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 3.  Fuel Bypass Valve (Fig. 1)
_________________
 A.  The fuel bypass valve stops possible high temperatures of the fuel and IDG oil.
 B.  The fuel bypass valve is attached to the inboard side of the fuel pump. It includes a fuel pressure bellows and a servo fuel pressure actuated piston.
 (1)  
The fuel pressure bellows, in the fuel bypass valve, is operated by fuel inlet pressure against the bypass pressure of the fuel metering unit. The position of the fuel pressure bellows determines which direction servo fuel pressure moves the valve piston.

 (2)  
At low speed (low fuel flow) condition, the fuel pressure bellows moves against the bypass pressure of the fuel metering unit, and makes the servo fuel pressure move the valve piston in. This lets the bypass fuel for the fuel metering unit flow through the fuel/oil coolers for the IDG and engine.

 (3)  
At high speed (high fuel flow) condition, the fuel pressure bellows is moved by the pressure of the fuel metering unit, and makes the servo fuel pressure move the valve piston out. This lets the bypass fuel of the fuel metering unit go around the IDG fuel/oil cooler and flow through the engine fuel/oil cooler only.

 4.  Fuel Distribution Valve (Fig. 1)
_______________________
 A.  The fuel distribution valve receives metered fuel flow from the fuel metering unit (AMM 73-21-00) and supplies it to the eight fuel manifolds.
 B.  The fuel distribution valve is installed to a bracket on the rear case of the high pressure compressor (HPC) at the 4 o'clock position.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
FUEL DISTRIBUTION SEE A VALVE
SEEC
FUEL FLOW TRANSMITTER
FUEL INJECTOR AND SUPPORT (24 LOCATIONS)
SEE E
FUEL MAIN FUEL METERING SUPPLY LINE UNIT
SEE BMAIN GEARBOX
FUEL PUMP (REF)
FWD SEE D
A
Fuel Distribution System Component Location Figure 1 (Sheet 1)
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
FUEL METERING MAIN GEARBOX
UNIT (REF)
PUMP FUEL  L-A2336 0487 
FWD  B  VALVE FUEL BYPASS 
SEE  F 
(8 LOCATIONS) FUEL OUT  ELEMENT STRAINER 

FUEL IN
STRAINER BYPASS VALVE
SHUTOFF PISTON
FUEL DISTRIBUTION VALVE
CROSS-SECTIONAL VIEW

C

Fuel Distribution System Component Location
Figure 1 (Sheet 2)

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
TO THE FUEL/OIL COOLER

PRESSURE SWITCH
FUEL PUMP FLOW SCHEMATIC

FUEL INJECTOR AND SUPPORT

Fuel Distribution System Component Location
Figure 1 (Sheet 3)

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
TO THE FUEL/OIL TO THE FUEL/OIL INLET FUEL COOLER COOLER (IDG AND PRESSURE SERVO (ENGINE OIL ENGINE OIL IN THE FUEL PORTION) PORTIONS) FUEL PUMP
FROM THE FMU BYPASS FUEL HIGH POWER MODE 
FUEL SERVO  TO THE FUEL/OIL COOLER (IDG AND ENGINE OIL PORTIONS)  INLET FUEL PRESSURE IN THE FUEL PUMP 
　
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