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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.

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.

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.

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.

Force measurements, surface flow patterns and wake total pressure surveys have been obtained for a wing, wing--body, wing-nacelle and wing-body--nacelle configuration at typical pre-and post-stall angle of attack (10° and 16°), for a general aviation twin-engine airplane. The data includes separated regions and combined flow field models. The results indicate the presence of highly three-dimensional separated regions above and beyond the surface at post-stall condition. Based upon the present experimental data, combined flow field models have been proposed for each of the configurations, at the pre-stall (10°) and post -stall (16°) angle of attack condition. In all cases, the flow is shown to be forming turbulent three-dimensional separation bubbles. These flow models should provide some guidelines for future analytical modeling of separated flow associted with interfering bodies.

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.