(a)
Defuel the applicable fuel tank (AMM 28-26-00/201).
(b)
Remove the applicable fuel tank access door (AMM 28-11-02/401, AMM 28-11-01/401).
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Dry Bay Drain Holes
Figure 613
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(c)
Do the Purging and Fuel Tank Entry procedure.
(d)
Put rubber stoppers in two of the four drain holes.
(e)
Connect the air pressure gage to one of the drain holes that does not have a rubber stopper installed.
(f)
Connect the air supply to the drain hole that does not have a rubber stopper or an air pressure gage installed.
(g)
Put one person or more in the fuel tank and one person out of the fuel tank.
CAUTION: WHEN YOU PRESSURIZE THE DRY BAY, DO NOT PRESSURIZE IT MORE
_______ THAN 5.0 PSIG. A HIGHER PRESSURE THAN 5.0 PSIG CAN CAUSE DAMAGE TO THE AIRPLANE STRUCTURE.
(h)
Open the shutoff valve of the Pressurization Equipment to pressurize the dry bay.
(i)
Pressurize the dry bay to 4.0 psig.
(j)
Close the shutoff valve of the Pressurization Equipment.
(k)
Apply noncorrosive soap solution to all dry bay sealed joint areas in leaking tank, including areas where sealant has been extended to adjacent structure.
(l)
Identify all the areas where there are air bubbles.
(m)
Identify all the areas where there is damaged sealant.
S 286-076
(4)
If you can not find the leak, do the steps that follow:
(a)
Disconnect the air supply from the drain hole.
(b)
Connect the vacuum source to the drain hole.
(c)
Apply a vacuum of 2.5 psi maximum to the dry bay.
NOTE: The vacuum is applied to the dry bay only.
____ This can loosen sealant that is not bonded correctly to the dry bay structure.
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