1-16. EQUIPMENT OPERATION (continued).
The APU is an 11.5-horsepower, overhead valve, two-cylinder, four-cycle, air-cooled diesel engine used to drive an
electrical generator and the hydraulic pump.
The chain-driven generator is used to recharge the batteries and provide electrical power for the operation of M992A1
components and a supported howitzer.
The hydraulic pump powers hydraulic system components.
HYDRAULIC SYSTEM OPERATION
The hydraulic system operates the upper rear door and conveyor assembly. The APU drives the hydraulic pump, which is
capable of delivering 4.5 gallons per minute of flow at a system pressure of 1550 psi. Hydraulic fluid is pumped from the 13-
gallon-capacity hydraulic reservoir to the hydraulic control panel. The hydraulic control panel contains two
electromechanically activated directional control valves. The upper directional control valve controls the upper rear door
actuator, extending or retracting the actuator to open or close the upper rear door. The lower directional control valve
controls the conveyor motor for forward or reverse travel of the conveyor chain. The hydraulic control panel also
incorporates a pressure gage that indicates system pressure. The conveyor control switch actuates the conveyor solenoid
at the conveyor control valve.
Change 1 1-23