*
Proximity sensor electronics unit (PSEU) 2

*
AIMS.

The smoke detector sends data to these:
*
Overhead panel ARINC 629 system (OPAS)

*
Warning electronics system (WES)

*
AIMS.

Electrical Power
Each channel continuously monitors the electrical power input to the opposite channel. If power to one channel is not within limits, the smoke detector sends a fault message to AIMS. This condition shows on the fire protection maintenance page.
System Tests
The smoke detectors have built-in-test equipment (BITE). BITE does a power-on test automatically when it gets electrical power, and a periodic test regularly during operation.
EFFECTIVITY
BEJ ALL

You can do a test (initiated test) with the fire/overheat test switch or the maintenance access terminal. The test switch sends a signal through the overhead panel cardfile and ASG cards to the smoke detector. BITE does a test of the system. When you use the MAT, AIMS tells the smoke detector to do a power-up BIT sequence.
Smoke Detection
If there is smoke in the cargo compartment, the detector sends an alarm signal through the ARINC 429 bus to the ASG cards. The ASG cards send the alarm signal through the systems ARINC 629 buses to these systems and components:
*
OPAS

*
WES

*
AIMS.

OPAS makes a ground to turn on the cargo fire warning light. The WES turns on the master warning lights and fire aural warning. The AIMS causes a warning message.
Ground Operation
The cargo smoke detector fans do not operate during cargo handling. This keeps contamination of the detectors to a minimum. The fans in the forward and aft compartments do not operate when all these conditions occur:
*
The airplane is on the ground

*
The forward cargo door is open

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LOWER CARGO COMPARTMENT SMOKE DETECTION -FUNCTIONAL DESCRIPTION -CIRCUIT

*
The aft or bulk cargo door is open

*
The right engine is not operating.

The WOW card supplies the air/ground signal. The proximity sensor electronics unit (PSEU 2) supplies the cargo door open signal. AIMS supplies the engine operating/not operating signal.
If the smoke detector does not receive the expected inputs, it continues to operate with these default values:
*
Air

*
Cargo doors closed

*
Right engine operating.

Airflow Sensing
The smoke detector airflow sensors make allowance for changes in air density. The detector uses air temperature and pressure data to do this. Cargo compartment temperature data comes from the left ECSMC. Cabin altitude comes from the AIMS.
If the smoke detector does not receive the expected inputs, it continues to operate with these default values:
*
Cabin altitude 8000 feet

*
Cargo compartment temperature 40 degrees F.

Training Information Point
The CMCS shows status and maintenance messages for the smoke detectors. A fire protection maintenance page shows information about the system.
The cargo smoke detectors keep fault data in memory. You can use the MAT to access this fault data. You can also use the MAT to access smoke detector hardware and software part numbers.
Use the CMCS download function to load new software into the smoke detector.
EFFECTIVITY BEJ ALL  26-16-00 
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D633W101-BEJ  Sep 05/2002 

LOWER CARGO COMPARTMENT SMOKE DETECTION -FUNCTIONAL DESCRIPTION -CIRCUIT

EFFECTIVITY BEJ ALL  26-16-00 
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D633W101-BEJ  Jan 05/2002 

LOWER CARGO COMPARTMENT SMOKE DETECTION -INDICATIONS

General You can use the fire/overheat test switch or the MAT to do a test
of the system at any time. Test results show on the primary Operation of the lower cargo compartment smoke detection
display system. system is automatic and does not need crew action. The system operates when the main ac buses have power.
Cargo Smoke Indication
If there is smoke in a lower cargo compartment, these indications occur in the flight deck:
*
A cargo fire EICAS warning message shows

*
The master warning lights come on

*
The fire warning aural operates

*
The cargo fire warning light comes on.

The master warning lights and fire warning aural do not operate during part of the takeoff if there is a fire.
Training Information Point
If the smoke detector fails while it supplies a fire alarm signal, the alarm signal latches. This condition occurs if soot from a cargo fire causes contamination of the smoke detector optics.
All these conditions must be true to make the alarm signal stop:
　
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