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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 505 records · Page 28

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NASA NTRS1973

Aero-acoustic design and test of a multiple splitter exhaust noise suppressor for a 0.914m diameter lift fan

A lift fan exhaust suppression system to meet future VTOL aircraft noise goals was designed and tested. The test vehicle was a 1.3 pressure ratio, 36 inch (91.44 cm) diameter lift fan with two chord rotor to stator spacing. A two splitter fan exhaust suppression system thirty inches (76.2 cm) long achieved 10 PNdB exhaust suppression in the aft quadrant compared to a design value of 20 PNdB. It was found that a broadband noise floor limited the realizable suppression. An analytical investigation of broadband noise generated by flow over the treatment surfaces provided very good agreement with the measured suppression levels and noise floor sound power levels. A fan thrust decrement of 22% was measured for the fully suppressed configuration of which 11.1% was attributed to the exhaust suppression hardware.

Stimpert, D. L.↗

NASA NTRS1973

Steady state analysis of Energy Transfer Control (ETC) and compressor bleed concepts of remote lift fan control

Two new concepts of control for VTOL aircraft remote lift fans are analyzed and discussed. Both concepts employ flow transfer among lift fans located in separate parts of the aircraft in order to obtain attitude control moments in hover and low-speed flight. The results presented are from a digital computer analysis of the YJ97/LF460 remote drive turbofan, although qualitative conclusions should apply to any remote fan system. The basic operating principles of the two systems are described, and their steady-state moment generating capabilities are discussed. Lift-recovery strategies for component failures are also analyzed.

Sellers, J. F.↗

NASA NTRS1973

Effects of helicopter noise and vibration on pilot performance (as measured in a fixed-base flight simulator)

The effects of noise and vibration on pilot performance are described. Pilot subjects were required to fly VTOL commercial IFR schedules using the computer simulation facilities. The routes flown simulated closely metropolitan routes flown currently by a helicopter airline. The duration of simulator flights ranged from 3 to 8 hours. Subjects were exposed to noise sound pressure levels ranging from 74dB (ambient) to 100dB and 17 Hz vibration stimuli ranging from .1 g to .3 g measured at the floor directly beneath the pilot's seat. Despite subject reports of extreme fatigue in these long flights, performance did not degrade. A curve of performance shows a slow improvement for the first three hours of exposure and a slight loss in performance during the remainder of the flight. As environmental stress conditions (noise, vibration, and time in the simulator) increased, subject performance improved. Within the limits of this study, the higher the stress the better the performance.

Stave, A. M.↗

NASA NTRS1974

Integrated propulsion/energy transfer control systems for lift-fan V/STOL aircraft

An integrated propulsion/control system for lift-fan transport aircraft is described. System behavior from full-scale experimental and piloted simulator investigations are reported. The lift-fan transport is a promising concept for short-to-medium haul civil transportation and for other missions. The lift-fan transport concept features high cruise airspeed, favorable ride qualities, small perceived noise footprints, high utilization, transportation system flexibility, and adaptability to VTOL, V/STOL, or STOL configurations. The lift-fan transport has high direct operating costs in comparison to conventional aircraft, primarily because of propulsion system and aircraft low-speed control system installation requirements. An integrated lift-fan propulsion system/aircraft low-speed control system that reduces total propulsion system and control system installation requirements is discussed.

Deckert, W. H.↗

NASA NTRS1974

The effect of engine component noise on V/STOL aircraft noise contours

An analytical study of fly-over noise using noise contours to show the effects of varying airplane and path parameters. The method of approach was to synthesize engine component noise spectra and exercise these components along given flight paths to measure the individual and total fly-over effect as a function of noise footprint area. The study was carried out in two phases. Phase 1 utilized a research type aircraft and Phase 2 used an advanced VTOL aircraft. The effect of cross flow was considered for both inlet and exhaust sections of the engine.

Fogg, R. G.↗

NASA NTRS1974

V/STOL lift fan commercial short haul transports: Continuing conceptual design study

A design study of commercial V/STOL transport airplanes for a 1985 operational time period has been made. The baseline mission considered was 400 nmi at a cruise speed of M = 0.75 and a 100-passenger payload with VTOL. Variations from the baseline included mission distance, payload, cruise speed, and propulsion system failure philosophy. All designs used propulsion systems consisting of multiple gas generators driving remote tip turbine lift and lift/cruise fans. By considering the fan to be designed for operational reliability, significant simplication of the airplane systems and reduction in airplane size and cost can be achieved.

Zabinsky, J. M.↗

NASA NTRS1974

Experimental and analytical studies in tilt-rotor aeroelasticity

An overview of an experimental and analytical research program underway for studying the aeroelastic and dynamic characteristics of tilt-rotor VTOL aircraft is presented. Selected results from several investigations of scaled models in the transonic dynamics tunnel, as well as some results from a test of a flight-worthy proprotor in the full-scale wind tunnel are shown and discussed with a view toward delineating various aspects of dynamic behavior peculiar to proprotor aircraft. Included are such items as proprotor/pylon stability, whirl flutter, gust response, and blade flapping. Theoretical predictions are shown to be in agreement with the measured stability and response behavior.

