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At least 73 records · Page 4

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NASA NTRS1978

A combined potential and viscous flow solution for V/STOL engine inlets

A potential flow routine and a viscous boundary layer routine have been combined into a single routine for estimating the flow in and around subsonic inlets. In this combined routine, the viscous flow solution about the inlet body is obtained by adding the viscous displacement thickness to the inlet geometry. Combination of the two flow solutions has resulted in cost savings, both in preparation time and in computer time. This routine is a useful tool in optimizing lip shapes for V/STOL inlets. The method of combining the routine, comparison with NASA test data, and utilization of the routine for V/STOL inlet design are presented.

Ybarra, A. H.↗

NASA NTRS1977

Development of the propulsion simulator - A test tool applicable to V/STOL configurations

A turbine engine multi-mission propulsion simulator, capable of representing inlet/airframe/nozzle flowfield interactions for supersonic V/STOL aircraft wind tunnel models, is described. The propulsion simulator replaces conventional aero flow-through and jet effects models with a single model; flow field interactions modeled by the simulator may include close-coupled inlets and nozzles, non-axisymmetric vectoring exhaust nozzles, and forward canards mounted near the inlets and wings. Wind tunnel tests of the simulation system at Mach numbers up to 1.2 are reported for a model typical of a F-15 aircraft installation. The possibility of applying the simulator to advanced V/STOL design programs is also discussed.

Eigenmann, M. F.↗

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 NTRS1979

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

An experimental research program for measuring the flow field around a 70 percent scale V/STOL aircraft model in ground effect is described. The velocity measurements were conducted with a ground-based laser Doppler velocimeter at an outdoor test pad. The remote sensing instrumentation, experimental tests, and results 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 heights above ground. The study shows 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 NTRS1979

Recent V/STOL aircraft designs

The paper reviews the V/STOL aircraft designs pursued by industry from 1971 to 1978, with emphasis on the 1975-1978 period. Consideration is given to those designs pertaining to vertical-attitude and horizontal-attitude V/STOL types. These are divided into such concepts as tilting jet engine, lift/cruise engine, lift engine, lift/cruise fan, ejector augmentor, tilt rotor, stowed rotor, and rotor wing.

Deckert, W. H.↗

NASA NTRS1979

Aerodynamic effects of an attitude control vane on a tilt-nacelle V/STOL propulsion system

One possible technique for obtaining longitudinal control on a tilt-nacelle V/STOL aircraft is the use of a variable attitude vane assembly mounted in the propulsion system exhaust. Deflecting the vane produces large forces and moments without depending on forward speed of the aircraft. Tests are carried out in the Ames 40 by 80 ft wind tunnel on a large-scale tilt-nacelle V/STOL propulsion system with and without a variable attitude control vane assembly. Aerodynamic characteristics are analyzed in terms of nacelle aerodynamics, vane aerodynamics, and vane-induced effects on the nacelle aerodynamics. It is shown that the aerodynamic forces due to the nacelle without the vane can be a significant part of the total forces produced by the propulsion system. The control vane effectively produces large changes in pitching moment which are accompanied by significant changes in total lift and drag. The vane has a substantial effect on the propulsion-system aerodynamics. Other pertinent results are also given.

Betzina, M. D.↗

NASA NTRS1979

Effect of nozzle spacing on ground interference forces for a two jet V/STOL aircraft

The effect of nozzle spacing on ground interference forces was investigated for a two jet V/STOL aircraft design. The need for information on the effect of jet spacing arises because of the tradeoff between mechanical complexity, which calls for close spacing, and roll control moments, which call for wider spacing. The ground interference forces on a two jet V/STOL aircraft model were measured for a range of nozzle spacings. Interference forces showed a complicated behavior with nozzle spacing, fuselage geometry, and height above ground. For some conditions a slight change in nozzle spacing resulted in a fourfold change in the interference force from 3% to 12% of the basic jet thrust. An understanding of the observed aircraft force behavior was developed using detailed measurements of the upwash flow properties, along with force and pressure measurements on a series of two dimensional fuselage representations.

