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Pressure fill port.
Indication Items
These items supply data you use to make a check of the operational status of the backup generator:
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Differential pressure indicator
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Differential pressure switch (internal)
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Charge pressure switch (internal)
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Remote oil level sensor (internal).
The differential pressure indicator has a red button. The red button moves out when the filter is clogged.
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GENERATOR DRIVE -BACKUP GENERATOR
The differential pressure switch monitors the oil pressure upstream and downstream of the oil filter. The switch sends a signal that tells if the oil filter is clogged.
The charge pressure switch connects to the backup generator converter. The switch monitors the oil pressure inside the backup generator.
Two probes in the remote oil level sensor send the backup generator oil level status to the backup generator converter. The electrical maintenance page shows the oil level status from the remote oil level sensor.
Training Information Point
The generator has keyhole mounting holes in its mounting flange. This lets you leave the nuts and washers on the mounting bolts while you remove or install a generator.
The only LRM on the backup generator is the oil filter.
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777 AIRCRAFT MAINTENANCE MANUAL
GENERATOR DRIVE -BACKUP GENERATOR
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777 AIRCRAFT MAINTENANCE MANUAL
THIS PAGE IS INTENTIONALLY LEFT BLANK
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GENERATOR DRIVE -BACKUP GENERATOR -HEAT EXCHANGER AND VALVE
General
The backup generator air/oil heat exchanger makes the backup generator oil cool.
The air/oil heat exchanger valve controls the fan or 2.5 bleed airflow through the air/oil heat exchanger. The air/oil heat exchanger valve has these components:
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Air inlets
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RVDT
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Servo fuel ports
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Oil Ports
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Position indicator
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Torque motor
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Electrical connector.
Air/Oil Heat Exchanger
The air/oil heat exchanger is a tube-and-fin type. An oil inlet tube lets oil into the heat exchanger. An oil outlet tube lets oil come out of the heat exchanger.
The air/oil heat exchanger has a pressure relief valve (not shown). If the heat exchanger is blocked, the pressure relief valve lets the oil flow directly from the inlet to the outlet.
Air/Oil Heat Exchanger valve
The air/oil heat exchanger valve has two butterfly valves. The butterfly valves connect engine fan air to the heat exchanger. A torque motor controls servo fuel flow to operate the valves. An electrical connector connects the torque motor to the EEC. An RVDT measures the position of the butterfly valves. A position indicator on the outside of the air/oil heat exchanger valve shows the position of the butterfly valves.
A heat shield cover (not shown) protects the air/oil heat exchanger valve from the heat of the engine.
Oil Temperature Sensors
Oil temperature sensors send signals to the EEC. The backup generator oil out temperature sensor is in the inlet line. The backup generator oil in temperature sensor is in the outlet line. The sensors monitor the temperature of the oil that comes in and goes out of the backup generator.
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GENERATOR DRIVE -BACKUP GENERATOR -HEAT EXCHANGER AND VALVE
Functional Description
The EEC uses the backup generator oil in temperature signal to make the decision to increase or reduce the airflow to the air/oil heat exchanger. The EEC uses the backup generator oil out temperature signal as a backup source. The air/oil heat exchanger valves are normally closed. The EEC sends a signal to the torque motor in the air/oil heat exchanger valve. This controls the servo fuel flow. The servo fuel moves the actuator positions the two butterfly valves. The butterfly valves send engine fan air to the air/oil heat exchanger.
The EEC gets data about the position of the butterfly valves from the RVDT. A status message shows if the valves do not open when the EEC commands them to be open. The position indicator on the air/oil heat exchanger valve shows the position of the two butterfly valves.
The EEC commands the backup generator air/oil heat exchanger valve to open fully if the two oil temperature sensors do not operate.
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