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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Reduction of wave drag by antisymmetric arrangement of wings and bodies

In theory, antisymmetric arrangements of wings and bodies can have smaller wave drag than corresponding mirror-symmetric arrangements. Thus, a long narrow oblique wing which presents the same aspect for two opposite directions of flight is potentially more efficient than corresponding (i.e., structurally equivalent) swept wing. The single continuous wing panel also adapts itself more readily to varying angles of obliquity, and hence, to varying flight speeds. Previous work on the aerodynamics and flight stability of oblique wing combinations is reviewed and a possible mode of application to transport aircraft operating at moderate supersonic speeds is suggested.

Jones, R. T.↗
NASA NTRS1976

Progress report on propeller aircraft flyover noise research

Initial results of a program to investigate the sources of noise in unshrouded propellers under forward flight conditions are reported. Tests were conducted using a three-blade full-scale instrumented propeller mounted on a twin-engine aircraft. Measurements included (1) far-field noise at fixed ground stations and at two aircraft wing tip locations, (2) blade surface pressures at seven locations on one of the propeller blades, (3) atmospheric turbulence encountered by the aircraft in flight, and (4) aircraft operating conditions. The results confirm that significantly lower levels of propeller noise are produced in forward flight than at static conditions. It is tentatively concluded that propeller noise generation in flight may be dominated by steady loading at blade passage frequency, but at higher frequencies unsteady loading due to interaction with natural atmospheric turbulence may be the dominant mechanism of noise generation. Under static conditions the total noise signature appears to be the result of interaction of the propeller with persistent turbulent eddies passing through the propeller disk.

Metzger, F. B.↗
NASA NTRS1976

Applications of oblique-wing technology - An overview

A summary of oblique-wing technology programs, including system studies and experimental activities, is presented. Oblique-wing civil transports were studied and compared with conventional configurations at design cruise Mach numbers of 0.95 and 1.2. Studies of military configurations employing oblique-wing technology considered aircraft concepts, remotely piloted vehicles, and a cruise missile. Experimental activities included wind-tunnel tests of high and low aspect ratio oblique wings; flight tests are planned using unmanned and manned vehicles. The research program suggests that oblique-wing technology offers improved performance over conventional concepts for aircraft operating in the transonic speed range.

Nelms, W. P., Jr.↗
NASA NTRS1977

Recent advances in aerodynamic energy concept for flutter suppression and gust alleviation using active controls

Control laws are derived, by using realizable transfer functions, which permit relaxation of the stability requirements of the aerodynamic energy concept. The resulting aerodynamic eigenvalues indicate that both the trailing edge and the leading edge-trailing edge control systems can be made more effective. These control laws permit the introduction of aerodynamic damping and stiffness terms in accordance with the requirements of any specific system. Flutter suppression and gust alleviation problems can now be treated by either a trailing edge control system or by a leading edge-trailing edge control system by using the aerodynamic energy concept. Results are applicable to a wide class of aircraft operating at subsonic Mach numbers.

Nissim, E.↗
NASA NTRS1977

Total ozone derived from UV spectrophotometer measurements on the NASA CV-990 aircraft for the fall 1976 latitude survey flights

An ultraviolet interference filter spectrophotometer was modified to use a photodiode and was flown on latitude survey flights in the fall of 1976. Comparison with Dobson station total ozone values shows agreement between UVS and Dobson total ozone of + or - 2 percent. The procedure used to convert UVS measured ozone above the aircraft altitude to total ozone above ground level introduces an additional 2 percent deviation for very high altitude UVS ozone data. Under stable aircraft operating conditions, the UVS derived ozone values have a variability, or reproducibility, of better than + or -1 percent. The UVS data from the latitude survey flights yield a detailed latitude profile of total ozone over the Pacific Ocean during November 1976. Significant latitudinal structure in total ozone is found at the middle latitudes (30 deg to 40 deg N and S).

Hanser, F. A.↗
NASA NTRS1977

Application of the aerodynamic energy concept to the selection of transfer functions for flutter suppression and gust alleviation using active controls

Changes are introduced in the aerodynamic energy approach which lead to an increase in the effectiveness of both the trailing-edge (TE) and the leading-edge (LE)-TE control systems. Control laws are determined, using realizable transfer functions, which permit the introduction of aerodynamic damping and stiffness terms in accordance with the requirements of any specific system. It is shown that flutter suppression and gust alleviation problems can successfully be treated either by a TE or by a LE-TE control system. The results obtained are applicable to a very wide class of aircraft operating within the subsonic Mach number range.

Nissim, E.↗
NASA NTRS1977

Summary report of the Aircraft Design Committee

Meetings were held concerning aircraft design with considerable interest shown in aircraft operations. Topics covered were: (1) structural design for turbulence; (2) flight control; (3) data needs; and (4) lightning. Other factors discussed were temperature, rain, hail, icing, pressure, density, corrosives, and abrasives.

Woodcock, R. J.↗
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 NTRS1978

Strapdown system redundancy management flight demonstration

The suitability of strapdown inertial systems in providing highly reliable short-term navigation for vertical take-off and landing (VTOL) aircraft operating in an intra-urban setting under all-weather conditions was assessed. A preliminary design configuration of a skewed sensor inertial reference system employing a redundancy management concept to achieve fail-operational, fail-operational performance, was developed.

