, natural resource management, climate change, invasive species, land use changes, energy development, and climate mitigation all pose significant scientific opportunities. The project activities use remotely sensed data to support spatial monitoring, provide sensitivity analyses across landscapes and large regions, and make the data and results available on the Internet with data access and distribution, decision support systems, and on-line modeling. Applications support sustainable natural resource use, carbon cycle science, biodiversity conservation, climate change mitigation, and robust simulation modeling approaches that evaluate ecosystem and landscape dynamics.

  2. A simulation study of the flight dynamics of elastic aircraft. Volume 1: Experiment, results and analysis

    NASA Technical Reports Server (NTRS)

    Waszak, Martin R.; Davidson, John B.; Schmidt, David K.

    1987-01-01

    The simulation experiment described addresses the effects of structural flexibility on the dynamic characteristics of a generic family of aircraft. The simulation was performed using the NASA Langley VMS simulation facility. The vehicle models were obtained as part of this research. The simulation results include complete response data and subjective pilot ratings and comments and so allow a variety of analyses. The subjective ratings and analysis of the time histories indicate that increased flexibility can lead to increased tracking errors, degraded handling qualities, and changes in the frequency content of the pilot inputs. These results, furthermore, are significantly affected by the visual cues available to the pilot.

  3. Stable H(infinity) Controller Design for the Longitudinal Dynamics of an Aircraft

    NASA Technical Reports Server (NTRS)

    Oezbay, Hitay; Garg, Sanjay

    1995-01-01

    This report discusses different approaches to stable H infinity controller design applied to the problem of augmenting the longitudinal dynamics of an aircraft. Stability of the H infinity controller is investigated by analyzing the effects of changes in the performance index weights, and modifications in the measured outputs. The existence of a stable suboptimal controller is also investigated. It is shown that this is equivalent to finding a stable controller, whose infinity norm is less than a specified bound, for an unstable plant which is determined from parametrization of all H infinity controllers. Examples are given for a gust alleviation and a command tracking problem.

  4. A simulation study of the flight dynamics of elastic aircraft. Volume 2: Data

    NASA Technical Reports Server (NTRS)

    Waszak, Martin R.; Davidson, John B.; Schmidt, David K.

    1987-01-01

    The simulation experiment described addresses the effects of structural flexibility on the dynamic characteristics of a generic family of aircraft. The simulation was performed using the NASA Langley VMS simulation facility. The vehicle models were obtained as part of this research project. The simulation results include complete response data and subjective pilot ratings and comments and so allow a variety of analyses. The subjective ratings and analysis of the time histories indicate that increased flexibility can lead to increased tracking errors, degraded handling qualities, and changes in the frequency content of the pilot inputs. These results, furthermore, are significantly affected by the visual cues available to the pilot.

  5. Development and Deployment of Unmanned Aircraft Instrumentation for Measuring Quantities Related to Land Surface-Atmosphere Interactions

    NASA Astrophysics Data System (ADS)

    de Boer, G.; Lawrence, D.; Elston, J.; Argrow, B. M.; Palo, S. E.; Curry, N.; Finamore, W.; Mack, J.; LoDolce, G.; Schmid, B.; Long, C. N.; Bland, G.; Maslanik, J. A.; Gao, R. S.; Telg, H.; Semmer, S.; Maclean, G.; Ivey, M.; Hock, T. F.; Bartram, B.; Bendure, A.; Stachura, M.

    2015-12-01

    Use of unmanned aircraft systems (UAS) in evaluation of geophysical parameters is expanding at a rapid rate. Despite limitation imposed by necessary regulations related to operation of UAS in the federal airspace, several groups have developed and deployed a variety of UAS and the associated sensors to make measurements of the atmosphere, land surface, ocean and cryosphere. Included in this grouping is work completed at the University of Colorado - Boulder, which has an extended history of operating UAS and expanding their use in the earth sciences. Collaborative projects between the department of Aerospace Engineering, the Cooperative Institute for Research in Environmental Sciences (CIRES), the Research and Engineering Center for Unmanned Vehicles (RECUV), the National Oceanographic and Atmospheric Administration (NOAA) and National Centers for Atmospheric Research (NCAR) have resulted in deployment of UAS to a variety of environments, including the Arctic. In this presentation, I will give an overview of some recent efforts lead by the University of Colorado to develop and deploy a variety of UAS. Work presented will emphasize recent campaigns and instrument development and testing related to understanding the land-atmosphere interface. Specifically, information on systems established for evaluating surface radiation (including albedo), turbulent exchange of water vapor, heat and gasses, and aerosol processes will be presented, along with information on the use of terrestrial ecosystem sensing to provide critical measurments for the evaluation of lower atmospheric flux measurements.

  6. Combustion Dynamics and Control for Ultra Low Emissions in Aircraft Gas-Turbine Engines

    NASA Technical Reports Server (NTRS)

    DeLaat, John C.

    2011-01-01

    Future aircraft engines must provide ultra-low emissions and high efficiency at low cost while maintaining the reliability and operability of present day engines. The demands for increased performance and decreased emissions have resulted in advanced combustor designs that are critically dependent on efficient fuel/air mixing and lean operation. However, all combustors, but most notably lean-burning low-emissions combustors, are susceptible to combustion instabilities. These instabilities are typically caused by the interaction of the fluctuating heat release of the combustion process with naturally occurring acoustic resonances. These interactions can produce large pressure oscillations within the combustor and can reduce component life and potentially lead to premature mechanical failures. Active Combustion Control which consists of feedback-based control of the fuel-air mixing process can provide an approach to achieving acceptable combustor dynamic behavior while minimizing emissions, and thus can provide flexibility during the combustor design process. The NASA Glenn Active Combustion Control Technology activity aims to demonstrate active control in a realistic environment relevant to aircraft engines by providing experiments tied to aircraft gas turbine combustors. The intent is to allow the technology maturity of active combustion control to advance to eventual demonstration in an engine environment. Work at NASA Glenn has shown that active combustion control, utilizing advanced algorithms working through high frequency fuel actuation, can effectively suppress instabilities in a combustor which emulates the instabilities found in an aircraft gas turbine engine. Current efforts are aimed at extending these active control technologies to advanced ultra-low-emissions combustors such as those employing multi-point lean direct injection.

  7. 14 CFR 135.183 - Performance requirements: Land aircraft operated over water.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... operated at an altitude that allows it to reach land in the case of engine failure; (b) It is necessary for..., with the critical engine inoperative, at least 50 feet a minute, at an altitude of 1,000 feet above...

  8. 14 CFR 135.183 - Performance requirements: Land aircraft operated over water.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... operated at an altitude that allows it to reach land in the case of engine failure; (b) It is necessary for..., with the critical engine inoperative, at least 50 feet a minute, at an altitude of 1,000 feet above...

  9. 14 CFR 135.183 - Performance requirements: Land aircraft operated over water.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... operated at an altitude that allows it to reach land in the case of engine failure; (b) It is necessary for..., with the critical engine inoperative, at least 50 feet a minute, at an altitude of 1,000 feet above...

  10. Downscaling of Aircraft, Landsat, and MODIS-bases Land Surface Temperature Images with Support Vector Machines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High spatial resolution Land Surface Temperature (LST) images are required to estimate evapotranspiration (ET) at a field scale for irrigation scheduling purposes. Satellite sensors such as Landsat 5 Thematic Mapper (TM) and Moderate Resolution Imaging Spectroradiometer (MODIS) can offer images at s...

  11. Use of steepest descent and various approximations for efficient computation of minimum noise aircraft landing trajectories

    NASA Technical Reports Server (NTRS)

    Cook, G.; Witt, R. M.

    1976-01-01

    The following areas related to landing trajectory optimization research were discussed: (1) programming and modifying the steepest descent optimization procedure, (2) successfully iterating toward the optimum for a four-mile trajectory, (3) beginning optimization runs for a twenty-mile trajectory, and (4) adapt wind tunnel data for computer usage. Other related areas were discussed in detail in the two previous annual reports.

  12. Response to actual and simulated recordings of conventional takeoff and landing jet aircraft

    NASA Technical Reports Server (NTRS)

    Mabry, J. E.; Sullivan, B. M.

    1978-01-01

    Comparability between noise characteristics of synthesized recordings of aircraft in flight and actual recordings were investigated. Although the synthesized recordings were more smoothly time-varying than the actual recordings and the synthesizer could not produce a comb-filter effect that was present in the actual recordings, results supported the conclusion that annoyance response is comparable to the synthesized and actual recordings. A correction for duration markedly improved the validity of engineering calculation procedures designed to measure noise annoyance. Results led to the conclusion that the magnitude estimation psychophysical method was a highly reliable approach for evaluating engineering calculation procedures designed to measure noise annoyance. For repeated presentations of pairs of actual recordings, differences between judgment results for identical signals ranged from 0.0 to 0.5 db.

  13. Comparative study of flare control laws. [optimal control of b-737 aircraft approach and landing

    NASA Technical Reports Server (NTRS)

    Nadkarni, A. A.; Breedlove, W. J., Jr.

    1979-01-01

    A digital 3-D automatic control law was developed to achieve an optimal transition of a B-737 aircraft between various initial glid slope conditions and the desired final touchdown condition. A discrete, time-invariant, optimal, closed-loop control law presented for a linear regulator problem, was extended to include a system being acted upon by a constant disturbance. Two forms of control laws were derived to solve this problem. One method utilized the feedback of integral states defined appropriately and augmented with the original system equations. The second method formulated the problem as a control variable constraint, and the control variables were augmented with the original system. The control variable constraint control law yielded a better performance compared to feedback control law for the integral states chosen.

  14. Terminal area automatic navigation, guidance, and control research using the Microwave Landing System (MLS). Part 2: RNAV/MLS transition problems for aircraft

    NASA Technical Reports Server (NTRS)

    Pines, S.

    1982-01-01

    The problems in navigation and guidance encountered by aircraft in the initial transition period in changing from distance measuring equipment, VORTAC, and barometric instruments to the more precise microwave landing system data type navaids in the terminal area are investigated. The effects of the resulting discontinuities on the estimates of position and velocity for both optimal (Kalman type navigation schemes) and fixed gain (complementary type) navigation filters, and the effects of the errors in cross track, track angle, and altitude on the guidance equation and control commands during the critical landing phase are discussed. A method is presented to remove the discontinuities from the navigation loop and to reconstruct an RNAV path designed to land the aircraft with minimal turns and altitude changes.

  15. The design, development, and flight test results of the Boeing 737 aircraft antennas for the ICAO demonstration of the TRSB microwave landing system

    NASA Technical Reports Server (NTRS)

    Campbell, T. G.; White, W. E.; Gilreath, M. C.

    1976-01-01

    The Research Support Flight System, a modified Boeing 737, was used to evaluate the performance of several aircraft antennas and locations for the Time Reference Scanning Beam (TRSB) Microwave Landing System (MLS). These tests were conducted at the National Aviation Facilities Experimental Center (NAFEC), Atlantic City, New Jersey on December 18, 1975. The flight tests measured the signal strength and all pertinent MLS data during a straight-in approach, a racetrack approach, and ICAO approach profiles using the independent antenna-receiver combinations simultaneously on the aircraft. Signal drop-outs were experienced during the various approaches but only a small percentage could be attributed to antenna pattern effects.

  16. An overview of the crash dynamics failure behavior of metal and composite aircraft structures

    NASA Technical Reports Server (NTRS)

    Carden, Huey D.; Boitnott, Richard L.; Fasanella, Edwin L.; Jones, Lisa E.

    1991-01-01

    An overview of failure behavior results is presented from some of the crash dynamics research conducted with concepts of aircraft elements and substructure not necessarily designed or optimized for energy absorption or crash loading considerations. Experimental and analytical data are presented that indicate some general trends in the failure behavior of a class of composite structures that includes fuselage panels, individual fuselage sections, fuselage frames, skeleton subfloors with stringers and floor beams without skin covering, and subfloors with skin added to the frame stringer structure. Although the behavior is complex, a strong similarity in the static/dynamic failure behavior among these structures is illustrated through photographs of the experimental results and through analytical data of generic composite structural models.

  17. Evapotranspiration dynamics of biofuel crops with different land use histories

    NASA Astrophysics Data System (ADS)

    Abraha, M. G.; Chen, J.; Chu, H.; Hamilton, S. K.; Zenone, T.; John, R.; Su, Y.; Robertson, G. P.

    2013-12-01

    Land use is increasingly being converted for biofuel crop production, both globally and nationally. Previous studies have focused on the dynamics and changes in carbon fluxes following land conversion, but few have studied water fluxes. We employ eddy covariance methods to examine the long-term dynamics (2009-2012) of evapotranspiration (ET) in response to land use conversion and management practices in cellulosic and grain biofuel crops in the Midwest US. Four of the converted fields had been managed under the USDA Conservation Reserve Program (CRP) for 22 years and three had been in conventional agriculture (AGR) soybean/corn rotation prior to conversion. In 2009, all sites were planted to no-till soybean except one CRP grassland that was left undisturbed as a reference site, and in 2010 three of the former CRP sites and the three former AGR sites were planted to corn, switchgrass and prairie. Daily ET responded to seasonal changes in weather variables, soil water content, canopy structure and management practices. During the initial land conversion period following herbicide application, a larger dip in ET was observed at the CRP sites than at the AGR sites because the CRP sites had a larger aboveground biomass that stopped contributing to ET after herbicide application. ET of the AGR fields (482 mm yr-1) was much greater than that of the CRP fields (399 mm yr-1) in the first two years after conversion. This was attributed to the mulch effect of preexisting grass thatch and the aboveground biomass that was killed by herbicide application on the CRP fields. However, as the crop residue and killed aboveground biomass were depleted through decomposition in the following two years, the ET of the CRP fields (467 mm yr-1) became slightly higher than that of the AGR fields (456 mm yr-1). ET at the reference grassland was significantly greater than at both the converted CRP and AGR fields in all four years. This study showed how the response of ET to land use conversion

  18. Computational fluid dynamics modeling of transport and deposition of pesticides in an aircraft cabin

    NASA Astrophysics Data System (ADS)

    Isukapalli, Sastry S.; Mazumdar, Sagnik; George, Pradeep; Wei, Binnian; Jones, Byron; Weisel, Clifford P.

    2013-04-01

    Spraying of pesticides in aircraft cabins is required by some countries as part of a disinsection process to kill insects that pose a public health threat. However, public health concerns remain regarding exposures of cabin crew and passengers to pesticides in aircraft cabins. While large scale field measurements of pesticide residues and air concentrations in aircraft cabins scenarios are expensive and time consuming, Computational Fluid Dynamics (CFD) models provide an effective alternative for characterizing concentration distributions and exposures. This study involved CFD modeling of a twin-aisle 11 row cabin mockup with heated manikins, mimicking a part of a fully occupied Boeing 767 cabin. The model was applied to study the flow and deposition of pesticides under representative scenarios with different spraying patterns (sideways and overhead) and cabin air exchange rates (low and high). Corresponding spraying experiments were conducted in the cabin mockup, and pesticide deposition samples were collected at the manikin's lap and seat top for a limited set of five seats. The CFD model performed well for scenarios corresponding to high air exchange rates, captured the concentration profiles for middle seats under low air exchange rates, and underestimated the concentrations at window seats under low air exchange rates. Additionally, both the CFD and experimental measurements showed no major variation in deposition characteristics between sideways and overhead spraying. The CFD model can estimate concentration fields and deposition profiles at very high resolutions, which can be used for characterizing the overall variability in air concentrations and surface loadings. Additionally, these model results can also provide a realistic range of surface and air concentrations of pesticides in the cabin that can be used to estimate potential exposures of cabin crew and passengers to these pesticides.

  19. Design considerations for attaining 200-knot test velocities at the aircraft landing loads and traction facility

    NASA Technical Reports Server (NTRS)

    Giles, G. L.; Stubbs, S. M.

    1979-01-01

    Design studies are presented which consider the important parameters in providing 200 knot test velocities at the landing loads and traction facility. Two major components of this facility, the hydraulic jet catapult and the test carriage structure, are considered. Suitable factors are determined to correlate analytical data for characteristics of the hydraulic jet catapult with data measured from the existing catapult system. The resulting equations are used to calculate test velocities for a range of jet nozzle diameters and carriage masses with both the current 122 m and an increased 183 m catapult stroke. Using the catapult characteristics, a target design point is selected and a carriage structure is sized to meet the target point strength requirements.

  20. A dynamical model of Kara Sea land-fast ice

    NASA Astrophysics Data System (ADS)

    Olason, Einar

    2016-05-01

    This paper introduces modifications to the traditional viscous-plastic sea-ice dynamical model, which are necessary to model land-fast ice in the Kara Sea in a realistic manner. The most important modifications are an increase in the maximum viscosity from the standard value of ζmax=>(2.5×108s>)P to ζmax=>(1013s>)P, and to use a solver for the momentum equation capable of correctly solving for small ice velocities (the limit here is set to 10-4 m/s). Given these modifications, a necessary condition for a realistic fast-ice simulation is that the yield curve give sufficient uniaxial compressive strength. This is consistent with the idea that land-fast ice in the Kara Sea forms primarily via static arching. The modified model is tested and tuned using forcing data and observations from 1997 and 1998. The results show that it is possible to model land-fast ice using this model with the modifications mentioned above. The model performs well in terms of modeled fast-ice extent, but suffers from unrealistic break-ups during the start and end of the fast-ice season. The main results are that fast ice in the Kara Sea is supported by arching of the ice, the arches footers resting on a chain of islands off shore.

  1. Land Surface Phenology from MODIS: Characterization of the Collection 5 Global Land Cover Dynamics Product

    NASA Technical Reports Server (NTRS)

    Ganguly, Sangram; Friedl, Mark A.; Tan, Bin; Zhang, Xiaoyang; Verma, Manish

    2010-01-01

    Information related to land surface phenology is important for a variety of applications. For example, phenology is widely used as a diagnostic of ecosystem response to global change. In addition, phenology influences seasonal scale fluxes of water, energy, and carbon between the land surface and atmosphere. Increasingly, the importance of phenology for studies of habitat and biodiversity is also being recognized. While many data sets related to plant phenology have been collected at specific sites or in networks focused on individual plants or plant species, remote sensing provides the only way to observe and monitor phenology over large scales and at regular intervals. The MODIS Global Land Cover Dynamics Product was developed to support investigations that require regional to global scale information related to spatiotemporal dynamics in land surface phenology. Here we describe the Collection 5 version of this product, which represents a substantial refinement relative to the Collection 4 product. This new version provides information related to land surface phenology at higher spatial resolution than Collection 4 (500-m vs. 1-km), and is based on 8-day instead of 16-day input data. The paper presents a brief overview of the algorithm, followed by an assessment of the product. To this end, we present (1) a comparison of results from Collection 5 versus Collection 4 for selected MODIS tiles that span a range of climate and ecological conditions, (2) a characterization of interannual variation in Collections 4 and 5 data for North America from 2001 to 2006, and (3) a comparison of Collection 5 results against ground observations for two forest sites in the northeastern United States. Results show that the Collection 5 product is qualitatively similar to Collection 4. However, Collection 5 has fewer missing values outside of regions with persistent cloud cover and atmospheric aerosols. Interannual variability in Collection 5 is consistent with expected ranges of

  2. Simulations of ozone distributions in an aircraft cabin using computational fluid dynamics

    NASA Astrophysics Data System (ADS)

    Rai, Aakash C.; Chen, Qingyan

    2012-07-01

    Ozone is a major pollutant of indoor air. Many studies have demonstrated the adverse health effect of ozone and the byproducts generated as a result of ozone-initiated reactive chemistry in an indoor environment. This study developed a Computational Fluid Dynamics (CFD) model to predict the ozone distribution in an aircraft cabin. The model was used to simulate the distribution of ozone in an aircraft cabin mockup for the following cases: (1) empty cabin; (2) cabin with seats; (3) cabin with soiled T-shirts; (4) occupied cabin with simple human geometry; and (5) occupied cabin with detailed human geometry. The agreement was generally good between the CFD results and the available experimental data. The ozone removal rate, deposition velocity, retention ratio, and breathing zone levels were well predicted in those cases. The CFD model predicted breathing zone ozone concentration to be 77-99% of the average cabin ozone concentration depending on the seat location. The ozone concentration at the breathing zone in the cabin environment can better assess the health risk to passengers and can be used to develop strategies for a healthier cabin environment.

  3. Preliminary performance of a vertical-attitude takeoff and landing, supersonic cruise aircraft concept having thrust vectoring integrated into the flight control system

    NASA Technical Reports Server (NTRS)

    Robins, A. W.; Beissner, F. L., Jr.; Domack, C. S.; Swanson, E. E.

    1985-01-01

    A performance study was made of a vertical attitude takeoff and landing (VATOL), supersonic cruise aircraft concept having thrust vectoring integrated into the flight control system. Those characteristics considered were aerodynamics, weight, balance, and performance. Preliminary results indicate that high levels of supersonic aerodynamic performance can be achieved. Further, with the assumption of an advanced (1985 technology readiness) low bypass ratio turbofan engine and advanced structures, excellent mission performance capability is indicated.

  4. Dynamic Predictions of Semi-Arid Land Cover Change

    NASA Astrophysics Data System (ADS)

    Foster-Wittig, T. A.

    2011-12-01

    Savannas make up about 18% of the global landmass and contain about 22% of the world's population (Falkenmark and Rockstrom, 2008). They are unique ecosystems in that they consist of both grass and trees. Depending on the land use, amount of precipitation, herbivory, and fire frequency, either trees or grasses can be more prevalent than the other (Sankaran et al., 2005). Savannas in sub-Saharan Africa are usually considered water-limited ecosystems due to the seasonal rainfall. It has been shown that the vegetation responds on a short timescale to the rainfall (Scanlon et al, 2002). Therefore, savannas are foreseen as vulnerable ecosystems to future changes in the land use and climate change (Sankaran et al, 2005). The goal of this research is to quantify the vulnerability of this ecosystem by projecting future changes in the savanna structure due to land use and climate change through the use of a dynamic vegetation model. This research will provide a better understanding of the relationship between precipitation and vegetation in savannas through the use of a Vegetation Dynamics Model developed to predict surface water fluxes and vegetation dynamics in water-limited ecosystems (Williams and Albertson, 2005). In this project, it will be used to model leaf area index (LAI) for point locations within sub-Saharan Africa between Kenya and Botswana with a range of annual rainfall and savanna type. With this model, future projections are developed for what can be anticipated in the future for the savanna structure based on three climate change scenarios; (1) decreased depth, (2) decreased frequency, and (3) decreased wet season length. The effect of the climate change scenarios on the plant water stress and plant water uptake will be analyzed in order to understand the dynamic effects of precipitation on vegetation. Therefore, this will allow conclusions to be drawn about how mean precipitation and a changing climate effect the sensitivity of savanna vegetation. It is

  5. Evaluation of Flying Qualities and Guidance Displays for an Advanced Tilt-Wing STOL Transport Aircraft in Final Approach and Landing

    NASA Technical Reports Server (NTRS)

    Frost, Chad R.; Franklin, James A.; Hardy, Gordon H.

    2002-01-01

    A piloted simulation was performed on the Vertical Motion Simulator at NASA Ames Research Center to evaluate flying qualities of a tilt-wing Short Take-Off and Landing (STOL) transport aircraft during final approach and landing. The experiment was conducted to assess the design s handling qualities, and to evaluate the use of flightpath-centered guidance for the precision approach and landing tasks required to perform STOL operations in instrument meteorological conditions, turbulence, and wind. Pilots rated the handling qualities to be satisfactory for all operations evaluated except those encountering extreme crosswinds and severe windshear; even in these difficult meteorological conditions, adequate handling qualities were maintained. The advanced flight control laws and guidance displays provided consistent performance and precision landings.

  6. Intelligent Aircraft Damage Assessment, Trajectory Planning, and Decision-Making under Uncertainty

    NASA Astrophysics Data System (ADS)

    Lopez, Israel; Sarigul-Klijn, Nesrin

    Situational awareness and learning are necessary to identify and select the optimal set of mutually non-exclusive hypothesis in order to maximize mission performance and adapt system behavior accordingly. This paper presents a hierarchical and decentralized approach for integrated damage assessment and trajectory planning in aircraft with uncertain navigational decision-making. Aircraft navigation can be safely accomplished by properly addressing the following: decision-making, obstacle perception, aircraft state estimation, and aircraft control. When in-flight failures or damage occur, rapid and precise decision-making under imprecise information is required in order to regain and maintain control of the aircraft. To achieve planned aircraft trajectory and complete safe landing, the uncertainties in system dynamics of the damaged aircraft need to be learned and incorporated at the level of motion planning. The damaged aircraft is simulated via a simplified kinematic model. The different sources and perspectives of uncertainties in the damage assessment process and post-failure trajectory planning are presented and classified. The decision-making process for an emergency motion planning and landing is developed via the Dempster-Shafer evidence theory. The objective of the trajectory planning is to arrive at a target position while maximizing the safety of the aircraft given uncertain conditions. Simulations are presented for an emergency motion planning and landing that takes into account aircraft dynamics, path complexity, distance to landing site, runway characteristics, and subjective human decision.

  7. Flight dynamics of a pterosaur-inspired aircraft utilizing a variable-placement vertical tail.

    PubMed

    Roberts, Brian; Lind, Rick; Chatterjee, Sankar

    2011-06-01

    Mission performance for small aircraft is often dependent on the turn radius. Various biologically inspired concepts have demonstrated that performance can be improved by morphing the wings in a manner similar to birds and bats; however, the morphing of the vertical tail has received less attention since neither birds nor bats have an appreciable vertical tail. This paper investigates a design that incorporates the morphing of the vertical tail based on the cranial crest of a pterosaur. The aerodynamics demonstrate a reduction in the turn radius of 14% when placing the tail over the nose in comparison to a traditional aft-placed vertical tail. The flight dynamics associated with this configuration has unique characteristics such as a Dutch-roll mode with excessive roll motion and a skid divergence that replaces the roll convergence.

  8. Quasi-Linear Parameter Varying Representation of General Aircraft Dynamics Over Non-Trim Region

    NASA Technical Reports Server (NTRS)

    Shin, Jong-Yeob

    2007-01-01

    For applying linear parameter varying (LPV) control synthesis and analysis to a nonlinear system, it is required that a nonlinear system be represented in the form of an LPV model. In this paper, a new representation method is developed to construct an LPV model from a nonlinear mathematical model without the restriction that an operating point must be in the neighborhood of equilibrium points. An LPV model constructed by the new method preserves local stabilities of the original nonlinear system at "frozen" scheduling parameters and also represents the original nonlinear dynamics of a system over a non-trim region. An LPV model of the motion of FASER (Free-flying Aircraft for Subscale Experimental Research) is constructed by the new method.

  9. Flight dynamics of a pterosaur-inspired aircraft utilizing a variable-placement vertical tail.

    PubMed

    Roberts, Brian; Lind, Rick; Chatterjee, Sankar

    2011-06-01

    Mission performance for small aircraft is often dependent on the turn radius. Various biologically inspired concepts have demonstrated that performance can be improved by morphing the wings in a manner similar to birds and bats; however, the morphing of the vertical tail has received less attention since neither birds nor bats have an appreciable vertical tail. This paper investigates a design that incorporates the morphing of the vertical tail based on the cranial crest of a pterosaur. The aerodynamics demonstrate a reduction in the turn radius of 14% when placing the tail over the nose in comparison to a traditional aft-placed vertical tail. The flight dynamics associated with this configuration has unique characteristics such as a Dutch-roll mode with excessive roll motion and a skid divergence that replaces the roll convergence. PMID:21558603

  10. Modeling XV-15 tilt-rotor aircraft dynamics by frequency and time-domain identification techniques

    NASA Technical Reports Server (NTRS)

    Tischler, Mark B.; Kaletka, Juergen

    1986-01-01

    Models of the open-loop hover dynamics of the XV-15 Tilt-Rotor Aircraft are extracted from flight data using two approaches: frequency-domain and time-domain identification. Both approaches are reviewed and the identification results are presented and compared in detail. The extracted models compare favorable, with the differences associated mostly with the inherent weighting of each technique. Step responses are used to show that the predictive capability of the models from both techniques is excellent. Based on the results of this study, the relative strengths and weaknesses of the frequency- and time-domain techniques are summarized, and a proposal for a coordinated parameter identification approach is presented.

  11. Dynamic response analysis of an aircraft structure under thermal-acoustic loads

    NASA Astrophysics Data System (ADS)

    Cheng, H.; Li, H. B.; Zhang, W.; Wu, Z. Q.; Liu, B. R.

    2016-09-01

    Future hypersonic aircraft will be exposed to extreme combined environments includes large magnitude thermal and acoustic loads. It presents a significant challenge for the integrity of these vehicles. Thermal-acoustic test is used to test structures for dynamic response and sonic fatigue due to combined loads. In this research, the numerical simulation process for the thermal acoustic test is presented, and the effects of thermal loads on vibro-acoustic response are investigated. To simulate the radiation heating system, Monte Carlo theory and thermal network theory was used to calculate the temperature distribution. Considering the thermal stress, the high temperature modal parameters are obtained with structural finite element methods. Based on acoustic finite element, modal-based vibro-acoustic analysis is carried out to compute structural responses. These researches are very vital to optimum thermal-acoustic test and structure designs for future hypersonic vehicles structure

  12. Land use change effects on GHG dynamics in Central Florida

    NASA Astrophysics Data System (ADS)

    DeLucia, N.; Bernacchi, C. J.; Gomez-Casanovas, N.

    2012-12-01

    The need for alternative energies is accelerating land use change as native or managed ecosystems are being converted to intense agricultural crops for biofuel purposes. Agriculture represents the single largest terrestrial flux of nitrous oxide (N2O) to the atmosphere resulting from nutrient applications. Livestock grazing also accounts for a significant release of methane (CH4) to the atmosphere. Together, CO2, N2O and CH4 represent the dominant greenhouse gasses (GHG) that are emitted to the atmosphere through anthropogenic influences. Significant alterations to the land surface, particularly associated with changes in nutrient application rates, ability of vegetation to uptake nutrients, or changes in the stocking density of livestock, could have a meaningful impact on GHG emissions. Therefore, understanding how these changes will affect soil GHG dynamics is essential to quantify the impact of land use change on the global climate system. Large-scale changes to land cover type in Central Florida Highlands County is currently occurring in which improved pasture (bahiagrass, Paspalum notatum L., as forage for cattle, Bos taurus L.) is being replaced by energy cane (genus Saccharum L.). Fluxes of nitrous oxide (N2O), soil carbon dioxide (CO2) and methane (CH4) were obtained over a complete wet-dry seasonal cycle in a grazed pasture and an energy cane plantation located in Highlands County, FL. In addition, we also investigated the biotic and environmental drivers that regulate soil GHG fluxes in these ecosystems. We predicted decreased rates of CH4 released to the atmosphere after the conversion process was completed to energy cane due to the absence of grazing cattle. We also predicted increased N2O emissions from aggressive fertilization of energycane. Using static chamber measurements, we collected gas samples from four energy cane crops at varying ages and improved pastures paired to each energy cane plot. The gas samples were analyzed using gas chromatography

  13. Technical evaluation report of AGARD Technical Evaluation Meeting on Unsteady Aerodynamics: Fundamentals and Applications to Aircraft Dynamics

    NASA Technical Reports Server (NTRS)

    Mabey, D. G.; Chambers, J. R.

    1986-01-01

    From May 6 to 9, 1985, the Fluid Dynamics Panel and Flight Mechanics Panel of AGARD jointly arranged a Symposium on Unsteady Aerodynamics-Fundamentals and Applications to Aircraft Dynamics at the Stadthall, Goettingen, West Germany. This Symposium was organized by an international program committee chaired by Dr. K. J. Orlik-Ruckemann of the Fluid Dynamics Panel. The program consisted of five sessions grouped in two parts: (1) Fundamentals of Unsteady Aerodynamics; and (2) Applications to Aircraft Dynamics. The 35 papers presented at the 4 day meeting are published in AGARD CP 386 and listed in the Appendix. As the papers are already available and cover a very wide field, the evaluators have offered brief comments on every paper, followed by an overall evaluation of the meeting, together with some general conclusions and recommendations.

  14. Predictive Understanding of Seasonal Hydrological Dynamics under Climate and Land Use-Land Cover Change

    NASA Astrophysics Data System (ADS)

    Batra, N.; Yang, Y. E.; Choi, H. I.; Kumar, P.; Cai, X.; Fraiture, C. D.

    2008-12-01

    Water has always been and will continue to be an important factor in agricultural production and any alteration in the seasonal distribution of water availability due to climate and land use-land cover change (LULCC) will significantly impact the future production. To achieve the ecologic, economic and social objectives of sustainability, physical understanding of the linkages between climatic changes, LULCC and hydrological response is required. Aided by satellite data, modeling and understanding of the interactions between physical processes of the climate system and society, more reliable regional LULCC and climate change projections are now available. However, resulting quantitative projection of changes on the regional scale hydrological components at the seasonal time scale are sparse. This study attempts to quantify the seasonal hydrological response due to projected LULCC and climate change scenario of Intergovernmental Panel on Climate Change (IPCC) in different hydro-climatic regions of the world. The Common Land Model (CLM) is used for global assessment of future hydrologic response with the development of a consistent global GIS based database for the surface boundary conditions and meteorological forcing of the model. Future climate change projections are derived from the IPCC Fourth Assessment Report: Working Group I - The Physical Science Basis. The study is performed over nine river basins selected from Asia, Africa and North America to present the broad climatic and landscape controls on the seasonal hydrological dynamics. Future changes in water availability are quite evident from our results based upon changes in the volume and seasonality of precipitation, runoff and evapotranspiration. Severe water scarcity is projected to occur in certain seasons which may not be known through annual estimates. Knowledge of the projected seasonal hydrological response can be effectively used for developing adaptive management strategies for the sustainability

  15. Integrating the system dynamic and cellular automata models to predict land use and land cover change

    NASA Astrophysics Data System (ADS)

    Xu, Xiaoming; Du, Ziqiang; Zhang, Hong

    2016-10-01

    Land use and land cover change (LULCC) is a widely researched topic in related studies. A number of models have been established to simulate LULCC patterns. However, the integration of the system dynamic (SD) and the cellular automata (CA) model have been rarely employed in LULCC simulations, although it allows for combining the advantages of each approach and therefore improving the simulation accuracy. In this study, we integrated an SD model and a CA model to predict LULCC under three future development scenarios in Northern Shanxi province of China, a typical agro-pastoral transitional zone. The results indicated that our integrated approach represented the impacts of natural and socioeconomic factors on LULCC well, and could accurately simulate the magnitude and spatial pattern of LULCC. The modeling scenarios illustrated that different development pathways would lead to various LULCC patterns. This study demonstrated the advantages of the integration approach for simulating LULCC and suggests that LULCC is affected to a large degree by natural and socioeconomic factors.

