Electro-hydraulic actuation of primary flight control surfaces

Increasingly demanding performance and certification requirements for next-generation aircraft flight control systems, together with a continuous development effort within the industry towards `all/more electric´ aircraft, have fostered the need to replace traditional hydraulic actuation systems by electric and/or electro-hydraulic technology. Digitally controlled brushless permanent-magnet drive systems with integrated power electronics, offer one possibility for rationalising the drive-train architecture of such aircraft actuation and control systems. The paper will discuss key issues pertinent to actuation systems based on electro-hydraulic actuators for large aircraft. Specifically, it considers an actuation system which has been developed for a primary control surface, viz. the rudder, for which aircraft aerodynamic loadings combined with environmental conditions require a high performance drive-train