Abstract: A fluid powered actuator system includes two identical fluid powered actuators operable by respective supply pressures which are controlled by respective identical valve arrangements. Operating positions of flow control elements of the valve arrangements are applied through respective couplings to a differential arrangement which operates, if these positions differ by an unacceptable amount, to apply an error indication through respective coupling to prevent the supply pressures from being applied to the respective actuators.

Abstract: A device for limiting the torque transmitted from an input shaft to an output shaft comprises a spring-loaded clutch interconnecting said shafts. Relative movement between parts of the clutch when a predetermined output torque is exceeded results in application of a brake which arrests the output shaft. A subsequent increase in torque load results in application of an increased braking force by a second spring whose deformation results in operation of a latched indicator. The indicator is not therefore responsive to low-level transient torque overloads.