36-11-01
 ALL  ú ú 01 Page 802 ú Feb 10/93
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 S 288-029
 (2)  
The surface roughness of the repaired area must not be more than 40 microinches (arithmetical average).

 S 228-022

 (3)  
The slope of the repaired area must not be more than 10%.

 S 228-023

 (4)  
The inner and the outer radius of the repaired area must not be more than 0.12 inch.

 S 228-024

 (5)  
The damage must not be found less than 0.25 inch from a primary welded joint.

 S 228-020

 (6)  
You must replace the duct if it cannot be repaired to these conditions.

 TASK 36-11-01-308-013
 5. Temporary Repair of Cracked Ducts (Fig. 801)
_________________________________
 A. General
 (1)  You can temporarily repair ducts that have a crack along the longitudinal axis.
 NOTE: This repair procedure is only permitted for ducts that
____ have a crack along the longitudinal axis. Replace ducts that have a crack along the circumference or have multiple cracks.
 (2)  
The repair is temporary and you must replace the duct as soon as possible.

 (3)  
A duct with a longitudinal crack that is less than three inches from the flange or pullout; a circumferential crack; or multiple cracks cannot be repaired by this procedure. It must be repaired in accordance to Overhaul Manual or be replaced.

 B.
Consumable Materials

 (1)  
Silicone rubber sheet - BMS 1-57GR50A - 0.10 to 0.15 inch thick

 (2)  
Stainless steel sheet - 0.010 inch thick

 (3)  
Adjustable stainless steel clamps - BACC10B

 C.
Repair the duct with the crack.

 S 328-018
 (1)  Stopdrill the cracks, size of drilled hole to be 3/16-1/4 inch diameter.
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 36-11-01
 ALL  ú ú 01 Page 803 ú Oct 10/95
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A
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MAINTENANCE MANUAL

 S 358-015
 (2)  Put a silicone rubber sheet on the crack and extend it three inches beyond the ends of the crack to ensure that there is sufficient seal and support.
 NOTE: The edge of the crack must not be less than three inches
____ from the flange and not interfere with the flange coupling when the duct is installed on the airplane.
 S 358-016
 (3)  
Put the stainless steel sheet on the rubber sheet.

 S 358-017

 (4)  
Put the clamps on the duct every 1 to 1 1/2 inches and tighten the clamps.

 TASK 36-11-01-308-015
 6. Duct Flange Repair
__________________
 A. Equipment
 (1)  
Flange Reforming Tool, Adams Flange Spider
 Adams-Bird, Inc.
 5296 Pebbletree Way
 San Jose, CA 95111

 U.
 S. A.

 B. References
 (1)  AMM 36-11-01/401, Pneumatic Manifold
 C. Procedure
 S 018-012
 (1)  
Get access to the duct flange that you will repair.

 S 328-013

 (2)  
Use the flange reforming tool and repair the duct flange.

 S 028-014

 (3)  
If you cannot repair the duct flange while the duct flange is installed, remove the duct to get access to the damaged flange (AMM 36-11-01/401).

 (4)  
Repair the duct flange with the flange reforming tool.

 (5)  
Install the duct (AMM 36-11-01/401).

 S 358-019
 S 428-016
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