(2)  
Mandril or ball (Mandril can be locally fabricated) - Short segment repair only

 B.  References
 (1)  AIPC 21-44-00 Figs. 1,2
 C.  Access
 (1)  Location Zone
 141 Aft Lower Lobe Compartment, LH
 142 Aft Lower Lobe Compartment, RH
 145 Bulk Cargo Compartment, LH
 146 Bulk Cargo Compartment, RH

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A

747-400 MAINTENANCE MANUAL
SEE A BULK COMPARTMENT
CONTAINERIZED COMPARTMENT
HEATOUTLET HOLES
HEAT DUCT
HEAT OUTLET
AFT CARGO HEAT DUCT
HOLES A
Aft Cargo Heating Duct - Repair Figure 801 (Sheet 1)
G08721
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 747-400 MAINTENANCE MANUAL
REPAIR SEGMENT

SLEEVES
METHOD II - LONG SEGMENT REPAIR
_____ CUT AND REMOVE DAMAGED SECTION TO ALLOW SUFFICIENT
NOTES: ACCESS FOR RIVETING REPAIR SECTION. SPACE SCRIVETS 1 TO 1-1/4 INCHES (25 TO 32 mm) APART WITH 0.35 INCH (9 mm) MINIMUM EDGE DISTANCE.
MAKE SURE HEAT OUTLET HOLES FACE UP. HEAT CAN DAMAGE INSULATION IF OUTLET HOLES ARE NOT POSITIONED CORRECTLY.
Aft Cargo Heating Duct - Repair
Figure 801 (Sheet 2)

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A
747-400 MAINTENANCE MANUAL
 D. Procedure
 S 358-002
 (1)  Repair a Short Section of the Heat Duct (Procedure 1):
 NOTE:____A short segment is 12 inches (305 mm) or less. A long segment is greater than 12 inches (305 mm).
 (a)  
Remove the damaged heat duct.

 (b)  
Make a sleeve (aluminum or titanium) which is 6 inches (152 mm) longer than the damaged heat duct.

 NOTE: Use an aluminum sleeve when you repair an aluminum heat
____ duct. Use a titanium sleeve when you repair a composite heat duct. The sleeve diameter must be larger than the heat duct diameter. Push a mandril or a ball into the sleeve a minimum of 3 inches (76 mm) to increase the sleeve diameter, if it is necessary.
 (c)  
Drill the same number of the heat outlet holes in the sleeve that are in the damaged heat duct.

 (d)  
Loosen the duct support clamps to permit the installation of the sleeve.

 (e)  
Install the sleeve as shown in Figure 801.

 NOTE: Make sure the heat outlet holes are on the top of the
____ duct when the sleeve is installed.
 The pressure is low in the heat duct. Air leakage at the duct repair joint is permitted.
 (f)  Tighten the duct support clamps.
 S 358-003
 (2)  Repair a Long Section of the Heat Duct (Procedure 2):
 NOTE:____A long segment is greater than 12 inches (305 mm). A Short segment is 12 inches (305 mm) or less.
 (a)  
Remove the damaged heat duct.

 (b)  
Make a replacement heat duct.

 NOTE: Use the BMI composite material to repair a composite
____ heat duct. Use the aluminum material to repair an aluminum heat duct. The length of the replacement heat duct must be approximately the same length as the damaged heat duct.
 (c)  Drill the same number of the heat outlet holes in the replacement heat duct that are in the damaged heat duct.
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