NACA-TN-1277

Abstract

INTRODUCTION <br>The problem of obtaining adequate maximum lift coefficient on highly swept wing for high-speed aircraft has brought to lift a need for a more thorough investigation of auxiliary high-lift devices, such as leading-edge flaps, leading-edge slots, and drooped leading-edge airfoils. Recent reports of tests of conventional unswept wings (references 1 and 2) which were obtained from the D.V.L, in Germany indicated that one of these devices, the leading-edge flap, when used in combination with a conventional split flap, produced a substantial increase in the maximum lift coefficient accompanied by an increase in the angle of attack at which the maximum lift coefficient was obtained. The German investigations, however, were carried out at very low Reynolds numbers on airfoil sections having maximum lift coefficients of only about 0.72. The present brief investigation was conducted in the Langley two-dimensional low-turbulence pressure tunnel to determine the characteristics of a lower-surface leading-edge flap similar to the flap tested by the Germ s but tested at a higher value of the Reynolds number (6.0 x 10⁶) and also to investigate am improved type (upper surface) leading-edge flap. The investigation included tests of an upper- and lower-surface lead5ng-edge flap on en NACA 6-series airfoil with and without a trailing-edge split flap.