(4)  
Repair all leaks each time a fuel leak is defueled to repair leaks.

 (5)  
The causes of most of the fuel leaks in the fuel tank structure are:

 (a)  
Surfaces are prepared incorrectly

 (b)  
Sealants are mixed or kept incorrectly

 (c)  
Sealants are applied incorrectly

 (d)  
Fasteners are loose

 (e)  
Fittings and connections are installed incorrectly.

 B.
References

 (1)  
AMM 28-11-00/801, Fuel Tanks

 C.
Access

 (1)  
Location Zones
 130 Center Wing Tank
 500 Wing Tanks, Left
 600 Wing Tanks, Right

 D.
Procedure - Fuel Leak Causes

 S 366-261
 (1)  
Surfaces are prepared incorrectly.

 (a)  
The surfaces must not contain unwanted materials such as grease, metal particles, hair, loose paint or wax.

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BOTTOM SPLICE STRINGER NO. 20
LEGEND
TOP SPLICE STRINGER NO. 27
PRIMARY SEAL SURFACE (FUEL TANK BOUNDRY)BOTTOM SPLICE STRINGER NO. 15
TOP SPLICE STRINGER (COVERS A SKIN JOINT) CENTER WING TANK
BOTTOM SPLICE STRINGER (COVERS A SKIN JOINT)
ACCESS DOOR SPANWISE BEAM NO. 3ACCESS HOLE (INCLUDES PARTIAL-DEPTH RIBS) SPANWISE BEAM NO. 2
REMOVABLE RIB
UNDERWING ACCESS DOOR MIDSPAR
SPANWISE BEAM NO. 1STRAIGHT TANK END CONFIGURATION NO. 2 MAIN TANK
1 REMOVABLE RIB ON AIRPLANES WITH A TOP SPLICE STRINGER NO. 14BOTTOM SPLICE STRINGER NO. 10
BOTTOM SPLICESTRINGER NO. 5 NO. 1 MAIN TANK REMOVABLE RIB1 NO. 2 RESERVE TANK
FWD
LEFT SURGE TANK

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Seal Surfaces on the Left Wing and Center Section
Figure 603

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BOTTOM SPLICE STRINGER NO. 20
TOP SPLICE STRINGER NO. 27
NO. 3 MAIN TANK

BOTTOM SPLICE STRINGER NO. 15
TOP SPLICE STRINGER NO. 14BOTTOM SPLICE STRINGER NO. 10
BOTTOM SPLICE STRINGER NO. 5
NO. 4 MAIN TANK
REMOVABLE RIB 1
NO. 3 RESERVE TANK
FWD LEGEND RIGHT SURGE TANKPRIMARY SEAL SURFACE (FUEL TANK BOUNDRY)TOP SPLICE STRINGER (COVERS A SKIN JOINT)BOTTOM SPLICE STRINGER (COVERS A SKIN JOINT)ACCESS DOORACCESS HOLE (INCLUDES PARTIAL-DEPTH RIBS)REMOVABLE RIBUNDERWING ACCESS DOOR
1
REMOVABLE RIB ON AIRPLANES WITH A STRAIGHT TANK END CONFIGURATION
Seal Surfaces on the Right Wing and Horizontal Stabilizer
Figure 604

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SKIN JOINTS SEALED WITH AERODYNAMIC SMOOTHER (ISOLATION SEALS AT INTERVALS OF 30 INCHES)

Splice Stringers and Fillet Seals of the Wing
Figure 605

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 (b)  Unwanted materials can cause the sealant not to bond correctly.
 S 366-262
 (2)  
Sealants are mixed or kept incorrectly (AMM 28-11-00/801).