  16. Simulation and analysis of dynamic heating in the ultrafast aircraft thermometer measurements

    NASA Astrophysics Data System (ADS)

    Rosa, Bogdan; Bajer, Konrad; Haman, Krzysztof E.; Szoplik, Tomasz

    2005-10-01

    The ultrafast aircraft thermometer is an airborne device designed for measuring temperature in clouds with centimeter spatial resolution. Its sensor consists of 5mm long and 2.5μm thick thermo-resistive wire protected against impact of cloud droplets by a shield in the form of a suitably shaped rod, placed upstream. However the disturbances of airflow around this rod result in noise in the temperature record. Suction applied through slits located on both sides of the rod reduces the noise generated by vortices shed from the rod and lowers the probability of droplet-wire collisions. Our recent theoretical analysis and numerical simulations led to optimization of this device and additionally clarified the role of the sampling method in processing of the analogue output of the thermometer. In this paper we try to deepen our understanding of the nature of the noise as well as to improve calculations of the corrections connected with the dynamic heating. For this purpose we have done extensive three-dimensional numerical simulations of the airflow around the protective rod and the sensing wire, which permitted precise computation of dynamic heating and showed how applying the suction removes the thermal boundary layer from the rod and damps the sources of the noise.

  17. Conceptual Design Optimization of an Augmented Stability Aircraft Incorporating Dynamic Response Performance Constraints

    NASA Technical Reports Server (NTRS)

    Welstead, Jason

    2014-01-01

    This research focused on incorporating stability and control into a multidisciplinary de- sign optimization on a Boeing 737-class advanced concept called the D8.2b. A new method of evaluating the aircraft handling performance using quantitative evaluation of the sys- tem to disturbances, including perturbations, continuous turbulence, and discrete gusts, is presented. A multidisciplinary design optimization was performed using the D8.2b transport air- craft concept. The con guration was optimized for minimum fuel burn using a design range of 3,000 nautical miles. Optimization cases were run using xed tail volume coecients, static trim constraints, and static trim and dynamic response constraints. A Cessna 182T model was used to test the various dynamic analysis components, ensuring the analysis was behaving as expected. Results of the optimizations show that including stability and con- trol in the design process drastically alters the optimal design, indicating that stability and control should be included in conceptual design to avoid system level penalties later in the design process.

  18. A new method to determine dynamically equivalent finite element models of aircraft structures from modal test data

    NASA Astrophysics Data System (ADS)

    Karaağaçlı, Taylan; Yıldız, Erdinç N.; Nevzat Özgüven, H.

    2012-08-01

    Flutter analysis is a major requirement to predict safe flight envelops and to decide on flutter testing conditions of newly designed or modified aircraft structures. In order to achieve reliable flutter analysis of an aircraft structure, it is necessary to obtain a good correlation between its finite element (FE) model and experimental modal data. Currently available model updating methods require construction of a detailed initial FE model in order to achieve convergence of the modes obtained from updated FE model to their experimental counterparts. If the updating procedure is not carried out by the original design team of the aircraft structure but a subsidiary company that makes certain modification on it, construction of an appropriate initial FE model from scratch becomes a tedious task requiring considerable amount of engineering work. To overcome the foregoing problem, this paper presents a new method that aims to derive dynamically equivalent FE model of an aircraft structure directly from its experimental modal data. The application of the method is illustrated with two case studies. In the first case study, the performance of the method is tested with the modal test data of a benchmark structure built to simulate dynamic behavior of an airplane, namely GARTEUR SM-AG 19 test bed, and very satisfactory results are obtained: the first 10 elastic FE modes of the test bed closely correlate with experimental data. In the second case study, the method is applied to the modal test data obtained from ground vibration test (GVT) of a real aircraft. In this application, it is observed that only the first 4 modes of the resultant FE model correlate well with experimental data. It is concluded that the method suggested works perfectly well for simple structures like GARTEUR test bed, and it gives quite promising results when applied to real aircraft structures.

  19. Influence of land-use dynamics on natural hazard risk

    NASA Astrophysics Data System (ADS)

    Piazza, Giacomo; Thaler, Thomas; Fuchs, Sven

    2016-04-01

    In the recent past the magnitude and frequency of natural hazard events has increased notably worldwide, along with global GDP. A higher number of elements are exposed to natural events, therefore the risk is higher. Both estimated losses and understanding about natural hazards have increased during the past decades, which is contradictory as we may logically think. Risk is increasing, due to climate change and societal change: more severe hazards are happening due to changing climatic patterns and conditions, while society is concentrating assets and people in punctual places leading to a higher exposure. Increasing surface of settled area and the concentration of highly valuable assets (e.g. technology) in exposed areas lead to higher probability of losses. Human use of land resources, namely landuse, is the product of human needs and biophysical characteristics of the land. Landuse involves arrangements, activities and inputs people undertake in a certain land cover type to produce, change or maintain it. These changes are due to many reasons, or driving factors: socio-economical, environmental, accessibility to land, land-tenure, etc. The change of those factors may cause many effects and impacts, at various levels and at different time spans. The relation between driving factors and impacts is not straight. It is although a complex interrelation that turns around two central questions: (1) what drives landuse changes and why and (2) what are the impacts on the environment and on the human society of these changes, regarding to natural hazards. The aim of this paper is to analyse the spatio-temporal environmental changes referring to exposure as well as to test the possibilities and limitations of the land use change model Dyna-CLUEs in a mountain region taking parts of the Republic of Austria as an example, and simulating the future landuse dynamics until 2030. We selected an area composed by eighteen municipalities in the Ill-Walgau in the Austrian federal

  20. Dynamic Root Distribution in the Community Land Model

    NASA Astrophysics Data System (ADS)

    Drewniak, B. A.

    2015-12-01

    Roots are responsible for water and nutrient uptake for plant needs, functioning to couple the above and belowground ecosystems as a photosynthesis driver. Roots respond to their environment with foraging strategies to maximize nutrient acquisition. However, roots have one of the simplest representations in Earth System Models (ESMs). Most root algorithms in ESMs consist of a fixed rooting depth and distribution, which varies only with plant functional type (PFT). Although this method works in general for many ecosystems, there are several regions (e.g., arid, boreal) where root distribution is either overestimated or underestimated resulting in plant stress induced lost productivity. In order to allow ecosystems to respond to changes in environment such as from climate change, roots require a time varying structure to adapt to heterogeneity of water and nitrogen in the soil. This work presents a new approach to representing roots in the Community Land Model. The methodology is designed to optimize root distribution for both water and nitrogen uptake, with a priority given to plant water needs. The roots can respond to the soil vertical profile of nutrients, influencing the plant extractable resources and therefore the above ground vegetation dynamics. The dynamic root profile results in an increase in gross primary productivity and crop yield.

  1. A state dynamics method for integrated GPS/INS navigation and its application to aircraft precision approach

    NASA Astrophysics Data System (ADS)

    Chan, Fang-Cheng

    In recent years, GPS navigation systems have found widespread use in many diverse applications. The achievements of GPS navigation systems in positioning and navigation services have been nothing short of extraordinary. With the use of carrier phase measurements and Differential GPS (DGPS), centimeter-level performance is achievable today. Therefore, the principal issues for modern navigation are not related to accuracy per se, but robustness. Unfortunately in this regard, all radionavigation systems are subject to Radio Frequency Interference (RFI). In response, this research is focused on the development of interference-robust navigation systems for aviation applications. A new dual-frequency Carrier-phase DGPS (CDGPS) architecture has been developed in this research and its performance was evaluated relative to the requirements for a unique shipboard landing application. RFI vulnerability was addressed for this application by directly incorporating a single frequency architecture as a back-up in the event of hostile jamming on one frequency. For critical civil aviation applications without access to dual frequency GPS signals, a novel method for tightly-coupling GPS and Inertial Navigation Sensors (INS) was developed to address the signal vulnerability issue. The new hybrid navigation system, based on the direct fusion of GPS and INS using state dynamics, is a mathematically rigorous approach, yet it is more direct and simpler to implement than existing GPS/INS integration schemes. The hybrid navigation system was validated with flight data, and predicted system performance was evaluated using a covariance analysis method. Necessary conditions on INS sensor and gravity model quality were derived to ensure that the hybrid system performance is compliant with navigation requirements for aircraft precision approach and landing. In addition, a new fault detection algorithm, based on integrated Kalman filter innovations, was developed and evaluated against other

  2. The Role of Turbulence in Chemical and Dynamical Processes in the Near-Field Wake of Subsonic Aircraft

    NASA Technical Reports Server (NTRS)

    Lewellen, D. C.; Lewellen, W. Steve

    2002-01-01

    During this grant, covering the period from September 1998 to December 2001, we continued the investigation of the role of turbulent mixing in the wake of subsonic aircraft initiated in 1994 for NASA's Atmospheric Effects of Aviation Project. The goal of the research has been to provide sufficient understanding and quantitative analytical capability to assess the dynamical, chemical, and microphysical interactions in the near-field wake that have the greatest potential to influence the global atmospheric impact of the projected fleet of subsonic aircraft. Through large-eddy simulations we have shown that turbulence in the early wake dynamics can have a strong effect on both the ice microphysics of contrail evolution and on wake chemistry. The wake vortex dynamics are the primary determinant of the vertical extent of the contrail; this together with the local wind shear largely determines the horizontal extent. The fraction of the initial ice crystals surviving the wake vortex dynamics, their spatial distribution, and the ice mass distribution are all sensitive to the aircraft type, assumed initial ice crystal number, and ambient humidity and turbulence conditions. Our model indicates that there is a significant range of conditions for which a smaller aircraft such as a B737 produces as significant a persistent contrail as a larger aircraft such as a B747, even though the latter consumes almost five times as much fuel. Large-eddy simulations of the near wake of a B757 provided a fine-grained chemical-dynamical representation of simplified NOx - HOx chemistry in wakes of ages from a few seconds to several minutes. By sampling the simulated data in a manner similar to that of in situ aircraft measurements it was possible to provide a likely explanation for a puzzle uncovered in the 1996 SUCCESS flight measurements of OH and HO2 The results illustrate the importance of considering fluid dynamics effects in interpreting chemistry results when mixing rates and species

  3. Temporal and spatial variability of daytime land surface temperature in Houston: Comparing DISCOVER-AQ aircraft observations with the WRF model and satellites

    NASA Astrophysics Data System (ADS)

    Huang, Min; Lee, Pius; McNider, Richard; Crawford, James; Buzay, Eric; Barrick, John; Liu, Yuling; Krishnan, Praveena

    2016-01-01

    Based on a semiempirical diurnal temperature cycle model and aircraft observations taken at different times of the day, daytime land surface temperature (LST) is derived at six locations in the Greater Houston area on the least cloudy day during NASA's DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) field campaign in September 2013. The aircraft-derived daytime LSTs show ranges (max-min) of 11-25°K varying by location, with the daily maxima occurring near 1300-1400 local time. Two Weather Research and Forecasting model simulations that were configured differently are compared with these aircraft-derived LST, indicating location- and time-dependent performance. The NOAA GOES geostationary satellite observed similar LST spatial patterns in Houston to those in finer resolution from two polar-orbiting satellite instruments (Moderate Resolution Imaging Spectroradiometer and Visible Infrared Imaging Radiometer Suite), and it provided useful information of the LST temporal variability missing from the polar-orbiting satellite products. However, spatial- and time-varying discrepancies are found among LSTs from these various platforms, which are worth further evaluation in order to benefit model evaluation and improvement. The aircraft and satellite LSTs are overall anticorrelated with satellite vegetation indexes. This emphasizes the importance of vegetation cover in urban planning due to its cooling effect and further impact on biogenic emissions and regional air quality. The approaches shown in this study are also suitable for applications under cloudless conditions at other locations and times, such as during the remaining DISCOVER-AQ deployments conducted in three other populated regions with diverse land uses.

  4. A simple dynamic engine model for use in a real-time aircraft simulation with thrust vectoring

    NASA Technical Reports Server (NTRS)

    Johnson, Steven A.

    1990-01-01

    A simple dynamic engine model was developed at the NASA Ames Research Center, Dryden Flight Research Facility, for use in thrust vectoring control law development and real-time aircraft simulation. The simple dynamic engine model of the F404-GE-400 engine (General Electric, Lynn, Massachusetts) operates within the aircraft simulator. It was developed using tabular data generated from a complete nonlinear dynamic engine model supplied by the manufacturer. Engine dynamics were simulated using a throttle rate limiter and low-pass filter. Included is a description of a method to account for axial thrust loss resulting from thrust vectoring. In addition, the development of the simple dynamic engine model and its incorporation into the F-18 high alpha research vehicle (HARV) thrust vectoring simulation. The simple dynamic engine model was evaluated at Mach 0.2, 35,000 ft altitude and at Mach 0.7, 35,000 ft altitude. The simple dynamic engine model is within 3 percent of the steady state response, and within 25 percent of the transient response of the complete nonlinear dynamic engine model.

  5. An investigation into the vertical axis control power requirements for landing VTOL type aircraft onboard nonaviation ships in various sea states

    NASA Technical Reports Server (NTRS)

    Stevens, M. E.; Roskam, J.

    1985-01-01

    The problem of determining the vertical axis control requirements for landing a VTOL aircraft on a moving ship deck in various sea states is examined. Both a fixed-base piloted simulation and a nonpiloted simulation were used to determine the landing performance as influenced by thrust-to-weight ratio, vertical damping, and engine lags. The piloted simulation was run using a fixed-based simulator at Ames Research center. Simplified versions of an existing AV-8A Harrier model and an existing head-up display format were used. The ship model used was that of a DD963 class destroyer. Simplified linear models of the pilot, aircraft, ship motion, and ship air-wake turbulence were developed for the nonpiloted simulation. A unique aspect of the nonpiloted simulation was the development of a model of the piloting strategy used for shipboard landing. This model was refined during the piloted simulation until it provided a reasonably good representation of observed pilot behavior.

  6. 19 CFR 122.24 - Landing requirements for certain aircraft arriving from areas south of U.S.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ..., DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY AIR COMMERCE REGULATIONS Private Aircraft § 122.... Houston, Tex William P. Hobby Airport. Key West, Fla Key West International Airport. Laredo, Tex...

  7. 19 CFR 122.24 - Landing requirements for certain aircraft arriving from areas south of U.S.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ..., DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY AIR COMMERCE REGULATIONS Private Aircraft § 122.... Houston, Tex William P. Hobby Airport. Key West, Fla Key West International Airport. Laredo, Tex...

  8. Hypersonic aircraft design

    NASA Technical Reports Server (NTRS)

    Alkamhawi, Hani; Greiner, Tom; Fuerst, Gerry; Luich, Shawn; Stonebraker, Bob; Wray, Todd

    1990-01-01

    A hypersonic aircraft is designed which uses scramjets to accelerate from Mach 6 to Mach 10 and sustain that speed for two minutes. Different propulsion systems were considered and it was decided that the aircraft would use one full scale turbofan-ramjet. Two solid rocket boosters were added to save fuel and help the aircraft pass through the transonic region. After considering aerodynamics, aircraft design, stability and control, cooling systems, mission profile, and landing systems, a conventional aircraft configuration was chosen over that of a waverider. The conventional design was chosen due to its landing characteristics and the relative expense compared to the waverider. Fuel requirements and the integration of the engine systems and their inlets are also taken into consideration in the final design. A hypersonic aircraft was designed which uses scramjets to accelerate from Mach 6 to Mach 10 and sustain that speed for two minutes. Different propulsion systems were considered and a full scale turbofan-ramjet was chosen. Two solid rocket boosters were added to save fuel and help the aircraft pass through the transonic reqion. After the aerodynamics, aircraft design, stability and control, cooling systems, mission profile, landing systems, and their physical interactions were considered, a conventional aircraft configuration was chosen over that of a waverider. The conventional design was chosen due to its landing characteristics and the relative expense compared to the waverider. Fuel requirements and the integration of the engine systems and their inlets were also considered in the designing process.

  9. Accuracy assessment of land cover dynamic in hill land on integration of DEM data and TM image

    NASA Astrophysics Data System (ADS)

    Li, Yunmei; Wang, Xin; Wang, Qiao; Wu, Chuanqing; Huang, Jiazhu

    2010-04-01

    To accurately assess the area of land cover in hill land, we integrated DEM data and remote sensing image in Lihe River Valley, China. Firstly, the DEM data was combined into decision tree to increase the accuracy of land cover classification. Secondly, a slope corrected model was built to transfer the projected area to surface area by DEM data. At last, the area of different land cover was calculated and the dynamic of land cover in Lihe River Valley were analyzed from 1998 to 2003. The results show that: the area of forestland increased more than 10% by the slope corrected model, that indicates the area correcting is very important for hill land; the accuracy of classification especially for forestland and garden plot is enhanced by integrating of DEM data. It can be greater than 85%. The indexes of land use extent were 266.2 in 1998, 273.1 in 2001, and 276.7 in 2003. The change rates of land use extent were 2.59 during 1998 to 2001 and 1.34 during 2001 to 2003.

  10. A compilation and analysis of typical approach and landing data for a simulator study of an externally blown flap STOL aircraft

    NASA Technical Reports Server (NTRS)

    Middleton, D. B.; Bergeron, H. P.

    1974-01-01

    A piloted simulation study has been made of typical landing approaches with an externally blown flap STOL aircraft to ascertain a realistic dispersion of parameter values at both the flare window and touchdown. The study was performed on a fixed-base simulator using standard cockpit instrumentation. Six levels of stability and control augmentation were tested during a total of 60 approaches (10 at each level). A detached supplement containing computer printouts of the flare-window and touchdown conditions for all 60 runs has been prepared.

  11. Application of variable structure system theory to aircraft flight control. [AV-8A and the Augmentor Wing Jet STOL Research Aircraft

    NASA Technical Reports Server (NTRS)

    Calise, A. J.; Kadushin, I.; Kramer, F.

    1981-01-01

    The current status of research on the application of variable structure system (VSS) theory to design aircraft flight control systems is summarized. Two aircraft types are currently being investigated: the Augmentor Wing Jet STOL Research Aircraft (AWJSRA), and AV-8A Harrier. The AWJSRA design considers automatic control of longitudinal dynamics during the landing phase. The main task for the AWJSRA is to design an automatic landing system that captures and tracks a localizer beam. The control task for the AV-8A is to track velocity commands in a hovering flight configuration. Much effort was devoted to developing computer programs that are needed to carry out VSS design in a multivariable frame work, and in becoming familiar with the dynamics and control problems associated with the aircraft types under investigation. Numerous VSS design schemes were explored, particularly for the AWJSRA. The approaches that appear best suited for these aircraft types are presented. Examples are given of the numerical results currently being generated.

  12. Analytical model for tilting proprotor aircraft dynamics, including blade torsion and coupled bending modes, and conversion mode operation

    NASA Technical Reports Server (NTRS)

    Johnson, W.

    1974-01-01

    An analytical model is developed for proprotor aircraft dynamics. The rotor model includes coupled flap-lag bending modes, and blade torsion degrees of freedom. The rotor aerodynamic model is generally valid for high and low inflow, and for axial and nonaxial flight. For the rotor support, a cantilever wing is considered; incorporation of a more general support with this rotor model will be a straight-forward matter.

  13. Static and Dynamic Structural Response of an Aircraft Wing with Damage Using Equivalent Plate Analysis

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, T.; Tsai, Frank J.

    2008-01-01

    A process to generate an equivalent plate based on an optimization approach to predict the static and dynamic response of flight vehicle wing structures is proposed. Geometric-scale and frequency-scale factors are defined to construct an equivalent plate with any desired scale to use in simulation and wind tunnel experiments. It is shown that the stiffness and the displacements are scaled linearly with the geometric-scale factor, whereas the load is scaled as the square of the geometric-scale factor. The scaled stiffness of the reference flight vehicle is matched first to construct the equivalent plate. Then the frequency-scale factor is defined to scale the flight vehicle frequencies. The scaled flight vehicle frequencies are matched by placing arbitrary point masses along the equivalent plate geometry. Two simple stiffened-plate examples, one with damage and another without damage, were used to demonstrate the accuracy of the optimization procedure proposed. Geometric-scale factors ranging from 0.2 to 1.0 were used in the analyses. In both examples, the static and dynamic response of the reference stiffened-panel solution is matched accurately. The scaled equivalent plate predicted the first five frequencies of the stiffened panel very accurately. Finally, the proposed equivalent plate procedure was demonstrated in a more realistic typical aircraft wing structure. Two scale equivalent plate models were generated using the geometric-scale factors 1.0 and 0.2. Both equivalent plate models predicted the static response of the wing structure accurately. The equivalent plate models reproduced the first five frequencies of the wing structure accurately.

  14. The effects of aeroelastic deformation on the unaugmented stopped-rotor dynamics of an X-Wing aircraft

    NASA Technical Reports Server (NTRS)

    Gilbert, Michael G.; Silva, Walter A.

    1987-01-01

    A new design concept in the development of VTOL aircraft with high forward flight speed capability is that of the X-Wing, a stiff, bearingless helicopter rotor system which can be stopped in flight and the blades used as two forward-swept and two aft-swept wings. Because of the usual configuration in the fixed-wing mode, there is a high potential for aeroelastic divergence or flutter and coupling of blade vibration modes with rigid-body modes. An aeroelastic stability analysis of an X-Wing configuration aircraft was undertaken to determine if these problems could exist. This paper reports on the results of dynamic stability analyses in the lateral and longitudinal directions including the vehicle rigid-body and flexible modes. A static aeroelastic analysis using the normal vibration mode equations of motion was performed to determine the cause of a loss of longitudinal static margin with increasing airspeed. This loss of static margin was found to be due to aeroelastic washin of the forward-swept blades and washout of the aft-swept blades moving the aircraft aerodynamic center forward of the center of gravity. This phenomenon is likely to be generic to X-Wing aircraft.

  15. Integration of visual and motion cues for simulator requirements and ride quality investigation. [computerized simulation of aircraft landing, visual perception of aircraft pilots

    NASA Technical Reports Server (NTRS)

    Young, L. R.

    1975-01-01

    Preliminary tests and evaluation are presented of pilot performance during landing (flight paths) using computer generated images (video tapes). Psychophysiological factors affecting pilot visual perception were measured. A turning flight maneuver (pitch and roll) was specifically studied using a training device, and the scaling laws involved were determined. Also presented are medical studies (abstracts) on human response to gravity variations without visual cues, acceleration stimuli effects on the semicircular canals, and neurons affecting eye movements, and vestibular tests.

  16. Survey of needs and capabilities for wind tunnel testing of dynamic stability of aircraft at high angles of attack

    NASA Technical Reports Server (NTRS)

    Orlik-Ruckemann, K. J.

    1973-01-01

    A survey was conducted relative to future requirements for dynamic stability information for such aerospace vehicles as the space shuttle and advanced high performance military aircraft. High-angle-of-attack and high-Reynolds number conditions were emphasized. A review was made of the wind-tunnel capabilities in North America for measuring dynamic stability derivatives, revealing an almost total lack of capabilities that could satisfy these requirements. Recommendations are made regarding equipment that should be constructed to remedy this situation. A description is given of some of the more advanced existing capabilities, which can be used to at least partly satisfy immediate demands.

  17. Low-order nonlinear dynamic model of IC engine-variable pitch propeller system for general aviation aircraft

    NASA Technical Reports Server (NTRS)

    Richard, Jacques C.

    1995-01-01

    This paper presents a dynamic model of an internal combustion engine coupled to a variable pitch propeller. The low-order, nonlinear time-dependent model is useful for simulating the propulsion system of general aviation single-engine light aircraft. This model is suitable for investigating engine diagnostics and monitoring and for control design and development. Furthermore, the model may be extended to provide a tool for the study of engine emissions, fuel economy, component effects, alternative fuels, alternative engine cycles, flight simulators, sensors, and actuators. Results show that the model provides a reasonable representation of the propulsion system dynamics from zero to 10 Hertz.

  18. Motion-base simulator study of control of an externally blown flap STOL transport aircraft after failure of an outboard engine during landing approach

    NASA Technical Reports Server (NTRS)

    Middleton, D. B.; Hurt, G. J., Jr.; Bergeron, H. P.; Patton, J. M., Jr.; Deal, P. L.; Champine, R. A.

    1975-01-01

    A moving-base simulator investigation of the problems of recovery and landing of a STOL aircraft after failure of an outboard engine during final approach was made. The approaches were made at 75 knots along a 6 deg glide slope. The engine was failed at low altitude and the option to go around was not allowed. The aircraft was simulated with each of three control systems, and it had four high-bypass-ratio fan-jet engines exhausting against large triple-slotted wing flaps to produce additional lift. A virtual-image out-the-window television display of a simulated STOL airport was operating during part of the investigation. Also, a simple heads-up flight director display superimposed on the airport landing scene was used by the pilots to make some of the recoveries following an engine failure. The results of the study indicated that the variation in visual cues and/or motion cues had little effect on the outcome of a recovery, but they did have some effect on the pilot's response and control patterns.

  19. [Land use pattern and its dynamic changes in Amur tiger distribution region].

    PubMed

    Li, Zhong-wen; Wu, Jian-guo; Kou, Xiao-jun; Tian, Yu; Wang, Tian-ming; Mu, Pu; Ge, Jian-ping

    2009-03-01

    Land use and land cover change has been the primary cause for the habitat loss and fragmentation in the distribution region of Amur tiger (Panthera tigris altaica). Based on the spatiotemporal changes of land use and land cover in the distribution region, as well as their effects on the population dynamics of Amur tiger, this paper analyzed the development process and its characteristics of the main land use types (agricultural land, forest land, and construction land) in this region, with the land use change history being divided chronically into three distinctive periods, i.e., ancient times (prior to 1860), modern times (1860-1949), and contemporary times (after 1949). The results showed that the sporadic land use in ancient times had no significant effects on the survival of Amur tiger, while the extensive and intensive land use after the 1860s was mainly responsible for the decrease of Amur tiger population and its living space. Since 1949, the Amur tiger distribution region has been divided into two parts, i.e., Northeast China and Russia Far East. The differences in land use pattern, policy, and intensity between these two parts led to different survival status of Amur tiger. The key driving forces for the land use change in Amur tiger distribution region were human population increase, policy change, and increased productivity.

  20. Land change variability and human-environment dynamics in the United States Great Plains

    USGS Publications Warehouse

    Drummond, M.A.; Auch, R.F.; Karstensen, K.A.; Sayler, K.L.; Taylor, J.L.; Loveland, T.R.

    2012-01-01

    Land use and land cover changes have complex linkages to climate variability and change, biophysical resources, and socioeconomic driving forces. To assess these land change dynamics and their causes in the Great Plains, we compare and contrast contemporary changes across 16 ecoregions using Landsat satellite data and statistical analysis. Large-area change analysis of agricultural regions is often hampered by change detection error and the tendency for land conversions to occur at the local-scale. To facilitate a regional-scale analysis, a statistical sampling design of randomly selected 10 km ?? 10 km blocks is used to efficiently identify the types and rates of land conversions for four time intervals between 1973 and 2000, stratified by relatively homogenous ecoregions. Nearly 8% of the overall Great Plains region underwent land-use and land-cover change during the study period, with a substantial amount of ecoregion variability that ranged from less than 2% to greater than 13%. Agricultural land cover declined by more than 2% overall, with variability contingent on the differential characteristics of regional human-environment systems. A large part of the Great Plains is in relatively stable land cover. However, other land systems with significant biophysical and climate limitations for agriculture have high rates of land change when pushed by economic, policy, technology, or climate forcing factors. The results indicate the regionally based potential for land cover to persist or fluctuate as land uses are adapted to spatially and temporally variable forcing factors. ?? 2011.

  1. Land change variability and human-environment dynamics in the United States Great Plains

    USGS Publications Warehouse

    Drummond, Mark A.; Auch, Roger F.; Karstensen, Krista A.; Sayler, Kristi L.; Taylor, Janis L.; Loveland, Thomas R.

    2012-01-01

    Land use and land cover changes have complex linkages to climate variability and change, biophysical resources, and socioeconomic driving forces. To assess these land change dynamics and their causes in the Great Plains, we compare and contrast contemporary changes across 16 ecoregions using Landsat satellite data and statistical analysis. Large-area change analysis of agricultural regions is often hampered by change detection error and the tendency for land conversions to occur at the local-scale. To facilitate a regional-scale analysis, a statistical sampling design of randomly selected 10 km x 10 km blocks is used to efficiently identify the types and rates of land conversions for four time intervals between 1973 and 2000, stratified by relatively homogenous ecoregions. Nearly 8% of the overall Great Plains region underwent land-use and land-cover change during the study period, with a substantial amount of ecoregion variability that ranged from less than 2% to greater than 13%. Agricultural land cover declined by more than 2% overall, with variability contingent on the differential characteristics of regional human–environment systems. A large part of the Great Plains is in relatively stable land cover. However, other land systems with significant biophysical and climate limitations for agriculture have high rates of land change when pushed by economic, policy, technology, or climate forcing factors. The results indicate the regionally based potential for land cover to persist or fluctuate as land uses are adapted to spatially and temporally variable forcing factors.

  2. [Land use pattern and its dynamic changes in Amur tiger distribution region].

    PubMed

    Li, Zhong-wen; Wu, Jian-guo; Kou, Xiao-jun; Tian, Yu; Wang, Tian-ming; Mu, Pu; Ge, Jian-ping

    2009-03-01

    Land use and land cover change has been the primary cause for the habitat loss and fragmentation in the distribution region of Amur tiger (Panthera tigris altaica). Based on the spatiotemporal changes of land use and land cover in the distribution region, as well as their effects on the population dynamics of Amur tiger, this paper analyzed the development process and its characteristics of the main land use types (agricultural land, forest land, and construction land) in this region, with the land use change history being divided chronically into three distinctive periods, i.e., ancient times (prior to 1860), modern times (1860-1949), and contemporary times (after 1949). The results showed that the sporadic land use in ancient times had no significant effects on the survival of Amur tiger, while the extensive and intensive land use after the 1860s was mainly responsible for the decrease of Amur tiger population and its living space. Since 1949, the Amur tiger distribution region has been divided into two parts, i.e., Northeast China and Russia Far East. The differences in land use pattern, policy, and intensity between these two parts led to different survival status of Amur tiger. The key driving forces for the land use change in Amur tiger distribution region were human population increase, policy change, and increased productivity. PMID:19637615

  3. Dynamism of Transportation and Land Use Interaction in Urban Context

    NASA Astrophysics Data System (ADS)

    Pandya, Rajesh J.; Katti, B. K.

    2012-10-01

    Transportation in urban areas is highly complex and the urban transport system is intricately linked with urban form and spatial structure. Urban transit is an important dimension of mobility, notably in high density areas. The spatial separation of human activities which creates the need for travel and goods transport is the underlying principle of transport analysis and forecasting. To understand the complex relationships between transportation and land use and to help the urban planning process, several models have been developed. Many theories, models are developed by different authors on land use and transportation interaction, which clearly indicate that change in land use transformation have a greater impact on transportation. Similarly, introducing new transportation facility or strengthening of existing transport facility makes an impact on the abutting land. In cities like Delhi, Navi Mumbai, Ahmedabad, introducing of new mass transport system or strengthening of existing transportation system had given greater impact on surrounding development. In this Paper the major theoretical approaches to explain the two-way interaction of land use and transport in metropolitan areas are summarized. The paper also reviews research on the two-way interaction between urban land use and transport, i.e. the location and mobility responses of private actors (households and firms, travelers) to changes in the urban land use and transport system at the urban regional level.

  4. Dynamic integration of land use changes in a hydrologic assessment of a rapidly developing Indian catchment.

    PubMed

    Wagner, Paul D; Bhallamudi, S Murty; Narasimhan, Balaji; Kantakumar, Lakshmi N; Sudheer, K P; Kumar, Shamita; Schneider, Karl; Fiener, Peter

    2016-01-01

    Rapid land use and land-cover changes strongly affect water resources. Particularly in regions that experience seasonal water scarcity, land use scenario assessments provide a valuable basis for the evaluation of possible future water shortages. The objective of this study is to dynamically integrate land use model projections with a hydrologic model to analyze potential future impacts of land use change on the water resources of a rapidly developing catchment upstream of Pune, India. For the first time projections from the urban growth and land use change model SLEUTH are employed as a dynamic input to the hydrologic model SWAT. By this means, impacts of land use changes on the water balance components are assessed for the near future (2009-2028) employing four different climate conditions (baseline, IPCC A1B, dry, wet). The land use change modeling results in an increase of urban area by +23.1% at the fringes of Pune and by +12.2% in the upper catchment, whereas agricultural land (-14.0% and -0.3%, respectively) and semi-natural area (-9.1% and -11.9%, respectively) decrease between 2009 and 2028. Under baseline climate conditions, these land use changes induce seasonal changes in the water balance components. Water yield particularly increases at the onset of monsoon (up to +11.0mm per month) due to increased impervious area, whereas evapotranspiration decreases in the dry season (up to -15.1mm per month) as a result of the loss of irrigated agricultural area. As the projections are made for the near future (2009-2028) land use change impacts are similar under IPCC A1B climate conditions. Only if more extreme dry years occur, an exacerbation of the land use change impacts can be expected. Particularly in rapidly changing environments an implementation of both dynamic land use change and climate change seems favorable to assess seasonal and gradual changes in the water balance.

  5. Carbon dynamics in the Elbe land-ocean transition zone

    NASA Astrophysics Data System (ADS)

    Amann, Thorben; Weiss, Andreas; Hartmann, Jens

    2010-05-01

    nitrate and phosphate concentrations as well as dissolved inorganic carbon. Presented analysis is used to develop a new spatial framework for quantification of carbon dynamics especially addressing sinks and sources of carbon in the land-ocean transition zone of the river Elbe. References Chen, C.-T.A. and Borges, A.V. (2009), „Reconciling opposing views on carbon cycling in the coastal ocean: Continental shelves as sinks and near-shore ecosystems as sources of atmospheric CO2', Deep-Sea Research II (56), 578-590. Cole, J. and Prairie, Y. and Caraco, N. and McDowell, W. and Tranvik, L. and Striegl, R. and Duarte, C. and Kortelainen, P. and Downing, J. and Middelburg, J. and Melack, J. (2007), "Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget", Ecosystems 10 (1), 172-185.

  6. [Dynamics of recent cultivated land in Zhejiang Province and relevant driving factors].

    PubMed

    Zhang, Hai-dong; Yu, Dong-sheng; Shi, Xue-zheng; Liu, Ying-an; Wang, Shi-hang; Zhang, Guang-xing; Liu, Yang

    2010-12-01

    Through the human-computer interactive interpretation of the 2000, 2005, and 2008 remote sensing images of Zhejiang Province with the help of RS and GIS techniques, the dynamic database of cultivated land change in the province in, 2000-2008 was established, and the driving factors of the cultivated land change were analyzed by ridge regression analysis. There was a notable cultivated land change in the province in 2000-2008. In 2000-2005 and 2005-2008, the annual cultivated land change in the province arrived -1.42% and -1.46%, respectively, and most of the cultivated land was changed into residential and industrial land. Non-agricultural population rate, real estate investment, urban green area, and orchard area were thought to be the main driving factors of the cultivated land change in Zhejiang Province, and even, in the developed areas of east China.

  7. Ultrasonic Measurement of Aircraft Strut Hydraulic Fluid Level

    NASA Technical Reports Server (NTRS)

    Allison, Sidney G.

