METHOD 2:
Fuel Pressure Leak Check. This method uses a visual inspection of
the fuel line in the strut area with the fuel spar valve open and
the fuel line pressurized with fuel from the fuel tank pumps.
S 784-053
(1) METHOD 1;
Air Pressure Leak Check.
NOTE: Use one of these equipment set-ups:
____ -G28018 air pressure equipment or,
-Air pressure check equipment set-up at the engine fuel pump (Fig. 403).
(a)
If available, install the G28018 equipment at the fuel quick-disconnect (service disconnect panel). 1) Connect the G28018 pressure check equipment to the air
pressure source.
(b)
To install the air pressure check equipment set-up at the applicable engine fuel pump, do these steps (AMM 73-11-01/401). 1) Remove the bolts and washers which hold the hose and the
bracket to the engine fuel pump. 2) Disconnect the hose for the fuel pump. 3) Remove the gasket. 4) If the gasket has no damage, keep it for the installation. 5) Install a cap on the open end of the fuel hose. 6) Connect the pressure check equipment to the air pressure
source and the flange on the airplane fuel supply tube on the applicable engine (Fig. 403).
(c)
Use the air pressure source to apply 40 psig pressurize to the fuel line from the airplane fuel supply tube to the fuel spar valve.
(d)
Close the shutoff valve on the pressure check equipment.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
(e) Monitor the pressure gage for 10 minutes.
1) If the pressure stays the same or the pressure decreases by less than 1.5 psig in 10 minutes, the fuel line is satisfactory. a) If the fuel line is satisfactory, remove the pressure
check equipment.
2) If the pressure decreases more than 1.5 psig in 10 minutes, there is a leak in the fuel line. a) If there is a leak, do the subsequent steps.
(f) Do a check for air leaks.
1) Use the air pressure source to apply 40 psig pressurize to the fuel line from the airplane fuel supply tube to the fuel spar valve.
2) Close the shutoff valve on the pressure equipment.
3) Listen for air leaks in the fuel line.
4) When you find the leak, remove the air pressure from the
fuel line.
CAUTION: YOU CANNOT TIGHTEN THE FUEL LINE COUPLING AFTER THE
_______ INITIAL INSTALLATION. YOU MUST INSTALL A NEW O-RING WHEN YOU TIGHTEN THE FUEL LINE COUPLING OR A FUEL LEAK CAN OCCUR.
5) If a coupling has a leak, disconnect the coupling, replace the O-rings, and then connect the coupling again (AMM 28-00-00/201). a) Make sure the O-ring(s) are lubricated with the
petrolatum. 6) If a fuel tube has a leak, replace the fuel tube. 7) After you have repaired the leak, remove the air pressure
equipment.
(g)
If disconnected, install the fuel supply hose at the
quick-disconnect.
(h)
If disconnected, do these steps to connect the main fuel supply hose to the engine fuel pump. 1) Put a gasket, main fuel supply hose and bracket on the
inlet port of the fuel pump. 2) Lubricate the threads of the bolts with engine oil. 3) Install the hose and the bracket to the inlet port of the
engine fuel pump with the bolts and the washers. 4) Tighten the bolts to 198-242 pound-inches
(22.4 - 27.3 Newton-meters).
S 784-054
(2) METHOD 2;
_________
Fuel Pressure Leak Check.
(a) Make sure the fuel line from the front spar to the engine pump is completely installed. 中國航空網 m.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：747-400 AMM 飛機維護手冊 燃油 FUEL 3(14)
