E.
Procedure
S 796-189
(1)
Find the location of the external leaks.
S 656-187
(2)
Defuel the tank that has the leak (AMM 28-26-00/201).
S 916-190
(3)
For the tank that has the leak, purge and enter the fuel tank (AMM 28-11-00/201).
S 166-191
(4)
Apply compressed air, to a maximum of 100 psig, to the external leak point to dry the fuel leak path.
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A
757
MAINTENANCE MANUAL
S 116-192
(5)
Completely clean and dry the area immediately around the external leak point with solvent.
S 486-193
(6)
Do one of these two steps:
(a)
If it is possible, install one of the pressure cups supplied in the HeliTest Wing Kit to contain the pressure of helium on the outer surface of the tank. 1) Install vacuum tape around the pressure cup.
a) Work the tape to stick it to the surface. 2) Attach the helium injection tube to the cup with the fittings supplied with the kit.
(b)
Build a custom plastic pressure chamber around the external leak point with plastic film. 1) Install vacuum tape around the leak area.
a) Work the tape to stick it to the surface. 2) Cut a piece of material, L-P-512, to the size of the
chamber formed by the tape. 3) Set the plastic over the tape. 4) Work the plastic to make sure it sticks well to the tape. 5) Make sure the chamber is as small as possible.
NOTE: A small chamber can contain more helium pressure
____
than a larger one.
6) Trim the plastic with a razor knife to follow the outline of the vacuum tape.
7) Apply high speed tape over the plastic chamber and work it well for the best adhesion. a) Use a sufficiently large quantity of tape to reinforce
the plastic helium chamber so it can handle more pressure.
8) Wrap the helium injection tube with vacuum tape to form a 2 inch (5 cm) diameter flange 1 to 2 inches (2.5 to 5 cm) from the end of the tube.
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