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
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