Redundant Damper Servoactuators for the F-111 Airplane 650361

This paper describes the design of the self-contained electrohydraulic servo damper packages used for stability augmentation control in each axis of the F-111 airplane. These servo-actuators incorporate integral error sensing and failure shut-off provisions through nonelectrical means. Each actuator is supplied with three simultaneous signal inputs, together with dual hydraulic system pressurization. Hydromechanical error comparisons are performed and these are used to control a logic network which shuts off a portion of the actuator should a sufficient error develop. The shut-off is accomplished automatically and with no significant change in actuator performance following shut-off. The basic operation, design and performance of these rather sophisticated actuators is described.