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Stator vane actuator
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2.5 bleed valve actuators
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Turbine cooling air valve actuator
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Turbine case cooling valves actuator
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IDG air/oil cooler valve actuator
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Backup generator air/oil cooler valve actuator
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Engine air/oil cooler valve actuator.
Thermal Popout Indicator
If the inlet fuel temperature is more than 105F (40C), a thermal bypass valve turns oil away from the heat exchanger core. This prevents continued heating of the fuel.
A thermal bypass popout indicator is on the top forward side of the servo fuel heater. The popout indicator in the out position shows that the thermal bypass valve or the thermostat is failed.
Fuel Filter Bypass Popout Indicator
An internal pressure relief valve is in the servo fuel heater fuel filter. The relief valve lets fuel go past the filter if the filter gets clogged.
The bottom of the filter element housing has a fuel filter bypass popout indicator. The popout indictor in the out position shows a bypassed filter condition.
EFFECTIVITY BEJ ALL 73-21-00
Page 46
D633W101-BEJ Sep 05/2002
PW4000 SERIES ENGINES
777 AIRCRAFT MAINTENANCE MANUAL
ENGINE FUEL CONTROL -SERVO FUEL HEATER
EFFECTIVITY BEJ ALL 73-21-00
Page 47
D633W101-BEJ Sep 05/2002
ENGINE FUEL CONTROL -ERU
General
The engine relay unit (ERU) has these two main functions in the engine fuel control system:
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Control the supply of airplane electrical power to engine loads
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Make two signals out of one-source signals; one for each EEC channel.
The ERU attaches to the fan case at around the 10:00 position. Six connectors supply the interface between the airplane and engine wiring.
Functional Description
Solid state electronics of the ERU do these things:
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Control
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Divide/collect
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Voltage monitor
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Current monitor.
Control
Each channel of the EEC may control switch devices in the ERU. The switches control airplane power to these engine loads:
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Ignition exciters
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Starter control valve solenoid
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P2/T2 probe heat.
Divide/Collect
The ERU makes two signals out of one-source signals (divides). This supplies one signal for each channel of the EEC. The ERU also makes two EEC signals into one output signal (collects).
Voltage Monitor
ERU voltage monitors sense the output voltage to the ignition exciters. They supply a discrete to the EEC to tell it that power was connected.
Current Monitor
A current monitor senses probe heat output current. It supplies a discrete to the EEC to tell it that power was connected.
EFFECTIVITY BEJ ALL 73-21-00
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