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Subject: Bell 206B2 Exhaust Stack Cracking Out
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MotorotorUser is Offline
JH Newbie
JH Newbie
Posts:3

04/09/2009 8:56 AM  

Does anyone have any experience with the exhaust stack cracking out in a bell 206 Jet Ranger?  This is an odd anomaly for me, here's a little background.  The hot section on the engine was just replaced and there's about 50 hrs on it since.  No problems with the exhaust stack for the 1st 40 hrs, then all of a sudden the left exhaust stack started cracking on the upper tip and down the top seam.  I looked at the engine mounts, cowling, tranny mounts, exhaust clamp and found all was in order.  I then replaced the exhaust stack and returned the machine to service with instructions to inspect after each fuel cycle....guess what,after 8hrs it was cracked out again on the same side (left) in the exact same place.  There has to be a vibration coming from somewhere, maybe the cowling....but it's not touching?  The company that sent the hot section suggested putting on another exhaust stack and trying it again, but it seems odd to me that 2 exhaust stacks cracked in the same place.  There are no vibrations asso with the engine and it makes good power with good t's and p's!  Any input would be greatly appriciated! 

JmanUser is Offline
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JH Newbie
Posts:1

04/11/2009 10:03 PM  
This was a common problem with the US Army OH-58 A models in the late 80s and early 90s, we never associated the cracking of the exhaust stacks with anything other that a material failure of the stack (other units may have experienced something else though). The A models were upgraded to C models or an A+ model with a different exhaust stack called an IR Suppressor we never had any cracking again, we did have chaffing damage were the IR Suppressor would rub against the engine cowling if the modification was not done correctly.
I'm still flying a civilian Bell 206 (not the same aircraft everyday ,we have a large fleet), with the old exhaust stacks and have not seen one crack in a very long time.
An engine vibe check is a good ideal just to rule out any abnormal engine vibration, then I would check with the manufacture of the exhaust stacks, I'm curious if the part number would be the same as the old OH-58A model stacks.
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