I took the day off Friday to do some pre-Oshkosh maintenance. I did a short flight to warm up the oil, then changed the oil and filter. I changed the upper spark plugs (automotive plugs fired by the LightSpeed electronic ignition), as other users reported degraded ignition performance if the plugs had more than 200 hours on them. Unlike aviation spark plugs, these automotive ones are very cheap (I got four new ones, plus one spare for less than $20), so changing them every 200 hours isn’t a financial hardship.

Then I did a full inspection of all the stuff ahead of the firewall.

The last thing I checked was the exhaust system, and I was very dismayed to find that the #3 exhaust pipe was cracked at the edge of the weld at the flange. Drat!

Those who have been keeping score will know that his is the third exhaust system crack in 250 hours of flying. Two years ago the #3 exhaust pipe failedas we were over top of North Bay airport, on our way back from Oshkosh. I sent the pipe back to Vetterman exhaust for repair. Last year, in early July, I discovered a significant crack at one of the Y joints further down on the exhaust. Now the #3 pipe has cracked again.

I removed the exhaust system, and pondered how to get it repaired. I didn’t have time to send it back to Vetterman Exhaust in South Dakota, and get it back here in time to make Oshkosh. I talked to one of the other pilots who was at the airport, and he suggested I talk to Peter Wright at Wright’s Welding in North Gower. Peter flies a nice Murphy Rebel that he built. I stopped by there on the way home, and Peter said that he could weld it, but given that I have had several previous cracks on this exhaust he doubted that it would be a permanent repair. But, it should get me to Oshkosh and back. I waited while the pipe was welded, then went home.

I’m not sure why my aircraft is having so many exhaust system issues. Maybe there is something strange about my exhaust that is making it more likely to crack. Or, maybe my engine vibrates more than most, or maybe there is some deficiency about the way I have the exhaust mounted. Or ?? I’ll talk to some experienced folks at Oshkosh to see if anyone has any useful ideas.

Saturday morning I reinstalled the exhaust system, then did a test flight. The engine was definitely running smoother at idle, probably due to the new spark plugs.