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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 (5)  
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 424-007
 CAUTION: DO NOT TOUCH THE FUEL QUANTITY PROCESSOR UNIT BEFORE YOU DO THE
_______ PROCEDURE FOR DEVICES THAT ARE SENSITIVE TO ELECTROSTATIC DISCHARGE. ELECTROSTATIC DISCHARGE CAN CAUSE DAMAGE TO THE FUEL QUANTITY PROCESSOR UNIT.
 (1)  
Do the procedure for devices that are sensitive to electrostatic discharge (AMM 20-41-02/201).

 S 424-012

 (2)  
Install the refuel valve relay card in the M7860 FQPU.

 S 414-008

 (3)  
Close the front cover on the processor unit.

 S 864-009

 (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
 4) 180C26, FUELING LTS RECP

 (c)  
On the left power distribution center, P414:
 1) 414F17, FUELING VALVE
 2) 414F22, FUELING PWR

 (5)  
Close the electronics access door, 125B.

 S 414-010
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 VOLUMETRIC TOP OFF ADJUSTMENT CARD - ADJUSTMENT/TEST
____________________________________________________
 TASK 28-21-32-825-001
 1.  VTO Card Calibration Adjustment_______________________________
 A. General
 (1)  
This procedure contains instructions to calibrate the volumetric top off (VTO) adjustment card. The card is in the M7860 fuel quantity processor unit (FQPU).

 (2)  
The FQPU is in the center of the equipment center. The FQPU is installed on the E6 equipment rack. You can get access to the FQPU through the electronics access door, 125B.

 (3)  
To get to the VTO adjustment card screws, the hinged panel on the FQPU is opened and the switch bracket on the VTO adjustment card is removed.

 (4)  
The VTO card is calibrated to the values written on a volumetric top off level decal (VTO decal). The VTO decal is found in the center equipment center, P54 panel, adjacent to the FQPU.

 (5)  
The values on the VTO decal are values that are calibrated at the factory. The VTO decal values are related to the the airplane system installation and not related to (dependent on) the FQPU. These values are for one airplane only and do not change. When a new FQPU is installed, you must adjust the VTO card potentiometers in the FQPU to equal the factory calibrated values recorded on the VTO decal.

 (6)  
The VTO setting is shown on the real time EICAS fuel maintenance page on the auxiliary EICAS display.

 (7)  
The volumetric top off adjustment card has nine potentiometers. When you turn the potentiometers, the level of fuel permitted before the automatic shutoff in the applicable tank is adjusted. The potentiometers on the two ends are the spare potentiometers.

 (8)  
The VTO set values on the EICAS display can fluctuate about the VTO decal values. The fluctuation limits are as follows:

 -Main tanks No. 2 and 3: |10 gallons (40 liters)
 -Center wing tank: |10 gallons (40 liters)
 -
Main tanks No. 1 and 4: |05 gallons (20 liters)

 B.
References

 (1)  
AMM 20-41-02/201, Electrostatic Discharge Sensitive Devices

 (2)  
AMM 24-22-00/201, Manual Control

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