SQUIB TEST SWITCHES
ARMING (WHITE) SWITCH
SQUIB
AND SMOKE (AMBER)
INDICATING
INDICATION (RED)
LIGHTS
SWITCHES

Lower Cargo Compartment Fire Extinguishing System - Component Location
Figure 1 (Sheet 1)

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
C79761
A
747-400
MAINTENANCE MANUAL

HALON 1301 METERING DISTRIBUTION TUBING BOTTLE

CEILING LINING
PRESSURE

SQUIB
(TYPICAL)

Lower Cargo Compartment Fire Extinguishing System Component Location
Figure 1 (Sheet 2)

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 C.  Safety Relief/Filler Port
 (1)  
The safety relief and filler port is combined. The safety relief valve is a thermal expansion over-pressure rupture disc. If bottle pressure reaches 1200 to 1400 psi at 70°F, the safety relief ruptures, allowing the bottle to discharge. The filler port is for introducing the extinguishing agent and pressurizing the gas in the bottle.

 D.  
Discharge Cartridge (Squib)

 (1)  
An electrical squib is provided to ignite a powder charge which in turn ruptures the diaphragm. A diaphragm is welded over the discharge port in the bottle.

 E.  
Fire Extinguishing Tubing

 (1)  
Fire extinguishing tubing is used to move the agent from the fire extinguisher bottles to the applicable cargo compartment. To prevent cross-connection of the fire extinguishing tubing, the tubing and related fittings are of different dimensions for the different cargo compartments. The tubing is also attached to the bulkhead adjacent to the connection with the fire extinguisher bottle.

 3.  Fire Control Module (Fig. 1)
___________________
 A.  The fire control module is located on P5 pilot's overhead panel. The panel contains engine fire/overheat, APU fire, and lower cargo fire detection and extinguishing (AMM 26-21-01/401).
 B.  In the event smoke is detected in the lower cargo compartment, the appropriate forward or aft arming switch lights up. When the arming switch is pressed, E/E cooling is reconfigured to the override mode and shuts off the appropiate air conditioning packs, all compartment vent fans, all cargo heating air and the E6/E9 equipment cooling air. The forward overboard valve will close for a forward cargo compartment and open for an aft compartment cargo fire. Power will be provided to the discharge switch for squib actuation. By pressing the discharge switch, squibs are detonated and extinguishing agents are released.
 4.  Squib Test Module (Fig. 1)
_________________
 A.  The squib test module is located P461 pilot's overhead maintenance panel (AMM 26-21-02/401).
 B.  The squib test module is able to test engine, APU, and lower cargo compartment fire extinguisher bottle squibs.
 C.  The squib test panel consists of 2 test buttons, and indicating lights for engine, APU, and lower cargo fire extingushing system. The test 1 button tests A squibs on each system and test 2 button tests B squibs. The test buttons check the continuity between the discharge switch and the fire bottle squib cartridges. A green test indicating light illuminates for a successful test. Press each test indicating light to test each light bulb.
 D.  The test 1 button tests the forward squibs and the test 2 button tests the aft squibs on the bottle A, B, C, and D.
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