Educate me on exhaust flame tube inspection

[RogueOne]

-How long do they last?

-How do you inspect to see if they are functional?

-Cost to replace?

Thanks for the education.

[carusoam]

Flame tubes...  

are at the center of the muffler in direct contact with the super heated exhaust streams leaving the engine... they help complete the burning of leftover fuel components... and keep the hottest gasses away from the exhaust system walls as they cool adiabatically... (expansion of gas)

1) they last eons... normally.

2) susceptible to poor heat management, high EGTs...

3) When they devolve, they have a tendency to send the hotspots to other parts of the exhaust system...

4) The other parts of the exhaust system can fail at a high rate... breaking welds.

5) The Heat muff surrounds this part of the muffler...

6) inspection is usually done externally at annual... by disassembling the heat muff...

7) A few MSers have taken pictures using a dental camera... from the inside...

8) @Frozen Flying recently posted a great pic of a failing exhaust system weld...

9) Costs are typically replacing the muffler via OH using one of three aviation welding companies...

10) The higher limit on price is purchasing a PF exhaust system...

11) if you see mangled, bent, heat damaged, parts inside the muffler... these are probably signs of the flame tubes failing...

 

PP notes regarding flame tubes... things I learned around MS... not a mechanic.

Best regards,

-a-

 

 

[RogueOne]

What is involved in the disassembly of the heat muff?

You can visually SEE the flame tubes with the heat muff removed?

I would love to see photos.

[carusoam]

Cracks in the muffler can be seen by removing the heat muff...

Looking up the exhaust pipe is required to see the flame tubes...

The tubes are the center of the exhaust system.

it is hours of work, best done at annual when everything is exposed...

pics of the muff removed and a crack can be found in this thread...

There are several Mooney mufflers... which one are we thinking about?

Best regards,

-a-

[Guest]

The flame tubes will be inside the muffler, some are cone shaped, others are tubular.  Inserting a fibre borescope up the tailpipe and into the muffler will allow inspection.

Clarence

[RogueOne]

Just now, M20Doc said:

The flame tubes will be inside the muffler, some are cone shaped, others are tubular.  Inserting a fibre borescope up the tailpipe and into the muffler will allow inspection.

Clarence

Thanks Clarence.  I was curious if flame tubes can be visually inspected without removing the exhaust.  What is the normal life span of flame tubes in a 4 cylinder engine?

[Guest]

Just now, RogueOne said:

Thanks Clarence.  I was curious if flame tubes can be visually inspected without removing the exhaust.  What is the normal life span of flame tubes in a 4 cylinder engine?

No real need to remove the exhaust for flame tube inspection, as long as you can get a borescope up the tailpipe and into the muffler.  Life span is dependant on how hot they’ve been run and for how many hours, but a few thousand hours should be possible.

Clarence

[0TreeLemur]

9 hours ago, M20Doc said:

No real need to remove the exhaust for flame tube inspection, as long as you can get a borescope up the tailpipe and into the muffler.  Life span is dependant on how hot they’ve been run and for how many hours, but a few thousand hours should be possible.

Clarence

Borescope up the tailpipe...   Mooney colonoscopy? 

[N201MKTurbo]

If  you don't have a borescope, you can see them clearly if you remove the tail pipe. it takes 3 cotter pins and about 1/2 hour.

[RogueOne]

Thank you all.  Much appreciated.

[Andy95W]

1 hour ago, 0TreeLemur said:

Borescope up the tailpipe...   Mooney colonoscopy? 

Damn.  Fred beat me to it.

[Guest]

11 hours ago, 0TreeLemur said:

Borescope up the tailpipe...   Mooney colonoscopy? 

With the small stack on a Mooney, a Urologist may be better suited to the job.

Clarence

[Andy95W]

"It's not the size of your pen that matters, it's how you sign your name."

[cliffy]

Looking for cracks visually can be fun but the real way is to connect a shop vacuum in blowing mode to the tail pipe using a cut up inner tube and clamps to seal the connection and spray light soapy water on the muffler (after removing the heat shield or moving it around enough to see all sides) and on the ends also. Shows up leaks not visible just looking with the naked eye!

If you actually have to remove the muffler for some reason it really only takes about a half an hour to get it off and an hour to put it back on if the lower cowl is already off. . 

Always good to use new NO BLOW gaskets and new nuts on the two studs holding it on. I doubt that the ball joint hardware has ever been changed so it might be a good idea to order new springs and bolts and nuts and do it right. The springs collapse after 50 years and need to be renewed. 

[LucasC]

my mechanic at this years annual told me that the baffles are missing from my inside muffler? How does that happen? What will that do to performance? etc,  Said Im going to need a new muffler  

Thanks

[cliffy]

The exhaust flame comes down from the cylinders and goes into the muffler can through the "flame tubes".

If that is what he is calling "baffles"? The flame tubes do get eaten away after many hours of being red hot  They look like cones over 

over the ends of the tubes going into the muffler and they have large holes in them to allow the hot exhaust gases to disperse

into the muffler can and then go out the tail pipe. Sometimes they break up into little pieces and blow out the tail pipe 

without causing any issues (mine have) but sometimes they break into pieces too large to go out the tail pipe 

 and they block the outlet and you lose power because of the backed up exhaust gases. 

You may not need a "new" muffler. They can be taken apart and rewelded with new pieces and made to be as good as new by several different companies. You can see them with a "scope" up the tail pipe.

