TM 9-2350-256-34-2
boom, spade, main winch and hoist winch is controlled by the same control valves as used in the main hydraulic system.
The operation of the refuel-defuel system is controlled by a manually operated four-way selector valve and an adjustable
flow regulator. Description of operation of the basic circuits in the auxiliary hydraulic system will be found inb through l
below. Schematic diagrams of the auxiliary hydraulic system idling, the main winch inhaul and payout, the hoist winch
raise and lower, the hoisting boom raise and lower, the spade raise and lower, the refuel-defuel pump, and the impact
wrench are shown in figures FO-10 through FO-20.
NOTE
Refer to TM 9-2350-256-16 for operating instructions for the boom, winches, spade,
refuel-defuel and impact wrench system.
b. Auxiliary Hydraulic System-Idling (Fig. FO-10). With the auxiliary power unit operating, the system selector valve
in the MAIN position, and the auxiliary power unit (APU) emergency winch control valve in the CLOSED position, oil is
drawn from the hydraulic reservoir (port No. 243) into the pump (port No. 63), and the pump discharges low pressure oil
(port No. 64) to the system selector valve (port No. 48) and returns to the reservoir (port No. 236). The above valve
lever positions are used when the auxiliary power unit generator is being used to charge the batteries.
c. Main Winch-Inhaul (fig. FO-1 1). With the system selector valve in the AUXILIARY position, and the auxiliary power
unit (APU) emergency winch control valve in the OPEN position, hydraulic pressure is directed to the main winch
combination control valve (port Nos. 12 and 13), and returns to the reservoir (port No. 237). 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 valve, is directed to 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) which controls the movement of the cable level winder.
d. Main Winch-Payout (fig. FO-12). With the system selector valve in the AUXILIARY position, and the auxiliary
power unit (APU) emergency winch control valve in the OPEN position, hydraulic pressure is directed to the main winch
combination control valve (port Nos. 12 and 13), and returns to the reservoir (port No. 237). With the main winch control
valve placed in the PAYOUT position, the pilot pressure (port Nos. 15 and 16) tends to equal pump discharge pressure
and is directed to both ends of the pilot-operated directional control valve (port Nos. 8 and 10) in the main winch
combination control valve. The ends of the directional control valve differ in size, the larger end at port 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.
e. Hoist Winch-Raise (fig. FO-13). With the system selector valve in the AUXILIARY position, and the auxiliary power
unit (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 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 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.
f. Hoist Winch-Lower (fig. FO-14). With the system selector valve in the AUXILIARY position, and the auxiliary power
unit (APU) emergency 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
Change 1
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