26-20-00
 ALL  ú ú 01 Page 1 ú Jan 28/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757 MAINTENANCE MANUAL
 ENGINE FIRE EXTINGUISHING - DESCRIPTION AND OPERATION
_____________________________________________________
 1.  General_______
 A.  The engine fire extinguishing system has controls that release one or two applications of fire extinguishing agent to a fire in either engine compartment. The system has test capability.
 B.  The engine fire extinguishing system includes the following: two engine fire extinguisher bottles, engine fire control panel, and the squib test control panel.
 C.  The engine fire extinguishing system receives power from the 28 vdc hot battery bus, through the following circuit breakers on main power distribution panel P6.
 (1)  
6H1, FIRE EXTINGUISHING ENG L BTL 1

 (2)  
6H2, FIRE EXTINGUISHING ENG L BTL 2

 (3)  
6H3, FIRE EXTINGUISHING ENG R BTL 1

 (4)  
6H4, FIRE EXTINGUISHING ENG R BTL 2

 2.  Component Details (Fig. 1)_________________
 A.  Engine Fire Extinguisher Bottle
 (1)  
Engine fire extinguisher bottles are located forward of the aft cargo compartment. The extinguisher bottle includes two squib cartridges, a pressure switch, and the combined safety relief and filler port.

 (2)  
Two squib cartridges are on the discharge valves of each extinguisher bottle. When detonated the cartridge ruptures a retaining disc in the valve releasing the extinguishing agent.

 (3)  
The pressure switch detects a decrease in bottle pressure and activates the bottle discharge lights. The pressure switch can be manually tested.

 (4)  
The safety relief valve is a thermal expansion overpressure rupture disc. If bottle pressure is too high, the safety relief ruptures, allowing the bottle to discharge. The filler port is for introducing the extinguishing agent and pressurizing gas into the bottle.

 (5)  
The extinguishing agent is bromotrifluoromethane (halon), and the pressurising gas dry nitrogen. The agent leaves no residue when discharged.

 B.  Engine Fire Switch
 (1)  The left and right (L/R) engine fire switch handles are located on the engine fire control panel at pilots' aft control stand P8. When a engine fire is detected, the engine fire switch handle red warning light comes on. A solenoid energizes releasing a mechanical interlock on the fire switch handle shaft. When the mechanical interlock is released, the fire switch handle can be operated by pulling the handle out and rotating it. Rotating the handle releases the extinguishing agent. After rotation, the fire handle automatically returns to an off-center position. To push the handle back in it must be in the center horizontal position. The fire switch handle can be manually unlocked by pressing the button behind the handle.
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 ALL  ú ú 01 Page 1 ú Sep 28/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 757 MAINTENANCE MANUAL

SEE

ENG BTL  ENG BTL 
1 DISCH  a  2 DISCH  a 

A

SQUIB TEST

SQUIB TEST PANEL

Engine Fire Extinguishing System Component Location

Figure 1 (Sheet 1)

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 ú  01  Page 2
 ú  Mar 15/83 

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

757
MAINTENANCE MANUAL

BOTTLES EXTINGUISHING ENGINE FIRE CSEE  1186 STA  BOTTLE NO. 1 DSEE  RBL 37 TO RIGHT ENGINE  BOTTLE NO. 2 DSEE 
SWITCH PRESSURE 
HARD POINT CONNECTOR  WL 195 
FWD TO LEFT ENGINE  CONNECTOR HARD POINT 
C 
PRESSURE SWITCH GROUND TEST PUSHBUTTON OR HEX KEY  AND FILLER PORT SAFETY RELIEF  DISK RUPTURE 

DISCHARGE PORT
SEE  E  SCREEN  SQUIB 
ELECTRICAL 
D  CONNECTOR  DISCHARGE  ASSEMBLY 
　
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