Source record↗
NASA NTRS1979

A closed-loop control-loading system

Langley Differential Maneuvering Simulator (DMS) realistically simulates two aircraft operating in differential mode. It consists of two identical fixed-base cockpits and dome projection systems. Each projection system consists of sky/Earth projector and target-image generator and projector. Although programmable control forces are small part of overall system, they play large role in providing pilot with kinesthetic cues.

Ashworth, B. R.↗
NASA NTRS1978

Basic avionics module design for general aviation aircraft

The design of an advanced digital avionics system (basic avionics module) for general aviation aircraft operated with a single pilot under IFR conditions is described. The microprocessor based system provided all avionic functions, including flight management, navigation, and lateral flight control. The mode selection was interactive with the pilot. The system used a navigation map data base to provide operation in the current and planned air traffic control environment. The system design included software design listings for some of the required modules. The distributed microcomputer uses the IEEE 488 bus for interconnecting the microcomputer and sensors.

Smyth, R. K.↗
NASA NTRS1978

Summary report of the Turbulence Committee

The effects of atmospheric turbulence are discussed. Aircraft design and aircraft operations are reviewed. Turbulence in terms of intensity and scale in design considerations was examined. Turbulence models were used in the form of discrete gusts, spectral distributions, and probability distributions. Various aspects of the design and operations problems, simulation and training factors of pilots, and weather services and forecasts are reported.

Elderkin, C. E.↗
NASA NTRS1979

Advanced low emissions catalytic combustor program at Pratt and Whitney

The feasibility of employing catalytic combustion technology to control the emissions of oxides of nitrogen for subsonic, stratospheric cruise aircraft operations is the objective of this NASA contract. The existing Enivornmental Protection Agency standards for the landing and takeoff cycle were also required to be satisfied. Work for the first phase of a proposed three phase effort is reported and is concerned with analytical design studies.

Sturgess, G. J.↗
NASA NTRS1979

Investigation of a laser Doppler velocimeter system to measure the flow field around a large scale V/STOL aircraft in ground effect

The flow field measured around a hovering 70 percent scale vertical takeoff and landing (V/STOL) aircraft model is described. The velocity measurements were conducted with a ground based laser Doppler velocimeter. The remote sensing instrumentation and experimental tests of the velocity surveys are discussed. The distribution of vertical velocity in the fan jet and fountain; the radial velocity in the wall jet and the horizontal velocity along the aircraft underside are presented for different engine rpms and aircraft height above ground. Results show that it is feasible to use a mobile laser Doppler velocimeter to measure the flow field generated by a large scale V/STOL aircraft operating in ground effect.

Zalay, A. D.↗
NASA NTRS1977

Resource conservation through airborne electronics

Avionics can play a significant role in making aircraft more fuel-efficient through active controls and the accompanying structural and aerodynamic configuration changes. In addition, avionics can make aircraft operations more efficient through advanced guidance systems. This paper discusses some of these techniques, reviews their potential benefits, and examines certain related NASA programs.

Taylor, L. W., Jr.↗
NASA NTRS1978

The RSRA Active Isolation/Rotor Balance System

The Rotor Systems Research Aircraft (RSRA) includes provisions for the installation of an Active Transmission Isolation/Rotor Loads Balance System (AIBS). The purpose of this system is to enable aircraft operation with an arbitrary rotor system over a wide rotor speed range and maneuver envelope without vibration envelope restrictions, while simultaneously providing measurement of rotor system loads. The present paper reviews the history of the design and development of this system, which culminated in successful flight test evaluation in 1977. Consideration is given to highlights of the design, ground test, and flight test.

Kuczynski, W. A.↗
NASA NTRS1978

Stable boundary layer wind shear model for aircraft flight hazard definition

It is pointed out that wind shear, particularly at the lower altitudes in the terminal area, has been identified as being hazardous to aircraft operations. Accurate and reliable wind profiles are required for use in fast time and manned flight simulation studies aimed at fully defining and understanding the wind shear hazard. A description is presented of wind speed profiles for neutral and stable atmospheric conditions developed for the simulation studies to improve the safety and reliability of operations in the terminal area. The wind shear is mathematically modeled and the mathematical scenarios are presented in a format for direct application to wind shear hazard/flight simulation studies.

Frost, W.↗
NASA NTRS1978

The prediction of turbulence and wind shear associated with thunderstorm gust fronts

The parametric dependence of storm simulation is explored on the basis of the previously reported (1977) second-order closure model of turbulence designed to simulate a thunderstorm gust front. The model simulation results are intended for extrapolation to the conditions considered most hazardous to aircraft operation. It is shown that the presistence and strength of the gust front are enhanced significantly by increasing the spread of the downdraft shaft and the velocity at the top of the domain. Turbulence develops in the regions of high shear and is most intense near the corner and within the gust front itself. While the center shaft is certainly an area to be avoided, the gust front region is probably more critical because it may extend over a large region far from the center of the downdraft, in a highly transient state.

Teske, M. E.↗