Unmanned helicopter flight control actuator specification through mission profile analysis

Helicopter dronization is expanding, as for example with the VSR700 project, and leads to the design and the integration of electromechanical actuators (EMA) into the primary flight control system (PFCS). The PFCS is in charge of controlling the helicopter flight over its 4 axis (roll, pitch, yaw, vertical). It controls the blade pitch through dedicated mechanical kinematics and actuators. The hydraulic technology has been conventionally used in actuators for more than 60 years. On the other hand, the introduction of the EMA technology requires the reconsideration of design practices right at development start. Indeed, the establishment and synthesis of the specification need to deal with – new design drivers (high performance points, wear, fatigue) and - new inherent technological imperfections (friction, inertia and reduction ratio). To address these topics, this paper draws a list of the main EMA design drivers to focus on along with a brief description of the main EMA components. Then, it proposes indicators evaluated over a complete mission profile in time coming from measurement on a given applicative helicopter flight. These indicators are chosen and elaborated to provide an image of the design drivers responsible for rapid and gradual degradations of the actuator components. Also, they give an idea of the importance taken by the actuator imperfections into the global performance. Furthermore, we explain how mission profiles are processed depending of data sources. Finally, through a comparison with a standard aircraft mission profile, we emphasize the specificity of the helicopter application use case.