S 214-006

 (13)
 Make sure the applicable DEFUEL RH or DEFUEL LH OPEN light comes on.

 S 864-024

 (14)
 Put the applicable DEFUEL RH or DEFUEL LH switch on the P28 panel to the CLOSE position.

 S 214-007

 (15)
 Make sure the applicable DEFUEL RH or DEFUEL LH OPEN light goes off.

 S 414-008

 (16)
 Close the fueling station door, 621GB (AMM 06-44-00/201).

 S 864-025

 (17)
 Remove electrical power if it is not necessary (AMM 24-22-00/201).

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 28-26-02
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757 MAINTENANCE MANUAL
 FUEL QUANTITY INDICATING SYSTEM (FQIS)- DESCRIPTION AND OPERATION
_________________________________________________________________
 1.  General (Fig. 1)_______
 A.  The fuel quantity indicating system (FQIS) supplies fuel quantity measurement, calculation, and indication. The system contains tank units, compensators, densitometers, indicators, and a fuel quantity indicating processor (FQPU). The FQPU does quantity computation and fault isolation for the FQIS system. The FQPU also controls pressure fueling for the airplane (AMM 28-21-00/001).
 B.  The fuel quantity indicating system is a microcomputer controlled system using the variable capacitance principle for fuel quantity measurement. The capacitance measured by the tank units is approximately proportional to the quantity of fuel in the tank.
 C.  The FQIS contains the FQPU, a fuel quantity indicator, 3 load select indicators, a load select control, 3 compensators, 3 densitometers, 4 tank wiring harnesses, and 33 tank units.
 D.  The FQPU is the principle component of the FQIS. It is a digital, dual-channel, microprocessor base computer, located in the main equipment center on rack E3-4.
 E.  The FQPU transmits excitation signals to and reads signals from the tank units and compensators; it also receives densitometer data and computes fuel volume and weight. Each channel of the FQPU includes its own failure monitoring, and built-in test equipment (BITE). Fault isolation is provided for all sensors and the fuel quantity indicator. Faults both transient and permanent are stored in a non-volatile memory, for recall on demand by the maintenance crew. The FQPU gives the subsequent outputs:
 (1)  
Signals to EICAS and the FUEL CONFIG light to warn of low fuel, fuel imbalance or fuel in the center fuel tank with override pumps off, or system faults.

 (2)  
Digital fuel quantity (primary and total) shown on the fuel quantity indicator on the overhead panel, P5.
　
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