ELECTRONIC
REFLECTED LIGHT
VENTURI EJECTOR -SEE

(ON SOME  (ON SOME
AIRPLANES) AIRPLANES) VACUUM SENSE LINE

PRESSURE SUPPLY
LINE (REFERENCE)

PRESSURE SWITCH ELECTRICAL
FWD CONNECTOR

D

Lower Cargo Compartment Smoke Detection System - Component Location
Figure 1 (Sheet 2)

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 B.  There are four ejectors. Two located in the fwd cargo compartment and two located in the aft cargo compartment.
 4.  Pressure Switch
_______________
 A.  When the pressure falls below approximately seven inches of water, the pressure switch mounted on the ejector closes, and creates an EICAS message. When the pressure is eleven inches of water or greater, the pressure switch will open and an EICAS message will disappear.
 5.  Smoke Detector Tubing
_____________________
 A.  Smoke sampling vacuum manifolds contiuously draw air from the ceiling through the orifices along the length of the compartments. Two manifolds are located in the forward lower cargo compartment, and two additional manifolds are located in the aft lower cargo compartment.
 6.  Fire/Overheat Test Module (Fig. 1)
_________________________
 A.  The FIRE/OVHT TEST switch is located on M7317 miscellaneous switching panel (P5). The switch initiates tests for the various fire detection system. The operational test for each applicable section contains the FIRE/OVHT test. By pressing the switch, the switch sends a signal to a relay that simulates a fire/overheat signal. The test results in cockpit fire and overheat indicators, and appropriate EICAS messages.
 B.  To replace the module, refer to 26-10-02/401, Miscellaneous Switching Module.
 7.  Fire Control Module (Fig. 1)
___________________
 A.  The fire control module M7326 is located on P5 pilot's overhead panel. The panel contains engine fire, APU fire, and lower cargo fire detection and extinguishing.
 B.  In case smoke is detected in the lower cargo compartment, the following feature appears:
 (1)  
Cargo fire warning light: The red lights illuminate and enables the fire extinguishing agent discharge switch.

 C.  
To replace the module, refer to 26-21-01/401, Fire Control Module.

 8.  Fire Detection Card
___________________
 A.  Each detection zone has a corresponding detection card. The card constantly monitors and processes signals to detection cards. The card outputs alarm or fault signals to the EICAS and light in flight deck.
 B.  The cards are located in M826 card file.
 9.  Automatic Fire Overheat Logic Test System Cards (AFOLTS)
_______________________________________________
 A.  Two AFOLTS cards interpret detection control card signals, provide system functional test, and output fire warning and fault indication signals for lower cargo fire detection system. There are a total seven AFOLTS cards in fire detection card file.
 B.  The AFOLTS cards are located in the M826 card file.
 10. Modular Avionic & Warning Electronic Assembly (MAWEA)
_____________________________________________
 A.  The MAWEA is a part of multiplex system which transmit information about altitude alert, stall warning, takeoff warning, landing warning, master warning lights, and aural warning. It uses 115-volts AC power supply and has 18 printed circuit cards. For fire detection system, MAWEA sends aural warning and master warning light (if applicable) for engine, APU, and lower cargo from AFOLTS to EIU. All other functions are done in AFOLTS cards. For each plug in pin numbers, the wiring diagram manual will provide the information (Ref 31-51-00).
 11. Operation (Fig. 2)
_________
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