NACA-RM-L51J04

Abstract

INTRODUCTION <br>Previous investigations of sweptback wings (see, for example, references 1, 2, and 3) have shown that as the aspect ratio and sweepback are increased, it become increasingly difficult to provide longitudinal stability throughout the lift range with the various devices used to control the stalling of sweptback wings. In order to extend these investigations and to provide information in the low-speed range with which to evaluate design configuration suitable for high-subsonic, long-range airplanes, an investigation has been conducted in the Langley 19-foot pressure tunnel to determine the low-speed longitudinal characteristics of a 45&#176; sweptback wing of aspect ratio 8. A wing of this sweep &#8211; aspect-ratio combination is well in the longitudinally unstable region as set forth in reference 4, and on the basis of present manufacturing methods appears to be approaching a limit outside of which a wing would be structurally impractical. <br>This present paper contains the results of an investigation to determine the effects of leading-edge and trailing-edge flaps, upper-surface flow-control fences, and a fuselage on the longitudinal characteristics of the wing. The effects of leading-edge roughness on the basic wing and on a representative flap-deflected configuration were determined. The tests were conducted at a Reynolds number of 4.0 x 10⁶ and a Mach number of approximately 0.19. Additional tests were made at Reynolds numbers from 1.5 x 10⁶ to 4.8 x 10⁶ on the basic wing, wing with fences, and on a representative flap-deflected configuration. <br>Results of measurements of the pressure distribution over the wing and the effect of a horizontal tail on the longitudinal stability are presented in references 5 and 6, respectively.