ADAPTIVE AIRCRAFT ACTUATOR FAULT DETECTION

The operation of an actuator (16) is monitored by comparing its position (21) with the position (31, 136) indicated by a model which integrates (45, 135) a limited amount of the difference between the position command (24) applied to the actuator and the achieved model position (31, 136), the limited amount being variable (63, 67, 124) from a nominal limit (61, 65, 124) in dependence upon limited functions (74, 90, 114, 116) of the difference (33, 109) between the actuator position and the model position, and additionally reduced (80, 94, 122) when pilot input overrides (50, 108) the position of the actuator.