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At least 1,441 records · Page 80
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Subsonic dynamic stability characteristics of two close-coupled canard-wing configurations

The pitch, yaw, and roll damping, as well as the oscillatory stability in pitch and in yaw, were measured for two canard wing configurations with wing sweeps of 44 deg and 60 deg. Tests were made at free stream Mach numbers of 0.3, 0.4, and 0.7 and for angles of attack from about -4 deg to 20 deg. The effects of various components such as the canard, nose strakes, wings, vertical tail, and horizontal tail were determined. The basic canard wing, vertical tail configurations generally had positive damping in pitch, yaw, and roll. The effect of the canard was generally beneficial except for its tendency to decrease the oscillatory directional stability.

Boyden, R. P.↗
NASA NTRS1978

Estimation of leading-edge thrust for supersonic wings of arbitrary planform

A numerical method for the estimation of leading edge thrust for supersonic wings of arbitrary planform was developed and was programmed as an extension to an existing high speed digital computer method for prediction of wing pressure distributions. The accuracy of the method was assessed by comparison with linearized theory results for a series of flat delta wings. Application of the method to wings of arbitrary planform, both flat and cambered, is illustrated in several examples.

Carlson, H. W.↗
NASA NTRS1978

An investigation of wing buffeting response at subsonic and transonic speeds. Phase 2: F-111A flight data analysis. Volume 1: Summary of technical approach, results and conclusions

A detailed investigation of the flight buffeting response of the F-111A was performed in two phases. In Phase 1 stochastic analysis techniques were applied to wing and fuselage responses for maneuvers flown at subsonic speeds and wing leading edge sweep of 26 degrees. Power spectra and rms values were obtained. This report gives results of Phase 2 where the analyses were extended to include maneuvers flown at wing leading edge sweep values of 50 and 75.5 degrees at subsonic and supersonic speeds and the responses examined were expanded to include vertical shear, bending moment, and hingeline torque of the left and right horizontal tails. Power spectra, response time histories, variations of rms response with angle of attack and effects of wing sweep and Mach number are presented and discussed. Some Phase 1 results are given for comparison purposes.

Benepe, D. B.↗
NASA NTRS1978

Computational wing optimization and wind tunnel test of semi-span model

A computational transonic wing design procedure has been developed and verified by a wind tunnel test of a variable camber semi-span wing model. The Bailey-Ballhaus transonic potential flow analysis code linked to Vanderplaat's constrained minimization routine was used to optimize test configurations at 0.9 Mach number. Based on wind tunnel test results, computationally optimized designs were as efficient as the best configurations determined by previous parametric testing and performed better at off-design points. Wind tunnel wing pressures agreed well with predictions from the improved Bailey-Ballhaus code at moderate CL's. Computational optimization was shown to be an effective transonic wing design tool.

Haney, H. P.↗
NASA NTRS1978

Strake-wing analysis and design

The technology is still evolving for improving the transonic maneuver capability of strake-wing configurations. Much of the work to date has been of an experimental nature; whereas, the theories that are available to handle vortex-flow aerodynamics have mostly treated wings of constant sweep. Hence, two efforts were undertaken. They are: (1) to extend the suction analogy to more general configurations and evaluate the method by using selected critical planforms; and (2) to develop a procedure for strake planform shaping and test the resulting shape in conjunction with a wing-body. The conclusions from this study are that (1) some improvement has been made in estimating high-angle-of-attack longitudinal aerodynamics, and (2) the gothic strake designed with the developed procedure does produce a stable vortex system in the presence of a wing body and flat post-maximum-lift characteristics.

Lamar, J. E.↗
NASA NTRS1978

A method for localizing wing flow separation at stall to alleviate spin entry tendencies

A wing leading-edge modification has been developed, applicable at present to single-engine light aircraft, which produces stabilizing vortices at stall and beyond. These vortices have the effect of fixing the stall pattern of the wing such that the various portions of the wing upper surface stall nearly symmetrically. The lift coefficient produced is essentially constant to very high angles of attack above the stall angle of the unmodified wing. It is hypothesized that these characteristics will help prevent inadvertent spin entry after a stall. Results are presented from recent large-scale wind-tunnel tests of a complete light aircraft, both with and without the modification.

Feistel, T. W.↗
NASA NTRS1978

Improved sonic-box computer program for calculating transonic aerodynamic loads on oscillating wings with thickness

A computer program was developed to account approximately for the effects of finite wing thickness in transonic potential flow over an oscillation wing of finite span. The program is based on the original sonic box computer program for planar wing which was extended to account for the effect of wing thickness. Computational efficiency and accuracy were improved and swept trailing edges were accounted for. Account for the nonuniform flow caused by finite thickness was made by application of the local linearization concept with appropriate coordinate transformation. A brief description of each computer routine and the applications of cubic spline and spline surface data fitting techniques used in the program are given, and the method of input was shown in detail. Sample calculations as well as a complete listing of the computer program listing are presented.

