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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.

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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Propulsive-lift concepts for improved low-speed performance of supersonic cruise arrow-wing configurations

Low-aspect-ratio highly swept arrow-wing supersonic aircraft possess high levels of aerodynamic efficiency at supersonic cruising speeds, however, their inherently poor low-speed lift characteristics require design constraints that compromise supersonic performance. The data discussed in this paper were obtained in wind tunnel tests with supersonic crusing configurations, in which propulsive-lift concepts were used to improve low-speed performance. The data show that the increased low-speed lift provided by propulsive-lift permits reduction of both wing size and installed thrust. This yields a batter engine/airframe match for improved supersonic cruise efficiency and range, while still providing acceptable take-off field lengths.

Coe, P. L., Jr.↗
NASA NTRS1976

Maximum likelihood estimates of lift and drag characteristics obtained from dynamic aircraft maneuvers

A maximum likelihood estimation method for obtaining lift and drag characteristics from dynamic flight maneuvers was investigated. This paper describes the method and compares the estimates of lift and drag obtained by using the method with estimates obtained from wind-tunnel tests and from established methods for obtaining estimates from flight data. In general, the lift and drag coefficients extracted from dynamic flight maneuvers by the maximum likelihood estimation technique are in good agreement with the estimates obtained from the wind-tunnel tests and the other methods. When maneuvers that met the requirements of both flight methods were analyzed, the results of each method were nearly the same. The maximum likelihood estimation technique showed promise in terms of estimating lift and drag characteristics from dynamic flight maneuvers. Further studies should be made to assess the best mathematical model and the most desirable type of dynamic maneuver to get the highest quality results from this technique.

Iliff, K. W.↗
NASA NTRS1976

Prediction of longitudinal aerodynamic characteristics of STOL configurations with externally blown high lift devices

A theoretical method has been developed to predict the longitudinal aerodynamic characteristics of engine-wing-flap combinations with externally blown flaps (EBF) and upper surface blowing (USB) high lift devices. Potential flow models of the lifting surfaces and the jet wake are combined to calculate the induced interference of the engine wakes on the lifting surfaces. The engine wakes may be circular, elliptic, or rectangular cross-sectional jets, and the lifting surfaces are comprised of a wing with multiple-slotted trailing-edge flaps or a deflected trailing-edge Coanda surface. Results are presented showing comparisons of measured and predicted forces, pitching moments, span-load distributions, and flow fields.

Mendenhall, M. R.↗
NASA NTRS1976

Transonic wind-tunnel tests of a lifting parachute model

Wind-tunnel tests have been made in the Langley transonic dynamics tunnel on a 0.25-scale model of Sandia Laboratories' 3.96-meter (13-foot), slanted ribbon design, lifting parachute. The lifting parachute is the first stage of a proposed two-stage payload delivery system. The lifting parachute model was attached to a forebody representing the payload. The forebody was designed and installed in the test section in a manner which allowed rotational freedom about the pitch and yaw axes. Values of parachute axial force coefficient, rolling moment coefficient, and payload trim angles in pitch and yaw are presented through the transonic speed range. Data are presented for the parachute in both the reefed and full open conditions. Time history records of lifting parachute deployment and disreefing tests are included.

Foughner, J. T., Jr.↗
NASA NTRS1976

Flight with lift modulation inside a planetary atmosphere

A set of dimensionless variables (modified Chapman's variables) is introduced in a derivation of general equations for lifting flight and bank modulation within a planetary atmosphere. The atmosphere is assumed spherical and at rest, and a generalized lift-drag polar is also introduced. Corresponding equations for flight over a flat planet model are attained via a straightforward transformation. Two planar flight cases: flight at constant absolute speed over a spherical planet, and flight at constant descent rate over a flat planet, are analyzed, and the required lift control law (with negative or positive lift) is exhibited in each case. Glide at very high descent rate and plane flows of trajectories are analyzed.

Vinh, N. X.↗
NASA NTRS1977

How good is jet lift VTOL technology

The status of technologies for jet-lift V/STOL aircraft is examined, and a critical review of the performance of jet-lift VTOL aircraft built to date is made. Most jet-lift aircraft have suffered from adverse propulsion-induced effects during takeoff and landing. Flight dynamics of jet-lift aircraft have suffered from shortcomings in static and dynamic stability, control characteristics, and flight path control. Some of the main problems to be considered during the selection of a propulsion system arrangement for a V/STOL fighter are discussed. At present, experimental and analytical data on supersonic V/STOL configurations are insufficient to permit evaluating propulsion system arrangements.

