(3)  
Fuel System Manifold Air Pressure Leak Check - Alternate Procedure

 (4)  
Remove the Air from the Fuel System Manifolds

 TASK 28-22-07-286-265
 2.  Fuel Tube Dent Criteria and Coupling Damage and Wear Limits___________________________________________________________
 A. General
 (1)  
This procedure applies to all alumimum fuel tubes which includes the fuel lines for these systems:

 (a)  
Fuel tank vent system

 (b)  
Fuel scavenge system

 (c)  
Reserve tank transfer system

 (d)  
Refuel system

 (e)  
Fuel-feed system

 (f)  
APU system

 (g)  
APU fuel-feed supply line shroud

 (h)  
Defuel system

 (i)  
Jettison system

 (2)  
This procedure applies to all fuel system tube couplings which includes the couplings for the fuel line in the engine struts.

 B.
References

 (1)  
AMM 28-22-07/401, Fuel Lines and Fittings

 (2)  
AMM 28-22-07/801, Fuel Line and Couplings

 C.
Fuel System Tubing Damage Check

 S 216-266
 (1)  
Visually examine all the fuel tubing to make sure it is tightly and correctly attached.

 S 436-267

 (2)  
Adjust the installation of the tubes which are not correctly attached (AMM 28-22-07/401).

 S 216-268

 (3)  
Visually examine all the fuel tubing for these types of damage and make sure the damage is permitted:

 (a)  
Make an inspection for cracks.
 1) No cracks are permitted.

 (b)  
Make an inspection for dents (areas that are pushed into the tubing). 1) All dents must have an area that is large compared to the

 depth of the dent. 2) No single dent in the tubing is permitted to decrease the diameter of the tube by more than 2.5 percent.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

SEE D COUPLING SHROUDED 
ASEE STRUT OUTBOARD  SEE D COUPLING SHROUDED  FRONT SPAR OF THE WING 
SEE C COUPLING HALF FLEXIBLE 
NACELLE STRUT 

FLEXIBLE FULL COUPLING
SEE B
FLEXIBLE FULL COUPLING
SEE B
OUTBOARD STRUT
A

FWD
NOTE: NACELLE FOR ENGINE NO. 1 SHOWN, COUPLINGS FOR THE OTHER STRUTS ARE ALMOST THE SAME.
GROOVES WORN INTO THE FERRULE AS A RESULT OF CONTACT WITH THE RETAINING
RING OR RETAINER CANNOT HAVE A GROOVE DEPTH OF MORE THAN 0.010 INCH (0.254 MM).

1
O-RING CONTACT AREA MINIMUM WIDTH IS 0.20 INCH (5.08 MM). THE O-RING CONTACT AREA IS DEFINED AS THE DISTANCE BETWEEN THE TWO GROOVES WORN INTO THE FUEL TUBE FERRULE AS SHOWN IN VIEW B-B AND VIEW D-D. THE GROOVES ARE A RESULT OF CONTACT WITH THE RETAINER AND OR RETAINING RING(S).
2
Fuel Coupling in the Nacelle Strut
Figure 601 (Sheet 1)

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
F21261
A
747-400 MAINTENANCE MANUAL
COUPLING NUT
A
COUPLING
A
TUBE B
O-RINGS COUPLING NUT
LOCKWIRE
FERRULE COUPLING FERRULE
TUBE A
FERRULE
FLEXIBLE FULL B COUPLING B
B
TUBE A
TUBE B
RETAINER HALVES RETAINING RINGS
A-A
COUPLING
(REF)

WEAR ON FERRULE FROM RETAINING RING (2 LOCATIONS)
1
WEAR ON FERRULE
FUEL TUBE FROM RETAINER O-RING CONTACT AREA(REF)
(2 LOCATIONS)  (2 LOCATIONS)
1 2
B-B
Fuel Coupling in the Nacelle Strut Figure 601 (Sheet 2)
F20043
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