Search NASA⌕ Search

SEARCH · Search NASA

Results for “STOL”

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.

At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

On the role of the radiation directivity in noise reduction for STOL aircraft.

The radiation characteristics of distributed randomly fluctuating acoustic sources when shielded by finite surfaces are discussed briefly. A number of model tests using loudspeakers as artificial noise sources with a given broadband power density spectrum are used to demonstrate the effectiveness of reducing the radiated noise intensity in certain directions due to shielding. In the lateral direction of the source array noise reductions of 12 dB are observed with relatively small shields. The same shields reduce the backward radiation by approximately 20 dB. With the results obtained in these acoustic model tests the potentials of jet noise reduction of jet flap propulsion systems applicable in future STOL aircraft are discussed. The jet flap configuration as a complex aerodynamic noise source is described briefly.

Gruschka, H. D.↗
NASA NTRS1974

Calculation of aerodynamic characteristics of STOL aircraft

Method predicts lift and pitching moment characteristics of STOL aircraft with externally-blown, jet-augmented wing-flap combinations using potential-flow approach which involves combination of two flow models. Method can accommodate multiple engines per wing panel and part-span flaps.

Dillenius, M. F. E.↗
NASA NTRS1973

Design integration and noise studies for jet STOL aircraft. Task 7C: Augmentor wing cruise blowing valveless system. Volume 1: Static testing of augmentor noise and performance

Static performance and acoustic tests were conducted on a two-dimensional one-third-scale augmentor flap model that simulated a cruise blowing augmentor system designed for a scale augmentor flap model that simulated a cruise blowing augmentor, which offers a degree of 150-passenger STOL airplane. The cruise blowing augmentor, which offers a degree of simplicity by requiring no fan air diverter valves, was simulated by fitting existing lobe suppressor nozzles with new nozzle fairings. Flow turning performance of the cruise blowing augmentor was measured through a large range of flap deflection angles. The noise suppression characteristics of a multilayer acoustic lining installed in the augmentor were also measured.

Campbell, J. M.↗
NASA NTRS1974

A compilation and analysis of typical approach and landing data for a simulator study of an externally blown flap STOL aircraft

A piloted simulation study has been made of typical landing approaches with an externally blown flap STOL aircraft to ascertain a realistic dispersion of parameter values at both the flare window and touchdown. The study was performed on a fixed-base simulator using standard cockpit instrumentation. Six levels of stability and control augmentation were tested during a total of 60 approaches (10 at each level). A detached supplement containing computer printouts of the flare-window and touchdown conditions for all 60 runs has been prepared.

Middleton, D. B.↗
NASA NTRS1974

Simulation of decelerating landing approaches on an externally blown flap STOL transport airplane

A fixed-base simulator program was conducted to define the problems and methods for solution associated with performing decelerating landing approaches on a representative STOL transport having a high wing and equipped with an external-flow jet flap in combination with four high-bypass-ratio fan-jet engines. Real-time digital simulation techniques were used. The computer was programed with equations of motion for six degrees of freedom and the aerodynamic inputs were based on measured wind-tunnel data. The pilot's task was to capture the localizer and the glide slope and to maintain them as closely as possible while decelerating from an initial airspeed of 140 knots to a final airspeed of 75 knots, while under IFR conditions.

Grantham, W. D.↗
NASA NTRS1974

Flight investigation of the VFR and IFR landing approach characteristics and terminal area airspace requirements for a light STOL airplane

A flight research program was conducted to determine the terminal area instrument flight capabilities of a light STOL airplane. Simulated (hooded) instrument landing approaches were made using steep single-segment and two-segment glide slopes. A brief investigation was also made of the visual flight terminal area capabilities of the aircraft. The results indicated that the airplane could be flown on a 7 deg glide-slope ILS-type approach in still air with an adequate 3 deg margin for downward correction.

