Figure 1-16. Hydraulic subplate assembly
right front view.
Main winch and hoist control valves. The main winch and hoist winch control valves are manually operated,
three-position, open-center, directional control valves and are springloaded to the HOLD or centered position.
Boom combination control valve. The boom combination control valve is a manually operated, three-position,
closed-center, directional control valve and is spring-loaded to the HOLD or center position. This control valve also
contains one-way check valves and maximum pressure relief valves.
Boom safety control valve. The boom safety control valve is a manually operated, two-position, single-
flowpath valve, and is springloaded to the LIVE or open position.
Power control valve. The power control valve is a manually operated, two-position, directional flow valve.
The valve is held in its selected position by an internal mechanical detent.
System selector control valve. The system selector control valve is a manually operated, three-position,
directional, combination control and relief valve. It is held in its selected position by an internal mechanical detent.
Auxiliary power unit (APU,) emergency winch control valve. The auxiliary power unit (APU) emergency winch
control valve is a manually operated, two-position (open-closed), single flow path, ball valve.
). Operation. The subplate itself serves as a manifold and directs the hydraulic oil through numerous