Purpose
The engine fire detection system does these functions:
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Gives warnings in the flight deck if there is a fire in an engine nacelle
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Gives caution indications in the flight deck if an engine has an overheat condition
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Measures nacelle temperature for the airplane condition monitoring system (ACMS).
The system has built-in test equipment. Failures cause EICAS messages, status messages, or maintenance messages.
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ENGINE FIRE DETECTION -INTRODUCTION
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ENGINE FIRE DETECTION -GENERAL DESCRIPTION
General
Each engine has two fire detection loops, loop 1 and loop 2. A fire detection card in the system card file monitors the loops for fires, overheat conditions, and faults. There is a fire detection card for each engine.
Overheat Detection
If the fire detection loops find an overheat condition, the fire detection card sends a signal to the AIMS and to the warning electronics unit. The AIMS shows a caution message and turns on the master caution light. The warning electronics unit turns on the caution aural.
When the overheat condition goes away, the indications go away.
Fire Detection
If an engine fire occurs, the fire detection card sends a signal to the AIMS and to the warning electronics unit. A warning message shows. The warning electronics unit turns on the master warning lights and the fire warning aural. Another fire alarm signal causes the fuel control switch fire warning light and the engine fire warning light to come on.
When the fire is extinguished, the indications go out of view.
Nacelle Temperature Recording
The fire detection card measures the average temperature of the loops. This data goes to the AIMS through the systems ARINC 629 buses. The airplane condition monitoring function records this data.
Continuous Fault Monitoring
The fire detection card monitors the two loops and their wiring for defects. In normal (dual loop) operation, both loops must have a fire or overheat condition to cause the flight deck indications.
If a failure occurs in a loop, the fire detection card sends the data to the AIMS. A status message shows and the system changes to single loop operation. In this mode, fire/overheat indications occur when one loop is defective and the other has a fire or overheat condition.
System Tests
Use the FIRE/OVHT TEST switch on the P5 overhead panel to do a test of the system. Test results show on the primary display system.
The fire and overheat detection system has a built-in-test function which does tests of the loops, system logic, and interface electronics. System failures show on the primary display system and the MAT.
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ENGINE FIRE DETECTION -GENERAL DESCRIPTION
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ENGINE FIRE DETECTION -FLIGHT DECK AND MEC COMPONENT LOCATIONS
Flight Deck Component Locations
The components in the flight deck that have an interface with the engine fire detection system are:
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Speakers
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Fire/overheat test switch
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Master warning/caution lights
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Fuel control switch fire warning lights
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Engine fire warning lights.
MEC Component Locations
These are the engine fire detection system components in the main equipment center (MEC):
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Left engine fire detection card
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Right engine fire detection card.
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ENGINE FIRE DETECTION -FLIGHT DECK AND MEC COMPONENT LOCATIONS
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ENGINE FIRE DETECTION -ENGINE COMPONENT LOCATIONS
Component Locations
These are the engine fire detection system components on the engines:
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Engine fire detector -upper
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Engine fire detector -lower
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Engine fire detector -lower forward.
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ENGINE FIRE DETECTION -ENGINE COMPONENT LOCATIONS
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777 AIRCRAFT MAINTENANCE MANUAL
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