How many hours on the muffler? Has it been pressure checked for other cracks? You do that by blowing up the tail pipe with a shop vacuum (sealed with tape and part of an inner tube) and spraying the entire outside with something like soapy water looking for bubbles. This is after the outer shell is removed (basically 4 screws). Any leaks (bubbles) shows where the welder will need to replace or repair that area. This is NOT a job for your local muffler shop. It needs to go to a specialty shop for aircraft mufflers. They cut it open and repair/replace the tubes and then weld the entire assembly back together again.

I just did mine with a new tail pipe also for around $1600. It looks brand new, I've also used Dawley in the past for the service also. 

Edited November 16, 2019 by cliffy
added text

[carusoam]

4 hours ago, LucasC said:

my mechanic at this years annual told me that the baffles are missing from my inside muffler? How does that happen? What will that do to performance? etc,  Said Im going to need a new muffler  

Thanks

Lucas,

Cliffy covered it well...

There are many threads on this topic... mostly because exhaust systems have been known to be killers...

The issue is...

• They were designed to do one thing...
• When parts fail or disappear... they no longer work as designed...
• The flame tubes were there to control where the hottest flames are...
• Without them, other parts often erode...
• eroding mufflers fail by cracking or losing welds...
• cracks allow exhaust to flow into the heat system..
• exhaust in the heat system may not be detectable without a CO monitor...
• relying on a CO monitor to cover for a known flaw in the exhaust system is poor risk management...

Consider yourself fortunate... if you had a turbo... things can get more expensive when pressured... 

Lets say you muffler is worn...

Around here people look to either OH or replacement...

There are at least three muffler OH/Welding shops...

There is one preferred/expensive new muffler supplier...   PFS...

Got a CO monitor?

Many people go through your challenge around here each year...

use the search function to find what you are looking for...

Get to know your muffler while it is apart... 

Best regards,

-a-

[Shiny moose]

HF HD or lowes sell 3 ft inspection cameras, theY are great for flame tube visual inspections and other looking arounds, not great for looking at valve coloration but will work 

[LucasC]

Cliffy

Who did you use to repair the muffler?Mech told me its gonna be like 3k for a “new” system. Would much rather have it repaired. 

Thanks

[carusoam]

Seeing if @cliffy is around today...  ^^^^

In the mean-time... This may help get you closer... https://mooneyspace.com/search/?q=Exhaust Welder&updated_after=any&sortby=relevancy&search_and_or=and

Best regards,

-a-

[Guest]

While not a Mooney muffler, this shows typical damage to the flame tubes.

Clarence

[Bob_Belville]

CO is a silent killer, mufflers need to be repaired or replaced whenever they’re found to be failing. They will not heal themselves. Skimp somewhere else.

You’re unlikely to be as lucky as Dan Bass when you pass out...


Sent from my iPad using Tapatalk

[cliffy]

You might try this guy-

http://www.customaircraft.com/

He's an A&P that does excellent TIG welding, He has all the jigs needed. He specializes in custom experimental a/c systems but he can weld any certified exhaust system also just as I could IF I had the  equipment and skills. 

I sent in my complete system and it came back looking like new. As an A&P he doesn't have a repair station so your A&P will need to look it over and sign it off as "exhaust system repaired by welding". I did that as I'm also an A&P but don't have the requisite skills n TIG welding. He's been doing it for many years,

If I get by the airport tomorrow I'll take a picture of mine and post it. 

Dawley also does good work but they seem to be backed up and turn around time seems to be long. I used them the last time many years ago. They might be more expensive than CAP. 

Edited November 18, 2019 by cliffy

[kortopates]

55 minutes ago, cliffy said:

You might try this guy-

http://www.customaircraft.com/

He's an A&P that does excellent TIG welding, He has all the jigs needed. He specializes in custom experimental a/c systems but he can weld any certified exhaust system also just as I could IF I had the  equipment and skills. 

I sent in my complete system and it came back looking like new. As an A&P he doesn't have a repair station so your A&P will need to look it over and sign it off as "exhaust system repaired by welding". I did that as I'm also an A&P but don't have the requisite skills n TIG welding. He's been doing it for many years,

If I get by the airport tomorrow I'll take a picture of mine and post it. 

Dawley also does good work but they seem to be backed up and turn around time seems to be long. I used them the last time many years ago. They might be more expensive than CAP. 

^ +++10  Clinton of Custom Aircraft Parts is local to me and I have been using him for years. You can't beat the quality of his work anywhere and his prices are reasonable. The only drawback is he gave up his FAA Repair Station license status years ago and thus you won't get FAA paperwork back. We lost of a couple of local ones that were also doing experimental or other work when the FAA started a policy of telling shops serving more than certified aircraft customers (e.g. experimental or any other work like automotive electrical) that they had to physically separate the premises used between any other work and their FAA work. I don't know of any that could afford to do that and keep their FAA repair station status. 

But like Cliff said above, it just takes a willing A&P to sign it off; which generally also means an A&P not working at a repair station since their policies will preclude subletting to non-approved vendors.

Edited November 18, 2019 by kortopates

[cliffy]

Like I said, nothing hinky about any A&P welding any certified exhaust system ALL it takes is an A&P to inspect the work and certify it is aircraft quality and in an airworthy condition. Any A&P can do it.

I learned how to weld 4130 aircraft tubing in A&P school and I was pretty good at it back then but today? I wouldn't do it either but I would sign off the work of another A&P who could weld 4130 :-)