Ruo, S. Y.↗
NASA NTRS1978

Free wing assembly for an aircraft

A free wing is attached to a fuselage of an aircraft in a manner such that the wing is free to pivot about a spanwise axis forward of its aerodynamic center. The wing is angularly displaced about the axis by aerodynamic pitching moments, resulting from lift, and is trimmed through a use of a trimmable free stabilizer comprising a floating canard mounted on a strut rigidly connected to the wing and projected forward from it.

Wolowicz, C. H.↗
NASA NTRS1978

Flight comparison of the transonic agility of the F-111A airplane and the F-111 supercritical wing airplane

A flight research program was conducted to investigate the improvements in maneuverability of an F-111A airplane equipped with a supercritical wing. In this configuration the aircraft is known as the F-111 TACT (transonic aircraft technology) airplane. The variable-wing-sweep feature permitted an evaluation of the supercritical wing in many configurations. The primary emphasis was placed on the transonic Mach number region, which is considered to be the principal air combat arena for fighter aircraft. An agility study was undertaken to assess the maneuverability of the F-111A aircraft with a supercritical wing at both design and off-design conditions. The evaluation included an assessment of aerodynamic and maneuver performance in conjunction with an evaluation of precision controllability during tailchase gunsight tracking tasks.

Friend, E. L.↗
NASA NTRS1979

Effects of spanwise blowing on the surface pressure distribution and vortex-lift characteristics of a trapezoidal wing-strake configuration

The effects of spanwise blowing on the surface pressures of a 44 deg swept trapezoidal wing-strake configuration were measured. Wind tunnel data were obtained at a free stream Mach number of 0.26 for a range of model angle of attack, jet thrust coefficient, and nozzle chordwise location. Results showed that spanwise blowing delayed the leading edge vortex breakdown to larger span distances and increased the lifting pressures. Vortex lift was achieved at span stations immediately outboard of the strake-wing junction with no blowing, but spanwise blowing was necessary to achieve vortex lift at increased span distances. Blowing on the wing in the presence of the strake was not as effective as blowing on the wing alone. Spanwise blowing increased lift throughout the angle-of-attack range, improved the drag polars, and extended the linear pitching moment to higher values of lift. The leading edge suction analogy can be used to estimate the effects of spanwise blowing on the aerodynamic characteristics.

Campbell, J. F.↗
NASA NTRS1979

Pressure and thermal distributions on wings and adjacent surfaces induced by elevon deflections at Mach 6

Surface pressure distributions and heat transfer distributions were obtained on wing half-models in regions where three dimensional separated flow effects are prominent. Unswept and 50 deg and 70 deg swept semispan wings were tested, for trailing-edge-elevon ramp angles of 0 deg, 10 deg, 20 deg, and 30 deg, with and without cylindrical and flat plate center bodies and with and without various wing-tip plates and fins. The data, obtained for a free stream Mach number of 6 and a wing-root-chord Reynolds number of 18.5 million, reveal considerably larger regions of increased pressure and thermal loads than would be anticipated using non-separated flow analyses.

Kaufman, L. G., II↗
NASA NTRS1978

Simulated propeller slipstream effects on a supercritical wing

To quantify the installed performance of high speed (M = 0.8) turboprop propulsion systems, an experimental program designed to assess the magnitude of the aerodynamic interference of a propeller slipstream on a supercritical wing has been conducted. The test was conducted in the NASA Ames 14-foot wind tunnel. An ejector-nacelle propeller slipstream simulator was used to produce a slipstream with characteristics typical of advanced propellers presently being investigated. A supercritical wing-body configuration was used to evaluate the interference effects. A traversing total pressure rake was used to make flow field measurements behind the wing and to calibrate the slipstream simulator. The force results indicated that the interference drag amounted to an increase of ten counts or about 3% of the wing-body drag for a two engine configuration at the nominal propeller operating conditions. However, at the higher swirl angles (11 deg vs. 7 deg nominally) the interference drag was favorable by about the same magnitude.

