Design and Testing of a Highly Redundant Electro-Mechanical Actuator for Aircraft Primary Flight Control Applications

In order to answer the demand for an electrical primary flight control system for smaller manned or unmanned VTOL aircraft, a novel rotatory actuator and the related control periphery has been designed, manufactured and tested. In contrast to most systems used for these applications today, the presented approach uses an architecture that from the beginning considers the option for certification to civil manned rotorcraft standards. The key idea was to design a single unit comprising all necessary redundancy and failure handling features that simplex COTS components are typically lacking. The over-all architecture, therefore, follows a dual-duplex concept with a minimum of single-pointfailure elements. This paper sketches the layout of the mechanical, electrical, and control unit components, explains the relevant design choices, and presents the realization of a demonstrator system. The subsequent sections describe the successful validation through a series of static and dynamic tests. Finally, the installation of a complete set of actuators onto the reference target platform, an ultra-light coaxial rotor helicopter is presented. Fitting such system to this beforehand manually/mechanically controlled aircraft now enables its unmanned operation. Other foreseen applications are briefly mentioned as well.