Abstract: A monitoring system for detecting a fault condition in any one of multiple power control actuator units used for positioning an aircraft's control surface includes sensors for producing sense signals corresponding to the load on each actuator unit under a given control surface loading condition. The sense signals are compared with a reference level signal corresponding to a maximum allowable load. An indication is produced in response to the load on any actuator unit exceeding its allowed value.

Abstract: A first path extends through the combined blocking and relief valve (10) from a first inlet/outlet port (44) to a first actuator port (88), and a second path extends from a second inlet/outlet port (46) to a second actuator port (82). The first path includes a spring biased poppet valve member (64) positioned to open in response to system pressure introduced into the valve (10) via the first inlet/outlet port (44). The second path extends between one end of a pilot piston (68) and one end of a relief piston (74). Pressure in the first path from port (44) acts on an area (A2) of the pilot piston (68) to produce a force on the pilot piston (68) tending to bias it away from the closure member (64). This same pressure is applied against an opposite side area (A5) on relief piston (74). This area (A5) is equal to the difference between the pilot valve area (A2) and the poppet valve area (A1) so that the pressure forces on the pistons (68) and (74) cancel each other out regardless of the pressure in the first path.

Abstract: A hydraulic blocking valve for use in an aircraft flight power actuator employs a unique stepped piston design referenced to return pressure which provides pressure relief at a fixed value independent of system pressure.

Abstract: A self-depressurizing hydraulic control valve having a sliding-type metering valve to control the flow of hydraulic fluid through the valve and also a shutoff valve to stop the flow automatically. The shutoff valve is responsive to the rate of flow of fluid through the control valve and stops the flow when the flow rate decreases to a preselected value. When the shutoff valve closes, the control edges of the metering valve are no longer exposed directly to high pressure fluid, and quiescent leakage across the edges is practically eliminated. Thus, electrochemical erosion of the metering edges resulting from such leakage is substantially reduced.

Abstract: A self-depressurizing hydraulic control valve having a sliding-type metering valve to control the flow of hydraulic fluid through the valve and also a shutoff valve to stop the flow automatically. The shutoff valve is responsive to the rate of flow of fluid through the control valve and stops the flow when the flow rate decreases to a preselected value. When the shutoff valve closes, the control edges of the metering valve are no longer exposed directly to high pressure fluid, and quiescent leakage across the edges is practically eliminated. Thus, electrochemical erosion of the metering edges resulting from such leakage is substantially reduced.