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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Theoretical and experimental study on the ejector augmented jet flap

The analytical concept used in determining the characteristics of jet flap or related propulsive systems suitable for VTOL and STOL applications was examined. The configuration chosen was a two dimensional wing with a biplane flap, having a jet injected on the upper surface of the wing at the flap hinge axis and discharging into the channel between the two elements of the flap. The experimental work was conducted in a two dimensional test installation in a subsonic wind tunnel. The model description, the test conditions, and a summary of the experimental results are presented.

Stewart, H. J.↗
NASA NTRS1975

Flutter suppression and gust alleviation using active controls

Application of the aerodynamic energy approach to some problems of flutter suppression and gust alleviation were considered. A simple modification of the control-law is suggested for achieving the required pitch control in the use of a leading edge - trailing edge activated strip. The possible replacement of the leading edge - trailing edge activated strip by a trailing edge - tab strip is also considered as an alternate solution. Parameters affecting the performance of the activated leading edge - trailing edge strip were tested on the Arava STOL Transport and the Westwind Executive Jet Transport and include strip location, control-law gains and a variation in the control-law itself.

Nissim, E.↗
NASA NTRS1973

A display evaluation methodology applied to vertical situation displays

An approach to display evaluation based on the optimal-control or state-variable model of the human operator is described. The approach evolved over the past several years, and is believed to have significant advantages for display evaluation. The foundations of the methodology are briefly described, and results are presented of its application to the analysis of vertical situation displays for STOL approach. This analysis includes the effects of both status and command displays on pilot workload and system performance.

Baron, S.↗
NASA NTRS1973

A model based technique for the design of flight directors

A new technique for designing flight directors is discussed. This technique uses the optimal-control pilot/vehicle model to determine the appropriate control strategy. The dynamics of this control strategy are then incorporated into the director control laws, thereby enabling the pilot to operate at a significantly lower workload. A preliminary design of a control director for maintaining a STOL vehicle on the approach path in the presence of random air turbulence is evaluated. By selecting model parameters in terms of allowable path deviations and pilot workload levels, a set of director laws is achieved which allows improved system performance at reduced workload levels. The pilot acts essentially as a proportional controller with regard to the director signals, and control motions are compatible with those appropriate to status-only displays.

Levison, W. H.↗
NASA NTRS1973

Analysis of response to wind-shears using the optimal control model of the human operator

The effects of wind-shears on the approach performance of a STOL aircraft are analyzed using the optimal-control model of the human operator. This analysis involves a time-varying situation that is more complex than is traditionally treated by human operator modelling techniques. The extensions to the time-varying case are discussed and results are presented that illustrate the effects of wind shears on category II window-performance and the effects on performance of pilot time-delay and of variations in pilot gain during approach.

Baron, S.↗
NASA NTRS1975

Noise data from tests of a 1.83 meter (6-ft-) diameter variable-pitch 1.2-pressure-ratio fan (QF-9)

Acoustic and aerodynamic data for a 1.83-meter (6-ft.) diameter fan suitable for a quiet engine for short-takeoff-and-landing (STOL) aircraft are documented. The QF-9 rotor blades had an adjustable pitch feature which provided a means for testing at several rotor blade setting angles, including one for reverse thrust. The fan stage incorporated features for low noise. Far-field noise around the fan was measured without acoustic suppression over a range of operating conditions for six different rotor blade setting angles in the forward thrust configuration, and for one in the reverse configuration. Complete results of one-third-octave band analysis of the data are presented in tabular form. Also included are power spectra, data referred to the source, and sideline perceived noise levels.

Glaser, F. W.↗
NASA NTRS1974

Passenger demographics and subjective response to commuter aircraft in the northeast

Results are compared for comfort and environmental studies taken in conjunction with a STOL program. Data were taken on flights of four different airlines, each flying different aircraft. Two of the lines are classified as commuter airlines flying between relatively close destinations. The aircraft involved are: the De Havilland Twin Otter, a Canadian aircraft; the French Nord 262; the Beechcraft 99 Airliner and the Sikorsky S-61 helicopter, both American.

Noskowitz, D.↗
NASA NTRS1975

A Kalman filter for the Stoland system

A simple Kalman filter for potential use in STOL navigation systems is described. The mathematical formulation of all the elements of the filter, its initialization and overall operation are presented. Simulation results show that a typical approach flight to landing, the Kalman filter has much smaller errors during navigation on TACAN data and during transition from TACAN to MODILS data than a complementary filter. Summary type flow charts of the Kalman filter logic designed for the Sperry 1819A computer are presented. Also, the memory and real time requirements of the Kalman filter and complementary filter are described. The Kalman filter is shown to gain its superior performance at the expense of real time and memory required in the onboard computer.

Schmidt, S. F.↗
NASA NTRS1975

Acoustic characteristics of a large scale wind-tunnel model of a jet flap aircraft

The expanding-duct jet flap (EJF) concept is studied to determine STOL performance in turbofan-powered aircraft. The EJF is used to solve the problem of ducting the required volume of air into the wing by providing an expanding cavity between the upper and lower surfaces of the flap. The results are presented of an investigation of the acoustic characteristics of the EJF concept on a large-scale aircraft model powered by JT15D engines. The noise of the EJF is generated by acoustic dipoles as shown by the sixth power dependence of the noise on jet velocity. These sources result from the interaction of the flow turbulence with flap of internal and external surfaces and the trailing edges. Increasing the trailing edge jet from 70 percent span to 100 percent span increased the noise 2 db for the equivalent nozzle area. Blowing at the knee of the flap rather than the trailing edge reduced the noise 5 to 10 db by displacing the jet from the trailing edge and providing shielding from high-frequency noise. Deflecting the flap and varying the angle of attack modified the directivity of the underwing noise but did not affect the peak noise. A forward speed of 33.5 m/sec (110 ft/sec) reduced the dipole noise less than 1 db.