Crane, H. L.↗
NASA NTRS1974

A wind model for an elevated STOL-port configuration

Measurements of mean velocity magnitude and direction as well as three-dimensional turbulence intensity were made in the flow over a model of an elevated STOL-port. A 1:300 scale model was placed in a wind tunnel flow simulating the mean velocity profile and turbulence characteristics of atmospheric winds over a typical city environment excluding detailed wake structures of possible nearby buildings. Hot-wire anemometer measurements of velocity and turbulence were made along approach and departure paths of aircraft operating on the runway centerline and at specified lateral distances from the centerline. Approach flow directions simulated were 0 and 30 degrees to the runway centerline.

Peterka, J. A.↗
NASA NTRS1974

Simulator study of minimum acceptable level of longitudinal stability for a representative STOL configuration during landing approach

A fixed-base simulator study was conducted to determine the minimum acceptable level of longitudinal stability for a representative turbofan STOL (short take-off and landing) transport airplane during the landing approach. Real-time digital simulation techniques were used. The computer was programed with equations of motion for six degrees of freedom, and the aerodynamic inputs were based on measured wind-tunnel data. The primary piloting task was an instrument approach to a breakout at a 60-m (200-ft) ceiling.

Grantham, W. D.↗
NASA NTRS1974

A flight investigation with a STOL airplane flying curved, descending instrument approach paths

A flight investigation using a De Havilland Twin Otter airplane was conducted to determine the configurations of curved, 6 deg descending approach paths which would provide minimum airspace usage within the requirements for acceptable commercial STOL airplane operations. Path configurations with turns of 90 deg, 135 deg, and 180 deg were studied; the approach airspeed was 75 knots. The length of the segment prior to turn, the turn radius, and the length of the final approach segment were varied. The relationship of the acceptable path configurations to the proposed microwave landing system azimuth coverage requirements was examined.

Benner, M. S.↗
NASA NTRS1974

Static noise tests on augmentor wing jet STOL research aircraft (C8A Buffalo)

Results are presented for full scale ground static acoustic tests of over-area conical nozzles and a lobe nozzle installed on the Augmentor Wing Jet STOL Research Aircraft, a modified C8A Buffalo. The noise levels and spectrums of the test nozzles are compared against those of the standard conical nozzle now in use on the aircraft. Acoustic evaluations at 152 m (500 ft), 304 m (1000 ft), and 1216 m (4000 ft) are made at various engine power settings with the emphasis on approach and takeoff power. Appendix A contains the test log and propulsion calculations. Appendix B gives the original test plan, which was closely adhered to during the test. Appendix C describes the acoustic data recording and reduction systems, with calibration details.

Marrs, C. C.↗
NASA NTRS1974

Gust alleviation for a STOL transport by using elevator, spoilers, and flaps

Control laws were developed to investigate methods of alleviating the response of a STOL transport to gusty air. The transport considered in the study had triple-slotted, externally blown jet flaps and a large T-tail. The control devices used were the elevator, spoilers, and flaps. A hybrid computing system was used to simulate linearized longitudinal dynamics of the aircraft and to implement a conjugate gradient optimal search algorithm. The aircraft was simulated in the low-speed approach condition only. Feedback control matrices were found which minimized the average of a quadratic functional involving passenger compartment accelerations, pitch angle and rate, flight path angle and speed variations. The optimization was performed for artificially designed gust inputs in the form of predetermined rectangular waveforms. Results were obtained for elevator, spoilers, and flaps acting singly and in combination. Additional results were obtained for unit sinusoidal gust inputs by using the gain matrices computed for the artificial test gusts. Various sensor configurations were also investigated.

Lallman, F. J.↗
NASA NTRS1974

Wind-tunnel investigation of an externally blown flap STOL transport model including and investigation of wall effects

A wind-tunnel investigation was conducted in the Langley V/STOL tunnel and in a scaled version of the Ames 40- by 80-foot tunnel test section installed as a liner in the Langley V/STOL tunnel to determine the effect of test-section size on aerodynamic characteristics of the model. The model investigated was a swept-wing, jet-powered, externally blown flap (EBF) STOL transport configuration with a leading-edge slat and triple-slotted flaps. The model was an 0.1645-scale model of a 11.58-meter (38.0-ft) span model designed for tests in a 40- by 80-foot tunnel. The data compare the aerodynamic characteristics of the model with and without the tunnel liner installed. Data are presented as a function of thrust coefficient over an angle-of-attack range of 0 deg to 25 deg. A thrust-coefficient range up to approximately 4.0 was simulated, most ot the tests being conducted at a free-stream dynamic pressure of 814 Newtons/sq m (17 lb sq ft). The data are presented with a minimum of analysis.

