ENGENG
12.3
12.3
12.3
LOAD SELECT
VALVE VALVE

SPARESPARELOAD SELECT LOAD SELECT LOAD SELECT
FUEL VALVEFUEL VALVE
FUEL CONTROL
CONTROL CONTROL
LR
FUEL SYSTEMRUN
LEFT WINGDEFUEL RH
OB
DEFUELING

DEFUEL LH
RICH

F A
DEFUELING
F T
CLOSE
CLOSE
P
OPEN
OPEN
OPEN OPEN
CUTOFF
O
W NR
PRESSURE FUELING
FUEL CONTROL PANEL (P10) P28 FUELING CONTROL PANEL
1
THE UNITS ARE IN LBS OR KGS.
2
AIRPLANES WITH SINGLE CROSSFEED VALVE (PRE-SB 28-29)
3
AIRPLANES WITH DUAL CROSSFEED VALVES (POST-SB 28-29 OR PRR 54396)
Fuel System Control and Indication Schematic
Figure 2

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757
MAINTENANCE MANUAL

 E. Engine and APU Fuel-Feed
 (1)  
The fuel-feed systems supply fuel to the main engines (AMM 28-22-00/001) and the APU (AMM 28-25-00/001). Four fuel boost pumps (AC), two in each main fuel tank, and two fuel override pumps (AC), in the center fuel tank, usually supply fuel to the engines. The left forward fuel boost pump in the left main fuel tank usually supplies fuel to the APU. Switchlights on the fuel management control panel on the P5 panel control the fuel boost pumps (AC).

 (2)  
An APU DC fuel pump supplies backup fuel-feed to the APU if the left forward fuel boost pump (AC) fails or AC power is not available. A pressure switch for APU fuel shutoff, found in the engine fuel-feed manifold in the left main fuel tank, supplies pressure information for the AC/DC pump control circuit during APU operation. A crossfeed system supplies fuel through a engine fuel crossfeed valve from any fuel tank to either engine. A switchlight on the P5 panel controls the engine fuel crossfeed valve.

 F.
Defueling

 (1)  
Two defueling valves let fuel go into the fueling manifold from the engine fuel-feed manifold for defueling. The main fuel tanks can be suction defueled or pressure defueled. The center fuel tank must be pressure defueled. A switch for each defueling valve on the fueling control panel, P28, controls the defueling valves.

 G.
Fuel Quantity Indicating and Measurement

 (1)  
The fuel quantity indicating system (AMM 28-41-00/001) has tank units, compensators, and densitometers that supply fuel volume and density measurements to the FQIS processor. The FQIS processor uses these measurements to compute the weight of the fuel in each fuel tank. The fuel quantity indicator on the P5 panel shows the fuel weight in each fuel tank as well as the total fuel quantity. Fuel measuring sticks attached to the inside of some fuel tank access doors supply a means to measure fuel quantity manually (AMM 28-44-00/001).
　
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