Windshield wiper schematic

Figure 12-68.—Windshield wiper schematic. Each door mechanism is powered by two hydraulic- actuating cylinders. The cylinders for the left door are powered by the No. 1 hydraulic system, and the cylinders for the right door are powered by the No. 2 hydraulic system. The main actuating levers are linked together so that in the event one system fails, the other will be capable of operating both doors. An unlock mechanism is incorporated in the forward linkage to secure the doors when hydraulic power is removed. A hand pump system provides for emergency opening and closing of the doors in the event both hydraulic and electrical systems fail. Shutoff valves are provided within each normal system and the emergency hand pump system to isolate the system. Two flow regulators are located upstream of the selector valve (dual system door control valve). The control valve has three positions-DOORS OPEN, NEUTRAL, and DOORS CLOSED. In the DOORS OPEN position, fluid is ported to the dual controllable check valve, which bypasses pressure to the opening side of the uplock mechanism cylinder. As the cylinder retracts it unlocks the mechanical uplocks, and then unseats the dud controllable check valve to port pressure to the open side of the door actuators. The control valve is normally operated by a two-position switch located on the pilot’s armament control panel. The switch energizes either pair of the four solenoids on the control valve to position the main spool to open or close the doors. The uplock mechanism incorporates an overcenter feature which prevents the assembly from locking until bearings on the doors trip the overcenter mechanism. Limit switches on the uplock mechanism break the electrical circuit to the control valve, and the spring-loaded valve returns to NEUTRAL. In this position, all fluid is ported to the return lines, and the doors are held closed by the mechanical locks. The 12-78