NACA-RM-L9E02

Abstract

INTRODUCTION <br>In an attempt to improve the low-speed longitudinal characteristics of sweptback wings, various combinations of high-lift and stall-control devices have been tested in the Langley 19-foot pressure tunnel on a 42&#176; sweptback wing having NACA 64₁-112 airfoil sections. The results of these tests are reported in references 1 and 2. <br>In order to supplement these tests, the present investigation has been conducted primarily to determine the effect of full-span and half-span split flaps on the 42&#176; sweptback wing through a flap-deflection range of 60&#176;. It is expected that sweptback-wing airplanes will require same leading-edge device to eliminate the inherent longitudinal instability usually associated with swept wings at stalling angles of attack. The split flaps have been tested therefore, in conjunction with a 0.575-semispan, round-nose, extensible, leading-edge flap which has been shown to provide stability at the stall with and without split flaps (reference 2). An analysis has been made t o determine the effect of split-flap span and deflection on the power-off gliding characteristics of the 42&#176; sweptback wing operating with an assumed-wing loading condition. <br>Roughness in the form of carborundum granules was applied to the leading edge of the wing to determine the effect of surface condition on the stability of a sweptback wing with a leading-edge flap deflected. <br>The split-flap tests were made at a Reynolds number of&#160; 6.8 x 10 ⁶ and a Mach number of approximately 0.16. The effect of roughness was determined at Reynolds numbers of 3.0 X 10⁶ and 4.7 X 10⁶.