Performance of an Airfoil with a Power-saving, Tab-assisted Flap System

Abstract

This study investigated the feasibility of reducing control surface input power with the use of a tab-assisted flap. Wind tunnel tests were conducted at the University of Illinois at Urbana-Champaign on a NACA 3415 airfoil model with a flap including an active trim tab. Measurements were taken for two configurations: a baseline fixed tab case where tab deflection was zero and a tabbed case where multiple flap and tab angle combinations were tested. Hinge moment measurements were taken for both the flap and tab and confirmed the ability to actuate and hold the flap with the trim tab. Lift, drag and moment measurements along with surface pressures were acquired to aid in the analysis of the concept. Results are presented for hinge moment reductions along with lift and drag penalties. An additional study on several flap deflection scenarios was conducted to assess approximate work savings. Computational studies were also performed and compared well to experimental values except when large regions of unsteady separated flow were present.