Hill, W. G., Jr.↗

NASA NTRS1980

Propulsion system mathematical model for a lift/cruise fan V/STOL aircraft

A propulsion system mathematical model is documented that allows calculation of internal engine parameters during transient operation. A non-realtime digital computer simulation of the model is presented. It is used to investigate thrust response and modulation requirements as well as the impact of duty cycle on engine life and design criteria. Comparison of simulation results with steady-state cycle deck calculations showed good agreement. The model was developed for a specific 3-fan subsonic V/STOL aircraft application, but it can be adapted for use with any similar lift/cruise V/STOL configuration.

Cole, G. L.↗

NASA NTRS1981

Conceptual/preliminary design study of subsonic v/stol and stovl aircraft derivatives of the S-3A

A computerized aircraft synthesis program was used to examine the feasibility and capability of a V/STOL aircraft based on the Navy S-3A aircraft. Two major airframe modifications are considered: replacement of the wing, and substitution of deflected thrust turbofan engines similar to the Pegasus engine. Three planform configurations for the all composite wing were investigated: an unconstrained span design, a design with the span constrained to 64 feet, and an unconstrained span oblique wing design. Each design was optimized using the same design variables, and performance and control analyses were performed. The oblique wing configuration was found to have the greatest potential in this application. The mission performance of these V/STOL aircraft compares favorably with that of the CTOL S-3A.

Kidwell, G. H., Jr.↗

NASA NTRS1981

Scale effects on turbulent boundary layer development and flow separation around V/STOL inlets at high incidence

Numerical methods for calculating laminar and turbulent boundary layers development around V/STOL engine inlets at high incidence angles, along with the procedures for predicting flow separation, are presented. Results of scale-effects, which are obtained by a numerical scaling procedure on the boundary layer characteristics and incidence angles at onset of separation are discussed. The interesting 'cross-over' phenomena, where the full-scale models actually exhibit earlier separation than the scaled-models, is illustrated for a typical V/STOL inlet at a certain operating condition. Some of the numerical results are compared with the existing wind-tunnel test data for a 1/6 scale inlet model to demonstrate the validity of the numerical approach.

Chou, D. C.↗

NASA NTRS1981

Numerical and classical analysis of V/STOL aircraft using selected propulsion systems

The development needed for the evolution of selected V/STOL research vehicles into optimized antisubmarine warfare (ASW) aircraft configurations, using numerical procedures and traditional analytical methods, has been examined. Three propulsion systems, which represent state-of-the-art development aimed at solving the thrust-vectoring and attitude-control problems of V/STOL aircraft, are analyzed. The use of NASA computer programs for aircraft synthesis (ACSYNT), and for optimizing configurations (COMMIN), coupled with contractor-supplied propulsion system data provides for accurate performance prediction of the selected ASW configurations. Particular emphasis on the transition phase between the research vehicle and the optimized configuration demonstrates the strengths and weaknesses of using generic research aircraft instead of building prototypes to demonstrate new technology

Wilson, S. B., III↗

NASA NTRS1981

Low speed testing of the inlets designed for a tamden-fan V/STOL nacelle

An approximately 0.25 scale model of a tandem fan nacelle, designed for a subsonic V/STOL aircraft, was tested in a Lewis wind tunnel. Model variables included long and short aft inlet cowls and the addition of exterior strakes to the short inlet cowl. Inlet pressure recoveries and distortion were measured at pitch angles to 40 deg and at combinations of pitch and yaw to 30 deg. Airspeeds covered a range to 135 knots (69 m/sec). The short aft inlet with added strakes had the best aerodynamic performance and is considered suitable for the intended V/STOL application.

