This AIR provides descriptions of aircraft actuation system failure-detection methods. The methods are those used for ground and in-flight detection of failures in electrohydraulic actuation systems for primary flight control. The AIR concentrates on full Fly-By-Wire (FBW) flight control actuation though it includes one augmented-control system. The background to the subject is discussed in terms of the impact that factors such as the system architecture have on the detection methods chosen for the flight control system. The types of failure covered by each monitoring technique are listed and discussed in general. The way in which these techniques have evolved is illustrated with an historical review of the methods adopted for a series of aircraft, arranged approximately in design chronological order.

Purpose:

The purpose of this document is to aid the designers of the systems of the future by showing what succeeded in the past.