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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Automatic detection of low altitude wind shear due to gust fronts in the terminal Doppler weather radar operational demonstration

A gust front is the leading edge of the cold air outflow from a thunderstorm. Wind shears and turbulence along the gust front may produce potentially hazardous conditions for an aircraft on takeoff or landing such that runway operations are significantly impacted. The Federal Aviation Administration (FAA) has therefore determined that the detection of gust fronts in the terminal environment be an integral part of the Terminal Doppler Weather Radar (TDWR) system. Detection of these shears by the Gust Front Algorithm permits the generation of warnings that can be issued to pilots on approach and departure. In addition to the detection capability, the algorithm provides an estimate of the wind speed and direction following the gust front (termed wind shift) and the forecasted location of the gust front up to 20 minutes before it impacts terminal operations. This has shown utility as a runway management tool, alerting runway supervisors to approaching wind shifts and the possible need to change runway configurations. The formation and characteristics of gust fronts and their signatures in Doppler radar data are discussed. A brief description of the algorithm and its products for use by Air Traffic Control (ATC), along with an assessment of the algorithm's performance during the 1988 Operational Test and Evaluation, is presented.

Klingle-Wilson, Diana↗
NASA NTRS1978

Turbulent transport model of wind shear in thunderstorm gust fronts and warm fronts

A model of turbulent flow in the atmospheric boundary layer was used to simulate the low-level wind and turbulence profiles associated with both local thunderstorm gust fronts and synoptic-scale warm fronts. Dimensional analyses of both type fronts provided the physical scaling necessary to permit normalized simulations to represent fronts for any temperature jump. The sensitivity of the thunderstorm gust front to five different dimensionless parameters as well as a change from axisymmetric to planar geometry was examined. The sensitivity of the warm front to variations in the Rossby number was examined. Results of the simulations are discussed in terms of the conditions which lead to wind shears which are likely to be most hazardous for aircraft operations.

Lewellen, W. S.↗
NASA NTRS1984

Airborne infrared low level wind shear predictor

The operating principles and test performance of an airborne IR (13-16 micron) temperature-sensing detection and warning system for low-level wind shear (LLWS) are presented. The physics of LLWS phenomena and of the IR radiometer are introduced. The cold density-current outflow or gust front related to LLWS is observed in the IR spectrum of CO2 by a radiometer with + or - 0.5-C accuracy at 0.5-Hz sampling rate; LLWS alerts are given on the basis of specific criteria. Test results from the JAWS experiments conducted at Denver in July 1982, are presented graphically and discussed. The feasibility of the passive IR system is demonstrated, with an average warning time of 51 sec, corresponding to a distance from touchdown of about 2 miles.

Kuhn, P. M.↗
NASA NTRS1993

Wind-shear endurance capability for powered-lift aircraft

The present treatment of safety margin considerations for powered-lift (upper wing surface blowing) STOL aircraft emphasizes wind shear endurance, in order to establish safety margin criteria for such aircraft that are equivalent to those of conventional transport aircraft. The simulation results obtained show that a 6.6 deg climb gradient at V(app) for STOL aircraft is required for equivalent shear endurance in approaching a long STOL airport runway, if the STOL aircraft is equipped with an elaborate control/display system and is permitted a change in configuration.

Bando, Toshio↗
NASA NTRS1985

Laboratory model of flight through wind shear

The simulation of an aircraft flying through a downdraft or microburst is presented. The simulation was performed under the conditions of constant takeoff thrust. The resulting wind shear conditions were filmed and examined for possible pilot corrective action in the future.

Frost, W.↗
NASA NTRS1984

Simulated flight through JAWS wind shear - In-depth analysis results

The Joint Airport Weather Studies (JAWS) field experiment was carried out in 1982 near Denver. An analysis is presented of aircraft performance in the three-dimensional wind fields. The fourth dimension, time, is not considered. The analysis seeks to prepare computer models of microburst wind shear from the JAWS data sets for input to flight simulators and for research and development of aircraft control systems and operational procedures. A description is given of the data set and the method of interpolating velocities and velocity gradients for input to the six-degrees-of-freedom equations governing the motion of the aircraft. The results of the aircraft performance analysis are then presented, and the interpretation classifies the regions of shear as severe, moderate, or weak. Paths through the severe microburst of August 5, 1982, are then recommended for training and operational applications. Selected subregions of the flow field defined in terms of planar sections through the wind field are presented for application to simulators with limited computer storage capacity, that is, for computers incapable of storing the entire array of variables needed if the complete wind field is programmed.

Frost, W.↗
NASA NTRS1992

Airborne Wind Shear Detection and Warning Systems: Fourth Combined Manufacturers' and Technologists' Conference, part 1

The purpose of the meeting was to transfer significant ongoing results of the NASA/FAA joint Airborne Wind Shear Program to the technical industry and to pose problems of current concern to the combined group. It also provided a forum for manufacturers to review forward-look technology concepts and for technologists to gain an understanding of the problems encountered by the manufacturers during the development of airborne equipment and the FAA certification requirements. The present document was compiled to record the essence of the technology updates and discussions which follow each.

Vicroy, Dan D.↗
NASA NTRS1988

Airborne Wind Shear Detection and Warning Systems: First Combined Manufacturers' and Technologists' Conference

The purpose of the meeting was to transfer significant, ongoing results gained during the first year of the joint NASA/FAA Airborne Wind Shear Program to the technical industry and to pose problems of current concern to the combined group. It also provided a forum for manufacturers to review forward-looking technology concepts and for technologists to gain an understanding of FAA certification requirements and the problems encountered by the manufacturers during the development of airborne equipment.

