NOTE: If INHIBITED shows above <SNGL PT SNSR CARD the test
____
will not operate.
(h) If INHIBITED shows above <SNGL PT SNSR CARD: 1) Push the LSK that is adjacent to the test prompt. 2) Do the steps shown on the CDU. 3) Push the LSK that is adjacent to <RETURN to show the ground
test menu again.
S 745-063
(6)
Push the LSK that is adjacent to the applicable prompt (<SNGL PT SNSR CARD).
(a)
Push the LSK that is adjacent to START TEST>.
NOTE: IN PROGRESS shows during the test.
____
S 745-064
(7) When IN PROGRESS goes out of view, look for PASS or FAIL> adjacent to the <SNGL PT SNSR CARD.
NOTE: If a PASS indication shows, no failure occured during the
____
test.
(a) IF FAIL> shows: 1) Push the LSK that is adjacent to FAIL> to see the GROUND TEST MSG page for the failure. 2) Push the NEXT PAGE key until you find the GROUND TEST MSG pages.
3) Make a list of all CMCS messages, CMCS message numbers that show on the GROUND TEST MSG pages.
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MAINTENANCE MANUAL
4) Go to the CMCS Message Index of the Fault Isolation Manual to find the corrective action for each CMCS message.
H. Put the Airplane Back to Its Usual Condition
S 865-065
(1)
Set the GND TESTS switch to the NORM position.
S 865-066
(2)
Remove the electrical power if it is not necessary
(AMM 24-22-00/201).
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747-400 MAINTENANCE MANUAL
FUEL QUANTITY INDICATING SYSTEM - DESCRIPTION AND OPERATION
___________________________________________________________
1. General_______
A. The fuel quantity indicating system measures the weight of usable fuel aboard the airplane. Total fuel quantity onboard is displayed on the main EICAS screen. Fuel quantity in the individual tanks is displayed when the EICAS fuel system synoptic is selected. Total quantity and individual tank fuel quantity is also displayed on the refuel control panel at the left wing fueling station.
B. The fuel quantity indicating system is a microprocessor-controlled system using the variable capacitance principle for fuel quantity measurement -the capacitance of each tank unit is proportional to the percentage of the tank unit which is immersed in fuel. The processor measures fuel capacitance, fuel density, and fuel dielectric, then uses this data to compute the fuel height and the fuel mass in each tank. The processor has an independent channel for each fuel tank so that component failure or contamination in one tank will not affect the quantity measurement for the other tanks.
C. Power for the fuel quantity indicating system is 28 volts dc from the DC BUS 3 and DC BUS 4 during normal operation or from the ground handling bus or hot battery bus during refueling.
2. Fuel Quantity Tank Unit (Fig._______________________1)
A. The tank units serve as the sensing elements for each subsystem. Each unit consists of two metallic cylinders, a terminal block, and two mounting brackets. The cylinders form a capacitor to provide a capacitance that varies with fuel height between the cylinders. The length of each tank unit is determined by the height of the fuel tank at its particular location.
B. Tank units are dispersed throughout the fuel tanks as follows:
Center wing tank - 5 units
Inboard main tanks - 11 units each
Outboard main tanks - 14 units each
Reserve tanks - 6 units each
C. Electrical connections are made to the terminal block on each unit. Each tank unit has separate low-impedence leadwires (LO-Z and COMP LO-Z) connecting it to the fuel quantity processor unit. All tank units are connected to a common, shielded, high-impedence leadwire (HI-Z) that transmits tank unit capacitive and resistive signals to the processor. The three mounting studs on the terminal block are sized differently to prevent improper terminal installation. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：747-400 AMM 飞机维护手册 燃油 FUEL 4(85)
