exhaust valve from opening until the launching valve isclosed and the keeper valve piston is shifted.HYDRAULIC-LOCK-VALVE PANELSThere are two hydraulic-lock-valve panels, one forthe launching valves (fig. 4-30) and one for the exhaustvalve (fig. 4-3 1). The launching-valve hydraulic-lock-valve panel consists of two air-solenoid valves, thehydraulic lock valve, the launch pilot latch solenoid,and piping connections. The launching-valve hydrauliclock valve (fig. 4-32) provides a hydraulic lock to holdthe launching-valve control valve in the FIRED positionuntil launching is completed or until the launching-valve emergency cutout valve is placed in the EMER-GENCY position, by controlling the flow of fluid to thelaunching-valve control valve.The launch pilot latch solenoid controls a plungerthat prevents the lock valve from being shifted to theFIRED position unless the catapult control system is inthe FINAL READY phase of operation. (A manual lockscrew [fig. 4-32] is provided to secure the valve duringnonoperational periods.) When the catapult FIRE circuitis energized, the fire air-solenoid valve directs airpressure to shift the lock valve to the fired position.This causes pressurized fluid to be directed from port Athrough port B to the launching-valve control valve, thekeeper valve, and port D via the launching-valveemergency cutout valve. Fluid pressure in port Dprovides a hydraulic lock to prevent the valve fromshifting. When the catapult LAUNCH COMPLETEcircuit is energized, the close launch valve air-solenoiddirects air pressure to again shift the lock valve, ventingport D to gravity and directing pressurized fluid fromport A through port C to the launching-valve controlvalve and closing the launching valves. (During aHANGFIRE condition, port D is vented and port C ispressurized when the launching-valve emergency cutoutvalve is placed in its EMERGENCY position, ensuringthat the launching valves remain closed.)The exhaust-valve hydraulic-lock-valve panelconsists of the exhaust-valve hydraulic lock valve, twoair-solenoid valves, and piping connections (fig. 4-31).The exhaust-valve hydraulic lock valve (fig. 4-33)opens and closes the exhaust valve by controlling theflow of hydraulic fluid to the exhaust-valve actuator.When the exhaust-valve open solenoid is energized, airpressure is directed to the opening side of the lockvalve, causing it to shift. This allows fluid to flow fromport A, out port B, through the keeper valve, and intothe opening chamber of the actuator. Fluid also flowsfrom port D to lock the valve in the OPEN position.When the exhaust-valve closed solenoid is energized,air pressure shifts the lock valve to the closed position,allowing fluid to flow from port A, out port C, and intothe closing chamber of the exhaust-valve actuator. TheFigure 4-30.—Launching-valve hydraulic-lock-valve panel.4-24
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