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H09562
A

757
MAINTENANCE MANUAL

Fuel Tank Access Doors
Figure 615

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 28-11-00
 ALL  ú ú 01 Page 644 ú Sep 28/99

H09511
A

757 MAINTENANCE MANUAL
 C. Leak Detection Tips
 S 806-133
 (1)  
Train several specialists to do leak detection.

 (a)  
Leak detection is not easy. The skill of specially trained persons is necessary.

 S 796-134
 (2) FIND THE EXTERNAL LEAK POINT(S) FIRST (Do the steps that follow):
_____________________________________
 (a)  
Refer to Fig. 613. This can help to find out which dry bay has the leak.

 (b)  
It is also possible for fuel to go down a rib or a stringer and come out of a different drain hole. The path from the internal leak point to the external leak point can be a long distance.

 (c)  
Do not open the fuel tank until you know which dry bay has the leak.

 S 866-135
 (3)
Leave fuel in the tank until you find the external leak point.

 S 796-136

 (4)  
Transfer fuel between the center tank and the main tank if it is necessary, to find the location of the internal leak with respect to the rib between Bay 3 and Bay 4 (Fig. 615). This is the tank end rib that separates the center fuel tank from the main wing tank.

 S 686-137

 (5)  
Have material and equipment ready to do these tasks
 (AMM 28-11-00/201):

 (a)  
Drain the tank.

 (b)  
Purge the tank.

 (c)  
Go into the tank.

 S 016-138
 (6) DO NOT remove any of the dry bay access doors unless you find that
______
 one of the access doors has a leak.

 (a)  Dry bay access doors are not easy to remove and to seal again.
 S 796-139
 (7)  
Find the internal leak point with the air pressure and bubble procedure in the task "Leak Detection in the Dry Bay" (above).

 (a)  
Keep the dry bay pressurized as specified in the task "Leak Detection in the Dry Bay" until all of the leaks are found.

 (b)  
It is possible there is more than one leak.

 (c)  
Make sure you do not apply more than the maximum pressure to the dry bay.

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