Experimental validation of robustness against failures of a fail-safe electro-mechanical actuator employed for the flap movables of a high-speed helicopter-plane

The work summarizes the main experimental results carried out for the performance qualification of a fail-safe rotary electro-mechanical actuator employed to control the flap movables of the Airbus RACER helicopter-plane. The RACER flaps, placed on both box-wing and vertical stabilizers, are used to adapt the vehicle atti-tude, to enhance stability, and to abate noise. Being the actuator requirements driven by disturbance-rejection capabilities, a special attention is dedicated to tests of quasi-static position-tracking and position-hold under high load disturbances, by characterizing the transients related to artificial injection of faults. The worst-case load scenarios are reproduced on a hydraulic test rig, equipped with four servo-actuators, to apply bending moment, axial and radial forces, and torsional hinge moment. Thanks to a closed-loop position control integrat-ing cascade loops on motor currents, motor speed and output rotation with a deformation loop for stiffness en-hancement, the position deviation during experiments is minimized when the actuator works without faults. If major faults are injected, the monitoring algorithms succeed in promptly detecting them and the actuator is re-verted in fail-safe blocked mode, with failure transients limited by a specifically-designed back-electromotive damper circuitry.