Aircraft load alleviation by robust yaw-lateral decoupling

Abstract

In an engine out/engine failure of an aircraft the human pilot has to compensate a yaw disturbance torque. Because of a delayed reaction possibly followed by an overreaction the pilot may cause high loads (shear forces) at the vertical tail. These shear forces determine the static design of the vertical tail in some areas and its structural weight. Such a situation and a corresponding weight increase can be avoided by an automatic yaw control system. It achieves a precise and early yaw moment compensation faster than the pilot can do it. To tackle both the load alleviation and the handling problem within the controller design, the yaw rate is made robustly non-observable from the lateral acceleration at a decoupling point and approximately from the shear force at the vertical tail. The parameters of the robust controller can be derived analytically. Nonlinear high precision simulations show that a significant load alleviation at the vertical tail is achieved and that the handling and the passenger comfort are improved.