TM 55-1520-240-23-67-135UTILITY HYDRAULIC SYSTEM(Continued)7-135Cargo Ramp and Door System DescriptionThe ramp is hinged to the fuselage at the floor line andsupported by two actuating cylinders. The cylindersare operated by hydraulic fluid through a control valveto raise the ramp. The ramp lowers by gravity, with theactuating cylinders serving as hydraulic dampers.NO BREAK - WORK HARDERThe ramp can be stopped at any intermediate point onits way up or down and hydraulically locked in position.NO BREAK - WORK HARDERA cargo door is an integral part of the ramp assembly.When the ramp is up, the door is fully extended tocompletely enclose the ramp area of the fuselage.NO BREAK - WORK HARDERWhen it is down, the door retracts into the ramp.Extension and retraction is by a motor inside the rampthat drives a sprocket and chain assembly. The motoris controlled through a sequence valve that times thedoors motion to the position of the ramp. An overridevalve allows the cargo door to remain open or closedregardless of ramp position.NO BREAK - WORK HARDERThe ramp system can be isolated from the rest of theutility hydraulic system by a solenoid valve in the utilitypressure control module. The normally-open valve isclosed through a switch on the overhead HYDRAULICcontrol panel in the cockpit.NO BREAK - WORK HARDERIf normal pressure is not available from the utilityhydraulic system, the ramp can be operated bypressurizing the system accumulator with thehandpump.7-614
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