Exhaust came apart in mid-air

jd21476

jd21476

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jd21476
I was departing KPBR (Paso Robles) after a nice lunch and heading for KREI (Redlands). At about 5500’ and midway between Paso Robles and San Luis Obispo I started to hear a very loud racket from my engine and it smelled like something burning and it was back firing.

I didnt have any smoke in the cockpit and the engine was running but not very well. I kept climbing but turned back to KPBR because it was directly behind me and did not have any mountains in-between.

I came straight in and taxiied off the runway. Climbed out expecting to see oil everywhere but there was nothing.


When I opened the cowl I found my exhaust had separated.

Good news is my engine was fine and I was on the ground in one piece. Bad news is Im not at my hone airport so a rental car is in my future
 

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Glad you are safe! Did you shut down the engine or keep it running on your way back in?
 
That could have been pretty ugly. I've seen exhaust leaks cause damage to engine mounts and other things because of the hot exhaust hitting them.
 
Years ago when wearing my (then new) Lightspeed 25K headphones, I kept hearing this clanking noise. When I'd try removing my headset to get a better listen, I couldn't hear it. Upon landing we found that one of the welds on the exhaust had broken and the piece of pipe was tangling by this mounting hardware.
 
That didn't just happen all at once. These things crack, and inspections are supposed to find the cracks. Before they fall apart.
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Gotta notice the little things.

On my bird I once noticed a small streak of soot right behind the joint where the cowling meets the fuselage. "Strange", I thought as I wiped it away for the first time. Next preflight and the streak was back. Time to dig into it.

Upon further examination, and with the thought that the soot was exhaust as it had those characteristics, I found that my #1 EGT probe clamp was loose and exhaust gases were leaking from the small hole where he probe enters the exhaust stack. One could draw a straight line from the leak to the soot stain.

Could have been much worse.
 
I guess it could have been much worse. The piece had fallen down into the cowling and with it sitting down in there it could have easily jammed in the landing gear as I lowered it. All in all I was lucky. The mechanic at the field already ordered a new part and it should be in tomorrow, he said he can probably have it back to me tomorrow late afternoon but I rented a car and drove home anyway. I figured with UPS the way it has been it could be two days so I'll just go back on Thursday and retrieve it...hopefully. It was a 5.5 hour drive home but its only time, right!!
 
Your landing gear retracts into the engine compartment?
 
jd21476 said:
Yes, on Comanche’s it comes right up under the engine
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Wow. Doesn't that get messy? I just saw a youtube video of someone's retract test. The Navion nose gear rises up in the same location but it's got a box around it to isolate it from the heat and grease of the engine compartment. Probably because the original Navion cowl brought the cooling air in below the prop and then up through the engine and you wouldn't want it running out the gear openings. With a downdraft arrangement, that's not a problem.
 
I have never actually looked inside when the gear was retracted and Ive only seen it in the down position. During my next annual I will try to get out to the airport when my mechanic does the gear swing and check it out. Ive never noticed it being dirty or greasy and I can only assume it works fine as the design has been like this for over 60 years.
 
WDD said:
1) JB Weld it back and fly home
2) Put a Harley sticker on your door and fly home
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Can we imagine if HD made airplanes? Loud STC exhausts. Ape hanger control yokes. Metal flake paint jobs. IO-720 engines and 95 kt cruise speeds. Meanwhile I'm over there handpropping my Triumph airplane, even though it has an electrical system and I confirmed that the **** battery is charged and the ****** starter is connected and the ****** alternator is charging and I-don't-have-a-clue-what's-wrong-with-this-thing-but-I-hate-Lucas-electrics-hey-gimme-a-push-will-ya?

But seriously glad you're okay and that the damage is minor!
 
Harley made planes. Chrome wire wheels and chrome exhaust. Pilots would have to wear all black leather jackets and dew rags. No one would actually fly and go anywhere. You’d just hang out next to the plane with other Harley plane owners.
 
Here's an indication of what an OEM thinks of exhaust system importance:

upload_2021-3-17_12-53-9.png

Cracked or broken exhaust systems can let carbon monoxide into the cabin, incapacitating the occupants. They can cause engine compartment fires. I long ago lost count of the cracks I found in exhaust risers, often right next to the cylinder flange, and in mufflers and other components used for cabin heat. I once found two out of the four risers cracked 3/4 of the way around right next to the flange welds, on an airplane that had just come out of an annual (by some other shop). That whole side of the exhaust was about ready to fall down and send flames everywhere. It got so that the exhaust system was the first thing I started inspecting right after I got the oil draining and the compressions done. Cracks mean ordering replacements, and you want to know ASAP if you need those things. Never had a lot of luck in getting the old stuff welded, either. That metal suffers a lot and is often just too far gone to expect a weld to last long on a high-time part.
 
