(c)
The Safety Port will break off of the bottle and release the contents of the bottle if the pressure in the bottle gets too high. The safety port is also used to fill the bottle.
B. Cargo Fire Control Panel
(1) The Cargo Fire Control Panel is installed in the flight compartment in the P8 panel. The components on the panel that control and monitor the cargo fire extinguishing system are the TEST switch, the ARM switches, the DISCH switch and the EXT lights.
(a)
The TEST switch is used to initiate a test of the squib circuit and the cargo smoke detection system (AMM 26-16-00). When the TEST switch is pushed, a low circuit (1 amp) signal is sent through the FWD and AFT squibs to check for continuity. If the squib circuit is continuous, then the FWD EXT and AFT EXT lights will come on.
(b)
When smoke is detected in the forward or aft cargo compartments, then the applicable ARM light will come on. The ARM switch must be pushed to the ARMED position before the bottles can be discharged. When the ARMED switch is pushed and the DISCH switch is pushed, then a signal is sent to the applicable squib to fire the squib and release the halon to the applicable area.
(c)
When the cargo fire extinguishing bottle is discharged, or the pressure in the bottle is too low, then the DISCH light will come on. The DISCH light is only tested by the Master Dim and Test switch.
(d)
The DISCH switch is a guarded, momentary action switch. The ARMED switch is an alternate (latched) action switch.
3. Operation (Fig 2)_________
A. Functional Description (Fig 1)
(1) When smoke is detected in the forward or aft cargo compartments, then the applicable (FWD or AFT) ARM light, on the Cargo Fire Control panel, P8, will come on. The ARM switch must be pushed to the ARMED position before the bottles can be discharged. A white ARMED sign will appear on the ARM switch when the system is armed. When the ARM switch is in the ARMED position and the DISCH switch is pushed, then a signal is sent to the applicable squib to fire the squib and release the halon to the applicable area.
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26-23-00
EXTINGUISHING SYSTEM ú ú 01 Page 4 ú Nov 15/97
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
Cargo Compartment Fire Extinguishing Schematic
Figure 2
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH LOWER CARGO FIRE ú
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EXTINGUISHING SYSTEM ú ú 02 Page 5 ú Nov 15/98
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
G96597
A
737-300/400/500MAINTENANCE MANUAL
(2)
When the applicable discharge disc is ruptured by the squib explosion, the halon flows through the applicable discharge port, into the tubing to the nozzles. The nozzles spray the halon throughout the cargo compartment. Flooding the compartment with halon gas decreases the amount of oxygen in the compartment and extinguishes the fire. The halon does not leave any residue and does not require any cleanup afterwards.
(3)
When the cargo fire extinguishing bottle is discharged, or the pressure in the bottle is too low, then the DISCH light will come on.
(4)
After a bottle is discharged, you must make sure there are no disc particles in the tubing or nozzles and you must replace the bottle.
B. Testing
(1)
Squib Test
(a)
The TEST switch on the Cargo Fire Control panel, P8, will initiate a continuity test of the fire extinguishing squib circuits. When you push the TEST switch, a low current signal will be sent through the FWD and AFT squib circuits. If both squib circuits are continuous, then the green FWD EXT light and the green AFT EXT light will come on. If one of the squib circuits is not continuous, then the applicable EXT light will not come on.
(b)
The squib test will not work if the FWD ARM switch or the AFT ARM switch is in the ARMED position.
(2)
Pressure Switch Test
(a) Manual activation of the bottle pressure switch will do a continuity test of the DISCH light circuit. Push the button on the switch to simulate a bottle discharge and the DISCH light, on the Cargo Fire Control panel, P8, will come on.
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