26-23-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
C99260
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757
MAINTENANCE MANUAL
(5)
To discharge an extinguisher bottle into the selected compartment, press the appropriate DISCH (bottle 1 or 2) switch on APU/CARGO fire control panel. The electrical signal from the bottle discharge switch detonates the squib cartridge, rupturing a retaining disc, and releasing the extinguishing agent. Extinguishing agent is discharged into distribution tubing leading to outlet nozzles in the compartment. The forward and aft compartments each have three nozzles in the ceiling. The spray hole pattern is designed to give maximum extinguishing agent coverage to the compartment areas. The aft nozzle in the aft compartment area satisfies requirements in the bulk cargo compartment area.
(6)
ALL EXCEPT GUN 051; A discharge line pressure switch (S633) on the forward distribution tubing is connected in parallel to the pressure switch on extinguisher bottle 1. The discharge line pressure switch recognizes bottle discharge prior to the temperature compensated pressure switch on the extinguisher bottle. The discharge line pressure switch gives an immediate indication (EICAS message: CARGO BTL 1) that extinguishing agent is being released in the forward compartment. A reset switch on the discharge line pressure switch should be pressed after servicing the fire extinguishing system.
(7)
GUN 051; A discharge line pressure switch (S633) on the forward distribution tubing is connected in parallel to the pressure switch on extinguisher bottle 1. Discharge line pressure switch (S10565) in the forward compartment distribution tubing for extinguisher bottle 2 is connected in parallel with the pressure switch on extinguisher bottle 2. The discharge line pressure switch recognizes bottle discharge prior to the temperature compensated pressure switch on the extinguisher bottle. The discharge line pressure switch gives an immediate indication (EICAS message: CARGO BTL 1) that extinguishing agent is being released in the forward compartment. A reset switch on the discharge line pressure switch should be pressed after servicing the fire extinguishing system. The regulators in the forward cargo compartment distribution tubing for bottle 2 provide a metered release of the extinguishing agent to provide fire protection. This, coupled with the protection from bottle 1 provides 120 minutes of fire protection for the forward and aft cargo compartment.
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26-23-00
ALL ú ú 11 Page 7 ú May 28/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL
(8) Decreasing bottle pressure, by discharge or leakage, activates the temperature compensated pressure switch. The switch sends a signal which turns on the appropriate amber DISCH light on the APU/CARGO fire control panel, and generates a CARGO BTL 1/2 DISCH message on the EICAS display.
B. Cargo Fire Extinguishing System Test
(1) Squib Test
(a) The squib test control panel checks the integrity of extinguisher bottle squibs. Pressing the TEST switch sends a signal to all extinguisher bottle squib discharge cartridge. If the squibs are good, the green CARGO FWD/AFT 1/2 lights on the panel will come on.
NOTE: When the forward or aft system is armed the
____ corresponding squibs will not test. (System must be disarmed to conduct squib test.)
(2) Pressure Switch Test
(a) Manual activation of the bottle pressure switch will do a test of the discharge light circuit continuity. Push the button or turn the hex key on the switch to simulate a bottle discharge. The appropriate amber DISCH light will come on and a CARGO BTL 1/2 DISCH message will appear on the EICAS display as a result of the test.
C. Control
(1)
Provide electrical power (Ref 24-22-00).
(2)
To place the system in operation, check that the following circuit breakers on main power distribution panel P6 are closed:
(a)
6H1, FIRE EXTINGUISHING ENG L BTL 1
(b)
6H5, FIRE EXTINGUISHING CARGO BTL 1
(c)
6H6, FIRE EXTINGUISHING CARGO BTL 2
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