Spady, Amos A., Jr.↗
NASA NTRS1990

Flight simulation for wind shear encounter

A real-time piloted flight simulator is under development in the Laboratory for Control and Automation at Princeton University. This facility will be used to study piloted flight through a simulated wind shear. It will also provide a testbed for real-time flight guidance laws. The hardware configuration and aerodynamic model used are discussed. The microburst model to be incorporated into the simulation is introduced, and some proposed cockpit display concepts are described.

Mulgund, Sandeep S.↗
NASA NTRS1981

Simulator evaluation of the effects of reduced spoiler and thrust authority on a decoupled longitudinal control system during landings in wind shear

The effect of reduced control authority, both in symmetric spoiler travel and thrust level, on the effectiveness of a decoupled longitudinal control system was examined during the approach and landing of the NASA terminal configured vehicle (TCV) aft flight deck simulator in the presence of wind shear. The evaluation was conducted in a fixed-base simulator that represented the TCV aft cockpit. There were no statistically significant effects of reduced spoiler and thrust authority on pilot performance during approach and landing. Increased wind severity degraded approach and landing performance by an amount that was often significant. However, every attempted landing was completed safely regardless of the wind severity. There were statistically significant differences in performance between subjects, but the differences were generally restricted to the control wheel and control-column activity during the approach.

Miller, G. K., Jr.↗
NASA NTRS1981

The development of convective instability, wind shear, and vertical motion in relation to convection activity and synoptic systems in AVE 4

Data from the Fourth Atmospheric Variability Experiment were used to investigate conditions/factors responsible for the development (local time rate-of-change) of convective instability, wind shear, and vertical motion in areas with varying degrees of convective activity. AVE IV sounding data were taken at 3 or 6 h intervals during a 36 h period on 24-25 April 1975 over approximately the eastern half of the United States. An error analysis was performed for each variable studied.

Davis, J. G.↗
NASA NTRS1985

Development of a wind shear performance envelope

It is quite important that the airplane performance during a continuing headwind loss be understood. Lack of consideration of this characteristic can result in assuming almost twice the performance than that which the airplane actually has during severe wind shear at high descent rates. The example data relates to the Boeing 727-200, but the characteristics are applicable to any airplane.

Bliss, J. H.↗
NASA NTRS1981

Microbursts as an aviation wind shear hazard

The downburst-related accidents or near-misses of jet aircraft have been occurring at the rate of once or twice a year since 1975. A microburst with its field comparable to the length of runways can induce a wind shear which endangers landing or liftoff aircraft; the latest near miss landing of a 727 aircraft at Atlanta, Ga. in 1979 indicated that some microbursts are too small to trigger the warning device of the anemometer network at major U.S. airports. The nature of microbursts and their possible detection by Doppler radar are discussed, along with proposed studies of small-scale microbursts.

Fujita, T. T.↗
NASA NTRS1991

An airborne FLIR detection and warning system for low altitude wind shear

It is shown through some preliminary flight measurement research that a forward looking infrared radiometer (FLIR) system can be used to successfully detect the cool downdraft of downbursts (microbusts/macrobursts) and thunderstorm gust front outflows that are responsible for most of the low altitude wind shear (LAWS) events. The FLIR system provides a much greater safety margin for the pilot than that provided by reactive designs such as inertial air speed systems. Preliminary results indicate that an advanced airborne FLIR system could provide the pilot with remote indication of microburst (MB) hazards along the flight path ahead of the aircraft. Results of a flight test of a prototype FLIR system show that a minimum warning time of one to four minutes (5 to 10 km), depending on aircraft speed, is available to the pilot prior to the microburst encounter.

Sinclair, Peter C.↗
NASA NTRS1987

History of wind shear turbulence models

The Office of Flight Operations, Flight Technical Programs Div., at the FAA Headquarters, interfaces with industry, R&D communities and air carriers during the introduction of new types of equipment into operational services. A brief highlight of the need which FAA operations sees for new wind shear and turbulence data sets from the viewpoint of equipment certification and simulation is presented.

Cusimano, Lou↗
NASA NTRS1991

Airborne Wind Shear Detection and Warning Systems: Third Combined Manufacturers' and Technologists' Conference, part 2

The Third Combined Manufacturers' and Technologists' Conference was held in Hampton, Va., on October 16-18, 1990. The purpose of the meeting was to transfer significant on-going results of the NASA/FAA joint Airborne Wind Shear Program to the technical industry and to pose problems of current concern to the combined group. It also provided a forum for manufacturers to review forward-look technology concepts and for technologists to gain an understanding of the problems encountered by the manufacturers during the development of airborne equipment and the FAA certification requirements.

Vicroy, Dan D.↗
NASA NTRS1990

Airborne Wind Shear Detection and Warning Systems. Second Combined Manufacturers' and Technologists' Conference, part 1

The Second Combined Manufacturers' and Technologists' Conference hosted jointly by NASA Langley (LaRC) and the Federal Aviation Administration (FAA) was held in Williamsburg, Virginia, on October 18 to 20, 1988. The purpose of the meeting was to transfer significant, ongoing results gained during the second year of the joint NASA/FAA Airborne Wind Shear Program to the technical industry and to pose problems of current concern to the combined group. It also provided a forum for manufacturers to review forward-look technology concepts and for technologists to gain an understanding of the problems encountered by the manufacturers during the development of airborne equipment and the FAA certification requirements.

Spady, Amos A., Jr.↗