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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1959

Flight Investigation of the Stability and Control Characteristics of a 1/4-Scale Model of a Tilt-Wing Vertical-Take-Off-and-Landing Aircraft

An experimental investigation has been conducted to determine the dynamic stability and control characteristics of a tilt-wing vertical-take-off-and-landing aircraft with the use of a remotely controlled 1/4-scale free-flight model. The model had two propellers with hinged (flapping) blades mounted on the wing which could be tilted up to an incidence angle of nearly 90 deg for vertical take-off and landing. The investigation consisted of hovering flights in still air, vertical take-offs and landings, and slow constant-altitude transitions from hovering to forward flight. The stability and control characteristics of the model were generally satisfactory except for the following characteristics. In hovering flight, the model had an unstable pitching oscillation of relatively long period which the pilots were able to control without artificial stabilization but which could not be considered entirely satisfactory. At very low speeds and angles of wing incidence on the order of 70 deg, the model experienced large nose-up pitching moments which severely limited the allowable center-of-gravity range.

Tosti, Louis P.↗
NASA NTRS1959

Force-Test Investigation of the Stability and Control Characteristics of a 1/4-Scale Model of a Tilt-Wing Vertical-Take-Off-and-Landing Aircraft

A wind-tunnel investigation has been made to determine the aerodynamic characteristics of a 1/4-scale model of a tilt-wing vertical-take-off-and-landing aircraft. The model had two 3-blade single-rotation propellers with hinged (flapping) blades mounted on the wing, which could be tilted from an incidence of 4 deg for forward flight to 86 deg for hovering flight. The investigation included measurements of both the longitudinal and lateral stability and control characteristics in both the normal forward flight and the transition ranges. Tests in the forward-flight condition were made for several values of thrust coefficient, and tests in the transition condition were made at several values of wing incidence with the power varied to cover a range of flight conditions from forward-acceleration (or climb) conditions to deceleration (or descent) conditions The control effectiveness of the all-movable horizontal tail, the ailerons and the differential propeller pitch control was also determined. The data are presented without analysis.

Newsom, William A., Jr.↗
NASA NTRS1971

Fundamental limitations on V/STOL terminal guidance due to aircraft characteristics

A review is given of limitations on approach flight paths of V/STOL aircraft, including limits on descent angle due to maximum drag/lift ratio. A method of calculating maximum drag/lift ratio of tilt-wing and deflected slipstream aircraft is presented. Derivatives and transfer functions for the CL-84 tilt-wing and X-22A tilt-duct aircraft are presented. For the unaugmented CL-84 in steep descents the transfer function relating descent angle to thrust contains a right-half plane zero. Using optimal control theory, it is shown that this zero causes a serious degradation in the accuracy with which steep flight paths can be followed in the presence of gusts.

Wolkovitch, J.↗
NASA NTRS1966

Comparison of wind-tunnel and flight results on a four-propeller tilt-wing configuration

Over the years aerodynamicists have learned to rely heavily on wind­-tunnel-model results in predicting the aerodynamic characteristics of con­ventional aircraft configurations. With the development of V/STOL con­figurations which have high slipstream deflection angles. such as the four-propeller tilt-wing XC-142A V/STOL aircraft, the reliability of small-scale wind-tunnel-model results in predicting full-scale airplane characteristics needs to be reexamined. Extensive tests have been made by NASA on several sizes of wind-tunnel models of the XC-142A V/STOL configuration and by Ling-Temco-Vought, Inc., on the airplane. These results show that models predict the slow-speed level-flight characteristics very well but that small models underpredict the descent capability of the airplane. Larger scale wind-tunnel models of approximately half size show better agreement with the airplane descent characteristics. It was found from smoke flow studies that small models can also pre­dict the region in which self-generated disturbances will be encountered by tilt-wing configurations in ground proximity.

WIND TUNNEL MODEL↗
NASA NTRS1964

Dynamic Tests of V/STOL Transport Models

This paper presents a summary of results obtained in dynamic tests of free-flight models of various configurations suitable for V/STOL transport aircraft at the NASA Langley Research Center. The configurations covered will be the tilt-wing propeller-driven type as represented by the XC-142A tri-service transport, the fan-in-wing type as represented by the XV-5A research airplane, and the jet-lift type as represented by the Dornier 00-31 transport. The test techniques themselves are not described in this paper since they have been described in detail previously in references 1 and 2.

Dynamic stability↗
NASA NTRS1966

Aerodynamic stability and control of ducted- propeller aircraft

Test results from studies of small and large powered models of a dual, tandem, ducted-propeller VTOL design are reviewed, with emphasis on stability and control characteristics through the transition speed range. The character­istics are generally satisfactory. Stability augmentation may be required to reduce Dutch roll tendencies. Further study is needed to evaluate the appar­ently large side-force gradients in sideslip. Reductions in control effective­ness due to ground proximity are similar to those for tilt-wing V /STOL designs.

AERODYNAMIC STABILITY↗
NASA NTRS1961

Aerodynamic Characteristics of Propeller-Driven VTOL Aircraft

This paper discusses the two major configurations that are usually considered for achieving VTOL while keeping the fuselage essentially horizontal - that is, the tilt-wing and the deflected-slipstream configurations. Because of the high turning losses incurred by deflected-slipstream configurations in hovering and because of the wing-stalling problem of the pure tilt-wing configurations during the transition, it appears that a combination of the two principles should be used. This tilt-wing and flap configuration should make use of a programmed extensible-chord slotted flap together with a leading-edge high-lift device in order to avoid the performance and handling qualities problems associated with wing stalling during the transition while keeping the wing area as low as possible for efficiency in cruising flight.

Kirby, Robert H.↗
NASA NTRS1972

Extraction of longitudinal aerodynamic coefficients from forward-flight conditions of a tilt-wing V/STOL airplane

A parameter-estimation algorithm was used to extract the longitudinal aerodynamic derivatives from flight data for the XC-142A airplane in a cruise condition. The flight data were the response to a tail-plane doublet input. Results of this study showed that a set of derivatives were determined which yielded a calculated aircraft response in close agreement with the measured response. This calculated response was in much closer agreement with the flight data than the response obtained by using derivatives which were calculated from empirical methods. There were large differences between some of the important derivatives extracted from flight data and those calculated from empirical methods. The reasons for these differences were not identified.

Williams, J. L.↗