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Broken Exhaust on the way back from Oshkosh

jj13

jj13

Active Member
The exhaust pipe connection to the heat muff separated on takeoff. Causing elevated c02 and burning the inside of the cowling. The c02 level was detected by a Home Depot c02 detector which only goes to 999ppm so I don't know what the actual level was. I am very glad I had that c02 detector in the plane. I was able to get back to the airport quickly with minimal damage to the cowling. I did feel light headed, but I'm not sure if that was just the stress of the moment seeing the 999s on the screen. I believe exhaust breaks a rare but I can now see how they can be very impactful if unable to land quickly.
 

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Potential cowl damage... for sure.

I'm not sure how this would cause really high CO in the cockpit... unless the cabin heat was on... or you have some big firewall leaks.
Maybe the CO was coming in the NACA air vents by leaking around the cowl to firewall joint?
 
The DOM at the shop where I used to work had what I considered to be pretty low standards but there was one thing that he had zero tolerance for, and that was potential problems with exhaust systems. It was always, “take it off and send it in for repairs”. I never saw that level of caution applied to other things.

A 1300 degree blow torch around fuel and copious amounts of O2, what could possibly go wrong…;)

Oh yeah, carbon monoxide the “ silent killer “, there is that too.
 
rmarshall234 said:
The DOM at the shop where I used to work had what I considered to be pretty low standards but there was one thing that he had zero tolerance for, and that was potential problems with exhaust systems. It was always, “take it off and send it in for repairs”. I never saw that level of caution applied to other things.

A 1300 degree blow torch around fuel and copious amounts of O2, what could possibly go wrong…;)

Oh yeah, carbon monoxide the “ silent killer “, there is that too.
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Yes it is going to be removed and sent back to Vetterman for repair.
 
Jpm757 said:
Make sure your new exhaust is properly braced to the engine, NOT the airframe.
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That does makes sense. I followed the instructions from Vetterman which has it supported by both the engine and the engine mount. I'm not sure how I could provide adequate support just by the engine?
 
I much prefer the std shrouds to trouble prone mufflers, not as much heat but zero chance of failure like this.
 
Glad the situation turned out well

This is good evidence of why a detailed inspection under the cowl at every oil change is a really good idea.

It may not have been caught but this type of failure doesn’t usually go from nothing visible to total failure in only a few hrs.
 
rvbuilder2002 said:
Glad the situation turned out well

This is good evidence of why a detailed inspection under the cowl at every oil change is a really good idea.

It may not have been caught but this type of failure doesn’t usually go from nothing visible to total failure in only a few hrs.
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Great advice! I do spend a few hours after each oil change checking firewall forward items. This failure would have been hard to see without purposely looking for this type of failure. It will now be on the oil change check list.

This is my fist inflight failure in the 9 years that I've been flying this plane. I've found plenty of potential failures in doing my oil change and yearly inspections. This is such a critical failure area I really should have been treating it as such. But for whatever reason I didn't think breakage of the exhaust piping system was something that happened that would not be obvious.
 
Walt said:
I much prefer the std shrouds to trouble prone mufflers, not as much heat but zero chance of failure like this.
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Thanks Walt. I agree. I would feel better eliminating this potential failure and just dressing warmer.
 
At one of the shops I worked at we used a shop vac to pressurize the exhaust system and then spray it down with soapy water. Worked well to identify leaks.

As for the suggestion of going lean of peak with a known exhaust leak to minimize CO exposure.

That’s a good suggestion and could have come in handy recently. I was getting dual instruction in a Great Lakes biplane and we cracked a cylinder on the last flight. My eyes started to sting and the smell of incomplete combustion/unburned hydrocarbons was really strong. I was pretty sure it was an exhaust problem until the cracked cylinder was discovered. The 15 minute flight returning to base at lean of peak would have been a good option to know of.
 
John, Is that a fracture on the top of the heat muff??

Maybe from a backfire during a start-up.....
fracture.JPG
 
jj13 said:
Thanks Walt. I agree. I would feel better eliminating this potential failure and just dressing warmer.
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Is that a muffler and a heat muff? My heat muff wraps around the existing exhaust pipe.
This failure could not happen on my exhaust.
 
jj13 said:
Great advice! I do spend a few hours after each oil change checking firewall forward items. This failure would have been hard to see without purposely looking for this type of failure. It will now be on the oil change check list.

.
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Good plan

A serious look at all weld points on the exhaust is my #1 inspection priority any time the cowl is off.
 
