*
PMA -permanent magnet alternator
*
PRSOV -pressure regulating and shutoff valve
*
QAD -quick attach detach
*
SAV -starter air valve
*
stby -standby
*
typ -typical
*
vlv -valve
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D633W101-BEJ Sep 05/2002
PW4000 SERIES ENGINES
777 AIRCRAFT MAINTENANCE MANUAL
ENGINE STARTING -INTRODUCTION
EFFECTIVITY BEJ ALL 80-00-00
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D633W101-BEJ Sep 05/2002
ENGINE STARTING -GENERAL DESCRIPTION
General
The EEC controls the engine starting system using these inputs:
*
Flight deck controls
*
Electrical power
*
Pneumatic power.
Start Selection
You can start the engines manually or automatically, but you normally do automatic starts. You control the type of start with the autostart switch.
The autostart switch sends a signal to the EEC on the systems ARINC 629 buses. When the autostart switch is in the ON position, the EEC controls fuel and ignition, and monitors the engine parameters. The fuel control switch (not shown) must be in the RUN position for the EEC to do an autostart.
When the autostart switch is in the OFF position, you manually control and monitor the engine start.
Engine Starting
When you put the start/ignition selector to the START position it does these functions:
* Energizes a relay in the ELMS to supply 115v ac power to the EEC
*
Energizes a relay in the ELMS to supply 28v dc power to the engine relay unit (ERU) to open the SAV
*
Sends analog and digital start signals to the EEC
*
Sends a discrete signal to the air supply cabin pressure controller (ASCPC).
The AIMS supplies a ground for a solenoid that holds the engine start/ignition selector in the START position. The EEC sends a digital signal to tell the AIMS when to release the selector. If the AIMS does not receive the signal from the EEC, it uses N2 to make a decision when to release the selector.
See the engine fuel control section for more information about the ERU (SECTION 73-21).
See the engine air supply section for more information about the ASCPC (SECTION 36-11).
Starter Air Valve and Starter
The EEC controls the starter air valve (SAV) with a switch in the ERU. The switch controls the power to the SAV solenoid. The SAV solenoid operates the SAV. When the SAV is open, pneumatic power from the airplane air supply goes to the starter. This causes the starter to turn the N2 rotor.
The EEC uses a signal from a speed sensor on the starter to control the SAV. The EEC can modulate the position of the SAV to control the air flow to the starter to prevent crash engagements during engine restarts.
EFFECTIVITY BEJ ALL 80-00-00
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