Control with trim tabs and history-dependent aerodynamic forces

This analytical study addresses three different, but closely related problems: time-history dependence of aerodynamic forces acting on a moving control surface, control by means of trim tabs, and control surface reaction upon abrupt actuator failure. Closed-form solutions are proposed to each of these problems. Perhaps the most conspicuous result is our conclusion that history-dependent aerodynamic effects have no significant influence on the transfer function between the trim tab and the surface it drives, provided that the chord of the surface is sufficiently small compared to the total chord.