(8)
The Central Maintenance Computer (CMC) provides built-in testing for the equipment cooling card and low flow detectors. When GROUND TEST is selected on the CMC main menu, a list will appear by ATA chapter. Under chapter 21 two selections are available. The EQUIPMENT COOLING selection will initiate a test on the equipment cooling card. Selection of E/E DETECTORS will initiate a test on the low flow detectors.
(9)
When the EQUIPMENT COOLING test is initiated the equipment cooling card performs the power-up self test and activates the clean cycle output for 25 seconds. The equipment cooling card checks that the equipment cooling system returns to normal operation within 55 seconds.
B. Forward Equipment Cooling Operating Modes (See Fig. 3)
(1)
MODE 1: On the ground, outside air temperature (OAT) less than 45 deg F, engines off.
(a)
Both the supply and exhaust fans operate. The inboard supply, inboard exhaust, and the E6/E9 valves are open. The ground exhaust, bypass, and smoke/override valves are closed.
(b)
If two or more packs are operating, the 3-way valve will supply conditioned air to the flight deck (valve open) providing the conditioned air temperature is less than 104 deg F (40 deg C).
(c)
If one or no packs are operating, the air from the supply fan will supply air to the flight deck (valve closed).
(2)
MODE 2: On the ground, OAT greater than 45 deg F, engines off.
(a) The system will be the same as mode 1, except the ground exhaust valve will open and the inboard exhaust valve will be closed.
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747-400
MAINTENANCE MANUAL
(3)
MODE 3: On the ground, engines running (at least two engines, one on each wing).
(a)
The supply and exhaust fans both operate, and the inboard supply, inboard exhaust, and E6/E9 valves are open. The ground exhaust, bypass, and smoke/override valves are closed.
(b)
The 3-way valve position is the same as in mode 1.
(4)
MODE 4: Standby mode, equipment cooling selector on STBY.
(a) The ground exhaust valve will close providing the airplane is in flight, the engines are running, and the forward cargo air conditioning is not operating.
(5)
MODE 5: Airplane in flight
(a) This mode is the same as modes 1, and 4.
(6)
MODE 6: Single fan failure.
(a)
When either the supply fan or exhaust fan fails, the airplane configures to the closed lope mode.
(b)
The inboard supply, inboard exhaust, ground exhaust, and the smoke/override valves are closed. The bypass and E6/E9 valves are open.
(c)
The 3-way valve position is the same as in mode 1.
(7)
MODE 7: Supply and exhaust fans fail, or equipment cooling system smoke.
(a)
With the equipment cooling selector on NORM, the inboard supply, inboard exhaust, ground exhaust, and bypass valve are closed. The smoke override valve and the E6/E9 valve are open.
(b)
The 3-way valve is closed.
(8)
MODE 8: Class C fire (lower forward, lower aft).
(a)
The supply fan and the exhaust fan will be off.
(b)
The inboard supply, inboard exhaust, ground exhaust, E6/E9, and bypass valves are closed. The smoke/ovrd valve is open.
(c)
If a cargo fire procedure for class C (lower lobe compartments) is initiated, the equipment cooling system will be configured the same as mode 7 (Override Mode), except that the E6/E9 valve will be closed.
(d)
The 3-way valve will be closed.
(9)
MODE 9: Class E fire (main deck).
(a)
The equipment cooling system configures to the closed loop mode with the supply fan as the primary cooling fan with the exhaust fan as a backup. If the supply fan fails, the exhaust fan will operate automatically.
(b)
The inboard supply, inboard exhaust, ground exhaust, E6/E9, and smoke/override valves are closed. The bypass valve is open.
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