    2002-01-01

    An ultrasonic method is presented for non-intrusively measuring hydraulic fluid level in aircraft struts in the field quickly and easily without modifying the strut or aircraft. The technique interrogates the strut with ultrasonic waves generated and received by a removable ultrasonic transducer hand-held on the outside of the strut in a fashion that is in the presence or absence of hydraulic fluid inside the strut. This technique was successfully demonstrated on an A-6 aircraft strut on the carriage at the Aircraft Landing Dynamics Research Facility at NASA Langley Research Center. Conventional practice upon detection of strut problem symptoms is to remove aircraft from service for extensive maintenance to determine fluid level. No practical technique like the method presented herein for locating strut hydraulic fluid level is currently known to be used.

  8. Verification of a landing dynamics computer program using Viking Lander data

    NASA Technical Reports Server (NTRS)

    Muraca, R. J.; King, C. A.

    1975-01-01

    An investigation was conducted to verify the accuracy of the Landing Dynamics Computer Program (LDCP) used to simulate the landing event of the Viking Lander (VL) on to the Martian surface. This verification was achieved by comparing the analytical data with results from a test program involving a dynamically scaled model of a VL configuration. A secondary objective of this study was to evaluate the sensitivity of the VL to initial rates and orientations, configuration modifications, and footpad friction.

  9. Stability boundaries for aircraft with unstable lateral-directional dynamics and control saturation

    NASA Technical Reports Server (NTRS)

    Shrivastava, Prakash C.; Stengel, Robert F.

    1989-01-01

    Aircraft that do not possess inherent (aerodynamic) stability must rely on closed-loop control systems for stable operation. Because there are limits on the deflections of an aircraft's control surfaces, the region of stable operation also is bounded. These boundaries are investigated for a lateral-directional example in which vertical fin size is inadequate to provide directional stability and where aileron and rudder deflections are subject to saturation. Fourth-order models are used in this study, with flight control logic based on minimum-control-energy linear-quadratic-regulatory theory. It is found that the stability boundaries can be described by unstable limit cycles surrounding stable equilibrium points. Variations in regions of stability with gain levels and command inputs are illustrated. Current results suggest guidelines for permissible limits on the open-loop instability of an aircraft's lateral-directional modes.

  10. A Flight Examination of Operating Problems of V/STOL Aircraft in STOL-Type Landing and Approach

    NASA Technical Reports Server (NTRS)

    Innis, Robert C.; Quigley, Hervey C.

    1961-01-01

    A flight investigation has been conducted using a large twin-engine cargo aircraft to isolate the problems associated with operating propeller-driven aircraft in the STOL speed range where appreciable engine power is used to augment aerodynamic lift. The problems considered would also be representative of those of a large overloaded VTOL aircraft operating in an STOL manner with comparable thrust-to-weight ratios. The study showed that operation at low approach speeds was compromised by the necessity of maintaining high thrust to generate high lift and yet achieving the low lift-drag ratios needed for steep descents. The useable range of airspeed and flight path angle was limited by the pilot's demand for a positive climb margin at the approach speed, a suitable stall margin, and a control and/or performance margin for one engine inoperative. The optimum approach angle over an obstacle was found to be a compromise between obtaining the shortest air distance and the lowest touchdown velocity. In order to realize the greatest low-speed potential from STOL designs, the stability and control characteristics must be satisfactory.

  11. The dynamics of the HSCT environment. [air pollution from High Speed Civil Transport Aircraft

    NASA Technical Reports Server (NTRS)

    Douglass, Anne R.; Rood, Richard B.

    1991-01-01

    Assessments of the impact of aircraft engine exhausts on stratospheric ozone levels are currently limited to 2D zonally-averaged models which, while completely representing chemistry, involve high parameterization of transport processes. Prospective 3D models under development by NASA-Goddard will use winds from a data-assimilation procedure; the upper troposphere/lower stratosphere behavior of one such model has been verified by direct comparison of model simulations with satellite, balloon, and sonde measurements. Attention is presently given to the stratosphere/troposphere exchange and nonzonal distribution of aircraft engine exhaust.

  12. Space life sciences: structure and dynamics of the global space radiation field at aircraft altitudes.

    PubMed

    2003-01-01

    This issue is devoted to research papers on the radiation environment encountered by aircraft crew members and the flying public, both of which are exposed to a higher than average radiation dose. Two types of space radiation are considered: galactic cosmic radiation and solar activity. The papers include reviews on atmospheric ionization radiation, the factors controlling this radiation, the modeling of this radiation, and measurements made on board specific aircraft flights during solar minimum and solar maximum conditions, and during the major solar proton events that occurred in 1989 and 2001.

  13. Analytical investigation of the landing dynamics of a large airplane with a load-control system in the main landing gear

    NASA Technical Reports Server (NTRS)

    Mcgehee, J. R.; Carden, H. D.

    1979-01-01

    The results of an evaluation of an active load-control landing gear computer program (ACOLAG) for predicting the landing dynamics of airplanes with passive and active main gears are presented. ACOLAG was used in an analytical investigation of the landing dynamics of a large airplane with both passive and active main gears. It was concluded that the program is valid for predicting the landing dynamics of airplanes with both passive and active main gears. It was shown that the active gear reduces airframe-gear forces and airplane motions following initial impact, and has the potential for significant reductions in structural fatigue damage relative to that which occurs with the passive gear.

  14. Simulating Spatial Pattern and Dynamics of Military Training Impacts for Allocation of Land Repair Using Images

    NASA Astrophysics Data System (ADS)

    Wang, Guangxing; Gertner, George; Anderson, Alan; Howard, Heidi

    2009-10-01

    The land management of US Army installations requires information on land conditions and their history for planning future military training activities and allocation of land repair. There is thus a strong need for methodology development to estimate the land conditions and cumulative military training impacts for the purpose of repair and restoration. In this study, we simulated at Fort Riley, USA, spatial patterns and temporal dynamics of military training impacts on land conditions quantified as percent ground cover using an image-aided spatial conditional co-simulation algorithm. Moreover, we estimated the historical percent ground cover as a measure of the cumulative impacts, and then calculated the allocation of land repair and restoration based on both current and historical land conditions. In addition, we developed a loss function method for allocation of land repair and restoration. The results showed: (1) this co-simulation algorithm reproduced spatial and temporal variability of percent ground cover and provided estimates of uncertainties with the correlation coefficients and root mean square errors between the simulated and observed values varying from 0.63 to 0.88 and from 23% to 78%, respectively; (2) with and without the cumulative impacts, the obtained spatial patterns of the land repair categories were similar, but their land areas differed by 5% to 40% in some years; (3) the combination of the loss function with the co-simulation made it possible to estimate and computationally propagate the uncertainties of land conditions into the uncertainties of expected cost loss for misallocation of land repair and restoration; and (4) the loss function, physical threshold, and probability threshold methods led to similar spatial patterns and temporal dynamics of the land repair categories, however, the loss function increased the land area by 5% to 30% for intense and moderate repairs and decreased the area by 5% to 30% for no repairs and light repairs for

  15. Simulating spatial pattern and dynamics of military training impacts for allocation of land repair using images.

    PubMed

    Wang, Guangxing; Gertner, George; Anderson, Alan; Howard, Heidi

    2009-10-01

    The land management of US Army installations requires information on land conditions and their history for planning future military training activities and allocation of land repair. There is thus a strong need for methodology development to estimate the land conditions and cumulative military training impacts for the purpose of repair and restoration. In this study, we simulated at Fort Riley, USA, spatial patterns and temporal dynamics of military training impacts on land conditions quantified as percent ground cover using an image-aided spatial conditional co-simulation algorithm. Moreover, we estimated the historical percent ground cover as a measure of the cumulative impacts, and then calculated the allocation of land repair and restoration based on both current and historical land conditions. In addition, we developed a loss function method for allocation of land repair and restoration. The results showed: (1) this co-simulation algorithm reproduced spatial and temporal variability of percent ground cover and provided estimates of uncertainties with the correlation coefficients and root mean square errors between the simulated and observed values varying from 0.63 to 0.88 and from 23% to 78%, respectively; (2) with and without the cumulative impacts, the obtained spatial patterns of the land repair categories were similar, but their land areas differed by 5% to 40% in some years; (3) the combination of the loss function with the co-simulation made it possible to estimate and computationally propagate the uncertainties of land conditions into the uncertainties of expected cost loss for misallocation of land repair and restoration; and (4) the loss function, physical threshold, and probability threshold methods led to similar spatial patterns and temporal dynamics of the land repair categories, however, the loss function increased the land area by 5% to 30% for intense and moderate repairs and decreased the area by 5% to 30% for no repairs and light repairs for

  16. Land-use dynamics in a southern Illinois (USA) watershed.

    PubMed

    Lant, C; Loftus, T; Kraft, S; Bennett, D

    2001-09-01

    The Cache River of southernmost Illinois is used as a case study for developing and demonstrating an approach to quantitatively link (1) national agricultural policy and global agricultural markets, (2) landowner's decisions on land use, (3) spatial patterns of land use at a watershed scale, and (4) hydrologic impacts, thus providing a basis to predict, under a certain set of circumstances, the environmental consequences of economic and political decisions made at larger spatial scales. The heart of the analysis is an estimation, using logistic regression, of the affect of crop prices and Conservation Reserve Program (CRP) rental rates on farmland owner's decisions whether to reenroll in the CRP or return to crop production. This analysis shows that reasonable ranges for crop prices (80%-150% of 1985-1995 values) and CRP rental rates (0-125% of 1985-1995 rates) result in a range of 3%-92% of CRP lands being returned to crop production, with crop prices having a slightly greater effect than CRP rental rates. Four crop price/CRP rental rate scenarios are used to display resulting land-use patterns, and their effect on sediment loads, a critical environmental quality parameter in this case, using the agricultural non point source (AGNPS) model. These scenarios demonstrate the importance of spatial pattern of land uses on hydrological and ecological processes within watersheds. The approach developed can be adapted for use by local governments and watershed associations whose goals are to improve watershed resources and environmental quality.

  17. Application of Time Series Landsat Images to Examining Land-use/Land-cover Dynamic Change.

    PubMed

    Lu, Dengsheng; Hetrick, Scott; Moran, Emilio; Li, Guiying

    2012-07-01

    A hierarchical-based classification method was designed to develop time series land-use/land-cover datasets from Landsat images between 1977 and 2008 in Lucas do Rio Verde, Mato Grosso, Brazil. A post-classification comparison approach was used to examine land-use/land-cover change trajectories, which emphasis is on the conversions from vegetation or agropasture to impervious surface area, from vegetation to agropasture, and from agropasture to regenerating vegetation. Results of this research indicated that increase in impervious surface area mainly resulted from the loss of cerrado in the initial decade of the study period and from loss of agricultural lands in the last two decades. Increase in agropasture was mainly at the expense of losing cerrado in the first two decades and relatively evenly from the loss of primary forest and cerrado in the last decade. When impervious surface area was less than approximately 40 km(2) before 1999, impervious surface area was negatively related to cerrado and forest, and positively related to agropasture areas, but after impervious surface area reached 40 km(2) in 1999, no obvious relationship exists between them. PMID:25328256

  18. Dynamic model and performance analysis of landing buffer for bionic locust mechanism

    NASA Astrophysics Data System (ADS)

    Chen, Dian-Sheng; Zhang, Zi-Qiang; Chen, Ke-Wei

    2016-06-01

    The landing buffer is an important problem in the research on bionic locust jumping robots, and the different modes of landing and buffering can affect the dynamic performance of the buffering process significantly. Based on an experimental observation, the different modes of landing and buffering are determined, which include the different numbers of landing legs and different motion modes of legs in the buffering process. Then a bionic locust mechanism is established, and the springs are used to replace the leg muscles to achieve a buffering effect. To reveal the dynamic performance in the buffering process of the bionic locust mechanism, a dynamic model is established with different modes of landing and buffering. In particular, to analyze the buffering process conveniently, an equivalent vibration dynamic model of the bionic locust mechanism is proposed. Given the support forces of the ground to the leg links, which can be obtained from the dynamic model, the spring forces of the legs and the impact resistance of each leg are the important parameters affecting buffering performance, and evaluation principles for buffering performance are proposed according to the aforementioned parameters. Based on the dynamic model and these evaluation principles, the buffering performances are analyzed and compared in different modes of landing and buffering on a horizontal plane and an inclined plane. The results show that the mechanism with the ends of the legs sliding can obtain a better dynamic performance. This study offers primary theories for buffering dynamics and an evaluation of landing buffer performance, and it establishes a theoretical basis for studies and engineering applications.

  19. Coupled Vortex-Lattice Flight Dynamic Model with Aeroelastic Finite-Element Model of Flexible Wing Transport Aircraft with Variable Camber Continuous Trailing Edge Flap for Drag Reduction

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan; Ting, Eric; Nguyen, Daniel; Dao, Tung; Trinh, Khanh

    2013-01-01

    This paper presents a coupled vortex-lattice flight dynamic model with an aeroelastic finite-element model to predict dynamic characteristics of a flexible wing transport aircraft. The aircraft model is based on NASA Generic Transport Model (GTM) with representative mass and stiffness properties to achieve a wing tip deflection about twice that of a conventional transport aircraft (10% versus 5%). This flexible wing transport aircraft is referred to as an Elastically Shaped Aircraft Concept (ESAC) which is equipped with a Variable Camber Continuous Trailing Edge Flap (VCCTEF) system for active wing shaping control for drag reduction. A vortex-lattice aerodynamic model of the ESAC is developed and is coupled with an aeroelastic finite-element model via an automated geometry modeler. This coupled model is used to compute static and dynamic aeroelastic solutions. The deflection information from the finite-element model and the vortex-lattice model is used to compute unsteady contributions to the aerodynamic force and moment coefficients. A coupled aeroelastic-longitudinal flight dynamic model is developed by coupling the finite-element model with the rigid-body flight dynamic model of the GTM.

  20. 36 CFR 331.14 - Aircraft.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 3 2012-07-01 2012-07-01 false Aircraft. 331.14 Section 331..., KENTUCKY AND INDIANA § 331.14 Aircraft. (a) The operation of aircraft on WCA lands and waters is prohibited... prohibited. (c) The provisions of this section shall not be applicable to aircraft engaged on...

  1. 36 CFR 331.14 - Aircraft.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 3 2013-07-01 2012-07-01 true Aircraft. 331.14 Section 331..., KENTUCKY AND INDIANA § 331.14 Aircraft. (a) The operation of aircraft on WCA lands and waters is prohibited... prohibited. (c) The provisions of this section shall not be applicable to aircraft engaged on...

  2. 36 CFR 331.14 - Aircraft.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 3 2014-07-01 2014-07-01 false Aircraft. 331.14 Section 331..., KENTUCKY AND INDIANA § 331.14 Aircraft. (a) The operation of aircraft on WCA lands and waters is prohibited... prohibited. (c) The provisions of this section shall not be applicable to aircraft engaged on...

  3. 36 CFR 331.14 - Aircraft.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 3 2011-07-01 2011-07-01 false Aircraft. 331.14 Section 331..., KENTUCKY AND INDIANA § 331.14 Aircraft. (a) The operation of aircraft on WCA lands and waters is prohibited... prohibited. (c) The provisions of this section shall not be applicable to aircraft engaged on...

  4. 36 CFR 331.14 - Aircraft.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false Aircraft. 331.14 Section 331..., KENTUCKY AND INDIANA § 331.14 Aircraft. (a) The operation of aircraft on WCA lands and waters is prohibited... prohibited. (c) The provisions of this section shall not be applicable to aircraft engaged on...

  5. Computational Fluid Dynamics (CFD) Simulations of a Humvee Airdropped from Aircraft

    NASA Astrophysics Data System (ADS)

    Reyes, Phillip M.

    Military airdrop is a means of transporting and delivering cargo to inaccessible locales faster and more efficiently. The Humvee, an all-terrain truck, is one such payload that the U.S. Army drops routinely. Here, interesting physics occurs both structurally and aerodynamically. From a fluid dynamics and trajectory standpoint, determining the aerodynamic forces and moments acting on the parachute and payload is crucial particularly for trajectory prediction. This study primarily used Computational Fluid Dynamics (CFD) to simulate the aerodynamics of an airdrop Humvee model in two regimes of fall, namely, right after clearing the aircraft ramp, and during descent under parachute. This study was performed at a Reynolds number of 3.07x10. 6 and at an airspeedof 9.144m/s (30ft/s). The first humvee part of the study analyzed the aerodynamic coefficients drag, lift, and pitching moment over a 360 degree range of pitch angles for the Humvee configured for extraction. The second set of humvee simulations focused on the aerodynamic coefficients at pitch angles of -40 degrees to +40 degrees with the platform and vehicle configured for descent under parachute. The Humvee after ramp tip-off has a parachute pack on its hood, but lacks one during the descent phase. The numerical data was compared with the results of geometries from previous studies. These geometries include: the flat plate, Type-V LVADS and 10K-JPADS containers, and a cargo-carrying platform outfitted with a bumper. Our results clearly show the effects of the many angular features that characterize the shape of a Humvee in comparison to those of a simple cuboid, particularly with regards to the loss of lift in a sub-range of pitch angle (-45 degrees to -180 degrees). First, the aerodynamic coefficients were calculated over one full-revolution of the humvee (-180 degrees to +180 degrees static pitch angles with respect to the humvee's platform) best matched in lift, drag, and moment those of the type V LVADS

  6. 43 CFR 423.41 - Aircraft.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Aircraft. 423.41 Section 423.41 Public... Aircraft. (a) You must comply with any applicable Federal, State, and local laws, and with any additional... this part 423, with respect to aircraft landings, takeoffs, and operation on or in the proximity...

  7. 43 CFR 423.41 - Aircraft.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 1 2014-10-01 2014-10-01 false Aircraft. 423.41 Section 423.41 Public... Aircraft. (a) You must comply with any applicable Federal, State, and local laws, and with any additional... this part 423, with respect to aircraft landings, takeoffs, and operation on or in the proximity...

  8. 43 CFR 423.41 - Aircraft.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 1 2013-10-01 2013-10-01 false Aircraft. 423.41 Section 423.41 Public... Aircraft. (a) You must comply with any applicable Federal, State, and local laws, and with any additional... this part 423, with respect to aircraft landings, takeoffs, and operation on or in the proximity...

  9. 43 CFR 423.41 - Aircraft.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Aircraft. 423.41 Section 423.41 Public... Aircraft. (a) You must comply with any applicable Federal, State, and local laws, and with any additional... this part 423, with respect to aircraft landings, takeoffs, and operation on or in the proximity...

  10. 43 CFR 423.41 - Aircraft.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 1 2012-10-01 2011-10-01 true Aircraft. 423.41 Section 423.41 Public... Aircraft. (a) You must comply with any applicable Federal, State, and local laws, and with any additional... this part 423, with respect to aircraft landings, takeoffs, and operation on or in the proximity...

  11. Effects of land use changes on the dynamics of selected soil properties in northeast Wellega, Ethiopia

    NASA Astrophysics Data System (ADS)

    Adugna, Alemayehu; Abegaz, Assefa

    2016-02-01

    Land use change can have negative or positive effects on soil quality. Our objective was to assess the effects of land uses changes on the dynamics of selected soil physical and chemical properties. Soil samples were collected from three adjacent soil plots under different land uses, namely forestland, grazing land, and cultivated land at 0-15 cm depth. Changes in soil properties on cultivated and grazing land were computed and compared to forestland, and ANOVA (analysis of variance) was used to test the significance of the changes. Sand and silt proportions, soil organic content, total nitrogen content, acidity, cation exchange capacity, and exchangeable Ca2+ content were higher in forestlands. Exchangeable Mg2+ was highest in grazing land, while clay, available phosphorous, and exchangeable K+ were highest in cultivated land. The percentage changes in sand, clay, soil organic matter, cation exchange capacity, and exchangeable Ca2+ and Mg2+ were higher in cultivated land than in grazing land and forestland. In terms of the relation between soil properties, soil organic matter, total nitrogen, cation exchange capacity, and exchangeable Ca2+ were strongly positively correlated with most of soil properties, while available phosphorous and silt have no significant relationship with any of the other considered soil properties. Clay has a negative correlation with all soil properties. Generally, cultivated land has the least concentration of soil physical and chemical properties except clay and available phosphorous, which suggests an increasing degradation rate in soils of cultivated land. So as to increase soil organic matter and other nutrients in the soil of cultivated land, the integrated implementation of land management through compost, cover crops, manures, minimum tillage, crop rotation, and liming to decrease soil acidity are suggested.

  12. GPS-based certification for the microwave landing system

    NASA Technical Reports Server (NTRS)

    Thornton, C. L.; Young, L. E.; Wu, S. C.; Thomas, J. B.

    1984-01-01

    An MLS (microwave landing system) certification system based on the Global Positioning System (GPS) is described. To determine the position history of the flight inspection aircraft during runway approach, signals from the GPS satellites, together with on-board radar altimetry, are used. It is shown that the aircraft position relative to a fixed point on the runway at threshold can be determined to about 30 cm vertically and 1 m horizontally. A requirement of the system is that the GPS receivers be placed on each flight inspection aircraft and at selected ground sites. The effects of different error sources on the determination of aircraft instantaneous position and its dynamics are analyzed.

  13. Analytical simulation and inversion of dynamic urban land surface effects

    NASA Astrophysics Data System (ADS)

    Bayer, P.; Rivera, J.; Blum, P.; Schweizer, D.; Rybach, L.

    2015-12-01

    Long-term thermal changes at the land surface can be backtracked from borehole temperature profiles. The main focus so far has been on past climate changes, assuming perfect coupling of surface air and ground temperature. In many urbanized areas, however, temperature profiles are heavily perturbed. We find a characteristic bending of urban profiles towards shallow depth, which indicates strong heating from the ground surface during recent decades. This phenomenon is generally described as subsurface urban heat island (UHI) effect, which exists beneath many cities worldwide. Major drivers are land use changes and urban structures that act as long-term heat sources that artificially load the top 100 m of the ground. While variability in land use and coverage are critical factors for reliable borehole climatology, temperature profiles can also be inverted to trace back the combined effect of past urbanization and climate. We present an analytical framework based on the superposition of specific Green's functions for simulating transient land use changes and their effects on borehole temperature profiles. By inversion in a Bayesian framework, flexible calibration of unknown spatially distributed parameter values and their correlation is feasible. The procedure is applied to four temperature logs which are around 200-400 m deep from the city and suburbs of Zurich, Switzerland. These were recorded recently by a temperature sensor and data logger introduced in closed borehole heat exchangers before the start of geothermal operation. At the sites, long-term land use changes are well documented for more than the last century. This facilitated focusing on a few unknown parameters, and we selected the contribution by asphalt and by basements of buildings. It is revealed that for three of the four sites, these two factors dominate the subsurface UHI evolution. At one site, additional factors such as buried district heating networks may play a role. It is demonstrated that site

  14. Creating a Test Validated Structural Dynamic Finite Element Model of the Multi-Utility Technology Test Bed Aircraft

    NASA Technical Reports Server (NTRS)

    Pak, Chan-Gi; Truong, Samson S.

    2014-01-01

    Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of Multi Utility Technology Test Bed, X-56A, aircraft is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of X-56A. The ground vibration test validated structural dynamic finite element model of the X-56A is created in this study. The structural dynamic finite element model of the X-56A is improved using a model tuning tool. In this study, two different weight configurations of the X-56A have been improved in a single optimization run.

  15. Modelling regional land change scenarios to assess land abandonment and reforestation dynamics in the Pyrenees (France)

    USGS Publications Warehouse

    Vacquie, Laure; Houet, Thomas; Sohl, Terry L.; Reker, Ryan; Sayler, Kristi L.

    2015-01-01

    Over the last decades and centuries, European mountain landscapes have experienced substantial transformations. Natural and anthropogenic LULC changes (land use and land cover changes), especially agro-pastoral activities, have directly influenced the spatial organization and composition of European mountain landscapes. For the past sixty years, natural reforestation has been occurring due to a decline in both agricultural production activities and rural population. Stakeholders, to better anticipate future changes, need spatially and temporally explicit models to identify areas at risk of land change and possible abandonment. This paper presents an integrated approach combining forecasting scenarios and a LULC changes simulation model to assess where LULC changes may occur in the Pyrenees Mountains, based on historical LULC trends and a range of future socio-economic drivers. The proposed methodology considers local specificities of the Pyrenean valleys, sub-regional climate and topographical properties, and regional economic policies. Results indicate that some regions are projected to face strong abandonment, regardless of the scenario conditions. Overall, high rates of change are associated with administrative regions where land productivity is highly dependent on socio-economic drivers and climatic and environmental conditions limit intensive (agricultural and/or pastoral) production and profitability. The combination of the results for the four scenarios allows assessments of where encroachment (e.g. colonization by shrublands) and reforestation are the most probable. This assessment intends to provide insight into the potential future development of the Pyrenees to help identify areas that are the most sensitive to change and to guide decision makers to help their management decisions.

  16. Dynamics of land use and land cover change (LULCC) using geospatial techniques: a case study of Islamabad Pakistan.

    PubMed

    Hassan, Zahra; Shabbir, Rabia; Ahmad, Sheikh Saeed; Malik, Amir Haider; Aziz, Neelam; Butt, Amna; Erum, Summra

    2016-01-01

    One of the detailed and useful ways to develop land use classification maps is use of geospatial techniques such as remote sensing and Geographic Information System (GIS). It vastly improves the selection of areas designated as agricultural, industrial and/or urban sector of a region. In Islamabad city and its surroundings, change in land use has been observed and new developments (agriculture, commercial, industrial and urban) are emerging every day. Thus, the rationale of this study was to evaluate land use/cover changes in Islamabad from 1992 to 2012. Quantification of spatial and temporal dynamics of land use/cover changes was accomplished by using two satellite images, and classifying them via supervised classification algorithm and finally applying post-classification change detection technique in GIS. The increase was observed in agricultural area, built-up area and water body from 1992 to 2012. On the other hand forest and barren area followed a declining trend. The driving force behind this change was economic development, climate change and population growth. Rapid urbanization and deforestation resulted in a wide range of environmental impacts, including degraded habitat quality. PMID:27390652

  17. Dynamics of land use and land cover change (LULCC) using geospatial techniques: a case study of Islamabad Pakistan.

    PubMed

    Hassan, Zahra; Shabbir, Rabia; Ahmad, Sheikh Saeed; Malik, Amir Haider; Aziz, Neelam; Butt, Amna; Erum, Summra

    2016-01-01

    One of the detailed and useful ways to develop land use classification maps is use of geospatial techniques such as remote sensing and Geographic Information System (GIS). It vastly improves the selection of areas designated as agricultural, industrial and/or urban sector of a region. In Islamabad city and its surroundings, change in land use has been observed and new developments (agriculture, commercial, industrial and urban) are emerging every day. Thus, the rationale of this study was to evaluate land use/cover changes in Islamabad from 1992 to 2012. Quantification of spatial and temporal dynamics of land use/cover changes was accomplished by using two satellite images, and classifying them via supervised classification algorithm and finally applying post-classification change detection technique in GIS. The increase was observed in agricultural area, built-up area and water body from 1992 to 2012. On the other hand forest and barren area followed a declining trend. The driving force behind this change was economic development, climate change and population growth. Rapid urbanization and deforestation resulted in a wide range of environmental impacts, including degraded habitat quality.

  18. Dynamic structural aeroelastic stability testing of the XV-15 tilt rotor research aircraft

    NASA Technical Reports Server (NTRS)

    Schroers, L. G.

    1982-01-01

    For the past 20 years, a significant effort has been made to understand and predict the structural aeroelastic stability characteristics of the tilt rotor concept. Beginning with the rotor-pylon oscillation of the XV-3 aircraft, the problem was identified and then subjected to a series of theoretical studies, plus model and full-scale wind tunnel tests. From this data base, methods were developed to predict the structural aeroelastic stability characteristics of the XV-15 Tilt Rotor Research Aircraft. The predicted aeroelastic characteristics are examined in light of the major parameters effecting rotor-pylon-wing stability. Flight test techniques used to obtain XV-15 aeroelastic stability are described. Flight test results are summarized and compared to the predicted values. Wind tunnel results are compared to flight test results and correlated with predicted values.

  19. A land data assimilation system for simultaneous simulation of soil moisture and vegetation dynamics

    NASA Astrophysics Data System (ADS)

    Sawada, Yohei; Koike, Toshio; Walker, Jeffrey P.

    2015-06-01

    Despite the importance of the coupling between vegetation dynamics and root-zone soil moisture in land-atmosphere interactions, there is no land data assimilation system (LDAS) that currently addresses this issue, limiting the capacity to positively impact weather and seasonal forecasting. We develop a new LDAS that can improve the skill of an ecohydrological model to simulate simultaneously surface soil moisture, root-zone soil moisture, and vegetation dynamics by assimilating passive microwave observations that are sensitive to both surface soil moisture and terrestrial biomass. This LDAS first calibrates both hydrological and ecological parameters of a land surface model, which explicitly simulates vegetation growth and senescence. Then, it adjusts the model states of soil moisture and leaf area index (LAI) sequentially using a genetic particle filter. We can adjust the subsurface soil moisture, which is not observed directly by satellites, because we simulate the interactions between vegetation dynamics and subsurface water dynamics. From a point-scale evaluation, we succeed in improving the performance of our land surface model and generate ensembles of the model state whose distribution reflects the combined information in the land surface model and satellite observations. We show that the adjustment of the subsurface soil moisture significantly improves the capacity to simulate vegetation dynamics in seasonal forecast timescales. This LDAS can contribute to the generation of ensemble initial conditions of surface and subsurface soil moisture and LAI for a probabilistic framework of weather and seasonal forecasting.

  20. Land cover dynamics and accounts for European Union 2001-2011

    NASA Astrophysics Data System (ADS)

    Grekousis, George; Kavouras, Marinos; Mountrakis, Giorgos

    2015-06-01

    Land cover dynamics information plays an important role in environmental research and related studies. We use the 500m NASA MODIS land cover dataset for the European Union (EU28) to calculate (a) land cover share trends on an annual temporal increment from 2001 to 2011 and (b) land cover accounts from 2001 to 2011. Raster products are firstly mosaicked to produce a single image per year, covering the study area. Reclassification for each final annual product follows to convert the original 17 IGBP MODIS classes into 7 simpler classes of broader interest. Zonal statistics are used to calculate the number of land cover pixels per class, per country, per year. Further calculations create land account tables revealing land cover trends during 2001 through 2011. Results show that for the 2001 through 2011 period forests and cropland dominated EU28, covering almost 70% of the total area. Forest has an increasing trend, with an annual change rate of 0,60%, while cropland has a negative rate of annual change (-0, 46%). On average, grassland covers approximately 21% of EU28. A closer look reveals that despite the relatively stable overall counts, grassland has experienced high turnover. Almost half (40%) of grassland original stock changed to other land cover classes during 2001 through 2011. At the same time, there was a large conversion to grassland from other land cover classes thus keeping a balance in the overall share. Our analysis provides useful information for environmental assessments in order to better frame policies for a sustainable future.

  1. Dynamic Aberration Correction for Conformal Window of High-Speed Aircraft Using Optimized Model-Based Wavefront Sensorless Adaptive Optics.

    PubMed

    Dong, Bing; Li, Yan; Han, Xin-Li; Hu, Bin

    2016-09-02

    For high-speed aircraft, a conformal window is used to optimize the aerodynamic performance. However, the local shape of the conformal window leads to large amounts of dynamic aberrations varying with look angle. In this paper, deformable mirror (DM) and model-based wavefront sensorless adaptive optics (WSLAO) are used for dynamic aberration correction of an infrared remote sensor equipped with a conformal window and scanning mirror. In model-based WSLAO, aberration is captured using Lukosz mode, and we use the low spatial frequency content of the image spectral density as the metric function. Simulations show that aberrations induced by the conformal window are dominated by some low-order Lukosz modes. To optimize the dynamic correction, we can only correct dominant Lukosz modes and the image size can be minimized to reduce the time required to compute the metric function. In our experiment, a 37-channel DM is used to mimic the dynamic aberration of conformal window with scanning rate of 10 degrees per second. A 52-channel DM is used for correction. For a 128 × 128 image, the mean value of image sharpness during dynamic correction is 1.436 × 10(-5) in optimized correction and is 1.427 × 10(-5) in un-optimized correction. We also demonstrated that model-based WSLAO can achieve convergence two times faster than traditional stochastic parallel gradient descent (SPGD) method.

  2. Dynamic Aberration Correction for Conformal Window of High-Speed Aircraft Using Optimized Model-Based Wavefront Sensorless Adaptive Optics.

    PubMed

    Dong, Bing; Li, Yan; Han, Xin-Li; Hu, Bin

    2016-01-01

    For high-speed aircraft, a conformal window is used to optimize the aerodynamic performance. However, the local shape of the conformal window leads to large amounts of dynamic aberrations varying with look angle. In this paper, deformable mirror (DM) and model-based wavefront sensorless adaptive optics (WSLAO) are used for dynamic aberration correction of an infrared remote sensor equipped with a conformal window and scanning mirror. In model-based WSLAO, aberration is captured using Lukosz mode, and we use the low spatial frequency content of the image spectral density as the metric function. Simulations show that aberrations induced by the conformal window are dominated by some low-order Lukosz modes. To optimize the dynamic correction, we can only correct dominant Lukosz modes and the image size can be minimized to reduce the time required to compute the metric function. In our experiment, a 37-channel DM is used to mimic the dynamic aberration of conformal window with scanning rate of 10 degrees per second. A 52-channel DM is used for correction. For a 128 × 128 image, the mean value of image sharpness during dynamic correction is 1.436 × 10(-5) in optimized correction and is 1.427 × 10(-5) in un-optimized correction. We also demonstrated that model-based WSLAO can achieve convergence two times faster than traditional stochastic parallel gradient descent (SPGD) method. PMID:27598161

  3. Dynamic Aberration Correction for Conformal Window of High-Speed Aircraft Using Optimized Model-Based Wavefront Sensorless Adaptive Optics

    PubMed Central

    Dong, Bing; Li, Yan; Han, Xin-li; Hu, Bin

    2016-01-01

    For high-speed aircraft, a conformal window is used to optimize the aerodynamic performance. However, the local shape of the conformal window leads to large amounts of dynamic aberrations varying with look angle. In this paper, deformable mirror (DM) and model-based wavefront sensorless adaptive optics (WSLAO) are used for dynamic aberration correction of an infrared remote sensor equipped with a conformal window and scanning mirror. In model-based WSLAO, aberration is captured using Lukosz mode, and we use the low spatial frequency content of the image spectral density as the metric function. Simulations show that aberrations induced by the conformal window are dominated by some low-order Lukosz modes. To optimize the dynamic correction, we can only correct dominant Lukosz modes and the image size can be minimized to reduce the time required to compute the metric function. In our experiment, a 37-channel DM is used to mimic the dynamic aberration of conformal window with scanning rate of 10 degrees per second. A 52-channel DM is used for correction. For a 128 × 128 image, the mean value of image sharpness during dynamic correction is 1.436 × 10−5 in optimized correction and is 1.427 × 10−5 in un-optimized correction. We also demonstrated that model-based WSLAO can achieve convergence two times faster than traditional stochastic parallel gradient descent (SPGD) method. PMID:27598161

  4. Urbanization suitability maps: a dynamic spatial decision support system for sustainable land use

    NASA Astrophysics Data System (ADS)

    Cerreta, M.; De Toro, P.

