is screwed onto the crosshead end of the cylinder and held in place by setscrews. The cap provides a fluid passage between the cylinder and the fluid manifold piping leading to the damper accumulator. The damper piston rod extends through the cap at the crosshead end of the cylinder. The damper piston is secured onto the opposite end of the piston rod and held in place by a castle nut and cotter pin. When the damper piston is in its BATTERY position, 3 1/2 inches of the piston rod extends from the cylinder at the crosshead end. The fluid manifold is bolted to the top and bottom of the cylinder cap. A reducing tee connects the upper and lower manifold piping and serves to divert fluid flow from the accumulator equally into the upper and lower manifolds. A flow control valve is located between the reducing tee and the accumulator. The flow control valve has a flapper-type (swing gate) orifice plate, which allows free flow of fluid from the cylinder to the accumulator and a restricted flow through an orifice in the center of the plate from the accumulator to the cylinder. The accumulator acts as a fluid stowage tank and has a high-pressure air connection from the upper head to the charging panel. The charging panel has a charging valve and a gauge valve with a gauge mounted between them, a high-pressure air supply valve, and a vent valve. The accumulator is charged to 750 psi and must have a reading of 2 (±1) inches of fluid on the fluid sight indicator when the sheave damper is in its BATTERY position. The end of the cylinder opposite the crosshead end has a flange threaded on it that mates with a flange on the buffer assembly. The two flanges are bolted together. The buffer assembly consists of a cydinder,  buffer ram,    spring, and fluid sight indicator. The purpose of the buffer assembly is to buffer the damper piston when returning to its BATTERY position. Preoperation Before you operate the sheave dampers, the hydraulic system must be filled and an air charge must be supplied. Use the following procedure in filling the hydraulic system: 1. Block the arresting engine crosshead and pull out the deck pendant until the crosshead of each sheave damper is fully extended. 2. Fill the accumulator until it is approximately one-half full. 3. Pressurize the accumulator to 100 psi. This will retract the sheave damper crosshead. 4. Open all needle valves in the hydraulic system until the flow of fluid is free of air and foam. 5. Fill or drain fluid from the accumulator to obtain a fluid-level gauge reading of 3 inches maximum, 1 inch minimum. 6. Increase the damper accumulator pressure to 750 psi. Operation An incoming aircraft engages the deck pendant, causing an increase of tension on the purchase cable. The purchase cable is reeved around the sheave damper crosshead in a manner that any increased tension experienced by the purchase cable will cause the sheave damper crosshead to move away from its BATTERY position. As the sheave damper crosshead moves, the damper piston moves, forcing fluid from the cylinder, through the fluid manifold, flow control valve, and fluid piping, into the accumulator. The resulting pressure buildup in the accumulator will be equal to the purchase cable pull. Retraction of the sheave damper is automatic and occurs when accumulator pressure becomes greater than cable tension. Retraction normally occurs prior to full runout of the aircraft. The pressure buildup in the accumulator forces the fluid from the accumulator, through the fluid piping, the orifice in the flapper of the flow control valve, the reducing tee, and the fluid manifold, to the damper cylinder, therefore forcing the damper piston back to its BATTERY position. Just before the damper piston reaches its BATTERY position, the end of the damper piston rod comes in contact with the buffer ram. The force of the damper piston rod pushing on the buffer ram compresses a spring inside the buffer cylinder. The spring is held in place by the buffer cylinder end plug. The compression of the spring buffers the return of the damper piston to its BATTERY position. 3-25