chapter  17
98 Pages

Prognostics and diagnostics

In relatively recent years, in flight command actuation systems, Electromechanical Actuators (EMAs) have gradually replaced the actuators based on the hydraulic power. Actuators are electric motors that transfer rotational or translational power to the control surfaces by means of gearings; they transfer power from different sources (mechanical, electrical, hydraulic, or pneumatic) into motion. It must be noticed that, compared to the electrohydraulic actuations, the electromechanical actuators offer many advantages: in particular, overall weight is reduced, maintenance is simplified and hydraulic fluids, which is often contaminant, flammable or polluting, can be elimination.As some of them are safety critical, in order to guarantee that the system always operates in safety conditions, scheduled programs of maintenance and redundancy are currently the main tools used to reduce the risks.