Bonanzatom said:
If you find yourself in the air with a CO leak, go to lean of peak operation and the CO emissions will go to zero…
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Sorry, but that is incorrect and dangerous advice. Yes, at peak EGT, both O2 and unburned hydrocarbons go to 0, Go leaner and hydrocarbons are still gone, but O2 comes back. No way to get rid of CO, as long as a fuel air mix is combusting, as CO is a natural byproduct of burning a gasoline and air mixture. This applies to pretty much all carbon based fuels.
 
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Is the "buick ball" frozen?

The "buick ball" joint needs lube/antisieze each decowl event.

The joints must move.

Walt said:
I much prefer the std shrouds to trouble prone mufflers, not as much heat but zero chance of failure like this.
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Huge agreement on this . . welding a pipe into a disc like that will fail in the exhaust. Bending of the pipe flexes that disc and is just poor design. Having a pipe that goes through as a continuous tube is much less prone to fatigue failure.

How many other builders use this muff? Who makes it?
 
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I use Mouse Milk. I initially thought the name was a joke, but it’s available and recommended for lubing that joint every time the cowl is off.
 
jjconstant said:
I use Mouse Milk. I initially thought the name was a joke, but it’s available and recommended for lubing that joint every time the cowl is off.
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Mouse Milk works. It isn’t a lubricant however, not trying to be picky, but it is a solvent and gets burned off almost immediately.
I believe it works by dissolving or loosening the carbon, or other exhaust “gunk” that builds up in the joint.

It is an excellent suggestion.
 
Did you hear a difference in the engine noise or was it just the CO detector that alerted you?
 
gasman said:
John, Is that a fracture on the top of the heat muff??

Maybe from a backfire during a start-up.....
View attachment 45950
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It sure looks like it. I drove to the airport this morning just to verify whether I should throw in the towel if I really missed this one. Thankfully I didn't. I've attached a picture from a different angle. I looks like a drip of pro-seal.
 

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rv6n6r said:
Did you hear a difference in the engine noise or was it just the CO detector that alerted you?
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I did not hear any difference in sound. Probably because the beeping of the c02 detector was fairly loud and distracting. I'm sure there was a difference. The engine sound should have gotten louder.
 
What happened next

I was able to fly the plane home the next day (LZU) (yesterday). This is the best part of the trip. Once I got back to the ramp and determined what had happened I wanted to find an A&P. There was a guy and his wife walking their dog. This airport KSER(Seymour) does not have any security fence around it. So it's just an open field to the street. There was nobody around, so I walked up the this guy (Robin is his name) and asked if he knew if an A&P worked at this airport. Turns out he a pilot and gave me the name and number for the A&P. He then offered to drive me to a place to get lunch. While eating lunch the A&P call back. He felt he could not repair the exhaust. At that point Robin said he could do it. Well I was not so sure about that. I told him I think I will just remove that section of the exhaust, sending it back for repair. I would hitch a ride home with a another pilot friend who was in Louisville visiting his sister on the way back from Oshkosh. I would leave all my stuff in my plane and my friend would leave all his camping stuff at his sisters. Then as the day went on, I started thinking more about it, I said to myself why not have Robin do it. So I called him, he said he'll be there in 10 minutes with tools. I took over an hour to remove the front muff connection from the exhaust pipe, but we finally got it. We put the parts in his truck, then drove to his house for the repair. I thought well what do I have to lose. If it doesn't look good back to shipping it out. Well he did a great job! We drove back to the airport and install it. I did a runup and then a few laps around the pattern. It was getting dark and even though a felt good about the repair I felt a morning Day Light flight would be more prudent. The next morning I was landing at LZU feeling really good because of the kindness given by Robin and his wife. I had a great time at Oshkosh and this event made it even better!
 

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Big thank you for all the good advice and what I'm doing

First I'm going to do a better job inspecting the exhaust and welds.

I going to take Walt's advice, removing the mufflers and installing std shrouds.

I'll bring a heated blanket when I fly up to NY.

Thanks again all for your help.
 
BillL said:
The "buick ball" joint needs lube/antisieze each decowl event.

The joints must move.



Huge agreement on this . . welding a pipe into a disc like that will fail in the exhaust. Bending of the pipe flexes that disc and is just poor design. Having a pipe that goes through as a continuous tube is much less prone to fatigue failure.

How many other builders use this muff? Who makes it?
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I bought the exhaust system from Vetterman Exhaust, Inc
 
+1 for LOP to eliminate carbon monoxide

Carbon monoxide or CO is a product of incomplete combustion. One cause of incomplete combustion is insufficient oxygen to burn all of the hydrocarbons present in a system. By going Lean of Peak, an excess of oxygen is available to burn hydrocarbons resulting in products of combustion including carbon dioxide or CO2. Any CO produced during the LOP combustion process is oxidized to CO2.
 
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