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747-400 MAINTENANCE MANUAL
(10)
MODE 10: On the ground, engines off, lower forward cargo air conditioning on.
(a) This mode is identical to modes 1 and 2 except that the ground exhaust valve will be open and the inboard exhaust valve will be closed regardless of the outside air temperature.
(11)
MODE 11: On the ground or in flight, at least 2 engines on (one on each wing), lower forward cargo air conditioning on with temperature selected greater than 50 deg F (10 deg C).
(a)
The system will configure to the inboard open loop mode.
(b)
The inboard supply valve, inboard exhaust valve, and E6/E9 valve are open. The ground exhaust valve, bypass valve, and smoke/override valve are closed.
(c)
The 3-way valve is open.
(12)
MODE 12: On the ground or in flight, forward cargo air conditioning on with temperature selected less than 50 deg F (10 deg C), with at least two engines on and two or more packs on.
(a)
The system will configure to the closed loop mode with the supply fan as the primary fan.
(b)
The inboard supply valve, inboard exhaust valve, ground exhaust valve, and the smoke/override are closed. The bypass valve and the E6/E9 valve are open.
(c)
The 3-way valve is open.
(13)
MODE 13 (Clean mode):
(a)
The supply and exhuast fans are off.
(b)
All of the valves except the smoke/override and E6/E9 valve are closed.
(14)
Mode 14 (Self Test):
(a)
The supply fan and the exhaust fan will be off.
(b)
The inboard supply valve, the inboard exhaust valve, the ground exhaust valve, the bypass valve are open. The smoke/ovrd valve and the E6/E9 valve will be closed.
C. Control
(1)
To place the equipment cooling system in operation, make sure that the EQUIP COOLING mode select switch on P5 overhead panel is set to NORM.
(2)
Supply electrical power (AMM 24-22-00/201).
(3)
Supplying power to the airplane automatically provides cooling to the equipment bays and panels. The mode of cooling is dependent on the position of the EQUIP COOLING switch. The Operating Modes section describes how the system works in each selector position.
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747-400
MAINTENANCE MANUAL
(4) During hot day ground operations it may be necessary to provide conditioned air to the airplane in order to ensure there is adequate cooling for electrical/electronic equipment. The conditions listed below specify when to provide conditioned air to the airplane. Refer to 21-00-00/201 to operate air conditioning packs or to provide ground cart conditioned air.
(a) Supply conditioned air or operate air conditioning packs when these conditions exist: 1) Outside ambient temperature is greater than 115°F (46°C)
and the equipment cooling system is operating in the overboard-open-loop mode (EQUIP COOLING switch set to NORM, both fans on, ground exhaust valve open).
2) Outside ambient temperature is greater than 95°F (35°C) and the equipment cooling system is operating in the inboard-open-loop mode (EQUIP COOLING switch set to STBY, both fans on, ground exhaust valve closed).
3) Outside ambient temperature is greater than 85°F (29°C) and the equipment cooling system is operating in the closed-loop mode (one fan off, bypass valve open).
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747-400 MAINTENANCE MANUAL
EQUIPMENT COOLING SYSTEM - ADJUSTMENT/TEST
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