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MAINTENANCE MANUAL
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MAINTENANCE MANUAL
A. The smoke detectors have built-in-test equipment (BITE). The BITE does a power-up test of the system. Faults cause alert messages, status messages, or maintenance messages. On Dual Loop systems, this check will reconfigure to single loop if the other loop is faulty. Where there is a fault found during the normal operation of system, the system will need to be reconfigured manually by the FIRE/OVHT TEST pushbutton.
B. The venturi ejector using engine bleed air, creates a vacuum condition which pulls the sample air through the lower cargo smoke detection system. Sample air in each compartment is drawn through the two detectors in each zone via a duct distribution system. Five to seven air sampling pick-up points per zone are located in the lower cargo compartment. There are eight zones in the lower compartments. Four in the fwd cargo comartment and four in the aft cargo compartment.
C. The AND logic circuitry is used in the lower cargo fire protection system. Therefore, both loops on each zone must indicate smoke conditions to cause a fire warning to be initiated. When both loops detect smoke through smoke detectors, a signal is sent to AFOLTS card. From AFOLTS card, appropriate signals are sent to Fire Control Panel, MAWEA, and to EIU. From the EIU, EICAS message will be created; from the MAWEA, master warning light will be created; and from AFOLTS, Fire Control Panel will be activated.
D. The system's integrity can be checked by pressing FIRE/OVHT TEST button. This simulates a fire condition to AFOLTS cards. After the button is pressed, all necessary fire warning condition should appear.
E. A pressure switch which is exposed to generated vacuum, monitors the vacuum in the venturi ejector. If the pressure falls below seven inches of water, a status EICAS message will illuminate.
F. The CMC can initiate the fire detection system ground test if either of the ground tests switches is enabled and the CMC test relays are closed. The CMC initiates a ground test to determine the integrity of the fire detection card file and its inputs/outputs using the LRU's built-in test equipment.
G. When the ground test is initiated, the CMC outputs five simultaneous test initiating signals which activate five test relays. These test relays send various discrete signals to the fire detection card file. From these inputs, the fire detection card file generates fire, overheat, and fault detection discretes which it sends to the EIUs and MAWEA. The MAWEA sends signals received from the fire detection card file to the CMC on an ARINC 429 bus, and the MAWEA also sends signals received from the fire detection card file to the EIUs or two ARINC 429 buses. While the test is in progress, the CMC monitors all fire detection system interf aces to the EIUs and the MAWEA. If the CMC detects an inoperative interface, it displays an appropriate fault message.
H. The test relays can also be activated by pressing FIRE/OVHT test switch on the M7317 (P5) miscellaneous switching panel, but the test initiated by the CMC is more effective at isolating failures. The FIRE/OVHT test switch on M7317 tests critical wiring paths, while the CMC tests all wiring paths and isolates to the failed interface with a text message.
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FAULT ISOLATION/MAINT MANUAL
LOWER CARGO COMPARTMENT SMOKE DETECTION SYSTEM
COMPONENT 102 FIG. QTY ACCESS/AREA REFERENCE AMM
SHT
CARD - AFOLTS SMOKE DET AFT CARGO, YLPA032 2 1 LEFT OF NOSE GEAR WHEEL WELL, 26-10-01
FIRE DETECTION CARD FILE, M826
CARD - AFOLTS SMOKE DET FWD CARGO, YLPA031 2 1 LEFT OF NOSE GEAR WHEEL WELL, 26-10-01
FIRE DETECTION CARD FILE, M826
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