Gentry, G. L., Jr.↗
NASA NTRS1974

Parameter estimation of powered-lift STOL aircraft characteristics including turbulence and ground effects

The estimation of longitudinal aerodynamic coefficients from data recorded during flight tests of a powered-lift STOL aircraft is considered. First, a comparison is made between the coefficient values determined by the regression and quasilinearization identification techniques from records taken during elevator pulse maneuvers. The results show that for these tests the regression method provides less scatter in coefficient estimates and provides better correlation with the predicted values. Special techniques are then developed which allow identification of the coefficients from records taken during landing maneuvers in which the aircraft encounters turbulence while flying in ground effect. Flight test results are presented to illustrate the effects of air turbulence and ground proximity on the estimated coefficient values.

Wingrove, R. C.↗
NASA NTRS1973

Highly noise suppressed bypass 6 engine for STOL application

A TF-34 engine with an acoustically treated ground test nacelle was built and tested to determine the feasibility of suppressing fan and core engine noise to the stringent levels required for STOL or short-haul commercial aircraft. The design incorporates wall treatment for the fan and core plus three treated splitter rings in the inlet and two treated splitters in the aft fan duct. Maximum suppression of fan tone noise of 40-45 dB was obtained from both the inlet and aft fan treatment. At rated fan speed, overall noise was reduced by 21 PNdB to a value of 94 PNdB on a 500-foot sideline. The overall noise reduction value was limited by the jet noise floor. Thrust losses due to the acoustic treatment are also discussed.

Jones, W. L.↗
NASA NTRS1974

The augmentor wing - Powered-lift STOL a proven concept

A jet-STOL powered-lift aircraft has the ability to perform a relatively steep (7.5 deg) final approach at high power setting and a low speed. The DHC-5 Buffalo/Spey Augmentor-Wing research aircraft is the first machine of its kind to accomplish this performance. The aircraft uses an approach in which the cold bypass thrust is vectored by the augmentor flap. Aspects of aircraft reliability are discussed together with taxi trials, stalling characteristics, lateral directional control, single-engine operations, roll acceleration, and flight in turbulent conditions.

Whittley, D. C.↗
NASA NTRS1974

A perspective on short-haul STOL

Discussion of the basic incentives motivating the development of the short-haul STOL air transportation system. The technological impact on the aircraft and its related economics required to achieve short field performance is generally detrimental. Considerations such as wing and empennage sizing, engine thrust sizing and cycle selection, thrust reverser requirements, cruise Mach number effects, noise, and fuel usage impacts are discussed. The direct operating economics are adversely affected, although it is thought that the indirect costs can be correspondingly reduced. A study of the total operating costs of the short-haul system and its related fare structure indicates that a definite potential exists for the evolution of an economically viable system yielding positive returns on investment to the operators. It is concluded that this potential is sufficient to warrant more detailed studies of these economics and the alternative implementation schemes.

Malthan, L. V.↗
NASA NTRS1974

Sonic inlet technology development and application to STOL propulsion

Recent developments in sonic inlet technology are presented with particular emphasis on STOL propulsion systems. Inlet noise reduction requirements are considered for an augmentor wing and an upper surface blowing type of propulsion system. The current state of the art is discussed with respect to performance and noise potential of different sonic inlet concepts. An acoustic and aerodynamic performance comparison is presented for several inlet configurations based on experimental results.

Klujber, F.↗
NASA NTRS1974

Configuration management during transition for a powered lift STOL aircraft

Presented in this paper are the analytical and moving-base simulation results of a study to improve flight safety and operations of V/STOL type aircraft. One of the more significant and novel aspects of the work accomplished has been the concept and implementation of a configuration management flight control system designed to take the guesswork out of, and improve the operational safety of, transition flight in the region from cruise to STOL.

Johnson, W. A.↗