SEARCH · Search NASA
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Wind tunnel tests to determine longitudinal aerodynamic characteristics of large scale semispan V/STOL tilt-wing configuration with single propeller
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.
Tilt-wing VTOL and jet-flap STOL designs for commercial passenger transport aircraft
Hybrid gas-electric aircraft propulsion architectures provide flexibility in the way that power and energy is managed when compared to their traditional pure-gas counterparts. In this paper, investigations are conducted for the impact this added flexibility has on the operability of turbomachinery. Specifically, the Turbine Electrified Energy Management (TEEM) concept is applied. It takes a controls approach to improving operability of the turbomachinery by utilizing electric hardware. In this paper, TEEM is applied to a propulsion system for a 15 passenger vertical lift concept vehicle. This is the first application of TEEM to a turbine engine that generates power. The study establishes TEEM as being applicable to this smaller thrust/power class of air transportation vehicle and explores how power can be otherwise managed in the propulsion system to benefit the aircraft. The simulation study demonstrates significant improvements in transient operability that expands the engine design space to enable a more efficient and lighter weight engine design. Simulation results also demonstrate tighter regulation of the power turbine and rotor speeds, a slight decrease in bulk fuel burn, and an increase in the maximum thrust of ~7%. This is achieved through the power management control strategy and modestly sized electric machines with re usable energy storage.
Hybrid gas-electric aircraft propulsion architectures provide flexibility in the way that power and energy is managed when compared to their traditional pure-gas counterparts. In this paper, investigations are conducted for the impact this added flexibility has on the operability of turbomachinery. Specifically, the Turbine Electrified Energy Management (TEEM) concept is applied. It takes a controls approach to improving operability of the turbomachinery by utilizing electric hardware. In this paper, TEEM is applied to a propulsion system for a 15 passenger vertical lift concept vehicle. This is the first application of TEEM to a turbine engine that generates power. The study establishes TEEM as being applicable to this smaller thrust/power class of air transportation vehicle and explore show power can be otherwise managed in the propulsion system to benefit the aircraft. The simulation study demonstrates significant improvements in transient operability that expands the engine design space to enable a more efficient and lighter-weight engine design. Simulation results also demonstrate tighter regulation of the power turbine and rotor speeds, a slight decrease in bulk fuel burn, and an increase in the maximum thrust of ~7%. This is achieved through the power management control strategy and modestly sized electric machines with re-usable energy storage.
Greased Lightning (GL-10) is an aircraft configuration that combines the characteristics of a cruise efficient airplane with the ability to perform vertical takeoffs and landings (VTOL). This presentation will summarize the results of the flight test experiments. Two key technologies have been utilized in this aircraft design. Namely, distributed electric propulsion and closed loop control laws to be able to fly an inherently unstable aircraft. For many decades we as an aviation industry have been attempting to build a vehicle that can combine the speed and efficiency of an airplane with the vertical takeoff and landing of a rotorcraft. Overall it has been determined thru flight test that a design that leverages these new technologies can yield a useful VTOL cruise efficient aircraft.
The Elytron 2S is a prototype aircraft concept to allow VTOL capabilities together with fixed wing aircraft performance. It has a box wing design with a centrally mounted tilt-wing supporting two rotors. This paper explores the aerodynamic characteristics of the aircraft using computational fluid dynamics in hover and low speed forward flight, as well as analyzing the unique control system in place for hover. The results are then used to build an input set for NASA Design and Analysis if Rotorcraft software allowing trim and flight stability and control estimations to be made with SIMPLIFLYD.
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.
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.
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.
The AV-95 Sun Devil must combine helicopter capabilities, such as vertical takeoff and landings (VTOL) and rotor-powered flight, along with long-duration cruise and high-speed dash capabilities unobtainable by conventional helicopters. To be able to perform both tasks, and perform them well, the AV-95 Sun Devil design incorporates several unconventional devices; the AV-95 uses two convertible turbofan engines, able to provide both shaft power for the main rotor and tall fan as well as jet thrust either separately or simultaneously. Other devices used for the AV-95 include a variable diameter main rotor and a blown flap. In helicopter mode, the AV-95 Sun Devil performs like a winged helicopter. The addition of wings to an attack helicopter results in two significant advantages. First, the addition of wings makes a helicopter more maneuverable than a wingless, but otherwise similar helicopter. Second, since the wings produce lift, rotor stall and compressibility effects can be significantly delayed at high tip velocities. In fixed-wing mode, the main rotor is completely off-loaded but slightly powered, and the rotor diameter has been minimized. The AV-95 Sun Devil has many advantages over other VTOL aircraft. The conversion process is simple and fast; conversion does not make the AV-95 vulnerable to enemy attack during conversion such as a tilt-wing or a tilt-rotor. Stop-rotor aircraft and a stowed rotor aircraft require heavy breaking of the rotor for conversion; this adds time for conversion and weight to the aircraft. Because the AV-95 never stops the rotor in flight, much weight is spared, and conversion is much simpler and faster.
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.
This paper presents an autonomous path-following control architecture for a tilt-wing, distributed electric propulsion, vertical take-off and landing unmanned aerial system in hover mode and presents indoor flight test results. The test-bed vehicle is a subscale model with the same configuration as the NASA GL-10 aircraft. The control architecture consists of an inner-loop attitude controller, outer-loop trajectory controller, and a trajectory generation scheme. The flight test results show that the vehicle can satisfactorily follow a path prescribed by a list of waypoints around the indoor flight room.
Explore the source record for details and available documents.
Lateral-directional dynamic stability derivatives are presented for a O.1-scale model of the XC-142A tilt-wing transport. The tests involved various descending flight conditions achieved at constant speed and wing incidence by varying the vehicle angle of attack. The propeller blade angle and the speed were also changed in the steepest descent case. The experimental data were analyzed assuming that the dynamic motions of the vehicle may be described by linearized equations, with the lateral-directional characteristics of the full-scale aircraft also presented and discussed. Results from this experimental investigation indicated that the full-scale aircraft would have a stable lateral-directional motion in level flight, with the dynamic motion becoming less stable as the descent angle was increased.