Falarski, M. D.↗
NASA NTRS1975

Low-speed upwash interference on a transport model in a rectangular slotted-wall wind tunnel

A study was made of the upwash interference caused by the wind tunnel walls at a Mach number of 0.20. The wind tunnel has slotted horizontal walls and solid vertical walls and the wind tunnel model is a wing-fuselage combination typical of a short take-off and landing (STOL) transport. Measurements were made of the model forces and angle of attack. The experimental results are compared to theoretical solutions for the upwash interference. This comparison enabled an indirect determination of one of the constants in the slotted wall boundary condition. The magnitude of the experimental upwash interference is also compared to the accuracy of the data. This comparison indicates that it is difficult to make definite conclusions based on the experimental data. Suggestions are made for future research which could provide a practical means of accurately determining the wall-interference velocities in wind tunnels with rigid slotted walls.

Mann, M. J.↗
NASA NTRS1975

Manual control displays for a four-dimensional landing approach

Six instrument rated pilots flew a STOL fixed base simulator to study the effectiveness of three displays for a four dimensional approach. The three examined displays were a digital readout of forward position error, a digital speed command, and an analog display showing forward position error and error prediction. A flight director was used in all conditions. All test runs were for a typical four dimensional approach in moderate turbulence that included a change in commanded ground speed, a change in flight path angle, and two standard rate sixty degree turns. Use of the digital forward position error display resulted in large overshoot in the forward position error. Some type of lead (rate or prediction information) was shown to be needed. The best overall performance was obtained using the speed command display. It was demonstrated that curved approaches can be flown with relative ease.

Silverthorn, J. T.↗
NASA NTRS1975

Rotary-wing aircraft systems for the short-haul market

This paper describes preliminary designs of tilt-rotor and tandem-rotor helicopter V/STOL aircraft for the 1958 short-haul market. These designs include a tilt-rotor aircraft designed for STOL-only operation. The baseline designs are presented with technological and cost data. The impact of noise and ride qualities on aircraft size and cost, and on passenger acceptance are discussed. The results of the study are compared against competitive alternatives in air transportation.

Magee, J. P.↗
NASA NTRS1974

An integrated PCM data system for full scale aeronautics testing

An integrated PCM data system is being developed at Ames Research Center to gather test data on advanced STOL propulsive lift, VTOL, rotary wing, and V/STOL control systems concepts as they pass through wind-tunnel, test-stand, flight-simulator and flight-test phases. Identical airborne signal conditioning and PCM encoding is used on test aircraft and wind tunnel models. An 80,000 word/second PCM installation will be the first all PCM-instrumented rotary wing development project. The system uses both dedicated and time-shared computers for fast data analysis with maximum use of resources. This system development shows one way to bring separate data user groups together over a common data base, while sharing computing resources for minimum cost.-

Reynolds, D. R.↗
NASA NTRS1974

Wind shear effects on landing touchdown point

In the study reported, an investigation was conducted concerning the shape of wind shear profiles during aircraft landings, taking into account also the values of the meteorological parameters which describe the wind shears. Attention is also given to the variation of wind shear effects in the case of different aircraft types. The study was conducted for commercial, military, and STOL aircraft. A digital landing simulation model was used in the investigations.

Luers, J. K.↗
NASA NTRS1975

Advanced subsonic aircraft concepts for passenger transportation

This paper discusses the potential for new subsonic transport aircraft designs that may evolve in the relatively near future, taking into account the added requirements for improved environmental compatibility and the potential constraints due to system congestion, substantial financial risk, and higher fuel costs or limited availability. Reflecting these additional requirements, potential aircraft developments are presented for new CTOL transports with significantly improved fuel economy, new STOL transports with improved short field capability, and new VTOL transports that could provide direct city-center service.

Waters, M. H.↗
NASA NTRS1975

Planning air transport network in Appalachia

Main issues to be considered in designing an air transport system are discussed, and a model for the selection of an optimal air network for a region is presented. It was desired to have the ability to consider a dense network of nodes and air routes and variations in schedules on routes, which in combination would represent virtually all conceivable alternatives. Linear and integer programming were chosen as the most promising analysis methodologies. Integer programming was found to be intractable, while linear programming provided efficient solutions. The model was applied to studying the feasibility of a STOL network in West Virginia. Based on allowable paths, an examination of intercity demands, and established growth points, desired levels of service expressed as minimum flights were determined for certain city pairs.

Carter, E. C.↗
NASA NTRS1975

Optimum flight profiles for short haul missions

An algorithm, based on the energy-state method, is derived for calculating optimum trajectories with a range constraint. The basis of the algorithm is the assumption that optimum trajectories consist of, at most, three segments: an increasing energy segment (climb); a constant energy segment (cruise); and a decreasing energy segment (descent). The algorithm is used to compute minimum fuel, minimum time, and minimum direct-operating-cost trajectories, with range as a parameter, for an in-service CTOL aircraft and for an advanced STOL aircraft. Use of a simplified trajectory increases the fuel consumption of the total descent trajectory by about 10 percent and the time to fly the descent by about 19 percent compared to the optimum.

Erzberger, H.↗
NASA NTRS1975

Aircraft concepts for advanced short haul systems

The results of recent NASA-sponsored high-density and medium-density short-haul (less than 500 miles) air transportation systems studies are summarized. Trends in vehicle characteristics, in particular of RTOL and STOL concepts, are noted, and their economic suitability and impact on the community are examined.

Galloway, T. L.↗