(6)
AIPC 28-41-02, Fig. 10
B.
Access
(1)
Location Zone 125 Area Below Forward Cargo Container Compartment, Left
(2)
Access Panel
125B Electronics Access Door
C.
Procedure
S 914-014
CAUTION: DO NOT TOUCH THE IOC CARD BEFORE YOU DO THE PROCEDURE FOR
_______ DEVICES THAT ARE SENSITIVE TO ELECTROSTATIC DISCHARGE. ELECTROSTATIC DISCHARGE CAN CAUSE DAMAGE TO THE IOC CARD.
(1)
Do the procedure for devices that are sensitive to electrostatic discharge (AMM 20-41-02/201).
S 424-016
(2)
Install the IOC card in FQPU the M7860 (AMM 20-11-22/401).
S 414-008
(3)
Close the door on the FQPU.
S 864-018
(4)
Remove the DO-NOT-CLOSE tags and close these circuit breakers:
(a)
On the main power distribution panel, P6:
1) 6D5, FUEL QTY 1
2) 6D6, FUEL QTY 2
(b)
On the DC power distribution panel, P180:
1) 180M8, FUELING VALVE 2
2) 180M9, FUELING PWR - HOT BAT
3) 180C25, FUELING LTS PANEL
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A 747-400 MAINTENANCE MANUAL
(c) 4) 180C26, FUELING LTS RECPOn the left power distribution center, P414: 1) 414F17, FUELING VALVE 2) 414F22, FUELING PWR
(5) S 214-017Make sure the LED indicator light on the I/O card is on and green.
(6) S 414-010Close the electronics access door, 125B.
(7) S 744-019Do this CMC ground test, <FUEL QUANTITY IND (AMM 28-41-00/501).
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1.
2.
3.
A
747-400 MAINTENANCE MANUAL
FUEL PRESSURE INDICATING SYSTEM - DESCRIPTION AND OPERATION
___________________________________________________________
General
_______
A. The fuel pressure indicating system provides fuel pressure indication for the fuel management control panel and the EICAS fuel synoptic. It also controls the operation of the APU dc boost pump.
Fuel Pressure Indicator Light (Fig. 1)
_____________________________
A. Amber PRESS lights for the fuel boost pumps and override/jettison pumps are located on the fuel management control module on the P5 pilots' overhead panel. Each light is an integral part of its pump's control switch.
B. The lights are powered by the master dim and test circuit. When a pump pressure switch provides an electrical ground (low pressure), its associated indicator light illuminates.
C. Lights for the boost pumps illuminate whenever power is available and the pump pressure is not up to normal operating level. Lights for the center wing tank override/jettison pumps illuminate only after the pumps are turned on. Lights for the main tank override/jettison pumps illuminate only after the pumps are armed at the fuel management control module and commanded on by the fuel system management cards or fuel jettison control cards.
Fuel Pressure Switch (Fig. 1)
____________________
A. The pressure switches control the electrical circuits operating the fuel pressure indicating lights, the fuel flow indication on the EICAS fuel synoptic, and some EICAS messages and CMCS fault messages.
B. Each switch consists of a cylindrical housing containing a diaphragm, a single-pole double-throw contact switch, and an inlet pressure port. When the fuel pressure at the inlet port exceeds 4-7 psi, the diaphragm forces the contact switch to open, breaking the electrical circuit associated with the switch.
C. The switches for the inboard main tank boost pumps are located next to the boost pump motors in the pump dry bays. A sensor line connects the switch pressure port with the boost pump discharge port.
D. The switches for the outboard main tank boost pumps are mounted side by side on the wing rear spar. This allows several feet of sensor line tubing to traverse inside of the fuel tank where the thermal protection of the fuel guards against water condensation, possible freezing, and/or blockage of the switch pressure port.
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