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Launching-valve hydraulic lock valve
Linear retraction engine

Aviation Boatswains Mate E 3 & 2 - Aviation theories and other practices
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Figure 4-33.—Exhaust-vaIve hydraulic lock valve. valve is locked in this position by pressure from port A LINEAR AND ROTARY RETRACTION acting on the larger working area of the lock valve piston. STEAM CUTOFF PRESSURE-SWITCH INSTALLATION The steam cutoff pressure-switch installation (fig. 4-34) is located at a point in the catapult power stroke determined during the catapult certification program. Flexible tubing connects the steam cutoff pressure switch assembly to a port in one of the launching cylinders. During a launch, the pistons pass the port, allowing steam to flow into the steam cutoff pressure-switch installation and energize the LAUNCH COMPLETE relays. These relays initiate closing of the launch valves, opening of the exhaust valve, and the subsequent automatic advancing of the grab. The steam cutoff pressure-switch installation must de-energize the LAUNCH COMPLETE relays before the catapult can complete the interlock circuit for the next launch cycle. The steam cutoff pressure-switch assembly is housed in an intrusion-proof enclosure outside the trough. The steam cutoff pressure-switch assembly contains two pressure switches, a disk orifice, and a steam manifold, which directs steam pressure from the flex hose to the switches. The switches are nonadjustable, and the contacts close at approximately 20 psi and open at approximately 10 psi. SYSTEMS The function of both the linear and the rotary retraction engines is to hydraulically control the movement of the grab and to maneuver the shuttle forward and aft when slow movement is required. Normally, the engines are located directly below the flight deck in close proximity to the launching engine so excessive cable reeving and hydraulic lines and piping are not required. LINEAR RETRACTION ENGINE Essentially, this system consists of the retraction engine cylinder and piston; the main hydraulic accumulator; air flasks; the grab; the cables, which couple the grab to the retraction engine; the crosshead sheaves; cable equalizers; associated valves; and electrical controls and piping. The general arrangement of a linear retraction engine is shown in figure 4-35. DRIVE SYSTEM As shown in figure 4-36, the linear retraction engine drive system consists of a grab, two advance cables, two retrieving cables, an advance cable equalizer, a retrieving cable equalizer, a crosshead, and the various sheaves. The drive system operates in conjunction with the retraction engine and the hydraulic 4-26







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