Welge, H. R.↗
NASA NTRS1979

Calculation of the longitudinal aerodynamic characteristics of upper-surface-blown wing-flap configurations

An investigation has been carried out to develop an engineering method for predicting the longitudinal aerodynamic characteristics of wing-flap configurations with upper surface blown (USB) high lift devices. Potential flow models of the lifting surfaces and the jet wakes are combined to calculate the induced interference of the engine wakes on the wing and flaps. The wing may have an arbitrary planform with camber and twist and multiple trailing edge flaps. The jet wake model has a rectangular cross section over its entire length and it is positioned such that the wake is tangent to the upper surfaces of the wing and flaps. Comparisons of measured and predicted pressure distributions, spanload distributions, and total lift and pitching-moment coefficients on swept and unswept USB configurations are presented for a wide range of thrust coefficients and flap deflection angles.

Mendenhall, M. R.↗
NASA NTRS1979

Transition aerodynamics for close-coupled wing-canard configuration

A series of wind-tunnel tests have been conducted in the Langley V/STOL tunnel to investigate the low-speed longitudinal aerodynamics of two powered close-coupled wing-canard fighter configurations. A brief review is provided of the high angle-of-attack data for the two wing-canard configurations tested showing the benefits and problem areas of powered lift. A takeoff and landing analysis is presented which defines the area in which a fighter-type aircraft must operate in order to achieve 305-m field lengths. The wing-canard configuration data are analyzed in detail showing the problems of obtaining high lift, high drag, and trimmed moments. Assuming that power will be used to trim the aircraft, data are presented comparing the transition aerodynamics of the wing-canard configuration using a nose jet with several V/STOL configurations.

Paulson, J. W., Jr.↗
NASA NTRS1979

Computational optimization and wind tunnel test of transonic wing designs

A practical procedure for the optimum design of transonic wings is demonstrated. The procedure uses an optimization program based on the method of feasible directions coupled with an aerodynamic analysis program which solves the three-dimensional potential equation for subsonic through transonic flow. Two new wings for the A-7 aircraft were designed by using the optimization procedure to achieve specified surface pressure distributions. The new wings, along with the existing A-7 wing, were tested in the Ames 11-foot transonic wind tunnel. The experimental data show that all of the performance goals were met.

Haney, H. P.↗
NASA NTRS1979

Recent advances in the solution of three-dimensional flow over wings with leading edge vortex separation

Recent advances in a panel method for the solution of three-dimensional flow about wing and wing-body combinations with leading-edge vortex separation are presented. These advances were achieved as part of an ultimately successful assault on two shortcomings of the method, namely convergence failures in seemingly random cases, and overprediction of lift coefficient for high aspect-ratio wings. Advances include the implementation of improved panel numerics for the purpose of eliminating the highly non-linear effects of ring vortices around doublet panel edges, and the development of a least squares procedure for damping vortex sheet geometry update instabilities. A variety of cases generated by the computer program implementing the method are presented. These cases are of two types. The first type consists of numerical studies, which verify the underlying mathematical assumptions of the method and moreover show that the results are strongly invariant with respect to such user dependent input as wing panel layout, initial sheet shape, sheet rollup, etc. The second type consists of cases run for the purpose of comparing computed results with experimental data, and these comparisons verify the underlying physical assumptions made by the method.

Johnson, F. T.↗
NASA NTRS1978

Propeller slipstream wing interactions at Mach no. 0.8

Configuration and results of a wind tunnel test of the aerodynamic interactions between propeller slipstream and a supercritical wing at transonic Mach numbers are discussed. The test was conducted over a free-stream Mach number range from 0.7 to 0.84, with the slipstream simulator and the wing-body model installed in the tunnel. The angle of attack and the spanning lift coefficients were varied from 1 to 3 deg and from 0.4 to 0.7 deg respectively, while the slipstream swirl angle was varied from 0 to 11 deg with an upwash on the inboard side of the wing. It was found that at a free-stream Mach number of 0.8 and a lift coefficient of 0.5, incremental drag results for 7 deg of swirl and a slipstream Mach number of 0.87 indicated a penalty equivalent to a 0.024 loss in propeller efficiency, whereas at 11 deg the drag increment was favorable. Swirl had significant effects on the chordwise pressure distributions of the inboard section of the wing within the slipstream. Neither surface nor wake pressures showed signs of significant flow separation induced by the slipstream.

Bencze, D. P.↗
NASA NTRS1979

Preliminary design and analysis of large delta wings for earth-to-orbit transports

Two studies are described in which CAD methods are used for preliminary design of advanced earth-to-orbit transport wings. The first structural concept was a multilayer honeycomb wing composed of diffusion-bonded Inconel 718; the second concept (in which structural simplicity was sought) involved a honeycomb sandwich wing, for which only a leading edge and trailing edge spar were used. Some new technologies applicable to advanced wing designs are briefly discussed.

Lemessurier, R. W.↗