Fellow Coupers, I found a crack in the left hand exhaust stack on my 66 Alon yesterday. I
recently had the RIGHT hand exhaust stack rebuilt by Dawley Aviation, because it had been cracked and rewelded about 10 times since the plane was new. Dawley did a great job rebuilding that stack and it seems to be holding up very well. (I understand from reading the service bulletins that the right hand stack on the Alons was a constant problem, and that the factory came out with a new design for that stack after several of them cracked in service.) I found the crack in the LEFT hand exhaust yesterday stack by using a mirror and a flashlight to look up behind the stack where it is bolted onto the cylinder exhaust port. This stack had one old crack welded on it on the opposite side of the pipe from where the new crack was found. The new crack was right at the edge of the factory pipe-to-flange weld. The crack had progressed approximately half way around the pipe. The cracked pipe was on the rear exhaust flange. The forward exhaust flange and pipe looked OK. (I wonder how long it would have stayed OK if the crack on the rear flange progressed all the way around the pipe!! Yikes!!) I'm just passing this info along in case anyone else might be interested in inspecting their Alon stacks for cracks. This new crack developed within the past 40 engine hours or so. Both I and my IA carefully inspected all of the exhaust system during the annual inspection about 40 engine hours ago, and the crack was not visible at that time. BTW, my engine has the rubber exhaust stack vibration dampner straps installed between the stack and the engine mount near the outlet end of the exhaust stack. Good Flying, Wayne DelRossi Alon N5618F Simpsonville SC
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