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PW4000 SERIES ENGINES
777 AIRCRAFT MAINTENANCE MANUAL
IGNITION -FUNCTIONAL DESCRIPTION
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PW4000 SERIES ENGINES
777 AIRCRAFT MAINTENANCE MANUAL
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IGNITION -OPERATION
The electronic engine control (EEC) controls the operation of the ignition system. The EEC gets the start/ignition selector position to set these modes of operation for the ignition system:
*
Engine start ignition
*
Automatic ignition
*
Continuous ignition.
The fuel control switch must be in the RUN position for the ignition system to operate.
Engine Start Ignition
When you do an autostart or manual start of the engine, the EEC selects which ignition exciter to operate. It operates that exciter for two successful engine starts (autostart or manual), then operates the other exciter for the next engine start.
On the first ground start (autostart or manual) the EEC uses one igniter plug. If the engine fails to start during an autostart attempt, the EEC aborts the start attempt, motors the engine for 30 seconds, and then attempts a second start using two igniter plugs.
For all in-flight restarts, the EEC operates the two igniter plugs.
During an autostart, the EEC operates the ignition system at the fuel-on speed, 15 -28 percent N2. For a manual start, the ignition system operates when you put the fuel control switch in the RUN position at 15 percent N2 (minimum).
The EEC removes power to the igniter plug(s) at starter cutout speed, 41 percent N2.
Automatic Ignition
When the start/ignition selector is in the NORM position, the EEC uses the two igniter plugs. The EEC automatically supplies power to the igniter plugs when any of these conditions occur:
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