TM 9-2350-256-34
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(port no. 18), causing the motor to drive the main winch in the PAYOUT direction. The pilot pressure is also directed to the main
winch brake cylinder to disengage the winch brake. Pump discharge pressure (port no. 52) is also directed to the level winder
valve (port no. 50) which controls the direction of movement of the cable level winder.
With the main winch control valve placed in the INHAUL position, the hydraulic pressure at the large area end of the pilot-
operated directional control valve in the main winch combination control valve is directed to the tank return (port no. 10). The
pilot pressure is directed to one end (port no. 8) of the pilot-operated directional control valve, positioning the valve to direct
pump pressure to one side of the main winch motor (port no. 17) and causing the motor to drive the main winch in the INHAUL
direction. The hydraulic pressure in the brake cylinder is ported to tank return, causing the brake cylinder springs to engage the
brake; and the brake ratchet and pawls are available for instant braking. Pump pressure is also being directed to the level winder
valve (port no. 50).
With the hoist winch control valve placed in the LOWER position, pilot pressure is directed to both ends of the pilot-operated
directional control valve (port nos. 19 and 24) in the hoist winch combination control valve. The differential across the direc-
tional control valve, due to the difference in size, positions the valve directing pump pressure (port no. 57) to one side of the hoist
winch motor (port no. 17). The hoist winch motor then drives the hoist winch in the LOWER direction. Pilot pressure is directed
to the hoist winch brake cylinder, overcoming the spring force, causing the brake band to expand, and allowing the brake drum
to rotate.
With the hoist winch control valve placed in the RAISE position, the hydraulic pressure at the large end (port no. 19) of the
pilot-operated directional control valve in the hoist winch combination control valve is directed to tank return. The pilot pressure
is directed to one end of the pilot-operated directional control valve (port no. 24), positioning the valve to direct pump pressure
to one side of the hoist winch motor (port no. 18) and causing the motor to drive the hoist winch in the RAISE position. The
brake cylinder pressure is directed to tank return, allowing the brake cylinder springs to compress the brake band around the
winch brake drum, and providing instant braking through the brake drum ratchet and pawls.
With the manually operated directional control valve, in the boom combination control valve, placed in the FORWARD position
and at the same time placing the boom safety valve in the STOW position, pilot pressure is blocked at both valves (port nos. 31
and 39). Pump discharge pressure (port no. 34) is directed to the boom cylinders, extending the piston rod and raising the boom.
The stayline cylinder pistons are retracted mechanically into the stayline cylinders by the crankarms and the fluid behind the
piston is forced out to tank return (port no. 62).
With the manually operated directional control valve, in the boom combination control valve, placed in the RETRACT/STOW
position, and at the same time placing the boom safety valve in the STOW position, pilot pressure is blocked at both valves (port
nos. 31 and 39). Pump discharge pressure is directed to one end of the boom (port no. 61) and stayline cylinders (port no. 62),
the opposite cylinder ends are ported to tank return (port nos. 61 and 62), causing boom cylinders to retract and the stayline
cylinders to extend.
With the manually operated directional control valve, in the spade combination control valve, placed in the RAISE position,
pilot pressure is blocked at the valve (port no. 30). Pump discharge pressure is directed to one end of the spade cylinders (port
no. 59), and the opposite end (port no. 60) is ported to the tank return, causing the cylinder rod to retract and raising the spade.
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