LOWER CARGO COMPARTMENT SMOKE DETECTION -LOWER CARGO SMOKE DETECTOR -FUNCTIONAL DESCRIPTION
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LOWER CARGO COMPARTMENT SMOKE DETECTION -FUNCTIONAL DESCRIPTION -AIR SAMPLING
General
The smoke detector installation for the forward lower cargo compartment is shown. The smoke detector installation in the aft cargo compartment operates the same.
The smoke detector has four air inlet ports. Three of the inlet ports connect to air sampling tubes. The fourth inlet port has a manifold that connects to the suction lines from the water separators. The sampling tubes are above the cargo compartment ceiling and in the left sidewall. Silicone rubber sampling ports attach to the ends of the tubes and go through the ceiling into the cargo compartment.
Air Sampling
The forward and aft cargo compartments each have three smoke sampling zones. Each smoke detector inlet port gets an air sample from one zone. Zone 1 is at the back of the compartments and zone 3 is at the front of the compartments.
The smoke detector fan pulls air in through the sampling ports and tubes. It also pulls condensation from the water separators. Exhaust air and water spray from the fan goes into the space behind the cargo compartment sidewall.
Training Information Point
Squeeze a blocked sampling port with your fingers to clean it, or blow compressed air laterally through the holes.
If a sampling tube is blocked, remove the sampling ports and disconnect the other end of the tube. Use compressed air to clean the tube.
The sampling tubes are made of aluminum and attach to the structure with clamps. This makes it difficult to connect them to the wrong inlet ports on the detector.
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LOWER CARGO COMPARTMENT SMOKE DETECTION -FUNCTIONAL DESCRIPTION -AIR SAMPLING
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LOWER CARGO COMPARTMENT SMOKE DETECTION -IN-LINE HEATER AND CONTROLLER
General
The in-line heater increases the temperature of the air that flows to the smoke detector. There is a controller for each in-line heater. The controller uses a sensor in the heater to control the temperature of the heater element to approximately 175F (79C). This increases the air temperature approximately 30F (17C).
The controllers only get power when the airplane is in the air.
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LOWER CARGO COMPARTMENT SMOKE DETECTION -IN-LINE HEATER AND CONTROLLER
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D633W101-BEJ May 05/2003
LOWER CARGO COMPARTMENT SMOKE DETECTION -WATER SEPARATOR
General
The water separator removes condensation from the air that flows to the smoke detector. The air that comes in changes direction quickly at the suction port. This lets condensation collect for removal.
The water separator is a sealed unit. It has no moving parts.
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LOWER CARGO COMPARTMENT SMOKE DETECTION -WATER SEPARATOR
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777 AIRCRAFT MAINTENANCE MANUAL
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LOWER CARGO COMPARTMENT SMOKE DETECTION -FUNCTIONAL DESCRIPTION -CIRCUIT
General
The circuit for the forward lower cargo compartment is shown. The circuit for the aft lower cargo compartment operates the same. The left and right main ac buses supply power to the smoke detectors. The smoke detector gets inputs from these:
*
Left ECS miscellaneous card (ECSMC)
*
Weight-on-wheels (WOW) card
*
Overhead panel ARINC 629 system (OPAS)
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