    2012-11-01

    Recent developments in land consumption assessment identify the need to implement integrated evaluation approaches, with particular attention to the development of multidimensional tools for guiding and managing sustainable land use. Land use policy decisions are implemented mostly through spatial planning and its related zoning. This involves trade-offs between many sectorial interests and conflicting challenges seeking win-win solutions. In order to identify a decision-making process for land use allocation, this paper proposes a methodological approach for developing a Dynamic Spatial Decision Support System (DSDSS), denominated Integrated Spatial Assessment (ISA), supported by Geographical Information Systems (GIS) combined with the Analytic Hierarchy Process (AHP). Through empirical investigation in an operative case study, an integrated evaluation approach implemented in a DSDSS helps produce "urbanization suitability maps" in which spatial analysis combined with multi-criteria evaluation methods proved to be useful for both facing the main issues relating to land consumption as well as minimizing environmental impacts of spatial planning.

  5. Coordination control of quadrotor VTOL aircraft in three-dimensional space

    NASA Astrophysics Data System (ADS)

    Do, K. D.

    2015-03-01

    This paper presents a constructive design of distributed coordination controllers for a group of N quadrotor vertical take-off and landing (VTOL) aircraft in three-dimensional space. A combination of Euler angles and unit-quaternion for the attitude representation of the aircraft is used to result in an effective control design, and to reduce singularities in the aircraft's dynamics. The coordination control design is based on a new bounded control design technique for second-order systems and new pairwise collision avoidance functions. The pairwise collision functions are functions of both relative positions and relative velocities between the aircraft instead of only their relative positions as in the literature. To overcome the inherent underactuation of the aircraft, the roll and pitch angles of the aircraft are considered as immediate controls. Simulations illustrate the results.

  6. 19 CFR 122.36 - Responsibility of aircraft commander.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Responsibility of aircraft commander. 122.36...; DEPARTMENT OF THE TREASURY AIR COMMERCE REGULATIONS Landing Requirements § 122.36 Responsibility of aircraft commander. If an aircraft lands in the U.S. and Customs officers have not arrived, the aircraft...

  7. 19 CFR 122.36 - Responsibility of aircraft commander.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Responsibility of aircraft commander. 122.36...; DEPARTMENT OF THE TREASURY AIR COMMERCE REGULATIONS Landing Requirements § 122.36 Responsibility of aircraft commander. If an aircraft lands in the U.S. and Customs officers have not arrived, the aircraft...

  8. 19 CFR 122.36 - Responsibility of aircraft commander.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Responsibility of aircraft commander. 122.36...; DEPARTMENT OF THE TREASURY AIR COMMERCE REGULATIONS Landing Requirements § 122.36 Responsibility of aircraft commander. If an aircraft lands in the U.S. and Customs officers have not arrived, the aircraft...

  9. 19 CFR 122.36 - Responsibility of aircraft commander.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 1 2014-04-01 2014-04-01 false Responsibility of aircraft commander. 122.36...; DEPARTMENT OF THE TREASURY AIR COMMERCE REGULATIONS Landing Requirements § 122.36 Responsibility of aircraft commander. If an aircraft lands in the U.S. and Customs officers have not arrived, the aircraft...

  10. 19 CFR 122.36 - Responsibility of aircraft commander.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 1 2013-04-01 2013-04-01 false Responsibility of aircraft commander. 122.36...; DEPARTMENT OF THE TREASURY AIR COMMERCE REGULATIONS Landing Requirements § 122.36 Responsibility of aircraft commander. If an aircraft lands in the U.S. and Customs officers have not arrived, the aircraft...

  11. Development of automatic and manual flight director landing systems for the XV-15 tilt rotor aircraft in helicopter mode

    NASA Technical Reports Server (NTRS)

    Hofmann, L. G.; Hoh, R. H.; Jewell, W. F.; Teper, G. L.; Patel, P. D.

    1978-01-01

    The objective of this effort is to determine IFR approach path and touchdown dispersions for manual and automatic XV-15 tilt rotor landings, and to develop missed approach criteria. Only helicopter mode XV-15 operation is considered. The analysis and design sections develop the automatic and flight director guidance equations for decelerating curved and straight-in approaches into a typical VTOL landing site equipped with an MLS navigation aid. These system designs satisfy all known pilot-centered, guidance and control requirements for this flying task. Performance data, obtained from nonstationary covariance propagation dispersion analysis for the system, are used to develop the approach monitoring criteria. The autoland and flight director guidance equations are programmed for the VSTOLAND 1819B digital computer. The system design dispersion data developed through analysis and the 1819B digital computer program are verified and refined using the fixed-base, man-in-the-loop XV-15 VSTOLAND simulation.

  12. System identification methods for aircraft flight control development and validation

    NASA Technical Reports Server (NTRS)

    Tischler, Mark B.

    1995-01-01

    System-identification methods compose a mathematical model, or series of models, from measurements of inputs and outputs of dynamic systems. The extracted models allow the characterization of the response of the overall aircraft or component subsystem behavior, such as actuators and on-board signal processing algorithms. This paper discusses the use of frequency-domain system-identification methods for the development and integration of aircraft flight-control systems. The extraction and analysis of models of varying complexity from nonparametric frequency-responses to transfer-functions and high-order state-space representations is illustrated using the Comprehensive Identification from FrEquency Responses (CIFER) system-identification facility. Results are presented for test data of numerous flight and simulation programs at the Ames Research Center including rotorcraft, fixed-wing aircraft, advanced short takeoff and vertical landing (ASTOVL), vertical/short takeoff and landing (V/STOL), tiltrotor aircraft, and rotor experiments in the wind tunnel. Excellent system characterization and dynamic response prediction is achieved for this wide class of systems. Examples illustrate the role of system-identification technology in providing an integrated flow of dynamic response data around the entire life-cycle of aircraft development from initial specifications, through simulation and bench testing, and into flight-test optimization.

  13. Braking performance of aircraft tires

    NASA Astrophysics Data System (ADS)

    Agrawal, Satish K.

    This paper brings under one cover the subject of aircraft braking performance and a variety of related phenomena that lead to aircraft hydroplaning, overruns, and loss of directional control. Complex processes involving tire deformation, tire slipping, and fluid pressures in the tire-runway contact area develop the friction forces for retarding the aircraft; this paper describes the physics of these processes. The paper reviews the past and present research efforts and concludes that the most effective way to combat the hazards associated with aircraft landings and takeoffs on contaminated runways is by measuring and displaying in realtime the braking performance parameters in the aircraft cockpit.

  14. 14 CFR 23.562 - Emergency landing dynamic conditions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... CFR Part 572, Subpart B, or an FAA-approved equivalent, with a nominal weight of 170 pounds and seated... on the ATD's pelvis during the impact. (5) The results of the dynamic tests must show that the... total strap loads may not exceed 2,000 pounds. (7) The compression load measured between the pelvis...

  15. 14 CFR 23.562 - Emergency landing dynamic conditions.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... CFR Part 572, Subpart B, or an FAA-approved equivalent, with a nominal weight of 170 pounds and seated... on the ATD's pelvis during the impact. (5) The results of the dynamic tests must show that the... total strap loads may not exceed 2,000 pounds. (7) The compression load measured between the pelvis...

  16. 14 CFR 23.562 - Emergency landing dynamic conditions.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... conducted with an occupant simulated by an anthropomorphic test dummy (ATD) defined by 49 CFR part 572... on the ATD's pelvis during the impact. (5) The results of the dynamic tests must show that the... between the pelvis and the lumbar spine of the ATD may not exceed 1,500 pounds. (d) For all...

  17. 14 CFR 23.562 - Emergency landing dynamic conditions.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... conducted with an occupant simulated by an anthropomorphic test dummy (ATD) defined by 49 CFR part 572... on the ATD's pelvis during the impact. (5) The results of the dynamic tests must show that the... between the pelvis and the lumbar spine of the ATD may not exceed 1,500 pounds. (d) For all...

  18. Perspective Imagery in Synthetic Scenes used to Control and Guide Aircraft during Landing and Taxi: Some Issues and Concerns

    NASA Technical Reports Server (NTRS)

    Johnson, Walter W.; Kaiser, Mary K.

    2003-01-01

    Perspective synthetic displays that supplement, or supplant, the optical windows traditionally used for guidance and control of aircraft are accompanied by potentially significant human factors problems related to the optical geometric conformality of the display. Such geometric conformality is broken when optical features are not in the location they would be if directly viewed through a window. This often occurs when the scene is relayed or generated from a location different from the pilot s eyepoint. However, assuming no large visual/vestibular effects, a pilot cad often learn to use such a display very effectively. Important problems may arise, however, when display accuracy or consistency is compromised, and this can usually be related to geometrical discrepancies between how the synthetic visual scene behaves and how the visual scene through a window behaves. In addition to these issues, this paper examines the potentially critical problem of the disorientation that can arise when both a synthetic display and a real window are present in a flight deck, and no consistent visual interpretation is available.

  19. OVRhyp, Scramjet Test Aircraft

    NASA Technical Reports Server (NTRS)

    Aslan, J.; Bisard, T.; Dallinga, S.; Draper, K.; Hufford, G.; Peters, W.; Rogers, J.

    1990-01-01

    A preliminary design for an unmanned hypersonic research vehicle to test scramjet engines is presented. The aircraft will be launched from a carrier aircraft at an altitude of 40,000 feet at Mach 0.8. The vehicle will then accelerate to Mach 6 at an altitude of 100,000 feet. At this stage the prototype scramjet will be employed to accelerate the vehicle to Mach 10 and maintain Mach 10 flight for 2 minutes. The aircraft will then decelerate and safely land.

  20. Machine processing of S-192 and supporting aircraft data: Studies of atmospheric effects, agricultural classifications, and land resource mapping

    NASA Technical Reports Server (NTRS)

    Thomson, F.

    1975-01-01

    Two tasks of machine processing of S-192 multispectral scanner data are reviewed. In the first task, the effects of changing atmospheric and base altitude on the ability to machine-classify agricultural crops were investigated. A classifier and atmospheric effects simulation model was devised and its accuracy verified by comparison of its predicted results with S-192 processed results. In the second task, land resource maps of a mountainous area near Cripple Creek, Colorado were prepared from S-192 data collected on 4 August 1973.

  1. A flight-test and simulation evaluation of the longitudinal final approach and landing performance of an automatic system for a light wing loading STOL aircraft equipped with wing spoilers

    NASA Technical Reports Server (NTRS)

    Brown, S. C.; Hardy, G. H.; Hindson, W. S.

    1984-01-01

    As part of a comprehensive flight-test investigation of short takeoff and landing (STOL) operating systems for the terminal systems for the terminal area, an automatic landing system has been developed and evaluated for a light wing-loading turboprop-powered aircraft. An advanced digital avionics system performed display, navigation, guidance, and control functions for the test aircraft. Control signals were generated in order to command powered actuators for all conventional controls and for a set of symmetrically driven wing spoilers. This report describes effects of the spoiler control on longitudinal autoland (automatic landing) performance. Flight-test results, with and without spoiler control, are presented and compared with available (basically, conventional takeoff and landing) performance criteria. These comparisons are augmented by results from a comprehensive simulation of the controlled aircraft that included representations of the microwave landing system navigation errors that were encountered in flight as well as expected variations in atmospheric turbulence and wind shear. Flight-test results show that the addition of spoiler control improves the touchdown performance of the automatic landing system. Spoilers improve longitudinal touchdown and landing pitch-attitude performance, particularly in tailwind conditions. Furthermore, simulation results indicate that performance would probably be satisfactory for a wider range of atmospheric disturbances than those encountered in flight. Flight results also indicate that the addition of spoiler control during the final approach does not result in any measurable change in glidepath track performance, and results in a very small deterioration in airspeed tracking. This difference contrasts with simulations results, which indicate some improvement in glidepath tracking and no appreciable change in airspeed tracking. The modeling problem in the simulation that contributed to this discrepancy with flight was

  2. Land-Use Change and Earth System Dynamics: Advancing the Science

    NASA Astrophysics Data System (ADS)

    Hurtt, George

    2010-05-01

    Quantifying the effects of land-use changes on Earth system dynamics requires adequate information on both past and future land-use activities in a format appropriate for models capable of tracking relevant impacts. This presentation will review past approaches to understanding the role of land-use change on the Earth system dynamics, and summarize new work involving ‘land-use harmonization' (Hurtt et al. 2009) to advance the understanding for IPCC-AR5 and beyond. Emphasis will be placed on the importance and accuracy of historical maps, uncertainties in future projections, and key challenges for the future. Hurtt, G. C., L. P. Chini, S. Frolking, R. Betts, J. Feedema, G. Fischer, K. Klein Goldewijk, K. Hibbard, A. Janetos, C. Jones, G. Kindermann, T. Kinoshita, K. Riahi, E. Shevliakova, S. Smith, E. Stehfest, A. Thomson, P. Thorton, D. van Vuuren, Y. Wang (2009), Harmonization of Global Land-Use Scenarios for the Period 1500-2100 for IPCC-AR5. Integrated Land Ecosystem-Atmosphere Processes Study (iLEAPS) Newsletter 7:6-8.

  3. Vegetation dynamics, and land use and land cover change in the Bale Mountains, Ethiopia.

    PubMed

    Kidane, Yohannes; Stahlmann, Reinhold; Beierkuhnlein, Carl

    2012-12-01

    Shifts in biological communities are occurring at rapid rates as human activities induced global climate change increases. Understanding the effects of the change on biodiversity is important to reduce loss of biodiversity and mass extinction, and to insure the long-term persistence of natural resources and natures' services. Especially in remote landscapes of developing countries, precise knowledge about on-going processes is scarce. Here we apply satellite imagery to assess spatio-temporal land use and land cover change (LULCC) in the Bale Mountains for a period of four decades. This study aims to identify the main drivers of change in vegetation patterns and to discuss the implications of LULCC on spatial arrangements and trajectories of floral communities. Remote sensing data acquired from Landsat MSS, Landsat ETM + and SPOT for four time steps (1973, 1987, 2000, and 2008) were analyzed using 11 LULC units defined based on the dominant plant taxa and cover types of the habitat. Change detection matrices revealed that over the last 40 years, the area has changed from a quite natural to a more cultural landscape. Within a representative subset of the study area (7,957.5 km(-2)), agricultural fields have increased from 1.71% to 9.34% of the total study area since 1973. Natural habitats such as upper montane forest, afroalpine grasslands, afromontane dwarf shrubs and herbaceous formations, and water bodies also increased. Conversely, afromontane grasslands have decreased in size by more than half (going from 19.3% to 8.77%). Closed Erica forest also shrank from 15.0% to 12.37%, and isolated Erica shrubs have decreased from 6.86% to 5.55%, and afroalpine dwarf shrubs and herbaceous formations reduced from 5.2% to 1.56%. Despite fluctuations the afromontane rainforest (Harenna forest), located south of the Bale Mountains, has remained relatively stable. In conclusion this study documents a rapid and ecosystem-specific change of this biodiversity hotspot due to

  4. Vegetation dynamics, and land use and land cover change in the Bale Mountains, Ethiopia.

    PubMed

    Kidane, Yohannes; Stahlmann, Reinhold; Beierkuhnlein, Carl

    2012-12-01

    Shifts in biological communities are occurring at rapid rates as human activities induced global climate change increases. Understanding the effects of the change on biodiversity is important to reduce loss of biodiversity and mass extinction, and to insure the long-term persistence of natural resources and natures' services. Especially in remote landscapes of developing countries, precise knowledge about on-going processes is scarce. Here we apply satellite imagery to assess spatio-temporal land use and land cover change (LULCC) in the Bale Mountains for a period of four decades. This study aims to identify the main drivers of change in vegetation patterns and to discuss the implications of LULCC on spatial arrangements and trajectories of floral communities. Remote sensing data acquired from Landsat MSS, Landsat ETM + and SPOT for four time steps (1973, 1987, 2000, and 2008) were analyzed using 11 LULC units defined based on the dominant plant taxa and cover types of the habitat. Change detection matrices revealed that over the last 40 years, the area has changed from a quite natural to a more cultural landscape. Within a representative subset of the study area (7,957.5 km(-2)), agricultural fields have increased from 1.71% to 9.34% of the total study area since 1973. Natural habitats such as upper montane forest, afroalpine grasslands, afromontane dwarf shrubs and herbaceous formations, and water bodies also increased. Conversely, afromontane grasslands have decreased in size by more than half (going from 19.3% to 8.77%). Closed Erica forest also shrank from 15.0% to 12.37%, and isolated Erica shrubs have decreased from 6.86% to 5.55%, and afroalpine dwarf shrubs and herbaceous formations reduced from 5.2% to 1.56%. Despite fluctuations the afromontane rainforest (Harenna forest), located south of the Bale Mountains, has remained relatively stable. In conclusion this study documents a rapid and ecosystem-specific change of this biodiversity hotspot due to

  5. Application of numerical optimization techniques to control system design for nonlinear dynamic models of aircraft

    NASA Technical Reports Server (NTRS)

    Lan, C. Edward; Ge, Fuying

    1989-01-01

    Control system design for general nonlinear flight dynamic models is considered through numerical simulation. The design is accomplished through a numerical optimizer coupled with analysis of flight dynamic equations. The general flight dynamic equations are numerically integrated and dynamic characteristics are then identified from the dynamic response. The design variables are determined iteratively by the optimizer to optimize a prescribed objective function which is related to desired dynamic characteristics. Generality of the method allows nonlinear effects to aerodynamics and dynamic coupling to be considered in the design process. To demonstrate the method, nonlinear simulation models for an F-5A and an F-16 configurations are used to design dampers to satisfy specifications on flying qualities and control systems to prevent departure. The results indicate that the present method is simple in formulation and effective in satisfying the design objectives.

  6. Soil analyses and evaluations at the impact dynamics research facility for two full-scale aircraft crash tests

    NASA Technical Reports Server (NTRS)

    Cheng, R. Y. K.

    1977-01-01

    The aircraft structural crash behavior and occupant survivability for aircraft crashes on a soil surface was studied. The results of placement, compaction, and maintenance of two soil test beds are presented. The crators formed by the aircraft after each test are described.

  7. A multiscale, hierarchical model of pulse dynamics in arid-land ecosystems

    USGS Publications Warehouse

    Collins, Scott L.; Belnap, Jayne; Grimm, N. B.; Rudgers, J. A.; Dahm, Clifford N.; D'Odorico, P.; Litvak, M.; Natvig, D. O.; Peters, Douglas C.; Pockman, W. T.; Sinsabaugh, R. L.; Wolf, B. O.

    2014-01-01

    Ecological processes in arid lands are often described by the pulse-reserve paradigm, in which rain events drive biological activity until moisture is depleted, leaving a reserve. This paradigm is frequently applied to processes stimulated by one or a few precipitation events within a growing season. Here we expand the original framework in time and space and include other pulses that interact with rainfall. This new hierarchical pulse-dynamics framework integrates space and time through pulse-driven exchanges, interactions, transitions, and transfers that occur across individual to multiple pulses extending from micro to watershed scales. Climate change will likely alter the size, frequency, and intensity of precipitation pulses in the future, and arid-land ecosystems are known to be highly sensitive to climate variability. Thus, a more comprehensive understanding of arid-land pulse dynamics is needed to determine how these ecosystems will respond to, and be shaped by, increased climate variability.

  8. Linking land cover dynamics with driving forces in mountain landscape of the Northwestern Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Regos, Adrián; Ninyerola, Miquel; Moré, Gerard; Pons, Xavier

    2015-06-01

    The mountainous areas of the northwestern Iberian Peninsula have undergone intense land abandonment. In this work, we wanted to determine if the abandonment of the rural areas was the main driver of landscape dynamics in Gerês-Xurés Transboundary Biosphere Reserve (NW Iberian Peninsula), or if other factors, such as wildfires and the land management were also directly affecting these spatio-temporal dynamics. For this purpose, we used earth observation data acquired from Landsat TM and ETM + satellite sensors, complemented by ancillary data and prior field knowledge, to evaluate the land use/land cover changes in our study region over a 10-year period (2000-2010). The images were radiometrically calibrated using a digital elevation model to avoid cast- and self-shadows and different illumination effects caused by the intense topographic variations in the study area. We applied a maximum likelihood classifier, as well as other five approaches that provided insights into the comparison of thematic maps. To describe the land cover changes we addressed the analysis from a multilevel approach in three areas with different regimes of environmental protection. The possible impact of wildfires was assessed from statistical and spatially explicit fire data. Our findings suggest that land abandonment and forestry activities are the main factors causing the changes in landscape patterns. Specifically, we found a strong decrease of the 'meadows and crops' and 'sparse vegetation areas' in favor of woodlands and scrublands. In addition, the huge impact of wildfires on the Portuguese side have generated new 'rocky areas', while on the Spanish side its impact does not seem to have been a decisive factor on the landscape dynamics in recent years. We conclude rural exodus of the last century, differences in land management and fire suppression policies between the two countries and the different protection schemes could partly explain the different patterns of changes recorded in

  9. Effects of anthropogenic land-subsidence on inundation dynamics: the case study of Ravenna, Italy

    NASA Astrophysics Data System (ADS)

    Carisi, Francesca; Domeneghetti, Alessio; Castellarin, Attilio

    2016-05-01

    Can differential land-subsidence significantly alter river flooding dynamics, and thus flood risk in flood prone areas? Many studies show how the lowering of the coastal areas is closely related to an increase in the flood-hazard due to more important tidal flooding and see level rise. The literature on the relationship between differential land-subsidence and possible alterations to riverine flood-hazard of inland areas is still sparse, although several geographical areas characterized by significant land-subsidence rates during the last 50 years experienced intensification in both inundation magnitude and frequency. We investigate the possible impact of a significant differential ground lowering on flood hazard over a 77 km2 area around the city of Ravenna, in Italy. The rate of land-subsidence in the study area, naturally in the order of a few mm year-1, dramatically increased up to 110 mm year-1 after World War II, primarily due to groundwater pumping and gas production platforms. The result was a cumulative drop that locally exceeds 1.5 m. Using a recent digital elevation model (res. 5 m) and literature data on land-subsidence, we constructed a ground elevation model over the study area in 1897 and we characterized either the current and the historical DEM with or without road embankments and land-reclamation channels in their current configuration. We then considered these four different topographic models and a two-dimensional hydrodynamic model to simulate and compare the inundation dynamics associated with a levee failure scenario along embankment system of the river Montone, which flows eastward in the southern portion of the study area. For each topographic model, we quantified the flood hazard in terms of maximum water depth (h) and we compared the actual effects on flood-hazard dynamics of differential land-subsidence relative to those associated with other man-made topographic alterations, which resulted to be much more significant.

  10. Effects of Aircraft Wake Dynamics on Measured and Simulated NO(x) and HO(x) Wake Chemistry. Appendix B

    NASA Technical Reports Server (NTRS)

    Lewellen, D. C.; Lewellen, W. S.

    2001-01-01

    High-resolution numerical large-eddy simulations of the near wake of a B757 including simplified NOx and HOx chemistry were performed to explore the effects of dynamics on chemistry in wakes of ages from a few seconds to several minutes. Dilution plays an important basic role in the NOx-O3 chemistry in the wake, while a more interesting interaction between the chemistry and dynamics occurs for the HOx species. These simulation results are compared with published measurements of OH and HO2 within a B757 wake under cruise conditions in the upper troposphere taken during the Subsonic Aircraft Contrail and Cloud Effects Special Study (SUCCESS) mission in May 1996. The simulation provides a much finer grained representation of the chemistry and dynamics of the early wake than is possible from the 1 s data samples taken in situ. The comparison suggests that the previously reported discrepancy of up to a factor of 20 - 50 between the SUCCESS measurements of the [HO2]/[OH] ratio and that predicted by simplified theoretical computations is due to the combined effects of large mixing rates around the wake plume edges and averaging over volumes containing large species fluctuations. The results demonstrate the feasibility of using three-dimensional unsteady large-eddy simulations with coupled chemistry to study such phenomena.

  11. THE INFLUENCE OF CATCHMENT LAND USE ON HYDROGRAPH DYNAMICS AND IMPLICATIONS FOR STREAM BIOLOGICAL ASSEMBLAGES

    EPA Science Inventory

    Catchment land use impacts the rise and fall dynamic of hydrographs, and may also help explain variation in biological assemblages known to be sensitive to flow regime. We collected continuous stream depth records for the 2002 water year (5 min. intervals) from eight streams dra...

  12. Using System Dynamics Analysis for Evaluating Neighborhood Economic Outcomes from Transportation and Land Use Decisions

    EPA Science Inventory

    Proposed Title: Using System Dynamics Analysis for Evaluating Neighborhood Economic Outcomes from Transportation and Land Use Decisions Topic (must choose one item from a drop-down list): Community Indicators Learning Objectives (must list 2): • What are the benefits and l...

  13. Study on the Similarity Criteria of Aircraft Structure Temperature/Stress/Dynamic Response

    NASA Astrophysics Data System (ADS)

    Liu, Lei; Gui, Ye-Wei; Du, Yan-Xia; Geng, Xiang-Ren; Wang, An-Ling

    The performance parameters of thermal protection system are essential for the design and optimization of high-speed aircraft. The flight-ground conversion is a valid method to provide the effective support to the design of the thermal protection structure (TPS), because the performance data of TPS were generally obtained from wind tunnel test and should be conversed to the corresponding environment. In this paper, the similarity parameters of heat conduction and thermoelasticity equations are studied, the similarity criteria proposed, and the effectiveness of some of the similar parameters are calculated and analyzed. The research results indicated that wind tunnel test can be better designed using the proposed similarity criteria, and the data obtained from wind tunnel test can be modified more rational to accommodate the reality flight condition so as to improve the precision and the efficiency of wind tunnel experiment.

  14. Integrated Aerodynamic/Structural/Dynamic Analyses of Aircraft with Large Shape Changes

    NASA Technical Reports Server (NTRS)

    Samareh, Jamshid A.; Chwalowski, Pawel; Horta, Lucas G.; Piatak, David J.; McGowan, Anna-Maria R.

    2007-01-01

    The conceptual and preliminary design processes for aircraft with large shape changes are generally difficult and time-consuming, and the processes are often customized for a specific shape change concept to streamline the vehicle design effort. Accordingly, several existing reports show excellent results of assessing a particular shape change concept or perturbations of a concept. The goal of the current effort was to develop a multidisciplinary analysis tool and process that would enable an aircraft designer to assess several very different morphing concepts early in the design phase and yet obtain second-order performance results so that design decisions can be made with better confidence. The approach uses an efficient parametric model formulation that allows automatic model generation for systems undergoing radical shape changes as a function of aerodynamic parameters, geometry parameters, and shape change parameters. In contrast to other more self-contained approaches, the approach utilizes off-the-shelf analysis modules to reduce development time and to make it accessible to many users. Because the analysis is loosely coupled, discipline modules like a multibody code can be easily swapped for other modules with similar capabilities. One of the advantages of this loosely coupled system is the ability to use the medium-to high-fidelity tools early in the design stages when the information can significantly influence and improve overall vehicle design. Data transfer among the analysis modules are based on an accurate and automated general purpose data transfer tool. In general, setup time for the integrated system presented in this paper is 2-4 days for simple shape change concepts and 1-2 weeks for more mechanically complicated concepts. Some of the key elements briefly described in the paper include parametric model development, aerodynamic database generation, multibody analysis, and the required software modules as well as examples for a telescoping wing, a

  15. Statistical evaluation of control inputs and eye movements in the use of instruments clusters during aircraft landing

    NASA Technical Reports Server (NTRS)

    Dick, A. O.; Brown, J. L.; Bailey, G.

    1977-01-01

    Two different types of analyses were done on data from a study in which eye movements and other variables were recorded while four pilots executed landing sequences in a Boeing 737 simulation. Various conditions were manupulated, including changes in turbulence, starting position, and instrumentation. Control inputs were analyzed in the context of the various conditions and compared against ratings of workload obtained using the Cooper-Harper scale. A number of eye-scanning measures including mean dwell time and transition from one instrument to another were entered into a principal components factor analysis. The results show a differentiation between control inputs and eye-scanning behavior. This shows the need for improved definition of workload and experiments to uncover the important differences among control inputs, eye-scanning and cognitive processes of the pilot.

  16. An inventory of irrigated lands for selected counties within the state of California based on LANDSAT and supporting aircraft data

    NASA Technical Reports Server (NTRS)

    Colwell, R. N. (Principal Investigator)

    1977-01-01

    The author has identified the following significant results: (1) Goals of the irrigated lands project were addressed by the design and implementation of a multiphase sampling scheme that was founded on the utilization of a LANDSAT-based remote sensing system. (2) The synoptic coverage of LANDSAT and the eighteen day orbit cycle allowed the project to study agricultural test sites in a variety of environmental regions and monitor the development of crops throughout the major growing season. (3) The capability to utilize multidate imagery is crucial to the reliable estimation of irrigated acreage in California where multiple cropping is widespread and current estimation systems must rely on single data survey techniques. (4) In addition, the magnitude of agricultural acreage in California makes estimation by conventional methods impossible.

  17. Noise generated by a flight weight, air flow control valve in a vertical takeoff and landing aircraft thrust vectoring system

    NASA Technical Reports Server (NTRS)

    Huff, Ronald G.

    1989-01-01

    Tests were conducted in the NASA Lewis Research Center's Powered Lift Facility to experimentally evaluate the noise generated by a flight weight, 12 in. butterfly valve installed in a proposed vertical takeoff and landing thrust vectoring system. Fluctuating pressure measurements were made in the circular duct upstream and downstream of the valve. This data report presents the results of these tests. The maximum overall sound pressure level is generated in the duct downstream of the valve and reached a value of 180 dB at a valve pressure ratio of 2.8. At the higher valve pressure ratios the spectra downstream of the valve is broad banded with its maximum at 1000 Hz.

  18. Landing performance of an air cushion landing system installed on a 1/10-scale dynamic model on the C-8 Buffalo airplane

    NASA Technical Reports Server (NTRS)

    Thompson, W. C.

    1973-01-01

    An experimental study was conducted to evaluate the landing behavior of a 1/10-scale dynamic model of the C-8 Buffalo airplane equipped with an air-cushion landing system (ACLS) on a variety of surfaces including both calm and rough water and a smooth hard surface. Taxi runs were made on the hard surface over several obstacles. Landings were made with the model at various pitch and roll attitudes and vertical velocities and at one nominal horizontal velocity. Data from the landings include time histories of the trunk and air-cushion pressures and accelerations at selected locations on the model.

  19. Low-speed wind-tunnel investigation of the flight dynamic characteristics of an advanced turboprop business/commuter aircraft configuration

    NASA Technical Reports Server (NTRS)

    Coe, Paul L., Jr.; Turner, Steven G.; Owens, D. Bruce

    1990-01-01

    An investigation was conducted to determine the low-speed flight dynamic behavior of a representative advanced turboprop business/commuter aircraft concept. Free-flight tests were conducted in the NASA Langley Research Center's 30- by 60-Foot Tunnel. In support of the free-flight tests, conventional static, dynamic, and free-to-roll oscillation tests were performed. Tests were intended to explore normal operating and post stall flight conditions, and conditions simulating the loss of power in one engine.

  20. Using land-cover change as dynamic variables in surface-water and water-quality models

    USGS Publications Warehouse

    Karstensen, Krista A.; Warner, Kelly L.; Kuhn, Anne

    2010-01-01

    Land-cover data are typically used in hydrologic modeling to establish or describe land surface dynamics. This project is designed to demonstrate the use of land-cover change data in surface-water and water-quality models by incorporating land-cover as a variable condition. The project incorporates three different scenarios that vary hydrologically and geographically: 1) Agriculture in the Plains, 2) Loon habitat in New England, and 3) Forestry in the Ozarks.

  1. Interactive effects of land use history and natural disturbance on seedling dynamics in a subtropical forest.

    PubMed

    Comita, Liza S; Thompson, Jill; Uriarte, Maria; Jonckheere, Inge; Canham, Charles D; Zimmerman, Jess K

    2010-07-01

    Human-impacted forests are increasing in extent due to widespread regrowth of secondary forests on abandoned lands. The degree and speed of recovery from human disturbance in these forests will determine their value in terms of biodiversity conservation and ecosystem function. In areas subject to periodic, severe natural disturbances, such as hurricanes, it has been hypothesized that human and natural disturbance may interact to either erase or preserve land use legacies. To increase understanding of how interactions between human and natural disturbance influence forest regeneration and recovery, we monitored seedlings in a human- and hurricane-impacted forest in northeastern Puerto Rico over a approximately 10-yr period and compared seedling composition and dynamics in areas that had experienced high- and low-intensity human disturbance during the first half of the 20th century. We found that land use history significantly affected the composition and diversity of the seedling layer and altered patterns of canopy openness and seedling dynamics following hurricane disturbance. The area that had been subject to high-intensity land use supported a higher density, but lower diversity, of species. In both land use history categories, the seedling layer was dominated by the same two species, Prestoea acuminata var. montana and Guarea guidonia. However, seedlings of secondary-successional species tended to be more abundant in the high-intensity land use area, while late-successional species were more abundant in the low-intensity area, consistent with patterns of adult tree distributions. Seedlings of secondary-forest species showed greater increases in growth and survival following hurricane disturbance compared to late-successional species, providing support for the hypothesis that hurricanes help preserve the signature of land use history. However, the increased performance of secondary-forest species occurred predominantly in the low-intensity land use area

  2. Assessing land-use history for reporting on cropland dynamics - A case study using the Land-Parcel Identification System in Ireland

    NASA Astrophysics Data System (ADS)

    Zimmermann, Jesko; González, Ainhoa; Jones, Michael; O'Brien, Phillip; Stout, Jane C.; Green, Stuart

    2016-04-01

    In developed countries, cropland and grassland conversions and management can be a major factor in Land Use and Land Use Change (LULUC) related Greenhouse Gas (GHG) dynamics. Depending on land use, management and factors such as soil properties land can either act as source or sink for GHGs. Currently many countries depend on national statistics combined with socio-economic modelling to assess current land use as well as inter-annual changes. This potentially introduces a bias as it neither provides information on direct land- use change trajectories nor spatially explicit information to assess the environmental context. In order to improve reporting countries are shifting towards high resolution spatial datasets. In this case study, we used the Land Parcel Identification System (LPIS), a pan-European geographical database developed to assist farmers and authorities with agricultural subsidies, to analyse cropland dynamics in Ireland. The database offer high spatial resolution and is updated annually. Generally Ireland is considered grassland dominated with 90 % of its agricultural area under permanent grassland, and only a small area dedicated to cropland. However an in-depth analysis of the LPIS for the years 2000 to 2012 showed strong underlying dynamics. While the annual area reported as cropland remained relatively constant at 3752.3 ± 542.3 km2, the area of permanent cropland was only 1251.9 km2. Reversely, the area that was reported as cropland for at least one year during the timeframe was 7373.4 km2, revealing a significantly higher area with cropland history than annual statistics would suggest. Furthermore, the analysis showed that one quarter of the land converting from or to cropland will return to the previous land use within a year. To demonstrate potential policy impact, we assessed cropland/grassland dynamics from the 2008 to 2012 commitment period using (a) annual statistics, and (b) data including land use history derived from LPIS. Under

  3. Climate change or land use dynamics: do we know what climate change indicators indicate?

    PubMed

    Clavero, Miguel; Villero, Daniel; Brotons, Lluís

    2011-04-21

    Different components of global change can have interacting effects on biodiversity and this may influence our ability to detect the specific consequences of climate change through biodiversity indicators. Here, we analyze whether climate change indicators can be affected by land use dynamics that are not directly determined by climate change. To this aim, we analyzed three community-level indicators of climate change impacts that are based on the optimal thermal environment and average latitude of the distribution of bird species present at local communities. We used multiple regression models to relate the variation in climate change indicators to: i) environmental temperature; and ii) three landscape gradients reflecting important current land use change processes (land abandonment, fire impacts and urbanization), all of them having forest areas at their positive extremes. We found that, with few exceptions, landscape gradients determined the figures of climate change indicators as strongly as temperature. Bird communities in forest habitats had colder-dwelling bird species with more northern distributions than farmland, burnt or urban areas. Our results show that land use changes can reverse, hide or exacerbate our perception of climate change impacts when measured through community-level climate change indicators. We stress the need of an explicit incorporation of the interactions between climate change and land use dynamics to understand what are current climate change indicators indicating and be able to isolate real climate change impacts.