Williams, R. C.↗

NASA NTRS1982

Jet V/STOL wind-tunnel simulation and groundplane effects

The pretest preparation necessary to define the objectives of an appropriate investigation into the jet V/STOL wind tunnel simulation and ground plane effects were examined. Low speed wind tunnel testing of V/STOL aircraft concepts to determine the aerodynamic propulsion interaction effects during the transition between hover and wingborne flight is a necessary step in the development cycle of this type of aircraft. Powered models are normally used to determine the aerodynamic performance characteristics. Several factors which influence the selection of the model concept and the engine simulator are discussed. Some of the test techniques important for this class of aircraft model are examined. Wind tunnel wall effects important to this aircraft testing with special emphasis on groundplane effects are reviewed.

Margason, R. J.↗

NASA NTRS1981

Experience with high performance V/STOL fighter projects at MBB

Flight control systems and aerodynamic aspects of experimental V/STOL aircraft are discussed. The VJ 101 C featured tilting engines for increased thrust, reheat for takeoff, simple translation, triangular decentralization of the engines for thrust modulation, and moderate ground effects. Two experimental aircraft were built, with and without reheat, capable of Mach 2 and Mach 1.04, respectively. The mechanical flight control system and tests are outlined, both for hover rig and flight configurations. Ground suction, acoustic and thermal loading, sodium silicate coatings to avoid ground corrosion, and recirculation are considered. Results of the follow-on project to the VJ 101 C, the AVS, which was developed by NASA, are reviewed, and it is noted that trends toward thrust-to-weight ratios exceeding one, in concert with low wing loading, favor the development of V/STOL aircraft.

Aulehla, F.↗

NASA NTRS1981

Development and validation of the V/STOL aerodynamics and stability and control manual

A V/STOL Aerodynamics and Stability and Control Manual was developed to provide prediction methods which are applicable to a wide range of V/STOL configurations in hover and transition flight, in and out of ground effect. Propulsion-induced effects have been combined with unpowered aerodynamics in a buildup of total forces and moments for the jet-lift concept, so that total aerodynamics can be used to predict aircraft stability, control, and flying qualities characteristics. Results of longitudinal aerodynamic predictions have been compared with test data, and indicate that the methods are fast, inexpensive, and within the desired accuracy for the objective preliminary design stage.

Henderson, C.↗

NASA NTRS1981

V/STOL propulsion control technology

Results of a NASA sponsored study of V/STOL Propulsion Control Analysis are presented. The study involved propulsion control requirements, design concepts and procedures, and control designs for supersonic V/STOL. A variable cycle engine with a remote augmented lift system was used as a basis for establishing typical operating requirements and control concepts, and a nonlinear engine model was developed for control development as a precursor to a real-time simulation capability. A simplified aircraft model was also used to investigate transition requirements, and a long-range technology plan was developed to define subsequent program requirements for achieving a real-time piloted simulation capability.

Brown, H.↗

NASA NTRS1981

Low speed testing of the inlets designed for a tandem-fan V/STOL nacelle

Williams, R. C.↗

NASA NTRS1982

Aerodynamic characteristics of a large-scale, twin tilt-nacelle V/STOL model

A subsonic tilt-nacelle V/STOL aircraft configuration is described which is powered by two turbofan engines, mounted on a single carry-through structure that is designed to maintain the thrust axis close to the center of gravity at nacelle incidences of 5-95 deg. Control during V/STOL operation, often from small ship platforms, is achieved by means of a vane assembly that is immersed in each turbofan's exhaust. Wind tunnel test data have been obtained with an 11.2-m wing span model for the vertical-to-horizontal flight transition capability of the concept. It is found that the aircraft can operate over a broad transition corridor, with sufficient maneuver capability about the trim points. The control vane exhibited linear response characteristics over a large deflection range, with little influence from power, angle of attack or ground proximity in hover. The model induced a positive ground effect in hover that increased as wheel height was approached and strake angle increased.

Falarski, M. D.↗