Robust Electromechanical Actuators For Primary Flight Controls

The paper describes an electromechanical actuation system presenting improved reliability, high integrity and prognostic functions able to alert of a developing failure. In this system a flight control surface is driven by two parallel rollerscrews, each driven by a brushless motor with gearhead and clutch; the motors electric drives are controlled by dual redundant electronic units performing closed loop position control as a function of the commands received from the flight control computer. Provisions are taken to provide damping in the event of simultaneous failure of both actuators. The electronic units perform control, diagnosis and prognosis of the actuation system and mutually exchange data via a cross channel data link. The actuation system thereby provides high integrity control of an aerodynamic surface with dual mechanical link, dual power source and quadruplex control, similarly to a fly-by-wire hydraulic flight control. The paper first addresses the critical design issues associated with the electromechanical actuation of flight control surfaces, then outlines configuration, characteristics and performance of the actuation system.