For the first automatic or manual engine start on the ground, the EEC supplies power to one ignition exciter only. During all other engine starts, the EEC supplies power to the two ignition exciters.
When an autostart occurs, the EEC supplies ignition power between 15-28 percent N2. For a manual start, the EEC supplies power when the fuel control switch is put in the RUN position.
During a ground or in-flight engine start, the EEC removes power to the ignition system at starter cutout speed (approximately 41 percent N2). The start/ignition selector moves to the NORM position just before the engine gets to idle speed.
Automatic Ignition
When the start/ignition selector is in the NORM position, the EEC automatically controls the two ignition exciters. The two ignitor plugs operate when the engine anti-ice is on, or the flaps are not retracted. The ACIPS supplies the engine anti-ice signal and the FSEU supplies flap position.
Continuous Ignition
When the start/ignition selector is in the CON position, the EEC causes the two ignition exciters to operate continuously. The start/ignition selector position goes through the AIMS or OPAS to the EDIU.

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PW4000 SERIES ENGINES

777 AIRCRAFT MAINTENANCE MANUAL

IGNITION -GENERAL DESCRIPTION

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IGNITION -ENGINE COMPONENT LOCATIONS

The ignition system components are on the right side of the engine. You open the right thrust reverser half to get access to these components:
*
Ignition exciter (2)

*
Exciter-to-igniter plug cables(2)

*
Igniter plug (2).

The two ignition exciters are on the upper right side of the accessory gearbox. The upper unit is the number 1 exciter. The lower unit is the number 2 exciter.
The two igniter plugs are on the right side of the engine diffuser case at the 4:00 position. The upper plug is number 1 the lower plug is number 2.
Fan air flows through the cooling duct to cool the ignition system components.
Training Information Point
WARNING: THE IGNITION SWITCH MUST BE IN THE NORM POSITION BEFORE YOU REMOVE IGNITION COMPONENTS. A MINIMUM OF FIVE MINUTES MUST GO BY BEFORE IT IS SAFE TO REMOVE IGNITION COMPONENTS. AFTER YOU REMOVE THE EXCITER-TO-IGNITER PLUG CABLE FROM THE IGNITER PLUG, IMMEDIATELY TOUCH THE CABLE TERMINAL TO THE IGNITER PLUG CASE (BODY) TO LET ALL OF THE ELECTRICAL ENERGY OUT OF THE SYSTEM. THE IGNITION SYSTEM VOLTAGE IS DANGEROUSLY HIGH. IF YOU DO NOT DO THIS PROCEDURE, INJURY CAN OCCUR.

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PW4000 SERIES ENGINES
　
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