  4. Towards Intelligent Control for Next Generation Aircraft

    NASA Technical Reports Server (NTRS)

    Acosta, Diana Michelle; KrishnaKumar, Kalmanje Srinvas; Frost, Susan Alane

    2008-01-01

    NASA Aeronautics Subsonic Fixed Wing Project is focused on mitigating the environmental and operation impacts expected as aviation operations triple by 2025. The approach is to extend technological capabilities and explore novel civil transport configurations that reduce noise, emissions, fuel consumption and field length. Two Next Generation (NextGen) aircraft have been identified to meet the Subsonic Fixed Wing Project goals - these are the Hybrid Wing-Body (HWB) and Cruise Efficient Short Take-Off and Landing (CESTOL) aircraft. The technologies and concepts developed for these aircraft complicate the vehicle s design and operation. In this paper, flight control challenges for NextGen aircraft are described. The objective of this paper is to examine the potential of state-of-the-art control architectures and algorithms to meet the challenges and needed performance metrics for NextGen flight control. A broad range of conventional and intelligent control approaches are considered, including dynamic inversion control, integrated flight-propulsion control, control allocation, adaptive dynamic inversion control, data-based predictive control and reinforcement learning control.

  5. Overview of high performance aircraft propulsion research

    NASA Technical Reports Server (NTRS)

    Biesiadny, Thomas J.

    1992-01-01

    The overall scope of the NASA Lewis High Performance Aircraft Propulsion Research Program is presented. High performance fighter aircraft of interest include supersonic flights with such capabilities as short take off and vertical landing (STOVL) and/or high maneuverability. The NASA Lewis effort involving STOVL propulsion systems is focused primarily on component-level experimental and analytical research. The high-maneuverability portion of this effort, called the High Alpha Technology Program (HATP), is part of a cooperative program among NASA's Lewis, Langley, Ames, and Dryden facilities. The overall objective of the NASA Inlet Experiments portion of the HATP, which NASA Lewis leads, is to develop and enhance inlet technology that will ensure high performance and stability of the propulsion system during aircraft maneuvers at high angles of attack. To accomplish this objective, both wind-tunnel and flight experiments are used to obtain steady-state and dynamic data, and computational fluid dynamics (CFD) codes are used for analyses. This overview of the High Performance Aircraft Propulsion Research Program includes a sampling of the results obtained thus far and plans for the future.

  6. NASA evaluation of Type 2 chemical depositions. [effects of deicer deposition on aircraft tire friction performance

    NASA Technical Reports Server (NTRS)

    Yager, Thomas J.; Stubbs, Sandy M.; Howell, W. Edward; Webb, Granville L.

    1993-01-01

    Recent findings from NASA Langley tests to define effects of aircraft Type 2 chemical deicer depositions on aircraft tire friction performance are summarized. The Aircraft Landing Dynamics Facility (ALDF) is described together with the scope of the tire cornering and braking friction tests conducted up to 160 knots ground speed. Some lower speed 32 - 96 km/hr (20 - 60 mph) test run data obtained using an Instrumented Tire Test Vehicle (ITTV) to determine effects of tire bearing pressure and transverse grooving on cornering friction performance are also discussed. Recommendations are made concerning which parameters should be evaluated in future testing.

  7. Information fusion based optimal control for large civil aircraft system.

    PubMed

    Zhen, Ziyang; Jiang, Ju; Wang, Xinhua; Gao, Chen

    2015-03-01

    Wind disturbance has a great influence on landing security of Large Civil Aircraft. Through simulation research and engineering experience, it can be found that PID control is not good enough to solve the problem of restraining the wind disturbance. This paper focuses on anti-wind attitude control for Large Civil Aircraft in landing phase. In order to improve the riding comfort and the flight security, an information fusion based optimal control strategy is presented to restrain the wind in landing phase for maintaining attitudes and airspeed. Data of Boeing707 is used to establish a nonlinear mode with total variables of Large Civil Aircraft, and then two linear models are obtained which are divided into longitudinal and lateral equations. Based on engineering experience, the longitudinal channel adopts PID control and C inner control to keep longitudinal attitude constant, and applies autothrottle system for keeping airspeed constant, while an information fusion based optimal regulator in the lateral control channel is designed to achieve lateral attitude holding. According to information fusion estimation, by fusing hard constraint information of system dynamic equations and the soft constraint information of performance index function, optimal estimation of the control sequence is derived. Based on this, an information fusion state regulator is deduced for discrete time linear system with disturbance. The simulation results of nonlinear model of aircraft indicate that the information fusion optimal control is better than traditional PID control, LQR control and LQR control with integral action, in anti-wind disturbance performance in the landing phase.

  8. Modeling the Spatial Dynamics of Regional Land Use: The CLUE-S Model

    NASA Astrophysics Data System (ADS)

    Verburg, Peter H.; Soepboer, Welmoed; Veldkamp, A.; Limpiada, Ramil; Espaldon, Victoria; Mastura, Sharifah S. A.

    2002-09-01

    Land-use change models are important tools for integrated environmental management. Through scenario analysis they can help to identify near-future critical locations in the face of environmental change. A dynamic, spatially explicit, land-use change model is presented for the regional scale: CLUE-S. The model is specifically developed for the analysis of land use in small regions (e.g., a watershed or province) at a fine spatial resolution. The model structure is based on systems theory to allow the integrated analysis of land-use change in relation to socio-economic and biophysical driving factors. The model explicitly addresses the hierarchical organization of land use systems, spatial connectivity between locations and stability. Stability is incorporated by a set of variables that define the relative elasticity of the actual land-use type to conversion. The user can specify these settings based on expert knowledge or survey data. Two applications of the model in the Philippines and Malaysia are used to illustrate the functioning of the model and its validation.

  9. Monitoring Land Cover Dynamics at Varying Spatial Scales Using High to Very High Resolution Optical Imagery

    NASA Astrophysics Data System (ADS)

    Lavender, S. J.

    2016-06-01

    Activities have focused on using the Landsat time-series and Sentinel-2 datasets to monitor land cover dynamics across the United Kingdom, with mapping of specific areas including missions such as Worldview and Kompsat. This short conference paper shows some of the preliminary results from the Landsat Operational Land Imager, Thematic Mapper and Enhanced Thematic Mapper data processing that has included the development of a pre-processing system that includes cloud masking and an atmospheric correction. The results are promising, but further research is needed.

  10. Estimation of Aircraft Unsteady Aerodynamic Parameters from Dynamic Wind Tunnel Testing

    NASA Technical Reports Server (NTRS)

    Murphy, Patrick C.; Klein, Vladislav

    2001-01-01

    Improved aerodynamic mathematical models, for use in aircraft simulation or flight control design, are required when representing nonlinear unsteady aerodynamics. A key limitation of conventional aerodynamic models is the inability to map frequency and amplitude dependent data into the equations of motion directly. In an effort to obtain a more general formulation of the aerodynamic model, researchers have been led to a parallel requirement for more general testing methods. Testing for a more comprehensive model can lead to a very time consuming number of tests especially if traditional single frequency harmonic testing is attempted. This paper presents an alternative to traditional single frequency forced-oscillation testing by utilizing Schroeder sweeps to efficiently obtain the frequency response of the unsteady aerodynamic model. Schroeder inputs provide signals with a flat power spectrum over a specified frequency band. For comparison, experimental results using the traditional single-frequency inputs are also considered. A method for data analysis to determine an adequate unsteady aerodynamic model is presented. Discussion of associated issues that arise during this type of analysis and comparison of results using traditional single frequency analysis are provided.

  11. Estimation of dynamic rotor loads for the rotor systems research aircraft: Methodology development and validation

    NASA Technical Reports Server (NTRS)

    Duval, R. W.; Bahrami, M.

    1985-01-01

    The Rotor Systems Research Aircraft uses load cells to isolate the rotor/transmission systm from the fuselage. A mathematical model relating applied rotor loads and inertial loads of the rotor/transmission system to the load cell response is required to allow the load cells to be used to estimate rotor loads from flight data. Such a model is derived analytically by applying a force and moment balance to the isolated rotor/transmission system. The model is tested by comparing its estimated values of applied rotor loads with measured values obtained from a ground based shake test. Discrepancies in the comparison are used to isolate sources of unmodeled external loads. Once the structure of the mathematical model has been validated by comparison with experimental data, the parameters must be identified. Since the parameters may vary with flight condition it is desirable to identify the parameters directly from the flight data. A Maximum Likelihood identification algorithm is derived for this purpose and tested using a computer simulation of load cell data. The identification is found to converge within 10 samples. The rapid convergence facilitates tracking of time varying parameters of the load cell model in flight.

  12. Vibration and aeroelasticity of advanced aircraft wings modeled as thin-walled beams: Dynamics, stability and control

    NASA Astrophysics Data System (ADS)

    Qin, Zhanming

    Based on a refined analytical anisotropic thin-walled beam model, aeroelastic instability, dynamic aeroelastic response, active/passive aeroelastic control of advanced aircraft wings modeled as thin-walled beams are systematically addressed. The refined thin-walled beam model is based on an existing framework of the thin-walled beam model and a couple of non-classical effects that are usually also important are incorporated and the model herein developed is validated against the available experimental, Finite Element Analysis (FEA), Dynamic Finite Element (DFE), and other analytical predictions. The concept of indicial functions is used to develop unsteady aerodynamic model, which broadly encompasses the cases of incompressible, compressible subsonic, compressible supersonic and hypersonic flows. State-space conversion of the indicial function based unsteady aerodynamic model is also developed. Based on the piezoelectric material technology, a worst case control strategy based on the minimax theory towards the control of aeroelastic systems is further developed. Shunt damping within the aeroelastic tailoring environment is also investigated. The major part of this dissertation is organized in the form of self-contained chapters, each of which corresponds to a paper that has been or will be submitted to a journal for publication. In order to fullfil the requirement of having a continuous presentation of the topics, each chapter starts with the purely structural models and is gradually integrated with the involved interactive field disciplines.

  13. Experimental investigation on dynamic response of aircraft panels excited by high-intensity acoustic loads in thermal environment

    NASA Astrophysics Data System (ADS)

    WU, Z. Q.; LI, H. B.; ZHANG, W.; CHENG, H.; KONG, F. J.; LIU, B. R.

    2016-09-01

    Metallic and composite panels are the major components for thermal protection system of aircraft vehicles, which are exposed to a severe combination of aerodynamic, thermal and acoustic environments during hypersonic flights. A thermal-acoustic testing apparatus which simulates thermal and acoustic loads was used to validate the integrity and the reliability of these panels. Metallic and ceramic matrix composite flat panels were designed. Dynamic response tests of these panels were carried out using the thermal acoustic apparatus. The temperature of the metallic specimen was up to 400 °C, and the temperature of the composite specimen was up to 600 °C. Moreover, the acoustic load was over 160 dB. Acceleration responses of these testing panels were measured using high temperature instruments during the testing process. Results show that the acceleration root mean square values are dominated by sound pressure level of acoustic loads. Compared with testing data in room environment, the peaks of the acceleration dynamic response shifts obviously to the high frequency in thermal environment.

  14. A new Methane and carbon dioxide eddy-covariance flux monitor for land-based, sea-based, and aircraft-based applications.

    NASA Astrophysics Data System (ADS)

    Crosson, Eric; Karion, Anna; Law, Beverly; Sweeney, Colm; Christoph, Thomas; Rahn, Thomas; Mc Gillis, Wade

    2010-05-01

    It is now recognized that a comprehensive understanding of global warming's full impact on local and global weather patterns still requires much more data, namely, mapping the atmospheric mixing ratios (concentrations) of carbon dioxide (CO2), methane (CH4). Moreover, even as this understanding becomes more complete, there will also be a major ongoing need to continuously map quantitative levels of these gases to monitor the effects of regional, national and international green house gas (GHG) reduction efforts, as well as to certify compliance. To carry out this effort will require analyzers that can produce continuous, parts-per-billion precision, high accuracy measurements of ambient levels of atmospheric gases at very high data rates over years of operation in land-based, sea-based, as well as aircraft-based applications. A challenge worth considering is to create a single analyzer that can address the GHG measurement needs of virtually all these applications. Such an analyzer would be required to produce slow time-response (e.g. minute to minute data is considered very fast time response), and very high accuracy (which can also be described as precision across a network of independent measurements) as required for atmospheric inversions and some mobile applications as well as fast time-response (e.g. 1 Hz to 10 Hz) and excellent relative precision (without the need for long-term accuracy, or comparability of mixing ratios across multiple sites) as needed for eddy covariance flux measurements. Such an analyzer would give the research community much more flexibility, a wider choice of research applications, reduce overall capital equipment cost, and improve the inter-comparability of GHG measurements across applications. Picarro, Inc. has developed a high speed Cavity Ring-Down Spectroscopy (CRDS) based analyzer, able to measure carbon dioxide (CO2) concentration to a precision (one standard deviation) of 200 parts-per-billion (ppbv), and methane (CH4

  15. Simulations and Experiments of Hot Forging Design and Evaluation of the Aircraft Landing Gear Barrel Al Alloy Structure

    NASA Astrophysics Data System (ADS)

    Ram Prabhu, T.

    2016-04-01

    In the present study, the hot forging design of a typical landing gear barrel was evolved using finite element simulations and validated with experiments. A DEFORM3D software was used to evolve the forging steps to obtain the sound quality part free of defects with minimum press force requirements. The hot forging trial of a barrel structure was carried out in a 30 MN hydraulic press based on the simulation outputs. The tensile properties of the part were evaluated by taking samples from all three orientations (longitudinal, long transverse, short transverse). The hardness and microstructure of the part were also investigated. To study the soundness of the product, fluorescent penetrant inspection and ultrasonic testing were performed in order to identify any potential surface or internal defects in the part. From experiments, it was found that the part was formed successfully without any forging defects such as under filling, laps, or folds that validated the effectiveness of the process simulation. The tensile properties of the part were well above the specification limit (>10%) and the properties variation with respect to the orientation was less than 2.5%. The part has qualified the surface defects level of Mil Std 1907 Grade C and the internal defects level of AMS 2630 Class A (2 mm FBh). The microstructure shows mean grain length and width of 167 and 66 µm in the longitudinal direction. However, microstructure results revealed that the coarse grain structure was observed on the flat surface near the lug region due to the dead zone formation. An innovative and simple method of milling the surface layer after each pressing operation was applied to solve the problem of the surface coarse grain structure.

  16. A flight test method for pilot/aircraft analysis

    NASA Technical Reports Server (NTRS)

    Koehler, R.; Buchacker, E.

    1986-01-01

    In high precision flight maneuvres a pilot is a part of a closed loop pilot/aircraft system. The assessment of the flying qualities is highly dependent on the closed loop characteristics related to precision maneuvres like approach, landing, air-to-air tracking, air-to-ground tracking, close formation flying and air-to air refueling of the receiver. The object of a research program at DFVLR is the final flight phase of an air to ground mission. In this flight phase the pilot has to align the aircraft with the target, correct small deviations from the target direction and keep the target in his sights for a specific time period. To investigate the dynamic behavior of the pilot-aircraft system a special ground attack flight test technique with a prolonged tracking maneuvres was developed. By changing the targets during the attack the pilot is forced to react continously on aiming errors in his sights. Thus the closed loop pilot/aircraft system is excited over a wide frequency range of interest, the pilot gets more information about mission oriented aircraft dynamics and suitable flight test data for a pilot/aircraft analysis can be generated.

  17. Land-cover change research at the U.S. Geological Survey-assessing our nation's dynamic land surface

    USGS Publications Warehouse

    Wilson, Tamara S.

    2011-01-01

    The U.S. Geological Survey (USGS) recently completed an unprecedented, 27-year assessment of land-use and land-cover change for the conterminous United States. For the period 1973 to 2000, scientists generated estimates of change in major types of land use and land cover, such as development, mining, agriculture, forest, grasslands, and wetlands. To help provide the insight that our Nation will need to make land-use decisions in coming decades, the historical trends data is now being used by the USGS to help model potential future land use/land cover under different scenarios, including climate, environmental, economic, population, public policy, and technological change.

  18. The Look-point Aircraft Coordinate Estimator (LACE) and potential applications

    NASA Technical Reports Server (NTRS)

    Anderson, W. W.

    1979-01-01

    A look-point aircraft coordinate estimator (LACE) consisting of a windshield runway symbol projector, pilot input controls, microprocessor, and eye-alignment device is described. The estimator is used by a pilot to determine his aircraft's position relative to a runway or other visible terrain or target. The pilot initially superimposes and then corrects the superposition of the runway symbol over the runway during approach during periods when the runway is visible. Using the pilot's inputs the microprocessor calculates the position of the aircraft in terms of runway coordinates, then generates an approach trajectory and issues instructions to an autopilot. The microprocessor contains a model of the aircraft's dynamics and calculates a theoretical aircraft trajectory. The theoretical position of the aircraft is then used to drive the runway symbol, with the pilot's input being additive. The system thus acts as an aid in making low visibility approaches and landings when only an occasional glimpse of the runway is possible and no ground referenced landing systems are available. The system can also be used as an independent landing monitor for ground referenced landing systems.

  19. Impacts of land cover data selection and trait parameterisation on dynamic modelling of species' range expansion.

    PubMed

    Heikkinen, Risto K; Bocedi, Greta; Kuussaari, Mikko; Heliölä, Janne; Leikola, Niko; Pöyry, Juha; Travis, Justin M J

    2014-01-01

    Dynamic models for range expansion provide a promising tool for assessing species' capacity to respond to climate change by shifting their ranges to new areas. However, these models include a number of uncertainties which may affect how successfully they can be applied to climate change oriented conservation planning. We used RangeShifter, a novel dynamic and individual-based modelling platform, to study two potential sources of such uncertainties: the selection of land cover data and the parameterization of key life-history traits. As an example, we modelled the range expansion dynamics of two butterfly species, one habitat specialist (Maniola jurtina) and one generalist (Issoria lathonia). Our results show that projections of total population size, number of occupied grid cells and the mean maximal latitudinal range shift were all clearly dependent on the choice made between using CORINE land cover data vs. using more detailed grassland data from three alternative national databases. Range expansion was also sensitive to the parameterization of the four considered life-history traits (magnitude and probability of long-distance dispersal events, population growth rate and carrying capacity), with carrying capacity and magnitude of long-distance dispersal showing the strongest effect. Our results highlight the sensitivity of dynamic species population models to the selection of existing land cover data and to uncertainty in the model parameters and indicate that these need to be carefully evaluated before the models are applied to conservation planning. PMID:25265281

  20. Advanced hypersonic aircraft design

    NASA Technical Reports Server (NTRS)

    Utzinger, Rob; Blank, Hans-Joachim; Cox, Craig; Harvey, Greg; Mckee, Mike; Molnar, Dave; Nagy, Greg; Petersen, Steve

    1992-01-01

    The objective of this design project is to develop the hypersonic reconnaissance aircraft to replace the SR-71 and to complement existing intelligence gathering devices. The initial design considerations were to create a manned vehicle which could complete its mission with at least two airborne refuelings. The aircraft must travel between Mach 4 and Mach 7 at an altitude of 80,000 feet for a maximum range of 12,000 nautical miles. The vehicle should have an air breathing propulsion system at cruise. With a crew of two, the aircraft should be able to take off and land on a 10,000 foot runway, and the yearly operational costs were not to exceed $300 million. Finally, the aircraft should exhibit stealth characteristics, including a minimized radar cross-section (RCS) and a reduced sonic boom. The technology used in this vehicle should allow for production between the years 1993 and 1995.

  1. 19 CFR 122.37 - Precleared aircraft.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 1 2014-04-01 2014-04-01 false Precleared aircraft. 122.37 Section 122.37 Customs... AIR COMMERCE REGULATIONS Landing Requirements § 122.37 Precleared aircraft. (a) Application. This section applies when aircraft carrying crew, passengers and baggage, or merchandise which has...

  2. 19 CFR 122.37 - Precleared aircraft.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Precleared aircraft. 122.37 Section 122.37 Customs... AIR COMMERCE REGULATIONS Landing Requirements § 122.37 Precleared aircraft. (a) Application. This section applies when aircraft carrying crew, passengers and baggage, or merchandise which has...

  3. 19 CFR 122.37 - Precleared aircraft.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 1 2013-04-01 2013-04-01 false Precleared aircraft. 122.37 Section 122.37 Customs... AIR COMMERCE REGULATIONS Landing Requirements § 122.37 Precleared aircraft. (a) Application. This section applies when aircraft carrying crew, passengers and baggage, or merchandise which has...

  4. 19 CFR 122.37 - Precleared aircraft.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Precleared aircraft. 122.37 Section 122.37 Customs... AIR COMMERCE REGULATIONS Landing Requirements § 122.37 Precleared aircraft. (a) Application. This section applies when aircraft carrying crew, passengers and baggage, or merchandise which has...

  5. 19 CFR 122.37 - Precleared aircraft.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Precleared aircraft. 122.37 Section 122.37 Customs... AIR COMMERCE REGULATIONS Landing Requirements § 122.37 Precleared aircraft. (a) Application. This section applies when aircraft carrying crew, passengers and baggage, or merchandise which has...

  6. Nonlinear robust control of hypersonic aircrafts with interactions between flight dynamics and propulsion systems.

    PubMed

    Li, Zhaoying; Zhou, Wenjie; Liu, Hao

    2016-09-01

    This paper addresses the nonlinear robust tracking controller design problem for hypersonic vehicles. This problem is challenging due to strong coupling between the aerodynamics and the propulsion system, and the uncertainties involved in the vehicle dynamics including parametric uncertainties, unmodeled model uncertainties, and external disturbances. By utilizing the feedback linearization technique, a linear tracking error system is established with prescribed references. For the linear model, a robust controller is proposed based on the signal compensation theory to guarantee that the tracking error dynamics is robustly stable. Numerical simulation results are given to show the advantages of the proposed nonlinear robust control method, compared to the robust loop-shaping control approach.

  7. Nonlinear robust control of hypersonic aircrafts with interactions between flight dynamics and propulsion systems.

    PubMed

    Li, Zhaoying; Zhou, Wenjie; Liu, Hao

    2016-09-01

    This paper addresses the nonlinear robust tracking controller design problem for hypersonic vehicles. This problem is challenging due to strong coupling between the aerodynamics and the propulsion system, and the uncertainties involved in the vehicle dynamics including parametric uncertainties, unmodeled model uncertainties, and external disturbances. By utilizing the feedback linearization technique, a linear tracking error system is established with prescribed references. For the linear model, a robust controller is proposed based on the signal compensation theory to guarantee that the tracking error dynamics is robustly stable. Numerical simulation results are given to show the advantages of the proposed nonlinear robust control method, compared to the robust loop-shaping control approach. PMID:27132149

  8. Aircraft mission analysis

    NASA Technical Reports Server (NTRS)

    Hauge, D. S.; Rosendaal, H. L.

    1979-01-01

    Aircraft missions, from low to hypersonic speeds, are analyzed rapidly using the FORTRAN IV program NSEG. Program employs approximate equations of motion that vary in form with type of flight segment. Takeoffs, accelerations, climbs, cruises, descents, decelerations, and landings are considered.

  9. Progressive Aerodynamic Model Identification From Dynamic Water Tunnel Test of the F-16XL Aircraft

    NASA Technical Reports Server (NTRS)

    Murphy, Patrick C.; Klein, Vladislav; Szyba, Nathan M.

    2004-01-01

    Development of a general aerodynamic model that is adequate for predicting the forces and moments in the nonlinear and unsteady portions of the flight envelope has not been accomplished to a satisfactory degree. Predicting aerodynamic response during arbitrary motion of an aircraft over the complete flight envelope requires further development of the mathematical model and the associated methods for ground-based testing in order to allow identification of the model. In this study, a general nonlinear unsteady aerodynamic model is presented, followed by a summary of a linear modeling methodology that includes test and identification methods, and then a progressive series of steps suggesting a roadmap to develop a general nonlinear methodology that defines modeling, testing, and identification methods. Initial steps of the general methodology were applied to static and oscillatory test data to identify rolling-moment coefficient. Static measurements uncovered complicated dependencies of the aerodynamic coefficient on angle of attack and sideslip in the stall region making it difficult to find a simple analytical expression for the measurement data. In order to assess the effect of sideslip on the damping and unsteady terms, oscillatory tests in roll were conducted at different values of an initial offset in sideslip. Candidate runs for analyses were selected where higher order harmonics were required for the model and where in-phase and out-of-phase components varied with frequency. From these results it was found that only data in the angle-of-attack range of 35 degrees to 37.5 degrees met these requirements. From the limited results it was observed that the identified models fit the data well and both the damping-in-roll and the unsteady term gain are decreasing with increasing sideslip and motion amplitude. Limited similarity between parameter values in the nonlinear model and the linear model suggest that identifiability of parameters in both terms may be a

  10. A dynamic simulation/optimization model for scheduling restoration of degraded military training lands.

    PubMed

    Önal, Hayri; Woodford, Philip; Tweddale, Scott A; Westervelt, James D; Chen, Mengye; Dissanayake, Sahan T M; Pitois, Gauthier

    2016-04-15

    Intensive use of military vehicles on Department of Defense training installations causes deterioration in ground surface quality. Degraded lands restrict the scheduled training activities and jeopardize personnel and equipment safety. We present a simulation-optimization approach and develop a discrete dynamic optimization model to determine an optimum land restoration for a given training schedule and availability of financial resources to minimize the adverse effects of training on military lands. The model considers weather forecasts, scheduled maneuver exercises, and unique qualities and importance of the maneuver areas. An application of this approach to Fort Riley, Kansas, shows that: i) starting with natural conditions, the total amount of training damages would increase almost linearly and exceed a quarter of the training area and 228 gullies would be formed (mostly in the intensive training areas) if no restoration is carried out over 10 years; ii) assuming an initial state that resembles the present conditions, sustaining the landscape requires an annual restoration budget of $957 thousand; iii) targeting a uniform distribution of maneuver damages would increase the total damages and adversely affect the overall landscape quality, therefore a selective restoration strategy may be preferred; and iv) a proactive restoration strategy would be optimal where land degradations are repaired before they turn into more severe damages that are more expensive to repair and may pose a higher training risk. The last finding can be used as a rule-of-thumb for land restoration efforts in other installations with similar characteristics.

  11. A dynamic simulation/optimization model for scheduling restoration of degraded military training lands.

    PubMed

    Önal, Hayri; Woodford, Philip; Tweddale, Scott A; Westervelt, James D; Chen, Mengye; Dissanayake, Sahan T M; Pitois, Gauthier

    2016-04-15

    Intensive use of military vehicles on Department of Defense training installations causes deterioration in ground surface quality. Degraded lands restrict the scheduled training activities and jeopardize personnel and equipment safety. We present a simulation-optimization approach and develop a discrete dynamic optimization model to determine an optimum land restoration for a given training schedule and availability of financial resources to minimize the adverse effects of training on military lands. The model considers weather forecasts, scheduled maneuver exercises, and unique qualities and importance of the maneuver areas. An application of this approach to Fort Riley, Kansas, shows that: i) starting with natural conditions, the total amount of training damages would increase almost linearly and exceed a quarter of the training area and 228 gullies would be formed (mostly in the intensive training areas) if no restoration is carried out over 10 years; ii) assuming an initial state that resembles the present conditions, sustaining the landscape requires an annual restoration budget of $957 thousand; iii) targeting a uniform distribution of maneuver damages would increase the total damages and adversely affect the overall landscape quality, therefore a selective restoration strategy may be preferred; and iv) a proactive restoration strategy would be optimal where land degradations are repaired before they turn into more severe damages that are more expensive to repair and may pose a higher training risk. The last finding can be used as a rule-of-thumb for land restoration efforts in other installations with similar characteristics. PMID:26895721

  12. Integrating remotely sensed land cover observations and a biogeochemical model for estimating forest ecosystem carbon dynamics

    USGS Publications Warehouse

    Liu, J.; Liu, S.; Loveland, T.R.; Tieszen, L.L.

    2008-01-01

    Land cover change is one of the key driving forces for ecosystem carbon (C) dynamics. We present an approach for using sequential remotely sensed land cover observations and a biogeochemical model to estimate contemporary and future ecosystem carbon trends. We applied the General Ensemble Biogeochemical Modelling System (GEMS) for the Laurentian Plains and Hills ecoregion in the northeastern United States for the period of 1975-2025. The land cover changes, especially forest stand-replacing events, were detected on 30 randomly located 10-km by 10-km sample blocks, and were assimilated by GEMS for biogeochemical simulations. In GEMS, each unique combination of major controlling variables (including land cover change history) forms a geo-referenced simulation unit. For a forest simulation unit, a Monte Carlo process is used to determine forest type, forest age, forest biomass, and soil C, based on the Forest Inventory and Analysis (FIA) data and the U.S. General Soil Map (STATSGO) data. Ensemble simulations are performed for each simulation unit to incorporate input data uncertainty. Results show that on average forests of the Laurentian Plains and Hills ecoregion have been sequestrating 4.2 Tg C (1 teragram = 1012 gram) per year, including 1.9 Tg C removed from the ecosystem as the consequences of land cover change. ?? 2008 Elsevier B.V.

  13. Lightning hazards to aircraft

    NASA Technical Reports Server (NTRS)

    Corn, P. B.

    1978-01-01

    Lightning hazards and, more generally, aircraft static electricity are discussed by a representative for the Air Force Flight Dynamics Laboratory. An overview of these atmospheric electricity hazards to aircraft and their systems is presented with emphasis on electrical and electronic subsystems. The discussion includes reviewing some of the characteristics of lightning and static electrification, trends in weather and lightning-related mishaps, some specific threat mechanisms and susceptible aircraft subsystems and some of the present technology gaps. A roadmap (flow chart) is presented to show the direction needed to address these problems.

  14. Projectiles Impact Assessment of Aircraft Wing Structures with Real Dynamic Load

    NASA Astrophysics Data System (ADS)

    Han, Lu; Han, Qing; Wang, Changlin

    2015-07-01

    This paper presents an analysis to achieve the impact damage of the wing structure under real dynamic load. MPCCI tools are utilized to convert wing aerodynamic load into structural Finite Element Method (FEM) node load. The ANSYS/LS-DYNA code is also used to simulate the dynamic loading effects of the wing structure hit by several projectiles, including both active damage mechanism and common damage mechanism. In addition, structural node force on the leading edge and the midline is compared to the aerodynamic load separately. Furthermore, the statistical analysis of the penetrating size and the stress concentration around the damage holes indicates that under the same load situation, the structural damage efficiency of active damage mechanism is significantly higher than the one of common damage mechanism.

  15. Dynamic-free bias-free differential GPS - Application to landing

    NASA Astrophysics Data System (ADS)

    Martin Neira, M.; Lucas, R.

    1992-08-01

    A method for accurate differential positioning free of dynamic and bias errors based on stand-alone GPS C/A code and carrier phase observables has been developed and tested using GPS hardware simulations. The algorithm has been evaluated against the navigation filter performance of commercially available GPS receivers intended for civil aviation applications showing a much better behavior particularly in high dynamic conditions. Hardware simulations for the case of the trajectory of the European space plane Hermes during its landing phase have shown meter level accuracies. Also real world dynamic tests using live GPS signals demonstrate similar performance. In all cases the filter output insensitivity to bias errors and dynamic conditions was clear.

  16. Soil organic carbon dynamics as related to land use history in the northwestern Great Plains

    USGS Publications Warehouse

    Tan, Z.; Liu, S.; Johnston, C.A.; Loveland, T.R.; Tieszen, L.L.; Liu, J.; Kurtz, R.

    2005-01-01

    Strategies for mitigating the global greenhouse effect must account for soil organic carbon (SOC) dynamics at both spatial and temporal scales, which is usually challenging owing to limitations in data and approach. This study was conducted to characterize the SOC dynamics associated with land use change history in the northwestern Great Plains ecoregion. A sampling framework (40 sample blocks of 10 ?? 10 km2 randomly located in the ecoregion) and the General Ensemble Biogeochemical Modeling System (GEMS) were used to quantify the spatial and temporal variability in the SOC stock from 1972 to 2001. Results indicate that C source and sink areas coexisted within the ecoregion, and the SOC stock in the upper 20-cm depth increased by 3.93 Mg ha-1 over the 29 years. About 17.5% of the area was evaluated as a C source at 122 kg C ha-1 yr-1. The spatial variability of SOC stock was attributed to the dynamics of both slow and passive fractions, while the temporal variation depended on the slow fraction only. The SOC change at the block scale was positively related to either grassland proportion or negatively related to cropland proportion. We concluded that the slow C pool determined whether soils behaved as sources or sinks of atmospheric CO2, but the strength depended on antecedent SOC contents, land cover type, and land use change history in the ecoregion. Copyright 2005 by the American Geophysical Union.

  17. SILHIL Replication of Electric Aircraft Powertrain Dynamics and Inner-Loop Control for V&V of System Health Management Routines

    NASA Technical Reports Server (NTRS)

    Bole, Brian; Teubert, Christopher Allen; Cuong Chi, Quach; Hogge, Edward; Vazquez, Sixto; Goebel, Kai; George, Vachtsevanos

    2013-01-01

    Software-in-the-loop and Hardware-in-the-loop testing of failure prognostics and decision making tools for aircraft systems will facilitate more comprehensive and cost-effective testing than what is practical to conduct with flight tests. A framework is described for the offline recreation of dynamic loads on simulated or physical aircraft powertrain components based on a real-time simulation of airframe dynamics running on a flight simulator, an inner-loop flight control policy executed by either an autopilot routine or a human pilot, and a supervisory fault management control policy. The creation of an offline framework for verifying and validating supervisory failure prognostics and decision making routines is described for the example of battery charge depletion failure scenarios onboard a prototype electric unmanned aerial vehicle.

  18. Aircraft Contrails

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Captured in this scene is a series of aircraft contrails in a high traffic region over the northern Gulf of Mexico (27.0N, 85.5W). Contrails are caused by the hot engine exhaust of high flying aircraft interacting with moisture in the cold upper atmosphere and are common occurrances of high flying aircraft.

