Review of propulsion-induced effects on aerodynamics of jet V/STOL aircraft
Propulsion device-induced effects on V/STOL aircraft aerodynamics in hover and transition flight
Margason, R. J.↗
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Summary of a flight-test evaluation of the CL-84 tilt-wing V/STOL aircraft
Flight test evaluation of second generation CL-84 tilt-wing aircraft in hover, transition, and cruise modes
Champine, R. A.↗
Decision processes in the adaptive behavior of human controllers
Decision algorithms simulating human controller adaptive behavior in controlling VTOL aircraft in hover following stability augmentation system failure
Bekey, G. A.↗
History of NACA/NASA rotating-wing aircraft research, 1915-1970. III Cont'd
NACA/NASA rotating wing aircraft research history 1915-1970, Part 3, covering rotor dynamics and flying qualities, hovering tests, rotor flow, loads, etc
Gustafson, F. B.↗
Gravity stabilized flying vehicle Patent
Hovering type flying vehicle design and principle mechanisms for manned or unmanned use
Johnson, H. I.↗
Flight investigation of a V/STOL transport model having six wing-mounted lift fans
Free flight tests in hoovering and forward flight free flight tests in hovering and forward flight lift fans
Grafton, S. B.↗
Flight investigation of a tilt-wing VTOL aircraft in the terminal area under simulated instrument conditions
Hovering and low speed flight capabilities of tilt wing VTOL aircraft in terminal area under near-zero visibility instrument landing conditions
Champine, R. A.↗
Wake and boundary layer effects in helicopter rotor aerodynamics
Helicopter wake and boundary layer effects on rotor aerodynamic performance in hovering, low and high speed forward flight
Clark, D. R.↗
An experimental investigation of the helicopter rotor blade element airloads on a model rotor in the blade stall regime
A wind tunnel test program was conducted on an eight foot diameter model rotor system to determine blade element airloads characteristics in the unstalled and stalled flight regimes. The fully articulated model rotor system utilized three blades with a Vertol 23010-1.58 airfoil section, the blades being 1/7.5 scale models of the Ch-47C rotor blades. Instrumentation was incorporated at the blade 75% radial station to measure pressure and skin friction distributions, surface streamline directions and local angle of attack. The test program was conducted in three phases; non-rotating, hover and forward flight at advance ratios of 0.15, 0.35 and 0.60. Test data were analyzed with respect to providing insight to the mechanisms affecting blade stall, particularly retreating blade stall during forward flight conditions. From such data, an assessment was made as to the applicability of current theoretical analyses used for the prediction of blade element airloads in the stall regime.
Fisher, R. K., Jr.↗
Effects of ground proximity on the aerodynamic characteristics of a six-jet V/STOL configuration with four swing-out lift jets
A wind-tunnel investigation has been made of the effects of ground proximity on the longitudinal and lateral-directional aerodynamic characteristics and jet-interference effects of a model of a jet V/STOL variable-sweep fighter airplane that employs four direct-lift engines which swing out from the fuselage ahead of the wing and two lift-cruise engines located in the rear part of the fuselage. Data were obtained through a range of angles of attack and sideslip at simulated speeds from hover through transition at various heights of the model above a moving-belt ground plane. Power-off data and power-on data at several power conditions are presented. The data are presented without analysis or discussion.
Carter, A. W.↗
Aerodynamic characteristics of a large scale lift fan transport model with podded fans forward and lift cruise fans mounted above the wing
The aerodynamic characteristics of a large scale V/STOL transport model powered by tip-turbine driven lift fans were investigated. The model had four fans; the forward fans were mounted in pods forward of the wing at midsemispan. The aft fans were placed in cruise nacelles behind and above the wing. A cascade of variable camber exit louvers was placed behind each of the lift-cruise fans to turn the fan flow in the lift direction for hover and transition to wing supported flight. The wing of the model was mounted above the fuselage, had an aspect ratio of 5.8, sweepback of 35 deg at the quarter chord line and a taper ratio of 0.3. Various configurations of the model were tested to explore the transition speed range. Fan performance, turning effectiveness of the variable camber exit louvers, longitudinal and lateral-directional characteristics with fan operation in crossflow are presented.
