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MAINTENANCE MANUAL

 FUEL TANKS - INSPECTION/CHECK
_____________________________
 1.  General
_______
 A.  This procedure contains these tasks:
 (1)  
Analysis of the Fuel Leak Type

 (2)  
Analysis of Fuel Leak Cause

 (3)  
Fuel Tank Leak Detection

 (4)  
Helitest Leak Detection Procedure

 (5)  
Wing Fuel Tanks - Air Pressure Leak Check

 (6)  
Leak Check of the Repaired Fuel Tank

 (7)  
Put the Airplane Back to the Usual Condition

 B.  
After you have found the external fuel leak and the internal leak source, then refer to these procedures to repair the fuel tank:

 (1)  
For sealant repairs in the fuel tank: Repair of Sealant Leaks in the Fuel Tank Structure (AMM 28-11-00/801).

 (2)  
For cleaning and painting of the fuel tank: Clean the Fuel Tank (AMM 28-11-00/701).

 C.  
Before you repair a leak, make an analysis of the source and cause of the leak with the Analysis of Fuel Leak Cause Task. If the cause is related to structural damage, refer to the Structural Repair Manual (SRM 51-00-00) and do the structural repair before you apply the sealant.

 TASK 28-11-00-706-075
 2.  Analysis of the Fuel Leak Type (Fig. 601, 602, 603, 604)
______________________________
 A.  General
 (1)  
This procedure finds the external fuel leak and evaluates the fuel leak type.

 B.  
References

 (1)  
AMM 12-11-01/301, Fuel

 (2)  
AMM 20-30-82/201, Airplane Structure Cleaning Solvents

 (3)  
AMM 27-51-00/201, Trailing Edge Flap System

 (4)  
AMM 27-81-00/201, Leading Edge Slat System

 (5)  
AMM 32-00-30/201, Landing Gear Door Locks

 (6)  
AMM 51-31-01/201, Seals and Sealing

 C.  
Equipment

 (1)  
Brushes - Camel Hair (to apply talcum powder to the external leak area)

 (2)  
Markers - non-lead, Berol hydromarker (or equivalent)

 D.  
Consumable Materials

 (1)  
B01002 Solvent, General Cleaning of Solvent Resistant Organic Coatings - Series 82 (AMM 20-30-82/201 or SOPM 20-30-82)

 (2)  
G00034 Cloth, Process Cleaning Absorbent Wiper (cheesecloth, gauze) BMS15-5

 (3)  
Talcum Powder (commercially available)

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747-400
MAINTENANCE MANUAL

FUEL LEAK TYPE  1WETTED AREA AFTER 15 MINUTES 

STAIN  NOT MORE THAN 1.5 INCHES (40 mm) 
SEEP  1.5-4 INCHES (40 mm-100 mm) 
HEAVY SEEP  4-6 INCHES (100 mm-150 mm) 
RUNNING LEAK  2MORE THAN 6 INCHES (150 mm) 

HEAVY SEEP  RUNNING LEAK

THE DIMENSION PATTERNS OF FUEL LEAKS ARE BASED ON AN EXAMINATION 15 MINUTES AFTER THE LEAK AREA WAS RUBBED DRY.
FUEL WILL USUALLY COME INTO VIEW AGAIN IMMEDIATELY AFTER YOU WIPE THE AREA DRY AND CAN RUN OR DRIP FROM THE SURFACE.
Fuel Leak Type Evaluation
Figure 601

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