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Unlatch Sustained Parallel Fault (LGCU)

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Unlatch Sustained Parallel Fault (RGCU).

There are four replacement tests for the main ac electrical power generation system:
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Auxiliary Generator Control Unit

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Bus Power Control Unit

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Left Generator Control Unit

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Right Generator Control Unit.

Unlatch Sustained Parallel Fault (AGCU)
When the APU generator control unit detects a fault in its sustained-parallel-source protection circuits, it latches a related fault message. You run this test to clear the latched fault message.
Unlatch Sustained Parallel Fault (LGCU)
When the left generator control unit detects a fault in its sustained-parallel-source protection circuits, it latches a related fault message. You run this test to clear the latched fault message.
Unlatch Sustained Parallel Fault (RGCU)
When the right generator control unit detects a fault in its sustained-parallel-source protection circuits, it latches a related fault message. You run this test to clear the latched fault message.
Auxiliary Generator Control Unit
This test makes the APU GCU do a BITE test of its internal circuits. The test is almost equivalent to the power-up test of the APU GCU.
Bus Power Control Unit
This test makes the BPCU do a BITE test of its internal circuits. The test is almost equivalent to the power-up test of the BPCU.
Left Generator Control Unit
This test makes the left GCU do a BITE test of its internal circuits. The test is almost equivalent to the power-up test of the left GCU.
Right Generator Control Unit
This test makes the right GCU do a BITE test of its internal circuits. The test is almost equivalent to the power-up test of the right GCU.
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AC GENERATION -IDG AND APU POWER CMCS GROUND TESTS

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AC GENERATION -BACKUP POWER CMCS GROUND TESTS

General
There is one operational test for the backup electrical power system. It is the Engine Start Test.
There is one LRU replacement test for the backup electrical power system. It is the Backup Converter Test.
Engine Start Test
To do this test, you must operate the engine for the backup generator you want to test. The test makes the backup converter do the engine start test that normally occurs after each engine start.
Backup Converter
This test makes the backup converter do a BITE test of its internal circuits. The test is almost equivalent to the power-up test of the backup converter.
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AC GENERATION -BACKUP POWER CMCS GROUND TESTS

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777 AIRCRAFT MAINTENANCE MANUAL

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TOWING POWER -GENERAL DESCRIPTION

General
The towing power system lets you supply power to items needed to safely tow the airplane. Towing power goes to these items:
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Position lights

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Audio management unit

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Captain’s audio control panel

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Captain’s speaker

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Captain’s panels flood lights

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Accumulator brake pressure indicator

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Accumulator brake pressure indicator back-lighting

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Brake source light

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Towing battery light.

The main battery supplies the dc power. The towing static inverter supplies the ac power.
Operation
To supply towing power to the airplane, put the battery switch in the OFF position and the towing power switch in the battery (BAT) position. If there is no ground handling dc power, the main tow bus relay energizes. This supplies power to the tow dc bus and the tow ac bus through the towing static inverter.
When there is tow dc bus power, the towing power light comes on.
Training Information Point
The towing static inverter is interchangeable with the standby power static inverter.
The main battery can supply the towing bus loads for approximately 45 minutes.
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777 AIRCRAFT MAINTENANCE MANUAL

TOWING POWER -GENERAL DESCRIPTION

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TOWING POWER -FUNCTIONAL DESCRIPTION
　
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