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A
747-400
MAINTENANCE MANUAL

SEE

Fuel Pressure Indicating System Component Location
Figure 1 (Sheet 1)

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B50455
A 747-400 MAINTENANCE MANUAL
PRESSURE SWITCH
NOTE: FRONT SPAR LOCATION SHOWN;
REAR SPAR LOCATION ALMOST
THE SAME.
FWD
FUEL FRONT SPAR BOOSTPRESSURE PUMPSENSING LINEFUEL BOOST PUMP
PRESSURE SWITCH FOR THE BOOST
TO BOOST
PUMP PRESSURE PUMP OF THE INBOARD MAIN TANK
SWITCH
A
INBD FWD
PRESSURE SENSINGFROM LINES
BOOST LOW PRESSURE SWITCH FOR PUMP THE FORWARD BOOST PUMP
BULKHEAD FITTING
PRESSURE SENSING LINE  BUNDLE WIRE 
B  FWD  INBD 

LOW PRESSURE SWITCH FOR THE AFT BOOST PUMP
WING REAR SPAR
CONNECTOR PLUG
PRESSURE SWITCHES FOR THE BOOST PUMPS OF THE OUTBOARD MAIN TANK
C
Fuel Pressure Indicating System Component Location Figure 1 (Sheet 2)
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747-400
MAINTENANCE MANUAL

PRESSURE SWITCH FOR THE OVERRIDE/JETTISON PUMP
REAR SPAR (REF)
OVERRIDE/JETTISON PUMP (EXAMPLE)
D
PRESSURE
SWITCH FOR THE
NO. 2 AFT MAIN
BOOST PUMP
PRESSURE SWITCH FOR THE APU FUEL PUMP
APU FUEL 
PUMP (REF) 
MAIN TANK 
NO. 2 AFT 
BOOST PUMP  FWD  INBD 
(REF) 
APU CONTROL 
PRESSURE SWITCH 
WING REAR SPAR 
(REF) 
PRESSURE SWITCH FOR THE APU FUEL PUMP
E 

Fuel Pressure Indicating System Component Location
Figure 1 (Sheet 3)

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B51147
A
747-400
MAINTENANCE MANUAL

FUEL MANAGEMENT
CONTROL MODULE

SEE F
FLIGHT COMPARTMENT 
CENTER WING TANK OVERRIDE/JETTISON PUMP SWITCH 
F W D A F T F W D A F T  (EXAMPLE) LOW PRESSURE INDICATION LIGHT 
PUMP SWITCH (4 LOCATIONS) INBOARD MAIN TANK OVERRIDE/JETTISON  (8 LOCATIONS) FUEL BOOST PUMP SWITCH 
G 
Figure 1 (Sheet 4) Fuel Pressure Indicating System - Component Location 

C20830
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A
747-400
MAINTENANCE MANUAL

 E.  The switches for the override/jettison and APU dc boost pumps are mounted directly on the pumps and are connected to the discharge side of the pumps through an internal passage.
 F.  During pressure defuel, fuel transfer or in-flight jettison, the low pressure light for the override/jettison pumps can show. No maintenance action is necessary. The illumination of the low pressure light during defueling, fuel transfer or in-flight jettison is acceptable and expected because the pressure switch is installed to monitor engine feed performance.
　
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