The cargo door actuating systems incorporate an independent hydraulic snubber to prevent the door from being rapidly driven from the uplock during closing. The snubber is located forward of the cargo door actuator. Hydraulic fluid MIL-H-5606 or MIL-H-83282 is used in the snubber.
The snubber assembly consists of two main sections; a damping chamber and a reservoir chamber. Snubbing is provided by the damping chamber while the reservoir chamber replenishes the damping chamber.
The damping chamber consists of an actuating piston and cylinder. A check valve and an orifice are incorporated in the head of the piston. When the cargo door is opened, hydraulic fluid flows through the check valve and orifice to the rod side of the damping chamber. Closing the cargo door causes the check valve to close so that fluid flow is restricted to the piston head side of the damping chamber through the orfice. This action snubs the closing of the cargo door.
The reservoir chamber consist of a spring-loaded type of accumulator which replenishes the damping chamber. A servicing indicator rod is attached to the piston in the reservoir chamber.
The rod is color coded; green for normal operation, blue for proper service, and yellow for servicing requirement.
A servicing data plate is located on the snubber for proper servicing procedures. A servicing unit with a hand pump or equivalent must be used to service the snubber. The servicing pressure must not exceed 150 PSI. When the yellow marker on the indicator rod is partially hidden by the end cap with the cylinder rod fully extended and the temperature is above 40 degee F, the snubber should be serviced. The snubber is properly serviced when the blue ring on the indicator rod protrudes 1/8 inch maximum beyond the cap with the cylinder rod fully extended. A filler port with an incorporated check valve is provided on the reservoir chamber.