Aerodynamic Influence of a Finite-Span Flap on a Simple Wing

A wind-tunnel test was conducted for an unswept wing with a half-span Fowler flap. Surface pressures, flow visualization, and wake surveys were obtained for two flap riggings representative of landing configurations. The primary influence of the half-span flap is to create spanwise pressure gradients on the main element and flap. Pressure distributions near the flap tip indicate the presence of two distinct suction peaks on the upper surface. Flow visualization using smoke verifies the existence of two co-rotating vortices near the flap tip that merge before reaching the trailing edge. Seven-hole-probe wake surveys yield values for both profile and induced drag.