(c)
An automatic shutdown.
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A
747-400 MAINTENANCE MANUAL
(2)
The APU will turn off automatically in these conditions:
(a)
The signal from the speed sensor N1 is not available
(b)
The N1 rotor speed is more than 110.8 percent
(c)
The N1 rotor speed is less than 90 percent during an APU operation
(d)
A fast change in the N1 rotor speed
(e)
The N2 rotor speed is more than 103.2 percent
(f)
The inlet temperature (T1) is more than 500°F (260°C)
(g)
The inlet temperature (T12) of the load compressor is more than 248°F (120°C)
(h)
The discharge temperature (T13) of the load compressor is more than 450°F (232°C)
(i)
The exhaust gas temperature (EGT) (T6) is more than 1292°F (700°C)
(j)
The signals for the speed sensor N2, the exhaust gas temperature (EGT) thermocouples T6 and the air temperature sensor T1/T6 are not available.
(k)
The signals for the speed sensor N2, the air temperature sensor T1/T6 and the load compressor inlet temperature sensor T12 are not available.
(l)
The signals for the speed sensor N2 and the inlet pressure sensor P1 are not available.
(m)
The N2 signal is not available mixed with the failures of the stepper motor resolver in the fuel metering unit
(n)
A failure of the fuel metering unit
(o)
The oil pressure is less than 55 psig
(p)
The oil temperature is more than 275°F (135°C)
(q)
The DC power from the two batteries is not available
(r)
A failure of the APU controller (APUC)
(s)
The APU air inlet door is closed
(t)
A fire in the APU compartment
(u)
The airframe ECS duct is too hot.
B.
Access
(1)
Location Zones
221 Control Cabin - Left
222 Control Cabin - Right
C.
Procedure
S 862-015
(1)
Remove the pneumatic load from the APU:
(a)
On the P5 overhead panel, turn off one air conditioning pack at a time.
NOTE: After you turn off one pack, permit the APU to become
____ stable before you turn off the next pack.
(b) Make sure the light, on the P5 overhead panel, for the APU bleed valve is OFF. 1) If the bleed valve light is on, push the switch to turn off
the light and close the valve.
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747-400
MAINTENANCE MANUAL
S 862-016
(2)
Remove the generator load from the APU:
(a)
Push the APU GEN 1 and the APU GEN 2 switches on the P5 overhead panel.
(b)
Make sure the AVAIL lights on the APU GEN 1 and APU GEN 2 are on.
S 862-018
(3) Set the APU control switch to the OFF position.
NOTE: When you set the APU control switch to the OFF position, the
____ APU will continue to operate in its cool-down cycle for one minute.
S 862-131
(4)
If the battery power is not necessary, remove the battery power:
(a)
Let the APU go through its one minute cool-down cycle.
(b)
Set the STANDBY POWER switch to the OFF position.
(c)
After the APU does its one minute cool-down cycle, wait three minutes and set the BATTERY switch to the OFF position.
NOTE: The wait period of three minutes will prevent CMCS
____ message 49043 to show on the EICAS display.
TASK 49-11-00-862-019
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