(2)  
Either one or both ignition system(s) may be used for ground and in-flight starts.

 (3)  
The ignition system is capable of continuous operation. However, both ignition systems should be off to conserve the life of the ignition system components whenever ignition is not necessary in flight or on the ground.

 (4)  
When the engine AUTOSTART switch is at the ON position and the engine is in operation, the ignition system will operate if you have one of the conditions listed below:

 -
the CONT switch is ON

 -
the thermal anti-ice is ON

 -
the flaps are out of zero detent

 -N2 decreases below 61 %N2 rpm with the fuel control switch set to RUN.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
28V DC
BUS 1

IGN
CONT

FLAPSRETRACTED115V ACBUS 1
TAI
R7532 AUTO
ENG 1FLAPS NOT
ON
IGN LEFT
IGN 1 RETRACTED
TO ENGINESFCU RELAY 2, 3, AND 4
115V ACR8331 IGNM7881 LEFT FLAP
R7634BUS 3R8311 AUTO
ENG 1 CNTL XFER
CONTROL UNITIGN 2 AUTO IGNIGN RELAY
RELAY (FCU)
TAI RELAY
R7738 AUTO115V AC
IGN 1 RELAY FLAPS
STBY BUS STBYRETRACTED
IGN
ENG 1
R7467 AUTO/

R7533 AUTO
FLAPS NOTTO STBY IGN 1 IGN RIGHT
RETRACTED START RELAY TO ENGINESFCU RELAY 2, 3, AND 4
CON SW M7879 RIGHT FCU
RELAY 28V DCBAT BUS
1
R7739 AUTO
START

ENG
IGN 2 RELAY
AIR

R8297 CONT
IGN RELAY
CONT

START SW M7351-EIUTO ENGINES
12, 3 AND 4
BOTH
2
1

OFF M7352-EIU
BOTH
2
1

BOTH
2

M7353-EIU
E2-6 EQUIPMENT SHELF
AUTO SWON DISCRETE RETURN
1
AUTO SINGLE IGNITION
NORM START SW
2
DUAL IGNITION1
SCUENG CONTM7330 ELEC
ARINCNORM EXCITER PWROUT
MODULE IGNITER PWR
2
1

EXCITER PWRNORMIGNITER PWR
12START 34
2
M6848 SCU
FUEL CONTROL
R7471 AUTO/
1234
STBY SW
STBY IGNITION AUTO  RUN RUN
STBY IGN 2
BOTH
1

NORM CON
DM7197
1
RELAY
2
2M7325 ENGINE IGN CONTROL
MODULE (P5)

ON
CUTOFF
CUTOFF
RUNM7197 IGN IGNITER PLUG 2
NORM
FUEL CONTROL SWITCHES
EXCITER 2
BAT BUS

28V DC DM7196
ENG 1 FUELCUTOFF
NOTE:____ ENG 1 SHOWN; ENG 2, 3, AND 4 SIMILAR. FIRE R7307 FUEL
CONT VALVE S211 ENG/
P6 MAIN POWER 1 DE-ENERGIZES AT >50% N2  M7196 IGN
CONT RELAY IGNITER PLUG 1
FIRE SW
DISTRIBUTION PANEL  EXCITER 1
Engine Ignition Control System Simplified Schematic
Figure 2

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
(5)  If the engine does not start, the SCU will select both ignitions for the second try of the engine start if you have all of the conditions listed below:
 -
The AUTO swith is not set to "BOTH"

 -
The engine start is on the ground

 -A hung start or a locked rotor is not detected during the first engine start.
 If the second engine start fails, EICAS status message(s) ENG X IGNITION 1 OR ENG X IGNITION 2 (where 'X' denotes engine 1,2,3, or 4) shows on the main EICAS display.
 (6)  For in-flight starts (Mach No.>0.12), the SCU selects both ignitions regardless of the AUTO switch position.
 B. Control
 NOTE: The procedure that follows assumes electrical and pneumatic power
____
 are supplied.

 (1)  
Make sure that the applicable engine ignition 1 and ignition 2 circuit breakers on P6 panel are closed.

 (2)  
Select AUTO switch to activate desired ignition system. Normally only one ignition system is used for ground start while both ignition systems are used for in-flight start.
　
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