(a)
Total fuel quantity is displayed in the lower right corner of the main EICAS screen.
(b)
Total and individual tank fuel quantity is displayed on the EICAS fuel synoptic page. Synoptic is selected for display on the auxiliary EICAS screen by pressing the FUEL button on the EICAS display select panel.
(c)
If one EICAS display is inoperative, fuel quantity is displayed on the main EICAS screen in a compressed format.
(d)
Individual tank fuel quantities are displayed on the auxiliary EICAS screen when the CMCS maintenance page for the fuel system is selected. The CMCS maintenance page also displays fuel density for each tank and capacitance measurements for each tank unit and compensator in the tank.
NOTE: Only two tanks can have data displayed at one time.
____ Maintenance pages must be scrolled through using controls on the CDU to view data for other tanks.
(9)
Digital fuel quantity data is transmitted to the CMCS vie the EIUs and directly to the fuel jettison control cards. The CMCS records fault data for in-tank components, processor control cards, or wiring for use during maintenance. The processor also transmits discrete signals to the fuel system management cards for use during automated fuel transfer operations.
(10)
Fuel quantity data is transmitted to the fueling quantity indicators via the ARINC 429 data bus when the refuel control panel access door is opened. Operation of the indicators is tested by pressing the TEST GAGES button on the refuel control panel. If the data from the processor is invalid or missing, the fueling quantity indicator(s) will display the last valid data for 4 seconds, then blank.
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A
747-400 MAINTENANCE MANUAL
(11)
The processor monitors the tank fuel quantities for imbalance or low-fuel conditions. If either condition exists, the processor transmits signals to display EICAS messages and change the EICAS fuel synoptic.
(a)
If the fuel quantity in any main tank decreases below 2000 pounds (910 kilograms) the FUEL QTY LOW caution message will display on EICAS and the box surrounding the fuel quantity on the fuel synoptic will change color from white to amber. The FUEL QTY LOW caution message will continue to show until the fuel quantity in each of the main tanks contain a minimum of 2500 pounds (1130 kilograms) of fuel.
(b)
If a fuel imbalance greater than 6000 pounds (2720 kilograms) occurs between the inboard main tanks, the FUEL IMBAL 2-3 advisory message will display on EICAS and the boxes surrounding the fuel quantities will change color from white to amber. The FUEL IMBAL 2-3 advisory message will continue to show until the difference in fuel quantity between the No. 2 and No. 3 main tanks is less than 1000 pounds (450 kilograms).
(c)
If a fuel imbalance greater than 3000 pounds (1360 kilograms) occurs between the outboard main tanks, the FUEL IMBAL 1-4 advisory message will display on EICAS and the boxes surrounding the fuel quantities will change color from white to amber. The FUEL IMBAL 1-4 advisory message will continue to show until the difference in fuel quantity between the No. 1 and No. 4 main tanks is less than 1000 pounds (450 kilograms).
(12)
The fuel quantity processor and data busses can be tested by initiating the FUEL QUANTITY test from the CMCS ground test menu. In the event of test failure, faults are recorded in the CMCS. Failure of either bus between the processor and the fuel jettison control cards or a failure which results in blanking of a tank quantity will also cause the FUEL QTY SYS status message to display on EICAS.
B.
Control
(1)
The fuel quantity indicating system operates whenever 28 volt dc power is available. No operator action is required.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
28-41-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 FAULT ISOLATION/MAINT MANUAL
FUEL QUANTITY INDICATING SYSTEM
COMPONENT SHT 102 FIG. QTY ACCESS/AREA REFERENCE
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