Anderson, S. B.↗
NASA NTRS1979

Low-speed wind-tunnel investigation of a large-scale VTOL lift-fan transport model

An investigation was conducted in the NASA-Ames 40 by 80 Foot Wind Tunnel to determine the aerodynamic characteristics of a large scale, VTOL, lift fan, jet transport model. The model had two lift fans at the forward portion of the fuselage, a lift fan at each wing tip, and two lift/cruise fans at the aft portion of the fuselage. All fans were driven by tip turbines using T-58 gas generators. Results were obtained for several lift fan, exit vane deflections and lift/cruise fan thrust deflections are zero sideslip. Three component longitudinal data are presented at several fan tip speed ratios. A limited amount of six component data were obtained with asymmetric vane settings. All of the data were obtained without a horizontal tail. Downwash angles at a typical tail location are also presented.

Aoyagi, K.↗
NASA NTRS1979

An experimental study of a jet issuing from a lifting wing

An experimental program was conducted to determine the behavior of a round turbulent jet issuing from a lifting two-dimensional wing in crossflow. The jet was located at 65% wing chord on an NACA 0021 airfoil fitted with a 30% chord NACA 4415 flap. The flowfield associated with the jet was surveyed extensively with directional pressure probes to determine local velocity vectors and pressures for three different values of lift coefficient at jet effective velocity ratios (square root of the ratio of the jet dynamic pressure to the freestream dynamic pressure) of 4, 6, and 8. Data describing the jet centerline and the path of the contrarotating vortices accompanying the deflected jet are presented and compared with similar data for a round jet issuing from a large flat plate. The spacing and strength of the vortices are calculated using a simple vortex model previously proposed for the flat plate case. The results show that the penetration of the jet and the vortices increases significantly with increasing lift for the range of test parameters covered in the study. The calculated vortex spacing and strength also show an increase with lift.

Mcmahon, H. M.↗
NASA NTRS1979

Analysis and correlation with theory of rotor lift-limit test data

A wind tunnel test program to define the cruise performance and determine any limitations to lift and propulsive force of a conventional helicopter rotor is described. A 2.96 foot radius model rotor was used. The maximum lift and propulsive force obtainable from an articulated rotor for advance ratios of 0.4 to 0.67, and the blade load growth as the lift approaches the limit are determined. Cruise rotor performance for advance ratios of 0.4 to 0.67 and the sensitivity of the rotor forces and moments to rotor control inputs as the lift limit is approached are established.

Sheffler, M.↗
NASA NTRS1980

QCSEE UTW engine powered-lift acoustic performance

Powered-lift acoustic test of the Quiet Clean Short Haul Experimental Engine (QCSEE) under the wing (UTW) engine are reported. Propulsion systems for two powered-lift concepts were designed, fabricated, and tested. In addition to low noise features, the designs included composite structures, gear-driven fans, digital control, and a variable pitch fan (UTW). The UTW engine was tested in a static ground test facility with wing and flap segments to simulate installation on a short haul transport aircraft of the future. Powered-lift acoustic performance of the UTW engine is compared with that of the previously tested and reported QCSEE over-the-wing (OTW) engine. Both engines were slightly above the noise goal but were significantly below current FAA and modern wide-body jet transport levels. The UTW system in the powered-lift mode was penalized by reflected engine noise from the wing and flap system, while the OTW system was benefitted by a wing noise shielding effect.

Loeffler, I. J.↗
NASA NTRS1979

Effects of lift force on ejecta transport

The possible effects of lift on individual ejecta trajectories after an impact event are examined, considering a dimensionless transport parameter (K), the initial velocity vector of the particles, and the ratio of the lift to drag coefficients. If this ratio is not equal to zero, the trajectory is greatly influenced by the lift coefficient, particularly for large values of K and high launch angles. It is suggested that lift potentially can affect small ejecta in the size range also affected by aerodynamic drag, thereby adding complexity to atmospheric effects discussed by Schultz and Gault (1978).

Pai, S. I.↗
NASA NTRS1981

Comparisons of AEROX computer program predictions of lift and induced drag with flight test data

The AEROX aerodynamic computer program which provides accurate predictions of induced drag and trim drag for the full angle of attack range and for Mach numbers from 0.4 to 3.0 is described. This capability is demonstrated comparing flight test data and AEROX predictions for 17 different tactical aircraft. Values of minimum (skin friction, pressure, and zero lift wave) drag coefficients and lift coefficient offset due to camber (when required) were input from the flight test data to produce total lift and drag curves. The comparisons of trimmed lift drag polars show excellent agreement between the AEROX predictions and the in flight measurements.

