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Compressor Stator Vane Control
The stator vane control system moves the inlet guide vanes and the 5th, 6th, and 7th stage variable stator vanes of the high pressure compressor (HPC). This controls the airflow through the compressor to increase compressor stability. The EEC controls the stator vane actuator and servo fuel pressure moves the actuator to move the vanes.
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AIR -GENERAL DESCRIPTION

Compressor Bleed Control
The bleed control system uses the 2.5 and 2.9 bleed valves to send air overboard that is not necessary during an engine start. The valves also bleed air during engine surge and reverse thrust conditions to increase the compressor stability. The EEC controls the 2.5 bleed valve actuator and the 2.9 bleed valve solenoid. PS3 servo air pressure closes the poppet-type 2.9 bleed valves. Servo fuel pressure moves the 2.5 bleed valve actuator to modulate the 2.5 bleed valve.
Thrust Balance Control
The LPT thrust balance control system reduces axial loads on the number 1 bearing. The thrust balance air shutoff valve sends 8th stage air to the LPT thrust balance annulus through the turbine exhaust case. The EEC controls the TVBC air shutoff valve solenoid. PS3 servo air pressure closes the poppet-type thrust balance air shutoff valve.
EFFECTIVITY BEJ ALL  75-00-00 
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PW4000 SERIES ENGINES

777 AIRCRAFT MAINTENANCE MANUAL

AIR -GENERAL DESCRIPTION

EFFECTIVITY BEJ ALL POST SB 777-71-0032  75-00-00 
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PW4000 SERIES ENGINES

777 AIRCRAFT MAINTENANCE MANUAL

AIR -GENERAL DESCRIPTION

EFFECTIVITY BEJ ALL  75-00-00 
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PW4000 SERIES ENGINES

777 AIRCRAFT MAINTENANCE MANUAL

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AIR -ENGINE COMPONENT LOCATIONS -LEFT

Component Locations
These engine air cooling and compressor control components are on the back of the intermediate case:
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2.9 (start/stability) bleed valve solenoid

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2.9 (start/stability) pneumatic relay valve

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2.5 bleed valve actuator.

You must remove a fan exit liner segment to get access to these components.
These components are on the left side of the high pressure compressor case:
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PS3 bleed air filters (2)

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TVBC air shutoff valves (2)

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TCA thermocouple probe

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2.9 stability bleed valve and thermocouple probes (2).

EFFECTIVITY BEJ ALL  75-00-00 
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PW4000 SERIES ENGINES

　
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