Feather-like control surfaces are shown to increase net lift at post-stall angles of attack, yielding benefits in efficiency and control for small aircraft and unmanned aerial vehicles (UAVs). Inspired by covert feathers on birds’ wings, ongoing wind tunnel experiments aim to optimize the design and configuration of passively-deployed aeroelastic flaps.

A single-degree-of-freedom model describes the aerodynamic forces on the flap due to the pressure differential over the wing surface, using a combination of analytical and numerical methods. The pressure distribution is integrated for the resulting forces; a user can determine the magnitude of the forces contributing to flap deployment for various locations (leading edge at 0.2 of the chord or trailing edge at 0.7 of the chord) and for distinct angles of attack and flow conditions.