TM 9-2350-256-34
0050 00
no. 10 and the hydraulic differential across the valve causes it to move, directing the flow of pump pressure to one side of the
main winch motor (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 is also directed to the level
winder valve (port no. 50) which controls the direction of movement of the cable level winder.
With the system selector valve in the AUXILIARY position, and the APU emergency winch control valve in the OPEN position,
hydraulic pressure is directed to the hoist winch combination control valve (port nos. 22 and 27), and returns through the main
combination control valve to the reservoir (port no. 237). 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 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
direction. The brake cylinder hydraulic 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 system selector valve in the AUXILIARY position, and the APU emergency winch control valve in the OPEN position,
hydraulic pressure is directed to the hoist winch combination control valve (port nos. 22 and 27), and returns through the main
winch combination control valve to the reservoir (port no. 237). 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 directional control valve, due to the difference in size, positions
the valve directing the pump pressure 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 APU emergency winch control valve in the CLOSED position, and the system selector valve in the AUXILIARY
position, the pressure is directed to the boom combination control valve and the spade combination control valve (port no. 33)
and is blocked. The oil then flows over the relief valve in the system selector valve and returns to the reservoir (port no. 236).
With the boom combination control valve placed in the FORWARD position, and at the same time placing the boom safety valve
in the STOW position, pump discharge pressure is directed to the boom cylinders. The pump pressure, directed to one end of the
cylinder (port no. 62) with the other end (port no. 61) ported to the tank return, causes the piston rod to extend, raising the boom.
The stayline cylinder pistons are retracted mechanically into the cylinders by the crankarms and the fluid behind the pistons is
forced out of the cylinders (port no. 62) to the tank return.
With the APU emergency winch control valve in the CLOSED position, and the system selector valve in the AUXILIARY
position, the pressure is directed to the boom combination control valve and the spade combination control valve (port no.
33) and is blocked. The oil then flows over the relief valve in the system selector valve and returns to the reservoir (port no.
236). With the boom combination control valve placed in the STOW position, pump discharge pressure is directed to the boom
cylinders (port no. 61) and stayline cylinders (port no. 62). The pump pressure, directed to one end of the cylinder while the
opposite end is ported to the tank return, causes the boom cylinders to retract and the stayline cylinders to extend.
With the APU emergency winch control valve in the CLOSED position, and the system selector valve in the AUXILIARY
position, the pressure is directed to the spade combination control valve and the boom combination control valve (port no. 33)
and is blocked. The oil then flows over the relief valve in the system selector valve and returns to the reservoir (port no. 236).
With the spade combination control valve placed in the RAISE position, pump pressure is directed to the rod end of the spade
cylinder (port no. 59). The back end of the cylinder is ported to tank return, (port no. 235). The differential across the piston
causes the rod to retract, raising the spade.
0050 00-2