Diagnostics for Electrohydraulic Primary Flight Control Servoactuators

Primary, fly-by-wire, flight control servoactuators are complex components. They are incorporated into systems with many elements which interact to make correct failure diagnosis difficult. However, the power of the microprocessor has been enlisted to aid the experience the industry is building with test technique and sensor application. This paper examines on-aircraft diagnostic technique and includes as background the impact of the architecture chosen. It lists the types of failure covered, describes the way in which the techniques used in primary flight control servoactuators have evolved to become more electronic and less hydromechanical and concludes with some “lessons-learned”,