777 AIRCRAFT MAINTENANCE MANUAL
APU FIRE DETECTION -INTRODUCTION
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APU FIRE DETECTION -GENERAL DESCRIPTION
General
The APU fire detection system has these components:
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APU fire detectors
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Fire detection card -APU.
There are two modes of operation: unattended mode and attended mode. A signal from the electrical load management system (ELMS) puts the card in the unattended mode when the airplane is on the ground with the engines not running. When the airplane is in the air, or an engine is running, the system operates in the attended mode.
Built-in-test equipment does tests of the system. Faults cause alert messages, status messages, and maintenance messages. Use the fire/overheat test switch to do a manual test of the system. See the fire protection section for more information about the fire/overheat test (SECTION 26-00).
Fire Detection Loops
The APU has two fire detection loops, loop 1 and loop 2. The APU fire detection card continually monitors the two loops for faults. If there are no faults, the card monitors both loops for fires. This is dual loop operation.
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If a loop fails, the card sends the data to the AIMS. Status and maintenance messages show. The system changes to single loop operation and monitors only the loop that has not failed. Fire alarms occur if the loop that has not failed has a fire.
Operation
If there is an APU fire, the detection card sends an alarm signal to these components and systems:
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The electrical load management system (ELMS)
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The APU controller
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The AIMS
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The warning electronics system (WES).
The ELMS and the APU controller stop the APU. The AIMS causes a warning message. The WES turns on the master warning lights and the fire warning aural.
A second fire alarm signal turns on the APU fire warning light in the fire switch. If the airplane is on the ground, a warning horn and a light come on at the P40 service and APU shutdown panel.
Attended Mode
Normal operation in the attended mode is dual loop with AND logic. Loop 1 AND loop 2 both must have a fire to cause fire alarms. AND logic helps prevent false alarms. A crew member decides whether or not to use the fire extinguishing system.
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APU FIRE DETECTION -GENERAL DESCRIPTION
Unattended Mode
Normal operation in the unattended mode is dual loop with OR logic. Loop 1 OR loop 2 must have a fire to cause fire alarms. OR logic gives maximum safety for unattended operation. The fire extinguishing system operates automatically.
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APU FIRE DETECTION -GENERAL DESCRIPTION
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APU FIRE DETECTION -FLIGHT DECK AND MEC COMPONENT LOCATIONS
Flight Deck Component Locations
The components in the flight deck that have an interface with the APU fire detection system are:
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Speakers
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Fire/overheat test switch
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Master warning lights
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APU fire warning light.
MEC Component Locations
The APU fire detection card is in the MEC.
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APU FIRE DETECTION -FLIGHT DECK AND MEC COMPONENT LOCATIONS
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APU FIRE DETECTION -NOSE LANDING GEAR COMPONENT LOCATIONS
Nose Landing Gear Component Location
The P40 service and APU shutdown panel is on the nose landing gear. The panel has an APU fire warning horn and an APU fire warning light.
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APU FIRE DETECTION -NOSE LANDING GEAR COMPONENT LOCATIONS
EFFECTIVITY BEJ ALL 26-15-00 中國航空網 m.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：777 AMM 飛機維護手冊 防火 Fire Protection(9)
