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A
747-400
MAINTENANCE MANUAL

NO. 2 MAIN FORWARD BOOST PUMP

NOTE: LEFT SIDE HYDROMECHANICAL FUEL SCAVENGE SYSTEM SHOWN. THE RIGHT SIDE IS ALMOST THE SAME.
Defueling Flow Diagram (Main Boost Pumps Operating)
Figure 3

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F49468
A
747-400 FAULT ISOLATION/MAINT MANUAL
DEFUELING
COMPONENT  FIG. 102 SHT  QTY  ACCESS/AREA  REFERENCE 
VALVE - LEFT WING DEFUELING CHECK VALVE - LEFT WING MANUAL DEFUELING VALVE - RIGHT WING DEFUELING CHECK VALVE - RIGHT WING MANUAL DEFUELING  2 2 2 2  1 1 1 1  546AB, LEFT FRONT SPAR TO MID SPAR OUTBD MAIN TANK 521BB, PRESSURE FUELING STATION 646AB, RIGHT FRONT SPAR TO MID SPAR OUTBD MAIN TANK 621BB, PRESSURE FUELING STATION  28-26-02 28-26-01 28-26-02 28-26-01

Defueling - Component Index
Figure 101

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747-400
FAULT ISOLATION/MAINT MANUAL

PRESSURE 
REFUEL 
STATION 
SEE  A 
PRESSURE 
REFUEL 
STATION 
SEE  A 
REFUEL 
STATION 
DOOR (REF) 

RECEPTACLE SHT 2BSEE  SHT 2SEE C VALVE DEFUELING  FWD  RECEPTACLE SHT 2BSEE 
PRESSURE REFUEL STATION 
A 
Defueling - Component Location Figure 102 (Sheet 1) 

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747-400
FAULT ISOLATION/MAINT MANUAL

LEVER RECEPTACLE ADAPTER 
B RECEPTACLE
WING MANUAL DEFUELING VALVE  TO THE RECEPTACLE FUELING 

VALVE 
THE FUEL FROM CROSSFEED  WING  (REF) HANDLE CONTROL 
MANIFOLD  DEFUELING 
CHECK VALVE  FRONT 
SPAR (REF) 

DEFUELING VALVE
C

Defueling - Component Location (Details From Sht 1)
Figure 102 (Sheet 2)

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747-400 MAINTENANCE MANUAL
 DEFUELING - MAINTENANCE PRACTICES
_________________________________
 1.  General_______
 A. This procedure contains these tasks:
 (1)  
Pressure Defueling

 (2)  
Tank to Tank Fuel Transfer

 (3)  
Defueling With the External Power Control Unit

 (4)  
Lateral Fuel Imbalance Limits

 B.
You must obey all of these safety precautions:

 (1)  
The safety precautions for defueling in this manual (in this procedure and in AMM 12-11-01/301, Fuel Servicing).

 (2)  
The safety precautions that the airport tells you to do

 (3)  
The safety precautions that the airline tells you to do.

 C.
Center of Gravity Changes During Defueling and Fuel Transfer

 (1)  
When you defuel or transfer fuel the center of gravity (CG) will change. Always refer to the Weight and Balance Manual for specific fuel loads limits on the airplane. If you cannot keep the airplane within the CG limits of the Weight and Balance Manual, you must use tail support.
　
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