TM 9-2350-256-34-2
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.
g. Hoisting Boom-Forward (fig. FO-15). With the auxiliary power unit (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.
h. Hoisting Boom-Retract/Stow (fig. FO-16). With the auxiliary power unit (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.
i. Spade-Raise (fig. FO-17). With the auxiliary power unit (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 and is blocked (port No. 33). 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.
j. Spade-Lower (fig. FO-18). With the auxiliary power unit (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 is blocked (port No. 33). 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 LOWER position, pump pressure is directed to the back end of the spade cylinder (port No. 60). The opposite end is
ported to the tank return (port No. 235). The differential across the piston causes the rod to extend, lowering the spade.
k. Refuel {fig. FO-19). With the auxiliary power unit (APU) emergency winch control valve in the CLOSED position,
the impact wrench disconnected, and the system selector valve placed in the REFUEL position, pump pressure is
directed to the adjustable flow regulator (port IN) and the four-way selector valve. The flow of the hydraulic pressure to
the pressure side of the four-way selector valve can be carried by the adjustable flow regulator. Placing the four-way
selector valve in the REFUEL position, directs the auxiliary pump pressure to the gear-type refuel-pump motor (port No.
65), which is coupled to and drives the refuel pump. The hydraulic oil (port No. 66) returns to the tank after passing
through the refuel pump motor. Placing the four-way selector valve in the DEFUEL position causes the opposite motor
and pump rotation.
l. Impact Wrench (fig. FO-20). With the impact wrench hoses connected, the auxiliary power unit (APU) emergency
winch control valve in the CLOSED position, and the system se-
Change 1
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