Muffler AD

G

gregbatt

New member
I have a 7KCAB that has a yearly AD that applies to the mufflers. I believe the AD specifies that the mufflers are to be removed and the inside baffles are to be examined. I am not trying to short cut the AD, but I am curious if during preflights or when the cowling is removed for oil changes if there is some way to take at look at the mufflers for any wear related to the AD. Additionally, are there any engine indications which might indicate a potential muffler problem? Thanks for any good tips.

GREG B
 
The muffler inspection is to check for three things. The first being for the possibility of a perforation in the muffler wall allowing for the introduction of CO into the cabin heat system, and the second to check for the integrity of the internal tube down the center of the muffler. The tube has drilled holes in it. The tube when it gets old will distort and crack. Should it break apart the pieces could restrict the flow of exhaust gases from the muffler. Lastly is a check of the integrity of the clamps securing the muffler to the exhaust. The exhaust pipe will rot out in the curve outside edge and will develop cracks in the holes where the clamp alignment dowels secure the muffler to the exhaust pipe.
Hope this helps.
 
Here's the AD's


AD #80-21-06 and CF90-03R280-21-06 BELLANCA (CHAMPION): Amendment 39-3939. Applies to Bellanca (Champion) Models 7GC, 7GCB, 7HC, 7KC, 7GCA, 7GCBA, 7ECA (Serial Numbers prior to 985-74), 7GCAA (Serial Numbers prior to 280-74), 7GCBC (Serial Numbers prior to 604-74), 7KCAB (Serial Numbers prior to 405-74), and 8KCAB (Serial Numbers prior to 120-74).

Compliance is required within the next 25 hours time in service, or 60 days after the effective date of this AD, whichever occurs first, and thereafter at intervals not to exceed 100 hours time in service, or 12 months from the last inspection, whichever occurs first. To prevent a degradation of the induction system icing protection or partial engine power loss, accomplish the following:

(1) Visually inspect the baffle installation within the muffler core and body assemblies, Bellanca (Champion) P/Ns 3-1079 or 3-1493, for cracking or deterioration, with the mufflers removed from the aircraft. Replace any muffler where baffle cracking or deterioration is evident, with an airworthy muffler core and body assembly of the same or other FAA approved part number.

(2) If an airplane is at an unsuitable base when compliance with this AD is required, the airplane may be issued a special flight permit in accordance with FAR 21.197 and 21.199 for the purpose of flying to a base where the required inspection may be performed.

(3) Equivalent methods of complying with this AD, including the installation of different exhaust systems, must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Great Lakes Region.

This amendment becomes effective October 16, 1980.



Cheers,

Simon.
 
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