  19. Dynamics of land use and common-resource pressures in terrestrial-aquatic environments

    NASA Astrophysics Data System (ADS)

    Lazarus, E.; Bell, K. P.

    2010-12-01

    Common-pool resource problems can arise in aquatic systems such as lakes, rivers, and open coastlines where individual land-use decisions produce collective, emergent effects at the watershed scale. A body of highly generalized modeling experiments has illustrated ways in which simple, opposing tendencies among individuals—imitative versus self-initiated actions, for example—can result in richly complex behaviors. If the dynamics of those opposing tendencies are translated into different land uses (development, extraction, working land, conservation), each entailing a different environmental consequence, then feedbacks between land-use decisions and resulting changes to the physical environment (which in turn influence subsequent land-use decisions) cause the environmental and social systems of the watershed to become coupled. We present the early results of an exploratory, spatially-extended model that couples a simplified riparian system to a hypothetical group of landowners, each of whom can choose between property development, placing property under a conservation easement, or taking no action and effectively maintaining the property's status quo. As in the generalized experiments, landowner behavior depends on two sets of opposing tendencies, one of which is imitation versus self-initiation. The other is a preference for property consolidation or subdivision; large property holdings can be subdivided into smaller parcels, and small parcels can be bought up by an owner to amass a larger property. Land-use decisions taken by landowners in the model affect the riparian system in process-based ways (sedimentation, eutrophication, water quality) that then inform subsequent social interactions and decisions. Isolating the basic dynamics of this kind of socio-environmental system allows us to pursue a number of questions relevant to resource management. What social and environmental circumstances in this framework result in continuous conservation corridors as

  20. Co-operation processes in dynamic environment management: evolution through training experienced pilots in flying a highly automated aircraft.

    PubMed

    Rogalski, J

    1996-01-01

    Dynamic environment management (process control, aircraft piloting, etc.) increasingly implies collective work components. Pragmatic purposes as well as epistemological interests raise important questions on collective activities at work. In particular, linked to the technological evolution in flight management, the role of the 'collective fact' appears as a key point in reliability. Beyond the development of individual competencies, the quality of the 'distributed' crew activity has to be questioned. This paper presents an empirical study about how experienced pilots co-ordinate their information and actions during the last period of training on a highly automated cockpit. A task of disturbance management (engine fire during takeoff) is chosen as amplifying cognitive requirements. Analysis focuses on the transitions between the main task and the incident to be managed. Crew performance and co-operation between two pilots are compared in three occurrences of the same task: the results are coherent with the hypothesis of a parallel evolution of the crew performance and its internal co-operation, and show that prescribed explicit co-operation is more present on action than on information about the 'state of the world'. Methodological issues are discussed about the possible effects of the specific situation of training, and about the psychological meaning of the results. PMID:11540153

  1. Preliminary Analysis of the Effect of Flow Separation Due to Rocket Jet Pluming on Aircraft Dynamic Stability During Atmospheric Exit

    NASA Technical Reports Server (NTRS)

    Dryer, Murray; North, Warren J.

    1959-01-01

    A theoretical investigation was conducted to determine the effects of body boundary-layer separation resulting from a highly underexpanded jet on the dynamic stability of a typical rocket aircraft during an atmospheric exit trajectory. The particular flight condition studied on a digital computer for five degrees of freedom was at Mach 6.0 and 150,000 feet. In view of the unknown character of the separated flow field, two estimates of the pressures in the separated region were made to calculate the unbalanced forces and moments. These estimates, based on limited fundamental zero-angle-of-attack studies and observations, are believed to cover what may be the actual case. In addition to a fixed control case, two simulated pilot control inputs were studied: rate-limited and instantaneous responses. The resulting-motions with and without boundary-layer separation were compared for various initial conditions. The lower of the assumed misalinement forces and moments led to a situation whereby a slowly damped motion could be satisfactorily controlled with rate-limited control input. The higher assumption led to larger amplitude, divergent motions when the same control rates were used. These motions were damped only when the instantaneous control responses were assumed.

  2. Modifying a dynamic global vegetation model for simulating large spatial scale land surface water balance

    NASA Astrophysics Data System (ADS)

    Tang, G.; Bartlein, P. J.

    2012-01-01

    Water balance models of simple structure are easier to grasp and more clearly connect cause and effect than models of complex structure. Such models are essential for studying large spatial scale land surface water balance in the context of climate and land cover change, both natural and anthropogenic. This study aims to (i) develop a large spatial scale water balance model by modifying a dynamic global vegetation model (DGVM), and (ii) test the model's performance in simulating actual evapotranspiration (ET), soil moisture and surface runoff for the coterminous United States (US). Toward these ends, we first introduced development of the "LPJ-Hydrology" (LH) model by incorporating satellite-based land covers into the Lund-Potsdam-Jena (LPJ) DGVM instead of dynamically simulating them. We then ran LH using historical (1982-2006) climate data and satellite-based land covers at 2.5 arc-min grid cells. The simulated ET, soil moisture and surface runoff were compared to existing sets of observed or simulated data for the US. The results indicated that LH captures well the variation of monthly actual ET (R2 = 0.61, p < 0.01) in the Everglades of Florida over the years 1996-2001. The modeled monthly soil moisture for Illinois of the US agrees well (R2 = 0.79, p < 0.01) with the observed over the years 1984-2001. The modeled monthly stream flow for most 12 major rivers in the US is consistent R2 > 0.46, p < 0.01; Nash-Sutcliffe Coefficients >0.52) with observed values over the years 1982-2006, respectively. The modeled spatial patterns of annual ET and surface runoff are in accordance with previously published data. Compared to its predecessor, LH simulates better monthly stream flow in winter and early spring by incorporating effects of solar radiation on snowmelt. Overall, this study proves the feasibility of incorporating satellite-based land-covers into a DGVM for simulating large spatial scale land surface water balance. LH developed in this study should be a useful

  3. Design criteria for integrated flight/propulsion control systems for STOVL fighter aircraft

    NASA Technical Reports Server (NTRS)

    Franklin, James A.

    1993-01-01

    As part of NASA's program to develop technology for short takeoff and vertical landing (STOVL) fighter aircraft, control system designs have been developed for a conceptual STOVL aircraft. This aircraft is representative of the class of mixed-flow remote-lift concepts that was identified as the preferred design approach by the US/UK STOVL Joint Assessment and Ranking Team. The control system designs have been evaluated throughout the powered-lift flight envelope on Ames Research Center's Vertical Motion Simulator. Items assessed in the control system evaluation were: maximum control power used in transition and vertical flight, control system dynamic response associated with thrust transfer for attitude control, thrust margin in the presence of ground effect and hot gas ingestion, and dynamic thrust response for the engine core. Effects of wind, turbulence, and ship airwake disturbances are incorporated in the evaluation. Results provide the basis for a reassessment of existing flying qualities design criteria applied to STOVL aircraft.

  4. Cancellation control law for lateral-directional dynamics of a supermaneuverable aircraft

    NASA Technical Reports Server (NTRS)

    Snell, Antony

    1993-01-01

    Cancellation control laws are designed which reduce the high levels of lateral acceleration encountered during aggressive rolling maneuvers executed at high angle of attack. Two independent problem are examined. One is to reduce lateral acceleration at the mass center, while the other focuses on lateral acceleration at the pilot's station, located 7.0 m forward of the mass center. Both of these problems are challenging and somewhat different in their limitations. In each case the design is based on a linearization of the lateral-directional dynamics about a high angle of attack condition. The controllers incorporate dynamic inversion inner loops to provide control of stability-axis roll- and yaw-rates and then employ cancellation filters in both feed-forward and feed-back signal paths. The relative simplicity of the control laws should allow nonlinear generalizations to be devised. Although it is shown that lateral acceleration can be reduced substantially by such control laws, this is at the cost of slowed roll response, poor dutch-roll damping or a combination of the two.

  5. Modifying a dynamic global vegetation model for simulating large spatial scale land surface water balances

    NASA Astrophysics Data System (ADS)

    Tang, G.; Bartlein, P. J.

    2012-08-01

    Satellite-based data, such as vegetation type and fractional vegetation cover, are widely used in hydrologic models to prescribe the vegetation state in a study region. Dynamic global vegetation models (DGVM) simulate land surface hydrology. Incorporation of satellite-based data into a DGVM may enhance a model's ability to simulate land surface hydrology by reducing the task of model parameterization and providing distributed information on land characteristics. The objectives of this study are to (i) modify a DGVM for simulating land surface water balances; (ii) evaluate the modified model in simulating actual evapotranspiration (ET), soil moisture, and surface runoff at regional or watershed scales; and (iii) gain insight into the ability of both the original and modified model to simulate large spatial scale land surface hydrology. To achieve these objectives, we introduce the "LPJ-hydrology" (LH) model which incorporates satellite-based data into the Lund-Potsdam-Jena (LPJ) DGVM. To evaluate the model we ran LH using historical (1981-2006) climate data and satellite-based land covers at 2.5 arc-min grid cells for the conterminous US and for the entire world using coarser climate and land cover data. We evaluated the simulated ET, soil moisture, and surface runoff using a set of observed or simulated data at different spatial scales. Our results demonstrate that spatial patterns of LH-simulated annual ET and surface runoff are in accordance with previously published data for the US; LH-modeled monthly stream flow for 12 major rivers in the US was consistent with observed values respectively during the years 1981-2006 (R2 > 0.46, p < 0.01; Nash-Sutcliffe Coefficient > 0.52). The modeled mean annual discharges for 10 major rivers worldwide also agreed well (differences < 15%) with observed values for these rivers. Compared to a degree-day method for snowmelt computation, the addition of the solar radiation effect on snowmelt enabled LH to better simulate monthly

  6. Reduced knee joint moment in ACL deficient patients at a cost of dynamic stability during landing.

    PubMed

    Oberländer, Kai Daniel; Brüggemann, Gert-Peter; Höher, Jürgen; Karamanidis, Kiros

    2012-05-11

    The current study aimed to examine the effect of anterior cruciate ligament deficiency (ACLd) on joint kinetics and dynamic stability control after a single leg hop test (SLHT). Twelve unilateral ACLd patients and a control subject group (n=13) performed a SLHT over a given distance with both legs. The calculation of joint kinetics was done by means of a soft-tissue artifact optimized rigid full-body model. Margin of stability (MoS) was quantified by the difference between the base of support and the extrapolated center of mass. During landing, the ACLd leg showed lower external knee flexion moments but demonstrated higher moments at the ankle and hip compared to controls (p<0.05). The main reason for the joint moment redistribution in the ACLd leg was a more anterior position of the ground reaction force (GRF) vector, which affected the moment arms of the GRF acting about the joints (p<0.05). For the ACLd leg, trunk angle was more flexed over the entire landing phase compared to controls (p<0.05) and we found a significant correlation between moment arms at the knee joint and trunk angle (r² = 0.48;p<0.01). The consequence of this altered landing strategy in ACLd legs was a more anterior position of the center of mass reducing the MoS (p<0.05). The results illustrate the interaction between trunk angle, joint kinetics and dynamic stability during landing maneuvers and provide evidence of a feedforward adaptive adjustment in ACLd patients (i.e. more flexed trunk angle) aimed at reducing knee joint moments at the cost of dynamic stability control. PMID:22440611

  7. Reduced knee joint moment in ACL deficient patients at a cost of dynamic stability during landing.

    PubMed

    Oberländer, Kai Daniel; Brüggemann, Gert-Peter; Höher, Jürgen; Karamanidis, Kiros

    2012-05-11

    The current study aimed to examine the effect of anterior cruciate ligament deficiency (ACLd) on joint kinetics and dynamic stability control after a single leg hop test (SLHT). Twelve unilateral ACLd patients and a control subject group (n=13) performed a SLHT over a given distance with both legs. The calculation of joint kinetics was done by means of a soft-tissue artifact optimized rigid full-body model. Margin of stability (MoS) was quantified by the difference between the base of support and the extrapolated center of mass. During landing, the ACLd leg showed lower external knee flexion moments but demonstrated higher moments at the ankle and hip compared to controls (p<0.05). The main reason for the joint moment redistribution in the ACLd leg was a more anterior position of the ground reaction force (GRF) vector, which affected the moment arms of the GRF acting about the joints (p<0.05). For the ACLd leg, trunk angle was more flexed over the entire landing phase compared to controls (p<0.05) and we found a significant correlation between moment arms at the knee joint and trunk angle (r² = 0.48;p<0.01). The consequence of this altered landing strategy in ACLd legs was a more anterior position of the center of mass reducing the MoS (p<0.05). The results illustrate the interaction between trunk angle, joint kinetics and dynamic stability during landing maneuvers and provide evidence of a feedforward adaptive adjustment in ACLd patients (i.e. more flexed trunk angle) aimed at reducing knee joint moments at the cost of dynamic stability control.

  8. 32 CFR 855.15 - Detaining an aircraft.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 6 2010-07-01 2010-07-01 false Detaining an aircraft. 855.15 Section 855.15 National Defense Department of Defense (Continued) DEPARTMENT OF THE AIR FORCE AIRCRAFT CIVIL AIRCRAFT USE OF UNITED STATES AIR FORCE AIRFIELDS Civil Aircraft Landing Permits § 855.15 Detaining an...

  9. 32 CFR 855.15 - Detaining an aircraft.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 32 National Defense 6 2013-07-01 2013-07-01 false Detaining an aircraft. 855.15 Section 855.15 National Defense Department of Defense (Continued) DEPARTMENT OF THE AIR FORCE AIRCRAFT CIVIL AIRCRAFT USE OF UNITED STATES AIR FORCE AIRFIELDS Civil Aircraft Landing Permits § 855.15 Detaining an...

  10. 32 CFR 855.15 - Detaining an aircraft.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 6 2011-07-01 2011-07-01 false Detaining an aircraft. 855.15 Section 855.15 National Defense Department of Defense (Continued) DEPARTMENT OF THE AIR FORCE AIRCRAFT CIVIL AIRCRAFT USE OF UNITED STATES AIR FORCE AIRFIELDS Civil Aircraft Landing Permits § 855.15 Detaining an...

  11. 32 CFR 855.15 - Detaining an aircraft.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 32 National Defense 6 2014-07-01 2014-07-01 false Detaining an aircraft. 855.15 Section 855.15 National Defense Department of Defense (Continued) DEPARTMENT OF THE AIR FORCE AIRCRAFT CIVIL AIRCRAFT USE OF UNITED STATES AIR FORCE AIRFIELDS Civil Aircraft Landing Permits § 855.15 Detaining an...

  12. 32 CFR 855.15 - Detaining an aircraft.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 32 National Defense 6 2012-07-01 2012-07-01 false Detaining an aircraft. 855.15 Section 855.15 National Defense Department of Defense (Continued) DEPARTMENT OF THE AIR FORCE AIRCRAFT CIVIL AIRCRAFT USE OF UNITED STATES AIR FORCE AIRFIELDS Civil Aircraft Landing Permits § 855.15 Detaining an...

  13. Future V/STOL Aircraft For The Pacific Basin

    NASA Technical Reports Server (NTRS)

    Albers, James A.; Zuk, John

    1992-01-01

    Report describes geography and transportation needs of Asian Pacific region, and describes aircraft configurations suitable for region and compares performances. Examines applications of high-speed rotorcraft, vertical/short-takeoff-and-landing (V/STOL) aircraft, and short-takeoff-and landing (STOL) aircraft. Configurations benefit commerce, tourism, and development of resources.

  14. [Influence of land use change on vegetation cover dynamics in Dapeng Peninsula of Shenzhen, Guangdong Province of South China].

    PubMed

    Liang, Yao-Qin; Zeng, Hui; Li, Jing

    2012-01-01

    To study the vegetation cover dynamics under urbanization is of significance to direct regional ecological conservation. Based on the 1995-2007 remote sensing data and the investigation data of 1996 and 2007 land use change in Shenzhen, and by using NDVI index tracking and algebraic overlay calculation, this paper analyzed the vegetation types and their spatial differentiation, land use change pattern, and the relationships between land use change and vegetation cover dynamics in Dapeng Peninsula of Shenzhen. In 1995-2007, the vegetation cover in 65% of the study area changed significantly, with an overall increasing trend. Land use change was mainly caused by the development of urbanization and commercial agriculture, with 31% of the land surface changed in land use function. The land use change was one of the main causes of vegetation cover dynamics, and about 35% of the region where vegetation cover significantly degraded was related to land use change. 55% of the region where land use function changed due to mechanical disturbance caused the degradation of vegetation cover, but by the end of the study period, the vegetation cover in most of the degraded region had being improved significantly.

  15. The insertion of human dynamics models in the flight control loops of V/STOL research aircraft. Appendix 2: The optimal control model of a pilot in V/STOL aircraft control loops

    NASA Technical Reports Server (NTRS)

    Zipf, Mark E.

    1989-01-01

    An overview is presented of research work focussed on the design and insertion of classical models of human pilot dynamics within the flight control loops of V/STOL aircraft. The pilots were designed and configured for use in integrated control system research and design. The models of human behavior that were considered are: McRuer-Krendel (a single variable transfer function model); and Optimal Control Model (a multi-variable approach based on optimal control and stochastic estimation theory). These models attempt to predict human control response characteristics when confronted with compensatory tracking and state regulation tasks. An overview, mathematical description, and discussion of predictive limitations of the pilot models is presented. Design strategies and closed loop insertion configurations are introduced and considered for various flight control scenarios. Models of aircraft dynamics (both transfer function and state space based) are developed and discussed for their use in pilot design and application. Pilot design and insertion are illustrated for various flight control objectives. Results of pilot insertion within the control loops of two V/STOL research aricraft (Sikorski Black Hawk UH-60A, McDonnell Douglas Harrier II AV-8B) are presented and compared against actual pilot flight data. Conclusions are reached on the ability of the pilot models to adequately predict human behavior when confronted with similar control objectives.

  16. Plume and wake dynamics, mixing, and chemistry behind an HSCT aircraft

    NASA Technical Reports Server (NTRS)

    Miake-Lye, R. C.; Martinez-Sanchez, M.; Brown, R. C.; Kolb, C. E.

    1991-01-01

    The chemical evolution and mixing and vortical motion of a High Speed Civil Transport's engine exhausts must be analyzed in order to track the gas and its speciation as emissions are mixed to atmospheric scales. Attention is presently given to an analytic model of the wake dynamical processes which accounts for the roll-up of the trailing vorticity, its breakup due to the Crow instability, and the subsequent evolution and motion of the reconnected vorticity. The concentrated vorticity is noted to wrap up the buoyant exhaust and suppress its continued mixing and dilution. The species tracked encompass those which could be heterogeneously reactive on the surfaces of the condensed ice particles, and those capable of reacting with exhaust soot particle surfaces to form active contrail and/or cloud condensation nuclei.

  17. Acoustic characteristics and dynamic structural loading of an ASTOVL aircraft in hover

    NASA Astrophysics Data System (ADS)

    Mitchell, L. K.; Norum, Thomas D.; Johns, Albert L.

    1992-01-01

    Measurements of surface dynamic loading and freestream acoustics were made for an ASTOVL model in hover, to quantify the effects of elevated temperature on the acoustic field and surface loading. Data were acquired for a many combinations of operating parameters: model height above the ground plane, nozzle pressure ratio, and jet exit stagnation temperature. For many conditions, strong tones were observed, with amplitudes up to 150 dB. The frequencies of the strongest tones were well predicted by a model assuming feedback between the nozzle exit and the ground plane. The model also accounts for many of the variations in frequency observed with changes in model height, nozzle pressure ratio, and jet temperature. Broadband sound pressure levels up to 170 dB were also recorded. The maximum levels occurred at approximately 3 equivalent jet diameters above the ground plane. For the majority of the cases, the increase in noise due to temperature was less than expected based on free jet correlations.

  18. Assessing Land Management Changes and Population Dynamics in Central Burkina Faso in Response to Climate Change.

    NASA Astrophysics Data System (ADS)

    Kabore Bontogho, P. E.; Boubacar, I.; Afouda, A.; Joerg, H.

    2015-12-01

    Assessing landscape and population's dynamics at watershed level contribute to address anthropogenic aspect of climate change issue owing to the close link between LULC and climate changes. The objective of this study is to explore the dependencies of population to land management changes in Massili basin (2612 km²) located in central Burkina Faso. A set of three satellite scenes was acquired for the years 1990 (Landsat 7 ETM), 2002 (Landsat 7 ETM+) and 2013 (Landsat 8 OLI/TIRS) from the Global Land Cover Facility's (GLCF) website. Census data were provided by the National institute of statistics and demographic (INSD). The satellites images were classified using object-oriented classification method which was supported by historic maps and field data. Those were collected in order to allow for class definition, verification and accuracy assessments. Based on the developed land use maps, change analysis was carried out using post classification comparison in GIS. Finally, derived land use changes were compared with census data in order to explore links between population dynamics and the land use changes. It was found in 1990 that Massili watershed LULC was dominated by Tree/shrub savannah (69%, 1802.28 km2 ), Farm/Fallow was representing 22%, Gallery forest (4%), Settlement (3%), Barre soil (1%), Water bodies (1%). In 2002, the major landscape was Farm (54%). Tree/Shrub savannas were reduced to 36% while the Gallery Forest was decreased to1% of the basin area. The situation has also slightly changed in 2013 with an increase of the area devoted to farm/fallow and settlement at a rate of 3% and Gallery forest has increased to 4%. The changes in land use are in agreement with a notable increase in population. The analysis of census data showed that the number of inhabitants increased from 338 inhabitants per km2 in 1990 to 1150 inhabitants per km2 in 2013. As shown by statistical analysis (Kendall correlation tau=0.9), there is a close relation between both dynamics.

  19. Impact of Land-use Dynamics on Water Resources of Upper Kharun Catchment (UKC), India

    NASA Astrophysics Data System (ADS)

    Kumar, N.

    2015-12-01

    Land-use and its spatial pattern and dynamics strongly influence water resources and demand which are the crucial elements to be considered in water management. The core of integrated water resources management consists of coordinating water supply and demand in a given socio-economic-ecological context and guided by a set of objectives (for example: sustainability, equity, impact awareness, stakeholder involvement). Fulfilling the coordinating function requires reliable information on the water balance components today and future developments which are under the strong influence of land-use dynamics. The information needs to be gained by simulation runs based on hydrological modeling tools with high resolution input regarding land-use (and further features of the basin relevant to runoff generation and precipitation). This research combines the Soil and Water Assessment Tool (SWAT) and an advanced procedure for spatio-temporal land-use mapping that considers and integrates the intra annual variation within a single map and hence better represents an area with different level of urbanization and multiple crop rotations. Due to its relevant impact on the water balance special attention is paid to aspects of irrigation. The study reveals that an increasing pumping rate of groundwater for irrigation is the main reason for decreasing the groundwater contribution to streamflow and subsequently a lowering in discharge and water yield. On the other hand, annual surface runoff is increased significantly by an expansion in built up areas over the decades in the respective parts of the study area. On the UKC scale, the impact of land-use change on the water balance until 2021 is small. However, the impact on water resources is clearly visible and significant at sub-catchment level (increase: surface runoff; decrease: percolation; decrease: groundwater contribution to streamflow and increase: actual evapotranspiration), where expanding urban areas and intensification of

  20. Carbon dynamics and land-use choices: building a regional-scale multidisciplinary model

    USGS Publications Warehouse

    Kerr, Suzi; Liu, Shu-Guang; Pfaff, Alexander S.P.; Hughes, R. Flint

    2003-01-01

    Policy enabling tropical forests to approach their potential contribution to global-climate-change mitigation requires forecasts of land use and carbon storage on a large scale over long periods. In this paper, we present an integrated modeling methodology that addresses these needs. We model the dynamics of the human land-use system and of C pools contained in each ecosystem, as well as their interactions. The model is national scale, and is currently applied in a preliminary way to Costa Rica using data spanning a period of over 50 years. It combines an ecological process model, parameterized using field and other data, with an economic model, estimated using historical data to ensure a close link to actual behavior. These two models are linked so that ecological conditions affect land-use choices and vice versa. The integrated model predicts land use and its consequences for C storage for policy scenarios. These predictions can be used to create baselines, reward sequestration, and estimate the value in both environmental and economic terms of including C sequestration in tropical forests as part of the efforts to mitigate global climate change. The model can also be used to assess the benefits from costly activities to increase accuracy and thus reduce errors and their societal costs.

  1. Landscape-scale modelling of soil carbon dynamics under land use and climate change

    NASA Astrophysics Data System (ADS)

    Lacoste, Marine; Viaud, Valérie; Michot, Didier; Christian, Walter

    2013-04-01

    Soil organic carbon (SOC) sequestration is highly linked to soil use and farming practices, but also to soil redistributions, soil properties, and climate. In a global change context, landscape, farming practice and climate changes are expected; and they will most probably impact SOC dynamics. To assess their respective impacts, we modelled the SOC contents and stocks evolution at the scale of an agricultural landscape, by taking into account the soil redistribution by tillage and water processes. The simulations were conducted from 2010 to 2100 under different scenarios of landscape and climate. These scenarios combined different land uses associated to specific farming practices (mixed dairy with rotations of crops and grasslands, intensive cropping with only crops rotations or permanent grasslands), landscape managements (hedges planting or removal), and climates (business-as-usual climate and climate change, with temperature and precipitations increase). We used a spatially SOC dynamic model (adapted from RothC), coupled to a soil redistribution model (LandSoil). SOC dynamics were spatially modelled with a lateral resolution of 2-m and for soil organic layers up to 105 cm. Initial SOC stocks were described with a 2-m resolution map based on field data and produced with digital soil mapping methods. The major factor of change in SOC stocks was land use change, the second factor of importance was climate change, and finally landscape management: for the total SOC stocks (0-to-105 cm soil layer) the change of land use, climate and landscape management induced a respective mean absolute variation of 10 to 20 tC ha-1, 9 tC ha-1 and 0.4 tC ha-1. When considering the 0-to-105 cm soil layer, the different modelled landscapes showed the same sensitivity to climate change, with induced a mean decrease of 10 tC ha-1. However, the impact of climate change was found different according to the different modelled landscape when considering the 0-to-7.5 and 0-to-30 cm soil

  2. Impacts of land use/land cover change on regional carbon dynamics: an investigation along an urban-to-rural gradient in Massachusetts, USA

    NASA Astrophysics Data System (ADS)

    Dunn, Allison L.; Briber, Brittain M.; Reinmann, Andrew B.; Hutyra, Lucy R.

    2016-04-01

    More than half the world's population lives in cities, a fraction which is projected to increase over the next century. Land use and land cover changes associated with the urbanization process have important implications for vegetation and soil carbon cycling. The impact of urbanization on carbon dynamics is poorly understood, representing a major uncertainty in constraining regional carbon budgets. We initiated a suite of field measurements, remote sensing analyses, and modeling activities in order to investigate how urbanization alters carbon dynamics. We found that conversion of forest to urban land uses resulted in a decrease in overall biomass but a marked increase in productivity of the remaining vegetation. We also found that land use patterns had a profound impact on atmospheric carbon dioxide concentrations on daily, seasonal, and annual timescales. Our results suggest that urbanization has a profound impact on regional carbon dynamics that extends from the time of land use change out well into the future, and the trajectory of urban carbon exchange in the future strongly depends on development patterns.

  3. Distributed Parallel Processing and Dynamic Load Balancing Techniques for Multidisciplinary High Speed Aircraft Design

    NASA Technical Reports Server (NTRS)

    Krasteva, Denitza T.

    1998-01-01

    Multidisciplinary design optimization (MDO) for large-scale engineering problems poses many challenges (e.g., the design of an efficient concurrent paradigm for global optimization based on disciplinary analyses, expensive computations over vast data sets, etc.) This work focuses on the application of distributed schemes for massively parallel architectures to MDO problems, as a tool for reducing computation time and solving larger problems. The specific problem considered here is configuration optimization of a high speed civil transport (HSCT), and the efficient parallelization of the embedded paradigm for reasonable design space identification. Two distributed dynamic load balancing techniques (random polling and global round robin with message combining) and two necessary termination detection schemes (global task count and token passing) were implemented and evaluated in terms of effectiveness and scalability to large problem sizes and a thousand processors. The effect of certain parameters on execution time was also inspected. Empirical results demonstrated stable performance and effectiveness for all schemes, and the parametric study showed that the selected algorithmic parameters have a negligible effect on performance.

  4. Calculations of hot gas ingestion for a STOVL aircraft model

    NASA Technical Reports Server (NTRS)

    Fricker, David M.; Holdeman, James D.; Vanka, Surya P.

    1992-01-01

    Hot gas ingestion problems for Short Take-Off, Vertical Landing (STOVL) aircraft are typically approached with empirical methods and experience. In this study, the hot gas environment around a STOVL aircraft was modeled as multiple jets in crossflow with inlet suction. The flow field was calculated with a Navier-Stokes, Reynolds-averaged, turbulent, 3D computational fluid dynamics code using a multigrid technique. A simple model of a STOVL aircraft with four choked jets at 1000 K was studied at various heights, headwind speeds, and thrust splay angles in a modest parametric study. Scientific visualization of the computed flow field shows a pair of vortices in front of the inlet. This and other qualitative aspects of the flow field agree well with experimental data.

  5. Dynamically downscaled simulations of the north Georgia flood of 2009 under different land-use scenarios

    NASA Astrophysics Data System (ADS)

    Shem, W.; Preston, B. L.; Parish, E. S.

    2011-12-01

    The Weather Forecasting and Research (WRF) model was used to simulate a week-long heavy rainfall event which occurred in north Georgia from September 15-23, 2009. Metropolitan area of Atlanta and the surrounding areas in northern Georgia experienced severe flooding. The study investigated whether the National Center for Environmental Prediction's (NCEP)-North American Regional Reanalysis (NARR) driven WRF dynamic downscaling simulates this extreme event in size and duration comparable to and consistent with the observational data. The study also explored the possibility that land-use change, particularly urbanization, might have facilitated boundary interactions leading to enhancement of precipitation in some localized, specific regions as suggested in some previous studies. The results indicate that the downscaling exercise, under certain land-use scenarios, does a better job than the NARR in reproducing the higher values of the accumulated rainfall totals from this event

  6. Analysing land and vegetation cover dynamics during last three decades in Katerniaghat wildlife sanctuary, India

    NASA Astrophysics Data System (ADS)

    Chitale, V. S.; Behera, M. D.

    2014-10-01

    The change in the tropical forests could be clearly linked to the expansion of the human population and economies. An understanding of the anthropogenic forcing plays an important role in analyzing the impacts of climate change and the fate of tropical forests in the present and future scenario. In the present study, we analyze the impact of natural and anthropogenic factors in forest dynamics in Katerniaghat wildlife sanctuary situated along the Indo-Nepal border in Uttar Pradesh state, India. The study site is under tremendous pressure due to anthropogenic factors from surrounding areas since last three decades. The vegetation cover of the sanctuary primarily comprised of Shorea robusta forests, Tectona grandis plantation, and mixed deciduous forest; while the land cover comprised of agriculture, barren land, and water bodies. The classification accuracy was 83.5%, 91.5%, and 95.2% with MSS, IKONOS, and Quickbird datasets, respectively. Shorea robusta forests showed an increase of 16 km2; while Tectona grandis increased by 63.01 km2 during 1975-2010. The spatial heterogeneity in these tropical vegetation classes surrounded by the human dominated agricultural lands could not be addressed using Landsat MSS data due to coarse spatial resolution; whereas the IKONOS and Quickbird satellite datasets proved to advantageous, thus being able to precisely address the variations within the vegetation classes as well as in the land cover classes and along the edge areas. Massive deforestation during 1970s along the adjoining international boundary with Nepal has led to destruction of the wildlife corridor and has exposed the wildlife sanctuary to human interference like grazing and poaching. Higher rates of forest dynamics during the 25-year period indicate the vulnerability of the ecosystem to the natural and anthropogenic disturbances in the proximity of the sanctuary.