Just an FYI on how Harley got a reputation for leaking oil. I can speak from experience owning a 1943 Harley. Back in the day Harley used a triple row chain from the engine to the transmission; I. E. Primary chain. The clutch was a dry clutch and the return oil pump would spray oil on the chain to keep it lubricated.The oil puddles up in the primary cover and runs out a drain in the primary cover. When on the kickstand the bike leans causing more pooled oil to run out. Indian of the day had a wet clutch and the primary was sealed and oil filled. My ‘43 engine is oil tight, it is just the primary oil that drips. Later years the primary was sealed and the oil recirculated but was prone to clogging from clutch debris. Belt primary’s eliminated the problem completely.
 
jd21476 said:
I was departing KPBR (Paso Robles) after a nice lunch and heading for KREI (Redlands). At about 5500’ and midway between Paso Robles and San Luis Obispo I started to hear a very loud racket from my engine and it smelled like something burning and it was back firing.

I didnt have any smoke in the cockpit and the engine was running but not very well. I kept climbing but turned back to KPBR because it was directly behind me and did not have any mountains in-between.

I came straight in and taxiied off the runway. Climbed out expecting to see oil everywhere but there was nothing.


When I opened the cowl I found my exhaust had separated.

Good news is my engine was fine and I was on the ground in one piece. Bad news is Im not at my hone airport so a rental car is in my future
Click to expand...


I had a similar event more than 20 years ago. I was flying around looking at the scenery around Lake Nacimiento - when all of a sudden something smelled hot.There was no change in engine noise that I noticed.
I wasted no time in flying to Paso Robles and landing. Examination revealed that my left exhaust collector had blown out (hole about the size of a quarter) on the side near the cowling. The smell had come from
scorched paint. Other than that, no damage. There was, of course the expected expense of replacing the exhaust collector. I bought a can of matching white paint and took the lower cowling to an auto body shop
for touch up (they did a fine job, BTW).

My daughter was with me on that flight. Some people visiting the airport noticed me looking in the engine compartment and asked what was wrong. When I told them the story, including being stuck there for the
time being, they offered to give daughter and self a ride home (and did so)!

Dave
 
Could someone share pics of what they saw? As I are they blatantly obvious with naked untrained eye? Or what is it to look for?
 
Huckster79 said:
Could someone share pics of what they saw? As I are they blatantly obvious with naked untrained eye? Or what is it to look for?
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You have to look closely. Like this:

proxy-image


That's from this lesson here: https://www.boldmethod.com/learn-to...oxide-poisoning-in-cold-winter-air-this-year/

In Canada we have an AD that applies to all aircraft that use exhaust heat for cabin heat. The area used for heat must be opened up (taking off the heat shroud) and inspected for exhaust stains, soot, cracks, pinholes, whatever. If there's any suspicion, you're supposed to put a little pressure on the exhaust pipe (vacuum cleaner outlet air is specified; make sure the vac is clean and won't blow dust into your engine. At least one exhaust valve will be open) and the area get sprayed with soap and water. 1/3 dish soap and 2/3 water works well. Mix it too weak and it won't bubble. Too much pressure will blow the liquid away and it won't bubble. Done right, It will show leaks not visible to your magnifier. I used to spray the whole exhaust system and often found unexpected cracks and leaks elsewhere.

Rinse if off well when done. Don't leave it soapy. Soap can be corrosive. The sparkplugs also have to be installed for this or you'll just lose the air.
 
charheep said:
If Harley made planes, there would be no changes in the amount of oil leaks
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That stereotype died in the 80s. I’ve had my Harley for five years (been to half the states on it) and my buddy owned it for eight years before that. It’s never had an oil leak. I don’t know anyone with a Harley who’s had a leak. Their bikes are wanting in the tech department, not gonna lie, but they’re oil-tight.
 
Sometimes they may be hidden depending on the plane and routing of the exhaust. I suspected a problem with mine (white exhaust residue on the outside of the plane where one wouldn't expect it and inside the engine compartment and a small reduction of power in a climb. I couldn't see it and neither could the MX shop. Persisted next flight - I did a thorough feel of the exhaust pipe after it cooled and found a small hole, out of sight, on the back side of the exhaust before the turbocharger. Confirmed it with a dental mirror. When we got it out, we discovered the crack was along a weld line in the exhaust just before the turbocharger.
 
WDD said:
Harley made planes. Chrome wire wheels and chrome exhaust. Pilots would have to wear all black leather jackets and dew rags. No one would actually fly and go anywhere. You’d just hang out next to the plane with other Harley plane owners.
Click to expand...
And they would be in the plane revving the throttle very few seconds,
 
flyingron said:
Years ago when wearing my (then new) Lightspeed 25K headphones, I kept hearing this clanking noise. When I'd try removing my headset to get a better listen, I couldn't hear it. Upon landing we found that one of the welds on the exhaust had broken and the piece of pipe was tangling by this mounting hardware.
Click to expand...

That's interesting. Some people say they want to stay away from ANR headsets to hear the engine, and I'm not saying they are wrong, but I had a very similar incident in my plane. I had the exhaust break and with every compression it made a kind of hissing sound. When I took my ANR's off, I couldn't hear it at all. It was just mixed in with all the other noise. Put them back on, I could hear it clearly.
 
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