(c)
Load Reserve 2 and Reserve 3 equally until full.
(d)
Load Main 2 and Main 3 equally until full.
(e)
Load Center Tank until full.
NOTE: Refer to the Weight and Balance manual for the
____ quantity of fuel required to fill the tanks to full capacity.
(5) To begin fueling operation, all refuel valves are opened using individual control switches, or using the preselect valve control switch if preselect function is selected. The fuel quantity processor unit applies power to the refuel valve control unit solenoids. Solenoid actuation opens a pilot valve on the refuel valve, allowing fuel flow through a large outlet passage from the tank side of the diaphragm. When fuel pressure is applied to the inlet port of the refuel valve, fuel flows through a passage to the back side of the valve control unit diaphragm. Pressure on the back side of the diaphragm will move the diaphragm forward, forcing a spring-loaded poppet from its seat. Fuel will then flow from the manifold into the tank.
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MAINTENANCE MANUAL
Pressure Fueling System Simplified Schematic
Figure 5 (Sheet 1)
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E17600
A
747-400
MAINTENANCE MANUAL
P42
WING TANK FUELING
Pressure Fueling System Simplified Schematic
Figure 5 (Sheet 2)
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MAINTENANCE MANUAL
28V DC
28V DC
SURGE TANK OVERFILL FLOAT SWITCHES
OVERFILL PROTECTION
Pressure Fueling System Simplified Schematic
Figure 5 (Sheet 3)
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MAINTENANCE MANUAL
(6)
If a refuel valve cannot be opened by the normal electrical means, it can be opened manually by rotating valve override screw in the direction indicated on the override screw retainer. When the desired fuel quantity has been reached, fueling must be stopped. After closing the refuel valve manually, fueling of other tanks can be resumed as required.
(7)
When the refuel manifold is pressurized, the operation of the refuel valves can be checked by pressing the TEST SYS switch on the refuel control panel. The indicator lights for the refuel valves should go off at approximately the same time. The valves will remain closed until the switch is released or 10 seconds has elapsed. Valves will then open and system will resume normal operation.
(8)
As the refueling operation progresses, the fuel quantity processor unit continuously calculates the actual fuel volume for each tank. If refueling by manual control method, the processor compares the actual volumes with the full tank shutoff volumes stored on the processor control cards. If refueling by preselect method, the processor compares the actual volumes with calculated shutoff volumes that are dependent on total fuel quantity selected.
(9)
When the two volumes become equal, the processor removes power from the refuel valve solenoid. When the solenoid is de-energized, the solenoid-actuated pilot valve closes the passage from the diaphragm to the tank. Fuel pressure equalizes on both sides of the valve diaphragm and the valve poppet is forced closed by spring pressure, preventing fuel flow through the valve and into the tank. The valve position light on the refueling control panel extinguishes.
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