Control of Impaired Aircraft with Unanticipated Elevator Jam to a Stable Level Flight

Abstract

Elevator jam is a challenging control problem since the feasible safe trim and dynamics of the impaired aircraft are heavily dependent on the elevator jam position, which is unknown until the event has occurred. Once it occurs, the window of time to react usually is small and the crisis may deepen quickly as time goes by. A simple effective approach is proposed to mitigate the crisis immediately after the jam to control the impaired aircraft to a safe stable level flight without wasting time–at the most critical crisis moment–on identifying the safe trim, the plant model, or even the elevator jam position, which actually are unnecessary.