  7. Microbial dynamics and enzyme activities in tropical Andosols depending on land use and nutrient inputs

    NASA Astrophysics Data System (ADS)

    Mganga, Kevin; Razavi, Bahar; Kuzyakov, Yakov

    2015-04-01

    Microbial decomposition of soil organic matter is mediated by enzymes and is a key source of terrestrial CO2 emissions. Microbial and enzyme activities are necessary to understand soil biochemical functioning and identify changes in soil quality. However, little is known about land use and nutrients availability effects on enzyme activities and microbial processes, especially in tropical soils of Africa. This study was conducted to examine how microbial and enzyme activities differ between different land uses and nutrient availability. As Andosols of Mt. Kilimanjaro are limited by nutrient concentrations, we hypothesize that N and P additions will stimulate enzyme activity. N and P were added to soil samples (0-20 cm) representing common land use types in East Africa: (1) savannah, (2) maize fields, (3) lower montane forest, (4) coffee plantation, (5) grasslands and (6) traditional Chagga homegardens. Total CO2 efflux from soil, microbial biomass and activities of β-glucosidase, cellobiohydrolase, chitinase and phosphatase involved in C, N and P cycling, respectively was monitored for 60 days. Total CO2 production, microbial biomass and enzyme activities varied in the order forest soils > grassland soils > arable soils. Increased β-glucosidase and cellobiohydrolase activities after N addition of grassland soils suggest that microorganisms increased N uptake and utilization to produce C-acquiring enzymes. Low N concentration in all soils inhibited chitinase activity. Depending on land use, N and P addition had an inhibitory or neutral effect on phosphatase activity. We attribute this to the high P retention of Andosols and low impact of N and P on the labile P fractions. Enhanced CO2 production after P addition suggests that increased P availability could stimulate soil organic matter biodegradation in Andosols. In conclusion, land use and nutrients influenced soil enzyme activities and microbial dynamics and demonstrated the decline in soil quality after landuse

  8. Archaeopedological analysis of land use dynamics in marginal areas in SW Germany

    NASA Astrophysics Data System (ADS)

    Henkner, Jessica; Ahlrichs, Jan; Scholten, Thomas; Knopf, Thomas; Kühn, Peter

    2016-04-01

    A common theory to explain human migration is climate change triggering migration and the shift of farming places. Populated areas might have been relocated or extended because of changing resources like a warming climate, soil erosion or a change in demands. But it also has to be taken into account that altered trading relations or changing religious attitudes might have caused migration into and settlement of formerly not used areas. In the case of Southwest Germany it is assumed that people migrated from the favorable Baar (more even areas, soils on loess, lower elevations) to the unfavorable Black Forest and the Swabian Jura with harsher environmental conditions (small valleys, acidic soils, steep slopes, higher elevation). Soils are generally considered as being an important resource related to human activities, especially farming, but also for using wood, water or iron ore. Colluvial deposits as geoarchives reveal the formative impact of humans on their environment: on the development of soil, relief, vegetation, and land use. Land use and therefore settlement history are inscribed in colluvial deposits, which we use as proxies for the kind and intensity of human activities. Especially in marginal areas land use and settlement dynamics are not well investigated. Important questions are how and why did people use the unfavorable land during different times? Which resources were important for different phases of settlement? In this project, soil science methods are used together with archaeological approaches, which is an essential part of archaeopedology. Using colluvial deposits from three study areas it is possible to create pedological and chronological stratigraphies reflecting land use dynamics in favorable and unfavorable areas. First AMS radiocarbon dates from the western Baar in transition to the Black Forest point to human land use with different intensity for 5500 years. Thick lower colluvial layers date back to the third millennium BC. Above

  9. A complex systems approach to dynamic spatial simulation modeling: LandUse and LandCover change in the Ecuadorian Amazon

    NASA Astrophysics Data System (ADS)

    Messina, Joseph Paul

    The Ecuadorian Amazon, lying in the headwaters of the Napo and Aguarico River valleys, is experiencing rapid change in LandUse and LandCover (LULC) conditions and regional landscape diversity uniquely tied to spontaneous agricultural colonization and oil exploration. Beginning in the early 1970s, spontaneous colonization occurred on squattered lands located adjacent to oil company roads and in government development sectors composed of multiple 50 ha land parcels organized into "piano key" shaped family farms or fincas. Since fincas are managed at the household level as spatially discrete, temporally independent units, land conversion at the finca-level is recognized as the chief proximate cause of deforestation within the region. Focusing on the spatial and temporal dynamics of deforestation, agricultural extensification, and plant succession at the finca-level, and urbanization at the community-level, cell-based morphogenetic models of LandUse and LandCover Change (LULCC) were developed as the foundation for predictive models of regional LULCC dynamics and landscape diversity. Two cellular automata models were developed and used to integrate biophysical, geographical, and social variables to characterize temporally dynamic landscapes. The human, geographical, and biophysical dimensions of land use and land cover change were examined, specifically deforestation, anthropogenic extensification, and reforestation. Remotely-sensed data ranging temporally from the 1970s through 1999, combined with thematic map coverages of biophysical gradients and geographical accessibility, were linked to household and community survey data collected in 1990 and 1999. Image processing techniques for LULC characterization and spatial analyses of landscape structure were used to assess the rate and nature of LULCC throughout the time-series. In addition, LULC and LULCC associated with secondary plant succession and agricultural extensification were assessed and simulated for specific

  10. How much does weather-driven vegetation dynamics matter in land surface modelling?

    NASA Astrophysics Data System (ADS)

    Ingwersen, Joachim; Streck, Thilo

    2016-04-01

    Land surface models (LSM) are an essential part of weather and climate models as they provide the lower boundary condition for the atmospheric models. In state-of-the-art LSMs the seasonal vegetation dynamics is "frozen". The seasonal variation of vegetation state variables, such as leaf area index or green vegetation fraction, are prescribed in lookup tables. Hence, a year-by-year variation in the development of vegetation due to changing weather conditions cannot be considered. For climate simulations, this is obviously a severe drawback. The objective of the present study was to quantify the potential error in the simulation of land surface exchange processes resulting from "frozen" vegetation dynamics. For this purpose we simulated energy and water fluxes from a winter wheat stand and a maize stand in Southwest Germany. In a first set of simulations, six years (2010 to 2015) were simulated considering weather-driven vegetation dynamics. For this purpose, we coupled the generic crop growth model GECROS with the NOAH-MP model (NOAHMP-GECROS). In a second set of simulations all vegetation-related state variables of the 2010 simulation were written to an external file and were used to overwrite the vegetation-related state variables of the simulations of the years 2011-2015. The difference between both sets was taken as a measure for the potential error introduced to the LSM due to the assumption of a "frozen" vegetation dynamics. We will present first results and discuss the impact of "frozen" vegetation dynamics on climate change simulations.

  11. Climate, invasive species and land use drive population dynamics of a cold-water specialist

    USGS Publications Warehouse

    Kovach, Ryan P.; Al-Chokhachy, Robert K.; Whited, Diane C.; Schmetterling, David A.; Dux, Andrew M; Muhlfeld, Clint C.

    2016-01-01

    Climate change is an additional stressor in a complex suite of threats facing freshwater biodiversity, particularly for cold-water fishes. Research addressing the consequences of climate change on cold-water fish has generally focused on temperature limits defining spatial distributions, largely ignoring how climatic variation influences population dynamics in the context of other existing stressors.We used long-term data from 92 populations of bull trout Salvelinus confluentus – one of North America's most cold-adapted fishes – to quantify additive and interactive effects of climate, invasive species and land use on population dynamics (abundance, variability and growth rate).Populations were generally depressed, more variable and declining where spawning and rearing stream habitat was limited, invasive species and land use were prevalent and stream temperatures were highest. Increasing stream temperature acted additively and independently, whereas land use and invasive species had additive and interactive effects (i.e. the impact of one stressor depended on exposure to the other stressor).Most (58%–78%) of the explained variation in population dynamics was attributed to the presence of invasive species, differences in life history and management actions in foraging habitats in rivers, lakes and reservoirs. Although invasive fishes had strong negative effects on populations in foraging habitats, proactive control programmes appeared to effectively temper their negative impact.Synthesis and applications. Long-term demographic data emphasize that climate warming will exacerbate imperilment of cold-water specialists like bull trout, yet other stressors – especially invasive fishes – are immediate threats that can be addressed by proactive management actions. Therefore, climate-adaptation strategies for freshwater biodiversity should consider existing abiotic and biotic stressors, some of which provide potential and realized opportunity for conservation

  12. [Application of optical flow dynamic texture in land use/cover change detection].

    PubMed

    Yan, Li; Gong, Yi-Long; Zhang, Yi; Duan, Wei

    2014-11-01

    In the present study, a novel change detection approach for high resolution remote sensing images is proposed based on the optical flow dynamic texture (OFDT), which could achieve the land use & land cover change information automatically with a dynamic description of ground-object changes. This paper describes the ground-object gradual change process from the principle using optical flow theory, which breaks the ground-object sudden change hypothesis in remote sensing change detection methods in the past. As the steps of this method are simple, it could be integrated in the systems and software such as Land Resource Management and Urban Planning software that needs to find ground-object changes. This method takes into account the temporal dimension feature between remote sensing images, which provides a richer set of information for remote sensing change detection, thereby improving the status that most of the change detection methods are mainly dependent on the spatial dimension information. In this article, optical flow dynamic texture is the basic reflection of changes, and it is used in high resolution remote sensing image support vector machine post-classification change detection, combined with spectral information. The texture in the temporal dimension which is considered in this article has a smaller amount of data than most of the textures in the spatial dimensions. The highly automated texture computing has only one parameter to set, which could relax the onerous manual evaluation present status. The effectiveness of the proposed approach is evaluated with the 2011 and 2012 QuickBird datasets covering Duerbert Mongolian Autonomous County of Daqing City, China. Then, the effects of different optical flow smooth coefficient and the impact on the description of the ground-object changes in the method are deeply analyzed: The experiment result is satisfactory, with an 87.29% overall accuracy and an 0.850 7 Kappa index, and the method achieves better

  13. Dynamic Visual Acuity and Landing Sickness in Crewmembers Returning from Long-Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Rosenberg, M.J.F; Peters, B.T.; Reschke, M. F.

    2016-01-01

    Long-term exposure to microgravity causes sensorimotor adaptations that result in functional deficits upon returning to a gravitational environment. At landing the vestibular system and the central nervous system, responsible for coordinating head and eye movements, are adapted to microgravity and must re-adapt to the gravitational environment. This re-adaptation causes decrements in gaze control and dynamic visual acuity, with astronauts reporting oscillopsia and blurred vision. Dynamic visual acuity (DVA) is assessed using an oscillating chair developed in the Neuroscience Laboratory at JSC. This chair is lightweight and easily portable for quick deployment in the field. The base of the chair is spring-loaded and allows for manual oscillation of the subject. Using a metronome, the chair is vertically oscillated plus or minus 2 cm at 2 Hz by an operator, to simulate walking. While the subject is being oscillated, they are asked to discern the direction of Landolt-C optotypes of varying sizes and record their direction using a gamepad. The visual acuity thresholds are determined using an algorithm that alters the size of the optotype based on the previous response of the subject using a forced-choice best parameter estimation that is able to rapidly converge on the threshold value. Visual acuity thresholds were determined both for static (seated) and dynamic (oscillating) conditions. Dynamic visual acuity is defined as the difference between the dynamic and static conditions. Dynamic visual acuity measures will be taken prior to flight (typically L-180, L-90, and L-60) and up to eight times after landing, including up to 3 times on R plus 0. Follow up measurements will be taken at R plus 1 (approximately 36 hours after landing). Long-duration International Space Station crewmembers will be tested once at the refueling stop in Europe and once again upon return to Johnson Space Center. In addition to DVA, subjective ratings of motion sickness will be recorded

  14. Spatio-temporal dynamics in the flood exposure due to land use changes

    NASA Astrophysics Data System (ADS)

    Cammerer, H.; Thieken, A.

    2012-04-01

    Flood risk is expected to intensify in the future in many regions of the world. Consequently, the resulting flood damage is very likely to increase further on. Comprehensive flood risk analyses which are not only reliable for the contemporary state require therefore the consideration of the main drivers that influence flood risk. Human-induced changes in land use as well as climate change impacts on hydrological processes turned out to play a key role in future-orientated flood risk assessments. Even if there is strong evidence that global climate change will amplify flood risk especially in mountainous areas like the European Alps the accumulation of people and their assets in flood plains are seen as main causes of increasing flood risk. Therefore the analysis of spatio-temporal dynamics in the flood exposure due to land use changes is a crucial part for long-term and more robust flood risk analyses. Within the frame of a study in the region of Reutte in Tyrol (Austria) flood risk time series for the next decades are developed by estimating the hazard potential as well as the flood impact, i.e. the flood losses. For the latter, future flood exposed residential and industrial areas are assessed by applying a spatially explicit land use change model and various inundation scenarios. The land use simulations for the alpine study area were calculated by means of the CLUE-S model, respectively the newer Version Dyna-CLUE. This model simulates the spatial pattern of land-use in reaction to pre-defined changes of the future land use demand, suitable locations which are identified by means of logistic regression and user-specified decision rules as well as spatial policies (e.g. area zoning plans and danger zoning plans). For now, inundation areas were derived from the past flood event in August 2005 and the HORA project where flood extents for different recurrence intervals were simulated. The intersection of these flood plains with various land use scenarios allows

  15. Dynamic Visual Acuity and Landing Sickness in Crewmembers Returning from Long-Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Rosenberg, M. J. F.; Peters, B. T.; Reschke, M. F.

    2016-01-01

    Long-term exposure to microgravity causes sensorimotor adaptations that result in functional deficits upon returning to a gravitational environment. At landing the vestibular system and the central nervous system, responsible for coordinating head and eye movements, are adapted to microgravity and must re-adapt to the gravitational environment. This re-adaptation causes decrements in gaze control and dynamic visual acuity, with astronauts reporting oscillopsia and blurred vision. Dynamic visual acuity (DVA) is assessed using an oscillating chair (Figure 1) developed in the Neuroscience Laboratory at JSC. This chair is lightweight and easily portable for quick deployment in the field. The base of the chair is spring-loaded and allows for manual oscillation of the subject. Using a metronome, the chair is vertically oscillated +/- 2 cm at 2 Hz by an operator, to simulate walking. While the subject is being oscillated, they are asked to discern the direction of Landolt-C optotypes of varying sizes presented on a screen 1 m from the subject and record their direction using a gamepad. The visual acuity thresholds are determined using an algorithm that alters the size of the optotype based on the previous responses of the subject using a forced-choice best parameter estimation that is able to rapidly converge on the threshold value. Visual acuity thresholds are determined both for static (seated) and dynamic (oscillating) conditions. Dynamic visual acuity is defined as the difference between the dynamic and static conditions.

  16. Effects of land use changes on the dynamics of selected soil properties in the Northeast Wollega, Ethiopia

    NASA Astrophysics Data System (ADS)

    Adugna, A.; Abegaz, A.

    2015-10-01

    Land use change can have negative or positive effects on soil quality. Our objective was to assess the effects of land uses changes on the dynamics of selected soil physical and chemical properties. Soil samples were collected from three adjacent land uses, namely forestland, grazing land and cultivated land at 0-15 cm depth, and tested in National Soil Testing Center, Ministry of Agriculture of Ethiopia. Percentage changes of soil properties on cultivated and grazing land was computed and compared to forestland, and Analysis of variance (ANOVA) was used to test the significance of the changes. The results indicate that sand, silt, SOM, N, pH, CEC and Ca were the highest in forestlands. Mg was the highest in grazing land while clay, P and K were the highest in cultivated land. The percentage changes in sand, clay, SOM, pH, CEC, Ca and Mg were higher in cultivated land than the change in grazing land compared to forestland, except P. In terms of relationship between soil properties; SOM, N, CEC and Ca were strongly positively correlated with most of soil properties while P and silt have no significant relationship with any of other considered soil properties. Clay has negative correlation with all of soil properties. Generally, cultivated land has the least concentration of soil physical and chemical properties except clay and AP which suggest increasing degradation rate in soils of cultivated land. So as to increase SOM and other nutrients in the soil of cultivated land, integrated implementation of land management through compost, cover crops, manures, minimum tillage and crop rotation; and liming to increase soil pH are suggested.

  17. The Typical General Aviation Aircraft

    NASA Technical Reports Server (NTRS)

    Turnbull, Andrew

    1999-01-01

    The reliability of General Aviation aircraft is unknown. In order to "assist the development of future GA reliability and safety requirements", a reliability study needs to be performed. Before any studies on General Aviation aircraft reliability begins, a definition of a typical aircraft that encompasses most of the general aviation characteristics needs to be defined. In this report, not only is the typical general aviation aircraft defined for the purpose of the follow-on reliability study, but it is also separated, or "sifted" into several different categories where individual analysis can be performed on the reasonably independent systems. In this study, the typical General Aviation aircraft is a four-place, single engine piston, all aluminum fixed-wing certified aircraft with a fixed tricycle landing gear and a cable operated flight control system. The system breakdown of a GA aircraft "sifts" the aircraft systems and components into five categories: Powerplant, Airframe, Aircraft Control Systems, Cockpit Instrumentation Systems, and the Electrical Systems. This breakdown was performed along the lines of a failure of the system. Any component that caused a system to fail was considered a part of that system.

  18. An aircraft sensor fault tolerant system

    NASA Technical Reports Server (NTRS)

    Caglayan, A. K.; Lancraft, R. E.

    1982-01-01

    The design of a sensor fault tolerant system which uses analytical redundancy for the Terminal Configured Vehicle (TCV) research aircraft in a Microwave Landing System (MLS) environment was studied. The fault tolerant system provides reliable estimates for aircraft position, velocity, and attitude in the presence of possible failures in navigation aid instruments and onboard sensors. The estimates, provided by the fault tolerant system, are used by the automated guidance and control system to land the aircraft along a prescribed path. Sensor failures are identified by utilizing the analytic relationship between the various sensor outputs arising from the aircraft equations of motion.

  19. Powered-lift aircraft technology

    NASA Technical Reports Server (NTRS)

    Deckert, W. H.; Franklin, J. A.

    1989-01-01

    Powered lift aircraft have the ability to vary the magnitude and direction of the force produced by the propulsion system so as to control the overall lift and streamwise force components of the aircraft, with the objective of enabling the aircraft to operate from minimum sized terminal sites. Power lift technology has contributed to the development of the jet lift Harrier and to the forth coming operational V-22 Tilt Rotor and the C-17 military transport. This technology will soon be expanded to include supersonic fighters with short takeoff and vertical landing capability, and will continue to be used for the development of short- and vertical-takeoff and landing transport. An overview of this field of aeronautical technology is provided for several types of powered lift aircraft. It focuses on the description of various powered lift concepts and their operational capability. Aspects of aerodynamics and flight controls pertinent to powered lift are also discussed.

  20. Dynamics of land use and land cover and its effects on hydrologic responses: case study of the Gilgel Tekeze catchment in the highlands of Northern Ethiopia.

    PubMed

    Haregeweyn, Nigussie; Tesfaye, Samuel; Tsunekawa, Atsushi; Tsubo, Mitsuru; Meshesha, Derege Tsegaye; Adgo, Enyew; Elias, Asres

    2015-01-01

    Unprecedented land use and land cover (LULC) changes in the Gilgel Tekeze catchment of the upper Nile River basin in Ethiopia may have far-reaching consequences for the long-term sustainability of the natural resources base. This study analyzed the dynamics and hydrologic effects of LULC changes between 1976 and 2003 as shown in satellite imagery. The effects of these LULC changes on the hydrologic response were investigated using the WetSpa model to estimate spatially distributed average annual evapotranspiration, surface runoff, and groundwater recharge. Digital image analysis revealed major increments of cultivated land and settlements of 15.4 and 9.9%, respectively, at the expense of shrubland and grazing lands. Population growth and the associated demand for land were found to be the major driving forces. The WetSpa simulation showed an increase in annual surface runoff of 101 mm and a decrease in groundwater recharge of 39 mm over the period 1976-2003. These results signify an increasing threat of moisture unavailability in the study area and suggest that appropriate land management measures under the framework of the integrated catchment management (ICM) approach are urgently needed.

  1. Land cover change and remote sensing: Examples of quantifying spatiotemporal dynamics in tropical forests

    SciTech Connect

    Krummel, J.R.; Su, Haiping; Fox, J.; Yarnasan, S.; Ekasingh, M.

    1995-06-01

    Research on human impacts or natural processes that operate over broad geographic areas must explicitly address issues of scale and spatial heterogeneity. While the tropical forests of Southeast Asia and Mexico have been occupied and used to meet human needs for thousands of years, traditional forest management systems are currently being transformed by rapid and far-reaching demographic, political, economic, and environmental changes. The dynamics of population growth, migration into the remaining frontiers, and responses to national and international market forces result in a demand for land to produce food and fiber. These results illustrate some of the mechanisms that drive current land use changes, especially in the tropical forest frontiers. By linking the outcome of individual land use decisions and measures of landscape fragmentation and change, the aggregated results shows the hierarchy of temporal and spatial events that in summation result in global changes to the most complex and sensitive biome -- tropical forests. By quantifying the spatial and temporal patterns of tropical forest change, researchers can assist policy makers by showing how landscape systems in these tropical forests are controlled by physical, biological, social, and economic parameters.

  2. Vegetation, land surface brightness, and temperature dynamics after aspen forest die-off

    NASA Astrophysics Data System (ADS)

    Huang, Cho-ying; Anderegg, William R. L.

    2014-07-01

    Forest dynamics following drought-induced tree mortality can affect regional climate through biophysical surface properties. These dynamics have not been well quantified, particularly at the regional scale, and are a large uncertainty in ecosystem-climate feedback. We investigated regional biophysical characteristics through time (1995-2011) in drought-impacted (2001-2003), trembling aspen (Populus tremuloides Michx.) forests by utilizing Landsat time series green and brown vegetation cover, surface brightness (total shortwave albedo), and daytime land surface temperature. We quantified the temporal dynamics and postdrought recovery of these characteristics for aspen forests experiencing severe drought-induced mortality in the San Juan National Forest in southwestern Colorado, USA. We partitioned forests into three categories from healthy to severe mortality (Healthy, Intermediate, and Die-off) by referring to field observations of aspen canopy mortality and live aboveground biomass losses. The vegetation cover of die-off areas in 2011 (26.9% of the aspen forest) was significantly different compared to predrought conditions (decrease of 7.4% of the green vegetation cover and increase of 12.1% of the brown vegetation cover compared to 1999). The surface brightness of the study region 9 years after drought however was comparable to predrought estimates (12.7-13.7%). Postdrought brightness was potentially influenced by understory shrubs, since they became the top layer green canopies in disturbed sites from a satellite's point of view. Satellite evidence also showed that the differences of land surface temperature among the three groups increased substantially (≥45%) after drought, possibly due to the reduction of plant evapotranspiration in the Intermediate and Die-off sites. Our results suggest that the mortality-affected systems have not recovered in terms of the surface biophysical properties. We also find that the temporal dynamics of vegetation cover holds

  3. Dynamics of Sylvatic Chagas Disease Vectors in Coastal Ecuador Is Driven by Changes in Land Cover

    PubMed Central

    Grijalva, Mario J.; Terán, David; Dangles, Olivier

    2014-01-01

    Background Chagas disease is a serious public health problem in Latin America where about ten million individuals show Trypanosoma cruzi infection. Despite significant success in controlling domiciliated triatomines, sylvatic populations frequently infest houses after insecticide treatment which hampers long term control prospects in vast geographical areas where vectorial transmission is endemic. As a key issue, the spatio-temporal dynamics of sylvatic populations is likely influenced by landscape yet evidence showing this effect is rare. The aim of this work is to examine the role of land cover changes in sylvatic triatomine ecology, based on an exhaustive field survey of pathogens, vectors, hosts, and microhabitat characteristics' dynamics. Methodology and Principal Findings The study was performed in agricultural landscapes of coastal Ecuador as a study model. Over one year, a spatially-randomized sampling design (490 collection points) allowed quantifying triatomine densities in natural, cultivated and domestic habitats. We also assessed infection of the bugs with trypanosomes, documented their microhabitats and potential hosts, and recorded changes in landscape characteristics. In total we collected 886 individuals, mainly represented by nymphal stages of one triatomine species Rhodnius ecuadoriensis. As main results, we found that 1) sylvatic triatomines had very high T. cruzi infection rates (71%) and 2) densities of T. cruzi-infected sylvatic triatomines varied predictably over time due to changes in land cover and occurrence of associated rodent hosts. Conclusion We propose a framework for identifying the factors affecting the yearly distribution of sylvatic T. cruzi vectors. Beyond providing key basic information for the control of human habitat colonization by sylvatic vector populations, our framework highlights the importance of both environmental and sociological factors in shaping the spatio-temporal population dynamics of triatomines. A better

  4. Aircraft Operations Classification System

    NASA Technical Reports Server (NTRS)

    Harlow, Charles; Zhu, Weihong

    2001-01-01

    Accurate data is important in the aviation planning process. In this project we consider systems for measuring aircraft activity at airports. This would include determining the type of aircraft such as jet, helicopter, single engine, and multiengine propeller. Some of the issues involved in deploying technologies for monitoring aircraft operations are cost, reliability, and accuracy. In addition, the system must be field portable and acceptable at airports. A comparison of technologies was conducted and it was decided that an aircraft monitoring system should be based upon acoustic technology. A multimedia relational database was established for the study. The information contained in the database consists of airport information, runway information, acoustic records, photographic records, a description of the event (takeoff, landing), aircraft type, and environmental information. We extracted features from the time signal and the frequency content of the signal. A multi-layer feed-forward neural network was chosen as the classifier. Training and testing results were obtained. We were able to obtain classification results of over 90 percent for training and testing for takeoff events.

  5. Studies for determining rapid thrust response requirements and techniques for use in a long range transport aircraft

    NASA Technical Reports Server (NTRS)

    Newirth, D. M.; Ferguson, W. W.

    1973-01-01

    Propulsion systems proposed for the next generation of long-range transport aircraft will utilize advanced technology to reduce the noise to levels that will be inoffensive to the community. Additional reductions can be realized by adopting steeper glide slopes during the landing approach. The aircraft dynamic characteristics and methods of obtaining rapid engine response during the go-around maneuver from an aborted landing approach are identified and discussed. The study concludes that the present levels of flight safety will not be compromised by the steeper approach.

  6. Aircraft hydraulic systems. Third edition

    SciTech Connect

    Neese, W.A.

    1991-12-31

    The first nine chapters concern hydraulic components including: tubing, hoses, fittings, seals, pumps, valves, cylinders, and motors. General hydraulic system considerations are included in chapters five and nine, while pneumatic systems are covered in chapter ten. Chapters eleven through fifteen are devoted to aircraft-specific systems such as: landing gear, flight controls, brakes, etc. The material is rounded out with excerpts from the Canadair Challenger 601 training guide to illustrate the use of hydraulic systems in a specific aircraft application.

  7. Integrated Assessment of Climate Change, Land-Use Changes, and Regional Carbon Dynamics in United States

    NASA Astrophysics Data System (ADS)

    Mu, J. E.; Sleeter, B. M.; Abatzoglou, J. T.

    2015-12-01

    The fact that climate change is likely to accelerate throughout this century means that climate-sensitive sectors such as agriculture will need to adapt increasingly to climate change. This fact also means that understanding the potential for agricultural adaptation, and how it could come about, is important for ongoing technology investments in the public and private sectors, for infrastructure investments, and for the various policies that address agriculture directly or indirectly. This paper is an interdisciplinary study by collaborating with climate scientist, agronomists, economists, and ecologists. We first use statistical models to estimate impacts of climate change on major crop yields (wheat, corn, soybeans, sorghum, and cotton) and predict changes in crop yields under future climate condition using downscaled climate projections from CMIP5. Then, we feed the predicted yield changes to a partial equilibrium economic model (FASOM-GHG) to evaluate economic and environmental outcomes including changes in land uses (i.e., cropland, pastureland, forest land, urban land and land for conservation) in United States. Finally, we use outputs from FASOM-GHG as inputs for the ST-SIM ecological model to simulate future carbon dynamics through changes in land use under future climate conditions and discuss the rate of adaptation through land-use changes. Findings in this paper have several merits compared to previous findings in the literature. First, we add economic components to the carbon calculation. It is important to include socio-economic conditions when calculating carbon emission and/or carbon sequestration because human activities are the major contribution to atmosphere GHG emissions. Second, we use the most recent downscaled climate projections from CMIP5 to capture uncertainties from climate model projections. Instead of using all GCMs, we select five GCMs to represent the ensemble. Third, we use a bottom-up approach because we start from micro-level data

  8. Airborne Sunphotometer Measurements of Aerosol Optical Depth and Columnar Water Vapor During the Puerto Rico Dust Experiment, and Comparison with Land, Aircraft, and Satellite Measurements

    NASA Technical Reports Server (NTRS)

    Livingston, John M.; Russell, Philip B.; Reid, Jeffrey; Redemann, Jens; Schmid, Beat; Allen, Duane A.; Torres, Omar; Levy, Robert C.; Remer, Lorraine A.; Holben, Brent N.; Hipskind, R. Stephen (Technical Monitor)

    2002-01-01

    Analyses of aerosol optical depth (AOD) and columnar water vapor (CWV) measurements obtained with the six-channel NASA Ames Airborne Tracking Sunphotometer (AATS-6) mounted on a twin-engine aircraft during the summer 2000 Puerto Rico Dust Experiment are presented. In general, aerosol extinction values calculated from AATS-6 AOD measurements acquired during aircraft profiles up to 5 km ASL reproduce the vertical structure measured by coincident aircraft in-situ measurements of total aerosol number and surface area concentration. Calculations show that the spectral dependence of AOD was small (mean Angstrom wavelength exponents of approximately 0.20) within three atmospheric layers defined as the total column beneath the top of each aircraft profile, the region beneath the trade wind inversion, and the region within the Saharan Air Layer (SAL) above the trade inversion. This spectral behavior is consistent with attenuation of incoming solar radiation by large dust particles or by dust plus sea salt. Values of CWV calculated from profile measurements by AATS-6 at 941.9 nm and from aircraft in-situ measurements by a chilled mirror dewpoint hygrometer agree to within approximately 4% (0.13 g/sq cm). AATS-6 AOD values measured on the ground at Roosevelt Roads Naval Air Station and during low altitude aircraft runs over the adjacent Cabras Island aerosol/radiation ground site agree to within 0.004 to 0.030 with coincident data obtained with an AERONET Sun/sky Cimel radiometer located at Cabras Island. For the same observation times, AERONET retrievals of CWV exceed AATS-6 values by a mean of 0.74 g/sq cm (approximately 21 %) for the 2.9-3.9 g/sq cm measured by AATS-6. Comparison of AATS-6 aerosol extinction values obtained during four aircraft ascents over Cabras Island with corresponding values calculated from coincident aerosol backscatter measurements by a ground-based micro-pulse lidar (MPL-Net) located at Cabras yields a similar vertical structure above the trade

  9. Aircraft Design

    NASA Technical Reports Server (NTRS)

    Bowers, Albion H. (Inventor); Uden, Edward (Inventor)

    2016-01-01

    The present invention is an aircraft wing design that creates a bell shaped span load, which results in a negative induced drag (induced thrust) on the outer portion of the wing; such a design obviates the need for rudder control of an aircraft.

  10. Seasonal Dynamics of Water Use Strategy of Two Salix Shrubs in Alpine Sandy Land, Tibetan Plateau.

    PubMed

    Zhu, Yajuan; Wang, Guojie; Li, Renqiang

    2016-01-01

    Water is a limiting factor for plant growth and vegetation dynamics in alpine sandy land of the Tibetan Plateau, especially with the increasing frequency of extreme precipitation events and drought caused by climate change. Therefore, a relatively stable water source from either deeper soil profiles or ground water is necessary for plant growth. Understanding the water use strategy of dominant species in the alpine sandy land ecosystem is important for vegetative rehabilitation and ecological restoration. The stable isotope methodology of δD, δ18O, and δ13C was used to determine main water source and long-term water use efficiency of Salix psammophila and S. cheilophila, two dominant shrubs on interdune of alpine sandy land in northeastern Tibetan Plateau. The root systems of two Salix shrubs were investigated to determine their distribution pattern. The results showed that S. psammophila and S. cheilophila absorbed soil water at different soil depths or ground water in different seasons, depending on water availability and water use strategy. Salix psammophila used ground water during the growing season and relied on shallow soil water recharged by rain in summer. Salix cheilophila used ground water in spring and summer, but relied on shallow soil water recharged by rain in spring and deep soil water recharged by ground water in fall. The two shrubs had dimorphic root systems, which is coincident with their water use strategy. Higher biomass of fine roots in S. psammophila and longer fine roots in S. cheilophila facilitated to absorb water in deeper soil layers. The long-term water use efficiency of two Salix shrubs increased during the dry season in spring. The long-term water use efficiency was higher in S. psammophila than in S. cheilophila, as the former species is better adapted to semiarid climate of alpine sandy land.

  11. Seasonal Dynamics of Water Use Strategy of Two Salix Shrubs in Alpine Sandy Land, Tibetan Plateau.

    PubMed

    Zhu, Yajuan; Wang, Guojie; Li, Renqiang

    2016-01-01

    Water is a limiting factor for plant growth and vegetation dynamics in alpine sandy land of the Tibetan Plateau, especially with the increasing frequency of extreme precipitation events and drought caused by climate change. Therefore, a relatively stable water source from either deeper soil profiles or ground water is necessary for plant growth. Understanding the water use strategy of dominant species in the alpine sandy land ecosystem is important for vegetative rehabilitation and ecological restoration. The stable isotope methodology of δD, δ18O, and δ13C was used to determine main water source and long-term water use efficiency of Salix psammophila and S. cheilophila, two dominant shrubs on interdune of alpine sandy land in northeastern Tibetan Plateau. The root systems of two Salix shrubs were investigated to determine their distribution pattern. The results showed that S. psammophila and S. cheilophila absorbed soil water at different soil depths or ground water in different seasons, depending on water availability and water use strategy. Salix psammophila used ground water during the growing season and relied on shallow soil water recharged by rain in summer. Salix cheilophila used ground water in spring and summer, but relied on shallow soil water recharged by rain in spring and deep soil water recharged by ground water in fall. The two shrubs had dimorphic root systems, which is coincident with their water use strategy. Higher biomass of fine roots in S. psammophila and longer fine roots in S. cheilophila facilitated to absorb water in deeper soil layers. The long-term water use efficiency of two Salix shrubs increased during the dry season in spring. The long-term water use efficiency was higher in S. psammophila than in S. cheilophila, as the former species is better adapted to semiarid climate of alpine sandy land. PMID:27243772

  12. Seasonal Dynamics of Water Use Strategy of Two Salix Shrubs in Alpine Sandy Land, Tibetan Plateau

    PubMed Central

    Zhu, Yajuan; Wang, Guojie; Li, Renqiang

    2016-01-01

    Water is a limiting factor for plant growth and vegetation dynamics in alpine sandy land of the Tibetan Plateau, especially with the increasing frequency of extreme precipitation events and drought caused by climate change. Therefore, a relatively stable water source from either deeper soil profiles or ground water is necessary for plant growth. Understanding the water use strategy of dominant species in the alpine sandy land ecosystem is important for vegetative rehabilitation and ecological restoration. The stable isotope methodology of δD, δ18O, and δ13C was used to determine main water source and long-term water use efficiency of Salix psammophila and S. cheilophila, two dominant shrubs on interdune of alpine sandy land in northeastern Tibetan Plateau. The root systems of two Salix shrubs were investigated to determine their distribution pattern. The results showed that S. psammophila and S. cheilophila absorbed soil water at different soil depths or ground water in different seasons, depending on water availability and water use strategy. Salix psammophila used ground water during the growing season and relied on shallow soil water recharged by rain in summer. Salix cheilophila used ground water in spring and summer, but relied on shallow soil water recharged by rain in spring and deep soil water recharged by ground water in fall. The two shrubs had dimorphic root systems, which is coincident with their water use strategy. Higher biomass of fine roots in S. psammophila and longer fine roots in S. cheilophila facilitated to absorb water in deeper soil layers. The long-term water use efficiency of two Salix shrubs increased during the dry season in spring. The long-term water use efficiency was higher in S. psammophila than in S. cheilophila, as the former species is better adapted to semiarid climate of alpine sandy land. PMID:27243772

  13. Satellite image simulations for model-supervised, dynamic retrieval of crop type and land use intensity

    NASA Astrophysics Data System (ADS)

    Bach, H.; Klug, P.; Ruf, T.; Migdall, S.; Schlenz, F.; Hank, T.; Mauser, W.

    2015-04-01

    To support food security, information products about the actual cropping area per crop type, the current status of agricultural production and estimated yields, as well as the sustainability of the agricultural management are necessary. Based on this information, well-targeted land management decisions can be made. Remote sensing is in a unique position to contribute to this task as it is globally available and provides a plethora of information about current crop status. M4Land is a comprehensive system in which a crop growth model (PROMET) and a reflectance model (SLC) are coupled in order to provide these information products by analyzing multi-temporal satellite images. SLC uses modelled surface state parameters from PROMET, such as leaf area index or phenology of different crops to simulate spatially distributed surface reflectance spectra. This is the basis for generating artificial satellite images considering sensor specific configurations (spectral bands, solar and observation geometries). Ensembles of model runs are used to represent different crop types, fertilization status, soil colour and soil moisture. By multi-temporal comparisons of simulated and real satellite images, the land cover/crop type can be classified in a dynamically, model-supervised way and without in-situ training data. The method is demonstrated in an agricultural test-site in Bavaria. Its transferability is studied by analysing PROMET model results for the rest of Germany. Especially the simulated phenological development can be verified on this scale in order to understand whether PROMET is able to adequately simulate spatial, as well as temporal (intra- and inter-season) crop growth conditions, a prerequisite for the model-supervised approach. This sophisticated new technology allows monitoring of management decisions on the field-level using high resolution optical data (presently RapidEye and Landsat). The M4Land analysis system is designed to integrate multi-mission data and is

  14. Temporal soil organic carbon dynamics following land-use change for lignocellulosic bioenergy production

    NASA Astrophysics Data System (ADS)

    McClean, Gary; Rowe, Rebecca; Sohi, Saran; Heal, Kate

    2014-05-01

    As the demand for renewable energy crops increases to assist in reducing anthropogenic carbon dioxide (CO2) emissions, the projected future expansion in bioenergy crop production is expected to cause significant land-use change (LUC). It has been reported that lignocellulosic crops such as Miscanthus and willow short rotation coppice (SRC) have the potential to mitigate CO2 emissions through fossil fuel replacement and by soil organic carbon (SOC) accumulation following direct LUC. Many studies have been carried out with the purpose of measuring site-specific changes, however results are often mixed demonstrating both increasing and decreasing carbon (C) stocks over time. Such variation demonstrates the sensitivity of SOC to many factors such as climate, soil texture, previous land-use and initial SOC content. This study examined a chronosequence of ~100 Miscanthus and willow plantations established on arable and grassland across Britain to provide an improved understanding of general effects on temporal SOC dynamics during LUC. Soil was sampled at each site to a depth of 30 cm and SOC stocks assessed over a 14 year time period. For each of the 4 LUCs no significant differences were observed between measured C stocks after 14 years and expected baseline values for land under arable and grassland management. Evidence will be presented that shows in all cases a 0% change lies within the 95% confidence intervals indicating no true average increase or decrease can be reported for the first 14 years of establishment. Therefore we find no evidence to suggest a short term CO2 mitigation effect provided from SOC storage following the establishment of Miscanthus or willow on arable or grassland. However, longer term measurements are required to assess SOC dynamics beyond this initial period.

