(a)
Build rag dams to soak up additional running fuel.
(b)
Completely dry hidden areas.
(c)
If fuel is drawn into the HeliTest probe, immediately remove it to a safe area and permit it to operate until all the fuel is vaporized. 1) Disconnect the Visual Probe gas line and permit it to run
dry also. 2) Replace the wet filter on the visual probe tip with a dry filter. 3) Do not shut the HeliTest off while it is contaminated with fuel because permanent damage can occur.
S 796-351
(20) If you do not find the leak, increase the helium pressure to
0.6 psig, and then 1.2 psig.
(a) Continue to increase the helium pressure in similar increments until the leak is found.
NOTE: The compression chamber can hold 2 to 5 psig maximum.
____ The maximum pressure depends on the size of the chamber. A smaller chamber can hold a larger pressure.
S 396-352
(21)
When you find the leak, repair it with the applicable repair procedure (AMM 28-11-00/801).
S 796-353
(22)
After the leak repair, do another test of the leak with the HeliTest equipment before you remove the helium chamber from the outside of the tank.
NOTE: This procedure makes sure the leak was repaired correctly.
____
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
S 796-354
(23)
Do these steps to put the area back to its usual condition:
(a)
Remove the pressure chamber or pressure cup and the tape.
(b)
Clean the area around the leak with solvent, Series 82 (AMM 20-30-82/201 or SOPM 20-30-82).
S 796-355
(24) Do this same procedure with the HeliTest equipment for other leaks.
TASK 28-11-00-706-224
6. Wing Fuel Tanks - Air Pressure Leak Check (Fig. 608, 609)_________________________________________
A. General
(1)
This method of fuel leak detection pressurizes the wing tank cavity and checks for external leaks.
(2)
Use this method after all other methods are tried. If the external fuel leak is difficult to find you can pressurize the fuel tanks and apply bubble solution to the external wing structure. Bubbles will show the external leak points.
B.
References
(1)
AMM 28-11-00/201, Fuel Tanks
(2)
AMM 28-11-00/801, Fuel Tanks
(3)
AMM 28-11-01/401, Center Wing Tank Doors
(4)
AMM 28-11-02/401, Reserve and Main Tank Doors
(5)
AMM 28-11-03/401, Surge Tank Access Doors
(6)
AMM 28-26-00/201, Defueling
(7)
AMM 51-31-01/201, Seals and Sealing
(8)
SRM 51-00-00, Structures
C.
Equipment
(1)
Air Source, Regulated, Dry Filtered, 0-150 psig
(commercially available)
(2)
Air Source, Regulated, Dry Filtered, 0-50 psig
(commercially available)
(3)
F72951-1 Manometer - Water, Test Equipment (2 required)
(4)
G28011, Plug - Fuel Vent Scoop Wing Tip
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
28-11-00
ALL ú ú 05 Page 630 ú Feb 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
(EXAMPLE)
A
Wing Fuel Tanks - Air Pressure Leak Check
Figure 609 (Sheet 1)
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