Kirk, J. V.↗
A flight evaluation of a vectored thrust jet V/STOL airplane during simulated instrument approaches using the Kestrel (XV-6A) airplane
An in-flight investigation was made to determine the terminal-area operating problems of a vectored-thrust-jet vertical and short take-off landing (V/STOL) airplane under simulated instrument conditions. Handling-qualities data pertinent to the terminal-area approach and landing task are presented in the text, and additional documentation is included in the appendixes. Problems dealing with the cruise letdown to localizer capture, conversion to powered-lift flight, precise control of the glide slope, approach velocity or deceleration schedule, hover, and landing are discussed.
Morello, S. A.↗
A Theoretical and Experimental Investigation of Flap-Lag Stability of Hingeless Helicopter Rotor Blades
The stability of hingeless rotor blade oscillations in hover is examined theoretically using a simplified centrally-hinged, spring-restrained, rigid blade to approximate the deflections of actual elastic blades. The aerodynamic and inertial coupling between the flap and lead-lag degrees of freedom is primarily responsible for instability, however elastic coupling and kinematic pitch-lag coupling both exert a powerful influence on hingeless rotor blade stability. Experimental results obtained from a two-bladed 1.81m diameter model rotor designed for minimum elastic coupling have confirmed the results of linear theory. For this model configuration rotor blade stall at high pitch angles was found to counteract the destabilizing flap-lag coupling and increase the damping of lead-lag oscillations. It was possible to account for this effect with the theory by using drag data for stalled airfoils.
Ormiston, R. A.↗
Wind-tunnel investigation at low speeds of a model of the Kestrel (XV-6A) vectored-trust V/STOL airplane
Longitudinal and lateral stability data were obtained with the model out of and in ground effect over a moving ground plane for a range of model angles of attack and sideslip at various thrust coefficients. These data were taken primarily at thrust coefficients which simulate transition speeds on the airplane between hover and 200 knots. Some data, however, represent the effect of thrust deflection at speeds up to 350 knots. Also presented are the effects of control-surface deflections and interference between the jets and free stream.
Margason, R. J.↗
Revisions to V/STOL handling qualities criteria of AGARD report 408
A brief review of selected handling qualities criteria for V/STOL aircraft shows that although a clearer understanding of the requirements for controversial areas such as roll control power, vertical flight path control, and transition is in hand, considerably more research is needed to refine these criteria for operational IFR activity. Because many items interact to influence the pilots' overall impression of the aircraft's behaviour, additional work of a systematic nature must be done to clarify this aspect. A better definition of a gust model which includes discrete gust effects is needed to firm up criteria for both hover and STOL operation.
Anderson, S. B.↗
A VTOL translational rate control system study on a six degrees-of-freedom motion simulator
A linearized translational rate system for near hover flight was optimized on a large motion simulator under the constraints of no disturbances and limited control power. Both lateral and longitudinal modes were considered with the primary variables of investigation being control sensitivity and response stiffness and secondarily system damping. Yaw and height control characteristics were represented by an angular rate and acceleration system, respectively. General regions of desired sensitivity and stiffness for the longitudinal and lateral modes were determined under VFR conditions for both the rapid maneuver task and the station keeping/mild maneuver task.
Corliss, L. D.↗
The inclusion of rotor dynamics in controller design for helicopters.
State-feedback-controllers and state-estimators (filters) are designed for the roll-pitch-horizontal motions of a helicopter near hover, using a new quadratic synthesis technique. One model (tenth order) uses a dynamic model of the rotor, whereas the other model (sixth order) assumes the rotor can be tilted instantaneously. It is shown that, for tight control, neglecting the rotor dynamics in designing the autopilot can produce unstable closed-loop response on the model that includes rotor dynamics. Two filters are designed to use only fuselage sensors and two are designed to use both fuselage and rotor sensors. It is shown that rotor states can be estimated with sufficient accuracy using only fuselage sensors so that it does not seem worthwhile to use rotor sensors. The mean square response of the vehicle to a gusty, random wind, using several different filter/state-feedback compensators, is shown to be satisfactory.
Hall, W. E., Jr.↗
Improved method for design of expansion-chamber mufflers with application to operational helicopter
Field test of muffler designed with aid of this method was conducted on helicopter with known exhaust-noise problem. When exhaust noises were compared for hover-flight conditions, muffler system was found to reduce exhaust noise by approximately 11 db. No significant degradation in engine performance was observed.
Parrott, T. L.↗