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Pulling an Engine Fire switch arms a squib in each bottle for discharge to the
related engine. Rotating the Fire switch selects a fire extinguishing bottle and
discharges it into the related engine nacelle.
The switches can be individually unlocked by pushing the Fire Override switch
beneath each Fire switch. The Engine Fire switches are unlocked when the related
Fuel Control switches are in CUTOFF.
APU Fire Extinguishing
There is one APU fire extinguisher bottle controlled by the APU Fire switch.
ENGINE FIRE EXTINGUISHING DIAGRAM
A
FIRE
EXT
B
FIRE
SQUIB EXT
BTL B
DISCH
BTL A
DISCH
2
DISCH
B A
DISCH
A B
1
N_O_T_E_: LEFT AND RIGHT
WING SIMILAR.
October 1, 2000
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
8.20.4 D6-30151-425
Fire Protection -
System Description
The APU Fire switch is mechanically locked in. If an APU fire occurs, the related
switch is electrically unlocked and can be pulled out. Pulling the APU Fire switch
arms the fire extinguisher discharge squibs. Rotating the APU Fire switch
discharges a fire extinguisher into the APU compartment.
The APU Fire switch can be unlocked by pushing the Fire Override switch
beneath the Fire switch.
Cargo Compartment Fire Extinguishing
There are four fire extinguisher bottles for the forward and aft cargo
compartments. Pushing the Cargo Fire Discharge switch discharges two bottles
immediately. The other two bottles discharge after a brief delay, or upon
touchdown.
Fire and Overheat Detection System FaultTest
The fire and overheat detection system has automatic and manual fault testing.
Fire and Overheat Detection SystemAutomatic FaultTest
The engine and APU detector loops are continuously monitored for faults. In
addition to continuous testing of engine and APU detection systems, testing of all
dual loop fire/overheat detectors and cargo compartment smoke detectors occurs
when electrical power is initially applied.
ARMED
FWD AFT
ARMED
FWD AFT
ARM
CARGO FIRE
DISCH
DISCH
FWD AFT
C
FIRE
EXT
A D
EXT
FIRE FIRE
EXT
FIRE
B
EXT
TIMER TIMER
December 01, 1999
747 Operations Manual
Fire Protection -
System Description
Copyright © The Boeing Company. See title page for details.
D6-30151-425 8.20.5
Fully operable systems configure for dual loop operation upon completion of any
test. Systems with a fault in one loop reconfigure for single loop operation. If the
operable loop senses a fire or overheat condition, the related fire warning or
overheat caution activates.
Fire and Overheat Detection System Manual FaultTest
The fire and overheat detection systems can be tested manually by pushing and
holding the Fire/Overheat Test switch.
The indications for a manual fire and overheat detection system test are:
• the fire bell rings
• the APU fire warning horn sounds (on the ground)
• the EICAS message FIRE TEST IN PROG is displayed
• these lights illuminate:
• the master WARNING lights
• the engine fire warning lights
• the APU fire warning light
• the FWD and AFT cargo fire warning lights
• the Fuel Control switch fire warning lights
When the test is complete, the EICAS warning message FIRE TEST PASS or
FIRE TESTFAIL replaces the FIRE TEST IN PROG message; the switch can be
released. Failed system EICAS messages are displayed with the FIRE TEST FAIL
message.
All test messages clear when the test switch is released. If the switch is released
with the FIRE TEST IN PROG message displayed, the test ends without
completing.
The wheel well fire detector loop and the bleed duct leak detector loops are tested
only during the manually initiated test.
Squib Test
All extinguisher discharge squibs are tested for electrical continuity and the squib
control circuit is tested using the SquibTest switches and Squib lights located on
the overhead maintenance panel.
October 1, 2000
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
8.20.6 D6-30151-425
Fire Protection -
System Description
Intentionally
Blank
October 1, 2000
747 Operations Manual
Fire Protection Chapter 8
EICAS Messages Section 30
Copyright © The Boeing Company. See title page for details.
D6-30151-425 8.30.1
Fire Protection EICAS Messages
The following EICAS messages can be displayed.
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