Abstract: A control surface lock (10) for flutter constraint of a control surface (14) of an aircraft in cooperative combination with an hydraulic actuator (12), wherein system pressure on the actuator maintains the lock in a dynamically bypassed configuration and loss of system pressure causes the lock to assume a constraint configuration providing a stiff link with the control surface, is comprised of a locking piston (82) secured to the control surface and disposed for reciprocable movement in a locking cylinder (90) upon actuation of the surface, first and second charged locking chambers (92, 94) within the cylinder disposed for series flow of fluid from one to the other upon movement of the locking piston through a bypass valve (100) biased to an open position and a flow splitter (74) having a parallel flow path from the actuator to serve for fluid exchange; wherein loss of system pressure interrupts the series flow and locks the piston in the constraint configuration for flutter protection of the control surface.

Abstract: A bifurcated feel unit for use in a dual path flight control system includes separate input levers for the pilot and copilot control paths. The input levers pivot about a common axis but are capable of independent rotation upon override of the breakout pogos associated with the control system external to the feel unit. Each input lever is coupled to a source of resistive force, preferably a piston within a hydraulic chamber. Normally the feel force supplied is the sum of the resistive forces applied to each input lever. In the event of a jam in one path of the flight control system, the feel force supplied to the remaining operable path is reduced in proportion to the reduction in available control surface.