  15. Six-degree-of-freedom aircraft simulation with mixed-data structure using the applied dynamics simulation language, ADSIM

    NASA Technical Reports Server (NTRS)

    Savaglio, Clare

    1989-01-01

    A realistic simulation of an aircraft in the flight using the AD 100 digital computer is presented. The implementation of three model features is specifically discussed: (1) a large aerodynamic data base (130,00 function values) which is evaluated using function interpolation to obtain the aerodynamic coefficients; (2) an option to trim the aircraft in longitudinal flight; and (3) a flight control system which includes a digital controller. Since the model includes a digital controller the simulation implements not only continuous time equations but also discrete time equations, thus the model has a mixed-data structure.

  16. Maintenance cost study of rotary wing aircraft

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The feasibility was studied of predicting rotary wing operation maintenance costs by using several aircraft design factors for the aircraft dynamic systems. The dynamic systems considered were engines, drives and transmissions, rotors, and flight controls. Multiple regression analysis was used to correlate aircraft design and operational factors with manhours per flight hour, and equations for each dynamic system were developed. Results of labor predictions using the equations compare favorably with actual values.

  17. A Dynamic Navigation Model for Unmanned Aircraft Systems and an Application to Autonomous Front-On Environmental Sensing and Photography Using Low-Cost Sensor Systems

    PubMed Central

    Cooper, Andrew James; Redman, Chelsea Anne; Stoneham, David Mark; Gonzalez, Luis Felipe; Etse, Victor Kwesi

    2015-01-01

    This paper presents an unmanned aircraft system (UAS) that uses a probabilistic model for autonomous front-on environmental sensing or photography of a target. The system is based on low-cost and readily-available sensor systems in dynamic environments and with the general intent of improving the capabilities of dynamic waypoint-based navigation systems for a low-cost UAS. The behavioural dynamics of target movement for the design of a Kalman filter and Markov model-based prediction algorithm are included. Geometrical concepts and the Haversine formula are applied to the maximum likelihood case in order to make a prediction regarding a future state of a target, thus delivering a new waypoint for autonomous navigation. The results of the application to aerial filming with low-cost UAS are presented, achieving the desired goal of maintained front-on perspective without significant constraint to the route or pace of target movement. PMID:26343680

  18. A Dynamic Navigation Model for Unmanned Aircraft Systems and an Application to Autonomous Front-On Environmental Sensing and Photography Using Low-Cost Sensor Systems.

    PubMed

    Cooper, Andrew James; Redman, Chelsea Anne; Stoneham, David Mark; Gonzalez, Luis Felipe; Etse, Victor Kwesi

    2015-01-01

    This paper presents an unmanned aircraft system (UAS) that uses a probabilistic model for autonomous front-on environmental sensing or photography of a target. The system is based on low-cost and readily-available sensor systems in dynamic environments and with the general intent of improving the capabilities of dynamic waypoint-based navigation systems for a low-cost UAS. The behavioural dynamics of target movement for the design of a Kalman filter and Markov model-based prediction algorithm are included. Geometrical concepts and the Haversine formula are applied to the maximum likelihood case in order to make a prediction regarding a future state of a target, thus delivering a new waypoint for autonomous navigation. The results of the application to aerial filming with low-cost UAS are presented, achieving the desired goal of maintained front-on perspective without significant constraint to the route or pace of target movement.

  19. A Dynamic Navigation Model for Unmanned Aircraft Systems and an Application to Autonomous Front-On Environmental Sensing and Photography Using Low-Cost Sensor Systems.

    PubMed

    Cooper, Andrew James; Redman, Chelsea Anne; Stoneham, David Mark; Gonzalez, Luis Felipe; Etse, Victor Kwesi

    2015-01-01

    This paper presents an unmanned aircraft system (UAS) that uses a probabilistic model for autonomous front-on environmental sensing or photography of a target. The system is based on low-cost and readily-available sensor systems in dynamic environments and with the general intent of improving the capabilities of dynamic waypoint-based navigation systems for a low-cost UAS. The behavioural dynamics of target movement for the design of a Kalman filter and Markov model-based prediction algorithm are included. Geometrical concepts and the Haversine formula are applied to the maximum likelihood case in order to make a prediction regarding a future state of a target, thus delivering a new waypoint for autonomous navigation. The results of the application to aerial filming with low-cost UAS are presented, achieving the desired goal of maintained front-on perspective without significant constraint to the route or pace of target movement. PMID:26343680

  20. An overview of the joint FAA/NASA aircraft/ground runway friction program

    NASA Technical Reports Server (NTRS)

    Yager, Thomas J.

    1989-01-01

    There is a need for information on runways which may become slippery due to various forms and types of contaminants. Experience has shown that since the beginning of all weather aircraft operations, there have been landing and aborted takeoff incidents and/or accidents each year where aircraft have either run off the end or veered off the shoulder of low friction runways. NASA Langley's Landing and Impact Dynamics Branch is involved in several research programs directed towards obtaining a better understanding of how different tire properties interact with varying pavement surface characteristics to produce acceptable performance for aircraft ground handling requirements. One such effort, which was jointly supported by not only NASA and the FAA but by several aviation industry groups including the Flight Safety Foundation, is described.

  1. A Dynamic Simulation of the Indirect Land Use Implications of Recent Biofuel Production and Use in the United States.

    SciTech Connect

    Oladosu, Gbadebo A; Kline, Keith L

    2013-01-01

    The global indirect land use change (ILUC) implications of biofuel use in the United States of America (USA) from 2001 to 2010 are evaluated with a dynamic general equilibrium model. The effects of biofuels production on agricultural land area vary by year; from a net expansion of 0.17 ha per 1000 gallons produced (2002) to a net contraction of 0.13 ha per 1000 gallons (2018) in Case 1 of our simulation. In accordance with the general narrative about the implications of biofuel policy, agricultural land area increased in many regions of the world. However, oil-export dependent economies experienced agricultural land contraction because of reductions in their revenues. Reducing crude oil imports is a major goal of biofuel policy, but the land use change implications have received little attention in the literature. Simulations evaluating the effects of doubling supply elasticities for land and fossil resources show that these parameters can significantly influence the land use change estimates. Therefore, research that provides empirically-based and spatially-detailed agricultural land-supply curves and capability to project future fossil energy prices is critical for improving estimates of the effects of biofuel policy on land use.

  2. Anthropogenic Land-use Change and the Dynamics of Amazon Forest Biomass

    NASA Technical Reports Server (NTRS)

    Laurance, William F.

    2004-01-01

    This project was focused on assessing the effects of prevailing land uses, such as habitat fragmentation, selective logging, and fire, on biomass and carbon storage in Amazonian forests, and on the dynamics of carbon sequestration in regenerating forests. Ancillary goals included developing GIs models to help predict the future condition of Amazonian forests, and assessing the effects of anthropogenic climate change and ENS0 droughts on intact and fragmented forests. Ground-based studies using networks of permanent plots were linked with remote-sensing data (including Landsat TM and AVHRR) at regional scales, and higher-resolution techniques (IKONOS imagery, videography, LIDAR, aerial photographs) at landscape and local scales. The project s specific goals were quite eclectic and included: Determining the effects of habitat fragmentation on forest dynamics, floristic composition, and the various components of above- and below-ground biomass. Assessing historical and physical factors that affect trajectories of forest regeneration and carbon sequestration on abandoned lands. Extrapolating results from local studies of biomass dynamics in fragmented and regenerating forests to landscape and regional scales in Amazonia, using remote sensing and GIS. Testing the hypothesis that intact Amazonian forests are functioning as a significant carbon sink. Examining destructive synergisms between forest fragmentation and fire. Assessing the short-term impacts of selective logging on aboveground biomass. Developing GIS models that integrate current spatial data on forest cover, deforestation, logging, mining, highway and roads, navigable rivers, vulnerability to wild fires, protected areas, and existing and planned infrastructure projects, in an effort to predict the future condition of Brazilian Amazonian forests over the next 20-25 years. Devising predictive spatial models to assess the influence of varied biophysical and anthropogenic predictors on Amazonian deforestation.

  3. High Speed Civil Transport Aircraft Simulation: Reference-H Cycle 1, MATLAB Implementation

    NASA Technical Reports Server (NTRS)

    Sotack, Robert A.; Chowdhry, Rajiv S.; Buttrill, Carey S.

    1999-01-01

    The mathematical model and associated code to simulate a high speed civil transport aircraft - the Boeing Reference H configuration - are described. The simulation was constructed in support of advanced control law research. In addition to providing time histories of the dynamic response, the code includes the capabilities for calculating trim solutions and for generating linear models. The simulation relies on the nonlinear, six-degree-of-freedom equations which govern the motion of a rigid aircraft in atmospheric flight. The 1962 Standard Atmosphere Tables are used along with a turbulence model to simulate the Earth atmosphere. The aircraft model has three parts - an aerodynamic model, an engine model, and a mass model. These models use the data from the Boeing Reference H cycle 1 simulation data base. Models for the actuator dynamics, landing gear, and flight control system are not included in this aircraft model. Dynamic responses generated by the nonlinear simulation are presented and compared with results generated from alternate simulations at Boeing Commercial Aircraft Company and NASA Langley Research Center. Also, dynamic responses generated using linear models are presented and compared with dynamic responses generated using the nonlinear simulation.

  4. [Dynamics of salinization land based on EVI series data and landscape pattern analysis in Songnen Plain: a case study in Da'an City].

    PubMed

    Liu, Shi-Liang; Dong, Yu-Hong; An, Nan-Nan; Wang, Jun; Zhao, Hai-Di

    2014-11-01

    The west part of Jilin Province is one of the most salinization regions in China and much attention has been paid to the dynamics and monitoring of the salinization land. Based on the land use data derived from TM images in 2000, 2005 and 2010 and the enhanced vegetation index (EVI) series data from 2000 to 2012 of Da'an City as a typical salinization region, we used landscape pattern analysis to elucidate the dynamics of salinization land, and used gray incidence method to analyze the main driving factors for the dynamics of land salinization. The results showed that the dominant land use types in Da'an City were cultivated land, grassland and salinization land. From 2000 to 2010, the area of salinization land and construction land showed an increasing trend, while that of grassland tended to decrease. Salinization land, which showed increased connectivity and integrity, was mainly transformed from grassland, swamp land and water area. Annual EVI values in Da'an City showed an overall increasing trend while the average values showed obvious spatial differences with the lowest EVI level in salinization land. From 2000 to 2012, the increment of vegetation cover area was larger than that of the degraded area. Landscape transformation affected the changing trends of EVI. Both natural factors and human activities affected the dynamics of salinization land, and human activities showed a greater impact on land salinization than climate factors.

  5. Chemical dynamics simulations of energy transfer, surface-induced dissociation, soft-landing, and reactive-landing in collisions of protonated peptide ions with organic surfaces.

    PubMed

    Pratihar, Subha; Barnes, George L; Hase, William L

    2016-07-01

    There are two components to the review presented here regarding simulations of collisions of protonated peptide ions peptide-H(+) with organic surfaces. One is a detailed description of the classical trajectory chemical dynamics simulation methodology. Different simulation approaches are used, and identified as MM, QM + MM, and QM/MM dependent on the potential energy surface used to represent the peptide-H(+) + surface collision. The second are representative examples of the information that may be obtained from the simulations regarding energy transfer and peptide-H(+) surface-induced dissociation, soft-landing, and reactive-landing for the peptide-H(+) + surface collisions. Good agreement with experiment is obtained for each of these four collision properties. The simulations provide atomistic interpretations of the peptide-H(+) + surface collision dynamics. PMID:26563571

  6. Seasonal dynamics of surface runoff in mountain grassland ecosystems differing in land use

    NASA Astrophysics Data System (ADS)

    Leitinger, Georg; Tasser, Erich; Newesely, Christian; Obojes, Nikolaus; Tappeiner, Ulrike

    2010-05-01

    SummaryBetter understanding of surface runoff quantity for distinct hydrological units becomes increasingly important as many rainfall-runoff models use static surface runoff coefficients and neglect key factors affecting ecohydrological dynamics, e.g. land cover and land use. Especially in small-scale alpine catchments, surface runoff and its contribution to mountain torrent runoff is frequently underestimated. In our study, the seasonal variability of surface runoff on abandoned areas and pastures in the alpine catchment 'Kaserstattalm' (Stubai Valley, Austria, Eastern Alps) was analyzed using a rain simulator along with soil water content ( SWC) and soil water tension ( SWT) measurements. Additionally, seasonal variability of soil physical and soil hydraulic properties were assessed. Analyzing more than 30 rainfall simulations on 10 m 2 plots at a rate of 90 mm h -1 (equivalent to convective precipitation events with 100 years return period) revealed a mean surface runoff coefficient of 0.01 on abandoned areas and 0.18 on pastures. Regarding seasonal variability, relevant surface runoff was limited to pastures in autumn with a maximum runoff coefficient of 0.25. The field capacity ( Fc) of all soils was found to be stable throughout the season. However, for pastures, cattle trampling led to a significant increase of dry bulk density ( BD) of up to +0.33 g cm -3 ( p ⩽ 0.01) in the top 0.1 m of the soil which is attributed to a compaction of macropores. Although measured infiltration rates decreased by more than 60%, BD could 'recover' during the winter season presumably due to freezing-and-thawing cycles and bioturbation processes decreasing soil compaction. This study highlights that impacts of land-use changes on soil physical properties make surface runoff difficult to model. Moreover, dynamic and interactive behaviour of soil parameters have to be considered in order to make realistic assessments and accurate predictions of surface runoff rates. Finally

  7. Carbon pool and biomass dynamics associated with deforestation, land use, and agricultural abandonment in the neotropics.

    PubMed

    Kauffman, J Boone; Hughes, R Flint; Heider, Chris

    2009-07-01

    Current rates of deforestation and the resulting C emissions in the tropics exceed those of secondary forest regrowth and C sequestration. Changing land-use strategies that would maintain standing forests may be among the least expensive of climate change mitigation options. Further, secondary tropical forests have been suggested to have great value for their potential to sequester atmospheric C. These options require an understanding of and capability to quantify C dynamics at landscape scales. Because of the diversity of physical and biotic features of tropical forests as well as approaches and intensities of land uses within the neotropics, there are tremendous differences in the capacity of different landscapes to store and sequester C. Major gaps in our current knowledge include quantification of C pools, rates and patterns of biomass loss following land-cover change, and quantification of the C storage potential of secondary forests following abandonment. In this paper we present a synthesis and further analyses from recent studies that describe C pools, patterns of C decline associated with land use, and rates of C accumulation following secondary-forest establishment--all information necessary for climate-change mitigation options. Ecosystem C pools of Neotropical primary forests minimally range from approximately 141 to 571 Mg/ha, demonstrating tremendous differences in the capacity of different forests to store C. Most of the losses in C and nutrient pools associated with conversion occur when fires are set to remove the slashed forest to prepare sites for crop or pasture establishment. Fires burning slashed primary forests have been found to result in C losses of 62-80% of prefire aboveground pools in dry (deciduous) forest landscapes and 29-57% in wet (evergreen) forest landscapes. Carbon emissions equivalent to the aboveground primary-forest pool arise from repeated fires occurring in the first 4 to 10 years following conversion. Feedbacks of climate

  8. Modeling the lubrication, dynamics, and effects of piston dynamic tilt of twin-land oil control rings in internal combustion engines

    SciTech Connect

    Tian, T.; Wong, V.W.

    2000-01-01

    A theoretical model was developed to study the lubrication, friction, dynamics, and oil transport of twin-land oil control rings (TLOCR) in internal combustion engines. A mixed lubrication model with consideration of shear-thinning effects of multigrade oils was used to describe the lubrication between the running surfaces of the two lands and the liner. Oil squeezing and asperity contact were both considered for the interaction between the flanks of the TLOCR and the ring groove. Then, the moments and axial forces from TLOCR/liner lubrication and TLOCR/groove interaction were coupled into the dynamic equations of the TLOCR. Furthermore, effects of piston dynamic tilt were considered in a quasi three-dimensional manner so that the behaviors of the TLOCR at different circumferential location could be studied. As a first step, variation of the third land pressure was neglected. The model predictions were illustrated via an SI engine. One important finding is that around thrust and anti-thrust sides, the difference between the minimum oil film thickness of two lands can be as high as several micrometers due to piston dynamic tilt. As a result, at thrust and anti-thrust sides, significant oil can pass under one land of the TLOCR along the bore, although the other land perfectly seals the bore. Then, the capabilities of the model were further explained by studying the effects of ring tension and torsional resistance on the lubrication and oil transport between the lands and the liner. The effects of oil film thickness on the flanks of the ring groove on the dynamics of the TLOCR were also studied. Friction results show that boundary lubrication contributes significantly to the total friction of the TLOCR.

  9. Active control landing gear for ground load alleviation

    NASA Technical Reports Server (NTRS)

    Mcgehee, J. R.; Morris, D. L.

    1985-01-01

    Results of analytical and experimental investigations of a series-hydraulic active control landing gear show that such a gear is feasible when using existing hardware and is very effective in reducing loads, relative to those generated by a conventional (passive year) gear, transmitted to the airframe during ground operations. Analytical results obtained from an active gear, flexible aircraft, take-off and landing analysis are in good agreement with experimental data and indicate that the analysis is a valid tool for study and initial design of series-hydraulic active control landing gears. An analytical study of a series-hydraulic active control main landing gear on an operational supersonic airplane shows that the active gear has the potential for improving the dynamic response of the aircraft and significantly reducing structural fatigue damage during ground operations.

  10. Climatic and land cover influences on the spatiotemporal dynamics of Holocene boreal fire regimes.

    PubMed

    Barrett, Carolyn M; Kelly, Ryan; Higuera, Philip E; Hu, Feng Sheng

    2013-02-01

    Although recent climatic warming has markedly increased fire activity in many biomes, this trend is spatially heterogeneous. Understanding the patterns and controls of this heterogeneity is important for anticipating future fire regime shifts at regional scales and for developing land management policies. To assess climatic and land cover controls on boreal forest fire regimes, we conducted macroscopic-charcoal analysis of sediment cores and GIS analysis of landscape variation in south-central Alaska, USA. Results reveal that fire occurrence was highly variable both spatially and temporally over the past seven millennia. At two of four sites, the lack of distinct charcoal peaks throughout much of this period suggests the absence of large local fires, attributed to abundant water bodies in the surrounding landscape that have likely functioned as firebreaks to limit fire spread. In contrast, distinct charcoal peaks suggest numerous local fires at the other two sites where water bodies are less abundant. In periods of the records where robust charcoal peaks allow identification of local-fire events over the past 7000 years, mean fire return intervals varied widely with a range of 138-453 years. Furthermore, the temporal trajectories of local-fire frequency differed greatly among sites and were statistically independent. Inferred biomass burning and mean summer temperature in the region were not significantly correlated prior to 3000 years ago but became positively related subsequently with varying correlation strengths. Climatic variability associated with the Medieval Climate Anomaly and the Little Ice Age, along with the expansion of flammable Picea mariana forests, probably have heightened the sensitivity of forest burning to summer temperature variations over the past three millennia. These results elucidate the patterns and controls of boreal fire regime dynamics over a broad range of spatiotemporal scales, and they imply that anthropogenic climatic warming and

  11. Impact of land use practices on faunal abundance, nutrient dynamics and biochemical properties of desert pedoecosystem.

    PubMed

    Tripathi, G; Sharma, B M

    2005-11-01

    Increased dependence of resource-poor rural communities on soils of low inherent fertility are the major problem of desert agroecosystem. Agrisilviculture practices may help to conserve the soil biota for maintaining essential soil properties and processes in harsh climate. Therefore, the impacts of different land use systems on faunal density, nutrient dynamics and biochemical properties of soil were studied in agrisilviculture system of Indian desert. The selected fields had trees (Zizyphus mauritiana, Prosopis cineraria, Acacia nilotica) and crops (Cuminum cyminum, Brassica nigra, Triticum aestivum) in different combinations. Populations of Acari, Myriapoda, Coleoptera, Collembola, other soil arthropods and total soil fauna showed significant changes with respect to different land use practices and tree species, indicating a strong relation between above and below ground biodiversity. The Coleoptera exhibited greatest association with all agrisilviculture fields. The Z. mauritiana system indicated highest facilitative effects (RTE value) on all groups of soil fauna. Soil temperature, moisture, organic carbon, nitrate- and ammonical-nitrogen, available phosphorus, soil respiration and dehydrogenase activity were greater under tree than that of tree plus cropping system. It showed accumulation of nitrate-nitrogen in tree field and more utilization by crops in cultivated lands. Positive and significant correlation among organic carbon, nitrate- and ammonical-nitrogen, phosphorus, soil respiration and dehydrogenase activity clearly reflects increase in soil nutrients with the increase in microbial and other biotic activity. P. cineraria field was the best pedoecosystem, while C. cyminum was the best winter crop for cultivation in desert agroforestry system for soil biological health and soil sustainability. The increase in organic carbon, soil nutrients and microbial activity is associated with the increase in soil faunal population which reflect role of soil fauna

  12. Climatic and land cover influences on the spatiotemporal dynamics of Holocene boreal fire regimes.

    PubMed

    Barrett, Carolyn M; Kelly, Ryan; Higuera, Philip E; Hu, Feng Sheng

    2013-02-01

    Although recent climatic warming has markedly increased fire activity in many biomes, this trend is spatially heterogeneous. Understanding the patterns and controls of this heterogeneity is important for anticipating future fire regime shifts at regional scales and for developing land management policies. To assess climatic and land cover controls on boreal forest fire regimes, we conducted macroscopic-charcoal analysis of sediment cores and GIS analysis of landscape variation in south-central Alaska, USA. Results reveal that fire occurrence was highly variable both spatially and temporally over the past seven millennia. At two of four sites, the lack of distinct charcoal peaks throughout much of this period suggests the absence of large local fires, attributed to abundant water bodies in the surrounding landscape that have likely functioned as firebreaks to limit fire spread. In contrast, distinct charcoal peaks suggest numerous local fires at the other two sites where water bodies are less abundant. In periods of the records where robust charcoal peaks allow identification of local-fire events over the past 7000 years, mean fire return intervals varied widely with a range of 138-453 years. Furthermore, the temporal trajectories of local-fire frequency differed greatly among sites and were statistically independent. Inferred biomass burning and mean summer temperature in the region were not significantly correlated prior to 3000 years ago but became positively related subsequently with varying correlation strengths. Climatic variability associated with the Medieval Climate Anomaly and the Little Ice Age, along with the expansion of flammable Picea mariana forests, probably have heightened the sensitivity of forest burning to summer temperature variations over the past three millennia. These results elucidate the patterns and controls of boreal fire regime dynamics over a broad range of spatiotemporal scales, and they imply that anthropogenic climatic warming and

  13. Impact of land use practices on faunal abundance, nutrient dynamics and biochemical properties of desert pedoecosystem.

    PubMed

    Tripathi, G; Sharma, B M

    2005-11-01

    Increased dependence of resource-poor rural communities on soils of low inherent fertility are the major problem of desert agroecosystem. Agrisilviculture practices may help to conserve the soil biota for maintaining essential soil properties and processes in harsh climate. Therefore, the impacts of different land use systems on faunal density, nutrient dynamics and biochemical properties of soil were studied in agrisilviculture system of Indian desert. The selected fields had trees (Zizyphus mauritiana, Prosopis cineraria, Acacia nilotica) and crops (Cuminum cyminum, Brassica nigra, Triticum aestivum) in different combinations. Populations of Acari, Myriapoda, Coleoptera, Collembola, other soil arthropods and total soil fauna showed significant changes with respect to different land use practices and tree species, indicating a strong relation between above and below ground biodiversity. The Coleoptera exhibited greatest association with all agrisilviculture fields. The Z. mauritiana system indicated highest facilitative effects (RTE value) on all groups of soil fauna. Soil temperature, moisture, organic carbon, nitrate- and ammonical-nitrogen, available phosphorus, soil respiration and dehydrogenase activity were greater under tree than that of tree plus cropping system. It showed accumulation of nitrate-nitrogen in tree field and more utilization by crops in cultivated lands. Positive and significant correlation among organic carbon, nitrate- and ammonical-nitrogen, phosphorus, soil respiration and dehydrogenase activity clearly reflects increase in soil nutrients with the increase in microbial and other biotic activity. P. cineraria field was the best pedoecosystem, while C. cyminum was the best winter crop for cultivation in desert agroforestry system for soil biological health and soil sustainability. The increase in organic carbon, soil nutrients and microbial activity is associated with the increase in soil faunal population which reflect role of soil fauna

  14. Pathfinder aircraft in flight

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Pathfinder solar-powered research aircraft heads for landing on the bed of Rogers Dry Lake at the Dryden Flight Research Center, Edwards, California, after a successful test flight Nov. 19, 1996. Pathfinder was a lightweight, solar-powered, remotely piloted flying wing aircraft used to demonstrate the use of solar power for long-duration, high-altitude flight. Its name denotes its mission as the 'Pathfinder' or first in a series of solar-powered aircraft that will be able to remain airborne for weeks or months on scientific sampling and imaging missions. Solar arrays covered most of the upper wing surface of the Pathfinder aircraft. These arrays provided up to 8,000 watts of power at high noon on a clear summer day. That power fed the aircraft's six electric motors as well as its avionics, communications, and other electrical systems. Pathfinder also had a backup battery system that could provide power for two to five hours, allowing for limited-duration flight after dark. Pathfinder flew at airspeeds of only 15 to 20 mph. Pitch control was maintained by using tiny elevators on the trailing edge of the wing while turns and yaw control were accomplished by slowing down or speeding up the motors on the outboard sections of the wing. On September 11, 1995, Pathfinder set a new altitude record for solar-powered aircraft of 50,567 feet above Edwards Air Force Base, California, on a 12-hour flight. On July 7, 1997, it set another, unofficial record of 71,500 feet at the Pacific Missile Range Facility, Kauai, Hawaii. In 1998, Pathfinder was modified into the longer-winged Pathfinder Plus configuration. (See the Pathfinder Plus photos and project description.)

  15. Dynamic temperature fields under Mars landing sites and implications for supporting microbial life.

    PubMed

    Ulrich, Richard; Kral, Tim; Chevrier, Vincent; Pilgrim, Robert; Roe, Larry

    2010-01-01

    While average temperatures on Mars may be too low to support terrestrial life-forms or aqueous liquids, diurnal peak temperatures over most of the planet can be high enough to provide for both, down to a few centimeters beneath the surface for some fraction of the time. A thermal model was applied to the Viking 1, Viking 2, Pathfinder, Spirit, and Opportunity landing sites to demonstrate the dynamic temperature fields under the surface at these well-characterized locations. A benchmark temperature of 253 K was used as a lower limit for possible metabolic activity, which corresponds to the minimum found for specific terrestrial microorganisms. Aqueous solutions of salts known to exist on Mars can provide liquid solutions well below this temperature. Thermal modeling has shown that 253 K is reached beneath the surface at diurnal peak heating for at least some parts of the year at each of these landing sites. Within 40 degrees of the equator, 253 K beneath the surface should occur for at least some fraction of the year; and, within 20 degrees , it will be seen for most of the year. However, any life-form that requires this temperature to thrive must also endure daily excursions to far colder temperatures as well as periods of the year where 253 K is never reached at all.

  16. Changes in Land Surface Water Dynamics since the 1990s and Relation to Population Pressure

    NASA Technical Reports Server (NTRS)

    Prigent, C.; Papa, F.; Aires, F.; Jimenez, C.; Rossow, W. B.; Matthews, E.

    2012-01-01

    We developed a remote sensing approach based on multi-satellite observations, which provides an unprecedented estimate of monthly distribution and area of land-surface open water over the whole globe. Results for 1993 to 2007 exhibit a large seasonal and inter-annual variability of the inundation extent with an overall decline in global average maximum inundated area of 6% during the fifteen-year period, primarily in tropical and subtropical South America and South Asia. The largest declines of open water are found where large increases in population have occurred over the last two decades, suggesting a global scale effect of human activities on continental surface freshwater: denser population can impact local hydrology by reducing freshwater extent, by draining marshes and wetlands, and by increasing water withdrawals. Citation: Prigent, C., F. Papa, F. Aires, C. Jimenez, W. B. Rossow, and E. Matthews (2012), Changes in land surface water dynamics since the 1990s and relation to population pressure, in section 4, insisting on the potential applications of the wetland dataset.

  17. Detection and assessment of land use dynamics on Tenerife (Canary Islands): the agricultural development between 1986 and 2010

    NASA Astrophysics Data System (ADS)

    Günthert, Sebastian; Naumann, Simone; Siegmund, Alexander

    2012-10-01

    Since Spanish colonial times, the Canary Islands and especially Tenerife have always been used for intensive agriculture. Today almost 1/4 of the total area of Tenerife are agriculturally affected, whereas especially mountainous areas with suitable climate conditions are drastically transformed for agricultural use by building of large terraces. In recent years, political and economical developments lead to a further transformation process, especially inducted by an expansive tourism, which caused concentration- and intensification-tendencies of agricultural land use in lower altitudes as well as agricultural set-aside and rural exodus in the hinterland. The overall aim of the research at hand is to address the agricultural land use dynamics of the past decades, to statistically assess the causal reasons for those changes and to model the future agricultural land use dynamics on Tenerife. Therefore, an object-based classification procedure for recent RapidEye data (2010), Spot 4 (1998) as well as SPOT 1 (1986-88) imagery was developed, followed by a post classification comparison (PCC). Older agricultural fallow land or agricultural set-aside with a higher level of natural succession can hardly be acquired in the used medium satellite imagery. Hence, a second detection technique was generated, which allows an exact identification of the total agriculturally affected area on Tenerife, also containing older agricultural fallow land or agricultural set-aside. The method consists of an automatic texture-oriented detection and area-wide extraction of linear agricultural structures (plough furrows and field boundaries of arable land, utilised and non-utilised agricultural terraces) in current orthophotos of Tenerife. Once the change detection analysis is realised, it is necessary to identify the different driving forces which are responsible for the agricultural land use dynamics. The statistical connections between agricultural land use changes and these driving forces

  18. Analysing land cover changes for understanding of forest dynamics using temporal forest management plans.

    PubMed

    Kadioğullari, Ali İhsan; Sayin, Mehmet Ali; Çelįk, Durmuş Ali; Borucu, Süleyman; Çįl, Bayram; Bulut, Sinan

    2014-04-01

    This study analyses forest dynamics and land use/land cover change over a 43-year period using spatial-stand-type maps of temporal forest management plans of Karaisalı Forest Enterprise in the Eastern Mediterranean Region of Turkey. Stand parameters (tree species, crown closures and developmental stages) of the dynamics and changes caused by natural or artificial intervention were introduced and mapped in a Geographic Information System (GIS) and subjected to fragmentation analysis using FRAGSTATS. The Karaisalı Forest Enterprise was first planned in 1969 and then the study area was planned under the Mediterranean Forest Use project in 1991 and five-term forest management plans were made. In this study, we analysed only four periods (excluding 1982 revision plans): 1969, 1991, 2002 and 2012. Between 1969 and 2012, overall changes included a net increase of 3,026 ha in forested areas. Cumulative forest improvement accounted for 2.12% and the annual rate of total forest improvement averaged 0.08%. In addition, productive forest areas increased from 36,174 to 70,205 ha between 1969 and 2012. This translates into an average annual productive forest improvement rate of 1.54%. At the same time, fully covered forest areas with crown closure of "3" (>70%) increased about 21,321 ha, and young forest areas in developmental stage of "a" (diameter at breast height (dbh) < 8 cm) increased from 716 to 13,305 ha over the 43-year study period. Overall changes show that productive and fully covered forest areas have increased egregiously with a focus on regenerated and young developmental stages. A spatial analysis of metrics over the 43-year study period indicated a more fragmented landscape resulting in a susceptible forest to harsh disturbances. PMID:24254492

  19. Scaling aircraft noise perception.

    NASA Technical Reports Server (NTRS)

    Ollerhead, J. B.

    1973-01-01

    Following a brief review of the background to the study, an extensive experiment is described which was undertaken to assess the practical differences between numerous alternative methods for calculating the perceived levels of individual aircraft flyover wounds. One hundred and twenty recorded sounds, including jets, turboprops, piston aircraft and helicopters were rated by a panel of subjects in a pair comparison test. The results were analyzed to evaluate a number of noise rating procedures, in terms of their ability to accurately estimate both relative and absolute perceived noise levels over a wider dynamic range (84-115 dB SPL) than had generally been used in previous experiments. Performances of the different scales were examined in detail for different aircraft categories, and the merits of different band level summation procedures, frequency weighting functions, duration and tone corrections were investigated.

  20. Flight tests of three-dimensional path-redefinition algorithms for transition from Radio Navigation (RNAV) to Microwave Landing System (MLS) navigation when flying an aircraft on autopilot

    NASA Technical Reports Server (NTRS)

    Hueschen, Richard M.

    1988-01-01

    This report contains results of flight tests for three path update algorithms designed to provide smooth transition for an aircraft guidance system from DME, VORTAC, and barometric navaids to the more precise MLS by modifying the desired 3-D flight path. The first algorithm, called Zero Cross Track, eliminates the discontinuity in cross-track and altitude error at transition by designating the first valid MLS aircraft position as the desired first waypoint, while retaining all subsequent waypoints. The discontinuity in track angle is left unaltered. The second, called Tangent Path, also eliminates the discontinuity in cross-track and altitude errors and chooses a new desired heading to be tangent to the next oncoming circular arc turn. The third, called Continued Track, eliminates the discontinuity in cross-track, altitude, and track angle errors by accepting the current MLS position and track angle as the desired ones and recomputes the location of the next waypoint. The flight tests were conducted on the Transportation Systems Research Vehicle, a small twin-jet transport aircraft modified for research under the Advanced Transport Operating Systems program at Langley Research Center. The flight tests showed that the algorithms provided a smooth transition to MLS.