EXHAUST DUCT MUFFLER - REMOVAL/INSTALLATION
1. General
A.  The exhaust duct muffler is an integral part of the aft fairing assembly which consists of the aft fairing, the exhaust duct heat shield, and the exhaust duct muffler. If the muffler is to be removed, the aft fairing assembly must be removed from the airplane.
2.  Remove Exhaust Duct Muffler (Fig. 401)
A.  Remove the aft fairing (AMM 49-81-31/401).
B.  AIRPLANES WITHOUT THE DUCT ALIGNMENT ASSEMBLY; Remove the bolts and washers that attach the exhaust duct muffler to the heat shield.
C.  Remove the exhaust duct muffler from the heat shield.
D.  Remove the fire detection element from the forward end of the exhaust duct muffler.
E.  Keep the fire detection element for the installation of the exhaust duct muffler.
3.  Install Exhaust Duct Muffler (Fig. 401)
A.  Install the fire detection element on the forward end of the exhaust duct muffler.
B.  AIRPLANES WITHOUT THE DUCT ALIGNMENT ASSEMBLY;
Install the exhaust duct muffler on the heat shield with the bolts and washers.

C.  AIRPLANES WITH THE DUCT ALIGNMENT ASSEMBLY;
Make sure the brackets on the exhaust duct muffler are the one piece type.

D.  AIRPLANES WITH THE DUCT ALIGNMENT ASSEMBLY;
Install the exhaust duct muffler on the heat shield without the bolts.

NOTE: The bolts are installed during the aft fairing assembly installation.
E.  Install the aft fairing assembly (AMM 49-81-31/401).
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Oct 20/93  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  49-81-11 Page 401 

C80513 C82153
Exhaust Duct Muffler Installation  503 
49-81-11 Page 402  Figure 401 (Sheet 1) BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Oct 20/93 

510  Exhaust Duct Muffler Installation 
Oct 20/93  Figure 401 (Sheet 2) BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  49-81-11 Page 403 

EXHAUST DUCT MUFFLER – INSPECTION/CHECK
1.  Exhaust Duct Muffler Inspection
A.  Remove the exhaust duct muffler (AMM 49-81-11/401).
B.  Do a visual inspection of the exhaust duct muffler:
(1)  
Examine the exhaust duct muffler for wrinkles.

(a)  Wrinkles lower than 1/4 inch and found along a smooth contour surface are permitted.

(2)  
Examine the exhaust duct muffler for cracks.

(a)  
A crack shorter than 2 inches is permitted on the exhaust duct muffler (shorter than 3 inches is permitted on the tube and liner assemblies).

(b)  
The minimum spacing between the cracks must be more than two times the length of the crack.

(c)  
The total length of all the cracks for one part must be less than 10 inches.

(d)  
Cracks not longer than 1/2 inch are permitted from the rivet hole.

(e)  
Cracks on adjacent rivet holes, on the edge of a part or on the bracket assemblies are not permitted.

(3)  
Examine the external surfaces of the exhaust duct muffler for missing rivets.

(a)  
Make sure there are at least three rivets installed between the two missing rivets for each row.

(b)  
Make sure all rivets are installed on the bracket assemblies.

(4)  
Examine the internal surfaces of the exhaust duct muffler for missing rivets and holes on the felt metal liner.

(a)  
One missing rivet is permitted for each row.

(b)  
APUs WITHOUT THE FULL-LENGTH FELT METAL LINER; Holes less than 0.20 inch in diameter are permitted on the felt metal liner.

NOTE:  Holes more than 0.20 inch in diameter can be repaired (OHM 49-13-01) if the adjacent surface material is not brittle (oxidized). If the adjacent surface material is oxidized and the holes are less than 0.50 inch in diameter, you must inspect the felt liner every 100 APU hours. You must replace the felt metal liner if the holes are more than 0.50 inch in diameter.

(c)  
APUs WITH THE FULL-LENGTH FELT METAL LINER; Holes less than 0.020 inch in diameter are permitted on the felt metal liner.

NOTE:  You must repair the felt metal liner with a welded patch or replace the felt metal liner if the holes are more than 0.20 inch in diameter.
(5)  If the visual inspection is not in the limits, replace the exhaust duct muffler (AMM 49-81-11/401).
C.  Install the exhaust duct muffler (AMM 49-81-11/401).
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May 01/99  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  49-81-11 Page 601 
　
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