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Technical Paper

Wind Tunnel and Flight Development of Spoilers for General Aviation Aircraft

Wind tunnel tests have been carried out to develop a spoiler lateral control system for use with the GA(W)-1 airfoil with a 30% Fowler flap. Tests show that unfavorable aerodynamic interactions can occur between spoiler and flap for large flap deflections. Providing venting of lower surface air through the spoiler opening substantially improves performance. Results of tests with a number of spoiler and cavity shapes are presented and discussed. Applications of two-dimensional wind tunnel results to the design of satisfactory manual lateral control systems are discussed.
Technical Paper

Studies of Light-Twin Wing-Body Interference

The results of an analytical study of aerodynamic interference effects for a light twin aircraft are presented. The data presented concentrates on the influence of a wing on a body (the fuselage). Wind tunnel comparisons of three fillets are included, with corresponding computational analysis. Results indicate that potential flow analysis is useful to guide the design of intersection fairings, but experimental tuning is still required. While the study specifically addresses a light twin aircraft, the methods are applicable to a wide variety of aircraft.
Technical Paper

Studies of Flow Separation and Stalling on One- and Two-Element Airfoils at Low Speeds

Research has been conducted on the nature of airfoil behavior at pre- and post-separated angles of attack. Detailed wind tunnel studies have been made of boundary layer and wake fields for the GA(W)-1 airfoil, and the airfoil with a 0.3 chord Fowler flap. Experimental data are compared with theoretical predictions from a multi-element viscous flow computer program. Theoretical predictions are reasonably accurate for unseparated flows, but have serious errors when separation is present. Some recent techniques for modeling post-separated flow behavior are discussed in light of the present experiments.
Technical Paper

Reflection-Plane Tests of Spoilers on an Advanced Technology Wing

Tests of a finite-span wing with an advanced technology GA(W)-1 airfoil, spoilers, and 30% full-span Fowler flap have been conducted utilizing a reflection-plane model in the WSU low speed wind tunnel. Flap settings from 0° to 40° were tested with a series of 10% chord spoilers of various cross-sectional shapes. Wing force and spoiler hinge moment measurements were made, as well as tuft studies of stalling patterns. Results show that a finite span (aspect ratio 9.5) CLmax value of 3.0 can be obtained with 40° flap at a Reynolds number of 1.0 x 106. Spoiler results correlate well with two-dimensional results, which show that satisfactory roll control can be obtained for all flap settings, with proper lower surface venting. Spoiler gap leak lift and drag penalties were found to be quite substantial, indicating a need for careful design of gaps and seals for flap and spoiler nested configurations.
Technical Paper

Low Speed Airfoil Analysis Using a Small Digital Computer

A computing routine has been developed for calculation of two-dimensional incompressible airfoil characteristics on a small (IBM 1130) digital computer. Theodorsen's method of conformal transformation is utilized to obtain potential flow pressure distributions. A selection of quadrature methods are utilized to obtain boundary layer characteristics, including laminar and turbulent layers, instability, transition, and separation. Selected results are presented which illustrate the capabilities and limitations of the program. Typical computing times and costs are presented. Several suggested improvements to the calculation routine are discussed.
Technical Paper

Further Results of Natural Laminar Flow Flight Test Experiments

Flight test experiments were conducted to measure the extent and nature of natural laminar flow on a smoothed test region of a swept-wing business jet wing. Surface hot film aneraometry and sublimating chemicals were used for transition detection. Surface pressure distributions were measured using pressure belts. Engine noise was monitored by a microphone attached to the wing surface to study possible acoustic effects on stability of the laminar boundary layer, Side-slip conditions were flown to simulate changes in effective wing sweep. Flight instrumentation and ground data analysis techniques and a method for measuring intermittency of turbulence are described, Correlation was obtained between the hot film gage signals and chemicals for transition detection. Cross-flow vortices were observed for some flight conditions. Results of spectral and statistical analysis of the hot film signals for various flight test conditions are presented.
Technical Paper

Application of Split-Film Anemometer and Mini-Computer for Measurement in Turbulent Separated Flow

A split-film anemometer has been adapted for measurement of highly turbulent intermittently reversing flows in regions of local separation around airfoils and flaps. Analog signals from the split-film anemometer are fed directly to a mini-computer for processing and analysis. Mean velocity magnitude and direction, intermittency of reversal, turbulence intensity and histograms of the velocity are obtained as outputs of the system.
Technical Paper

A Fowler Flap System for a High-Performance General Aviation Airfoil

As part of a general aviation airfoil development program being carried out under the direction of the NASA Langley Research Center, a 30% chord Fowler flap has been developed for the GA(W)-1 airfoil.. Wind tunnel tests at Wichita State University have demonstrated a c1max value of 3.80 for 40 deg flap deflection at a Reynolds number of 2.2 × 106. Effects of flap slot geometry have been systematically tested and optimum flap settings for any flight c1 have been obtained. Modification of the reflexed lower surface contour resulted in a reduced c1max with flap nested. Vortex generators provided an increase in c1max of 0.2 for flap nested and 40 deg flap along with a drag penalty at low c1 values. Flow visualization studies show that the stalling patterns for the new airfoil are characterized by an absence of leading edge separation for both the flap-nested and the 40 deg flap cases.