Abstract: The oscillatory failure often occurs because of the electronic equipment failure or the structure vibration in the modern commercial civil aircraft. The solution to the problem needs lots of sensors and control controllers and it make the control structure complex and leads to further fault. The mathematical model including the servo loop was built and the analytical redundancy was used for the fault detection. A combined control law was designed based on the detection result that was the residual of the servo signal and the state quantities. The design improves the control structure of the EFCS feedforward channel and the simulation result shows that the problem of the oscillatory is well solved. It provides reference for the designer of the commercial civil aircraft.

Key words: commercial civil aircraft, analytical redundancy, oscillatory failure, combined control law