Kvaternik, R. G.↗

NASA NTRS1974

Maximum likelihood identification of aircraft stability and control derivatives

Application of a generalized identification method to flight test data analysis. The method is based on the maximum likelihood (ML) criterion and includes output error and equation error methods as special cases. Both the linear and nonlinear models with and without process noise are considered. The flight test data from lateral maneuvers of HL-10 and M2/F3 lifting bodies are processed to determine the lateral stability and control derivatives, instrumentation accuracies, and biases. A comparison is made between the results of the output error method and the ML method for M2/F3 data containing gusts. It is shown that better fits to time histories are obtained by using the ML method. The nonlinear model considered corresponds to the longitudinal equations of the X-22 VTOL aircraft. The data are obtained from a computer simulation and contain both process and measurement noise. The applicability of the ML method to nonlinear models with both process and measurement noise is demonstrated.

Mehra, R. K.↗

NASA NTRS1973

Case studies in Aircraft Parameter Identification

Three case studies in Aircraft Parameter Identification using simulated data for X-22 VTOL aircraft and flight test data for HL-10 and M2/F3 lifting bodies. After a brief discussion of the previous techniques and their limitations, a technique based on the Maximum Likelihood criterion is described. The problems of identifiability and uniqueness in determining the Stability and Control derivatives from flight test data are discussed and several methods for alleviating these problems are presented. The flight test data is analyzed in several different ways for obtaining physically meaningful estimates for the aircraft parameters.

Mehra, R. K.↗

NASA NTRS1974

Calculation procedures for potential and viscous flow solutions for engine inlets

The method and basic elements of computer solutions for both potential flow and viscous flow calculations for engine inlets are described. The procedure is applicable to subsonic conventional, short-haul, and vertical takeoff aircraft engine nacelles operating in a compressible viscous flow. The calculated results compare well with measured surface-pressure distributions for a number of model inlets. The uses of the program in both the design and analysis of engine inlets are discussed, with several examples given for VTOL lift fans, acoustic splitters, and for STOL engine nacelles. Several test support applications are also given.

Albers, J. A.↗

NASA NTRS1974

Experimental and analytical studies in tilt-rotor aeroelasticity

An overview of an experimental and analytical research program for studying the aeroelastic and dynamic characteristics of tilt-rotor VTOL aircraft is presented. Selected results from several investigations of scaled models in the Langley transonic dynamics tunnel as well as some results from a test of a flight-worthy prop rotor in the NASA Ames full-scale wind tunnel are shown and discussed with a view toward delineating various aspects of dynamic behavior peculiar to prop rotor aircraft. Included are such items as prop rotor pylon stability, whirl flutter, gust response, and blade flapping. Theoretical predictions, based on analyses developed at Langley, are shown to be in agreement with the measured stability and response behavior.

Kvaternik, R. G.↗

NASA NTRS1974

Conceptual design of a lift fan plus lift/cruise fighter aircraft

Results of a design synthesis and mission analysis of a supersonic VTOL fighter aircraft are presented. Propulsive lift is provided by a single turbotip-driven lift fan and deflected thrust from a high performance turbofan cruise engine fitted with an afterburner for supersonic flight. The inlet and thrust diverter in the main engine tail-pipe are seen to be the principal design problems. V/STOL and supersonic design tradeoffs are addressed in lift fan sizing and placement, reaction and aerodynamic control sizing, fuselage volume requirements, and area ruling. Range and turn rate are used as figures of merit.-

Hill, G. C.↗

NASA NTRS1974

Ejector-powered lift systems for V/STOL aircraft

The paper takes a brief look at powered lift from the point of view of the operator and the designer, considers application of an ejector-powered lift system to both STOL and VTOL aircraft, and describes some of the advantages of an ejector concept. Performance and noise characteristics of a simple ejector are described, and some comments are made regarding the Buffalo/Spey Augmentor-Wing proof-of-concept aircraft.

Whittley, D. C.↗

NASA NTRS1974

Requirement for simulation in V/STOL research aircraft programs

The application of flight simulation to aircraft design and development is discussed. The general stages of aircraft development are defined. The application of flight simulation to the following projects is reported: (1) the development and flight research of the Augmented Jet-Flap STOL research aircraft and (2) design studies of advanced VTOL research aircraft. It is stated that the simulation projects proved significant in helping establish criteria for the aircraft design and in facilitating the study of problems associated with new flight profiles, new methods of control, and special emergency conditions.

Quigley, H. C.↗

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

Longitudinal aerodynamics of a low-wing lift-fan transport including hover characteristics in and out of ground effect

A wind-tunnel investigation was conducted in the Langley V/STOL tunnel to determine the longitudinal aerodynamic characteristics of a six-fan, tip-driven (remote) lift-fan VTOL transport throughout transition. The large midspan lift-fan pods and cruise fans were removed to determine their influence on the stability and control of the configuration. Data were obtained in the hovering mode for ranges of model height above ground. The data are presented without analysis or discussion.

Hoad, D. R.↗

NASA NTRS1975

A formal structure for advanced automatic flight-control systems

Techniques were developed for the unified design of multimode, variable authority automatic flight-control systems for powered-lift STOL and VTOL aircraft. A structure for such systems is developed to deal with the strong nonlinearities inherent in this class of aircraft, to admit automatic coupling with advanced air traffic control, and to admit a variety of active control tasks. The aircraft being considered is the augmentor wing jet STOL research aircraft.

Meyer, G.↗

NASA NTRS1974

Conceptual design study of a 1985 commercial STOL tilt rotor transport

Results of conceptual engineering design studies of a STOL tilt rotor commercial aircraft for the 1985 time frame are presented. The details of aircraft size, performance, flying qualities, noise, and cost are included. The savings in terms of fuel economy resulting from STOL operations compared with VTOL vehicles are determined.

Widdison, C. A.↗