If the fuel temperature continues to increase, the EEC sends a signal to the bypass valve torque motor. This lets servo oil pressure open the bypass valve and hold it open. The engine oil flows directly to the fuel/oil cooler outlet manifold. The IDG oil continues to flow through the IDG fuel/oil cooler core.
When fuel temperature decreases, the EEC removes the signal to the bypass valve torque motor. The spring then closes the bypass valve. This lets the engine oil flow through the fuel/oil cooler core.
Oil Strainers
The oil flows through the last chance oil strainers before the oil goes into the bearing compartments and gearboxes. If the main oil filter pressure relief valve opens, the strainers prevent blockage of the oil nozzles.
Oil Scavenge
The five scavenge pumps in the lubrication and scavenge oil pump remove the oil from the bearing compartments and gearboxes.
The scavenge oil flows past the magnetic chip detectors before the oil goes into the tank. A deaerator in the tank removes the air from the oil.
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OIL -DISTRIBUTION -FUNCTIONAL DESCRIPTION
Breather Air
The breather air (bearing seal pressurization air) bleeds from the bearing compartments and gearboxes to the deoiler. An impeller in the deoiler removes the oil mist from the breather air. The oil drains to the main gearbox sump. The air bleeds overboard through the deoiler vent duct.
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PW4000 SERIES ENGINES

777 AIRCRAFT MAINTENANCE MANUAL

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OIL -INDICATING -GENERAL DESCRIPTION

General
The oil indicating subsystem supplies data for indication to the AIMS.
These components monitor the oil system:
*
Oil quantity transmitter

*
Oil pressure transmitter

*
Oil temperature sensor

*
Oil filter differential pressure switch.

The EEC sends oil pressure, oil temperature, and filter condition to the AIMS. The oil quantity data is sent directly to the AIMS.
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PW4000 SERIES ENGINES

777 AIRCRAFT MAINTENANCE MANUAL

OIL -INDICATING -GENERAL DESCRIPTION

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OIL -INDICATING -COMPONENT LOCATIONS
　
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