Axelson, J.↗
NASA NTRS1982

Status of NASA advanced LFC airfoil high-lift study

The design of a high lift system for the NASA advanced LFC airfoil designed by Pfenninger is described. The high lift system consists of both leading and trailing edge flaps. A 3 meter semispan, 1 meter chord wing model using the above airfoil and high lift system is under construction and will be tested in the NASA Langley 4 by 7 meter tunnel. This model will have two separate full span leading edge flaps (0.10c and 0.12c) and one full span trailing edge flap (0.25c). The performance of this high lift system was predicted by the NASA two dimensional viscous multicomponent airfoil program. This program was also used to predict the characteristics of the LFC airfoils developed by the Douglas Aircraft Company and Lockheed-Georgia Aircraft Company.

Applin, Z. T.↗
NASA NTRS1981

Powered-lift takeoff performance characteristics determined from flight test of the Quiet Short-haul Research Aircraft /QSRA/

A powered-lift, reduced thrust takeoff performance program utilizing quiet short-haul research aircraft has been conducted. It has been shown that the powered-lift upper surface blowing concept greatly enhances aircraft takeoff performance. The improvements include: (1) takeoff field lengths may be shortened by approximately 30%; (2) Air Force critical field lengths may be shortened by approximately 60%; (3) powered lift upper surface blowing aircraft have better handling and performance characteristics than comparable conventional aircraft; and (4) the low speeds associated with powered-lift takeoff enhance safety margins.

Riddle, D. W.↗
NASA NTRS1983

Analysis of Nonplanar Wing-tip-mounted Lifting Surfaces on Low-speed Airplanes

Nonplanar wing tip mounted lifting surfaces reduce lift induced drag substantially. Winglets, which are small, nearly vertical, winglike surfaces, are an example of these devices. To achieve reduction in lift induced drag, winglets produce significant side forces. Consequently, these surfaces can seriously affect airplane lateral directional aerodynamic characteristics. Therefore, the effects of nonplanar wing tip mounted surfaces on the lateral directional stability and control of low speed general aviation airplanes were studied. The study consists of a theoretical and an experimental, in flight investigation. The experimental investigation involves flight tests of winglets on an agricultural airplane. Results of these tests demonstrate the significant influence of winglets on airplane lateral directional aerodynamic characteristics. It is shown that good correlations exist between experimental data and theoretically predicted results. In addition, a lifting surface method was used to perform a parametric study of the effects of various winglet parameters on lateral directional stability derivatives of general aviation type wings.

Vandam, C. P.↗
NASA NTRS1983

A lifting surface theory in rotational flow

The partial differential equation for small disturbance steady rotational flow in three dimensions is solved through an integral equation approach. The solution is obtained by using the method of weighted residuals. Specific applications are directed to wings in nonuniform subsonic parallel streams with velocity varying in vertical and spanwise directions and to airfoils in nonuniform freestream. Comparison with limited known results indicates that the present method is reasonably accurate. Numerical results for the lifting pressure of airfoil, lift, induced drag, and pitching moments of airfoil, lift, induced drag, and pitching moments of elliptic, rectangular, and delta wings in a jet, wake, or monotonic sheared stream are presented. It is shown that, in addition to the effect of local dynamic pressures, a positive velocity gradient tends to enhance the lift.

Shiau, M. J.↗
NASA NTRS1983

Models and analysis for twin-lift helicopter systems

The major limitation of a modern helicopter with respect to its employment in transport operations has been a relatively small payload size. Among several ideas for overcoming this limitation are a number of multiple-lift schemes using two or more helicopters to lift payloads too large for a single helicopter. On a number of occasions, pairs of helicopters carrying a single load have been successfully employed. However, a considerable amount of flying skill was required in these cases in connection with the manual control tasks involved. Some form of automatic control will, therefore, be needed until twin-lift operations become generally practical. The present investigation is concerned with the development of models of the Twin-Lift System which can be used as a basis for the design of automatic control.

Lewis, J.↗
NASA NTRS1984

Assessment of lift- and blockage-induced wall interference in a three-dimensional adaptive-wall tunnel

A three-dimensional adaptive-wall wind tunnel experiment was conducted at Ames Research Center. This experiment demonstrated the effects of wall interference on the upwash distribution on an imaginary surface surrounding a lifting wing. This presentation demonstrates how the interference assessment procedure used in the adaptive-wall experiments to determine the wall adjustments can be used to separately assess lift- and blockage-induced wall interference in a passive-wall wind tunnel. The effects of lift interference on the upwash distribution and on the model lift coefficient are interpreted by a simple horseshoe vortex analysis.

Schairer, E. T.↗