Ovation : power down, EGTs up ... ?

[N177MC]

So a client started complaining about his Ovation feeling lethargic and not performing as well as it usually did for the past 2300H he's flown it.

There were some EGT excursions, some slight vibrations but no other symptoms.

Compression check and  borescope showed the N3 cylinder was starting to burn a valve, still "airworthy" but definitely starting to go.

Checked mag timing, valve lift , poked around inside engine with borescope, nada.

So I started researching the subject (loss of full HP) and came up with a comprehensive checklist of items to check, rather than "second guessing" :

Item # 1, check for induction (air) blocage, removed air filter and ducting, ran borescope in induction pipes, all clear.

Item# 2, check  exhaust for obstructions, removed tail-pipes ran the borescope up the pipes .....    wait for it ......    :

 

 

 

 

[carusoam]

That sure can restrict some flow…

Any chance we can see some JPI data from that?

That must have an interesting signature in the data somewhere…

Thanks for sharing the pics…

Best regards,

-a-

Edited October 17, 2022 by carusoam

[Fly Boomer]

3 hours ago, N177MC said:

Item# 2, check  exhaust for obstructions, removed tail-pipes ran the borescope up the pipes .....    wait for it .

Great pic, but I don’t know what I’m looking at.  Is it a rag?  What’s keeping it in there?

[Guest]

1 hour ago, Fly Boomer said:

Great pic, but I don’t know what I’m looking at.  Is it a rag?  What’s keeping it in there?

Those are the internal flame tubes in the muffler.

[Shadrach]

I’ve never seen anything like that in a healthy running engine.I’ve seen flame tubes deteriorate and break off, but never deform like that.  For those of you that are pros, is this something you see occasionally? What’s the root cause?

[haymak3r]

Did something get really hot? Would love to see the engine monitor data as well. 

[Ragsf15e]

10 hours ago, N177MC said:

So a client started complaining about his Ovation feeling lethargic and not performing as well as it usually did for the past 2300H he's flown it.

There were some EGT excursions, some slight vibrations but no other symptoms.

Compression check and  borescope showed the N3 cylinder was starting to burn a valve, still "airworthy" but definitely starting to go.

Checked mag timing, valve lift , poked around inside engine with borescope, nada.

So I started researching the subject (loss of full HP) and came up with a comprehensive checklist of items to check, rather than "second guessing" :

Item # 1, check for induction (air) blocage, removed air filter and ducting, ran borescope in induction pipes, all clear.

Item# 2, check  exhaust for obstructions, removed tail-pipes ran the borescope up the pipes .....    wait for it ......    :

 

 

 

 

Glad you believed him and were thorough! That seems bad!

[Fly Boomer]

8 hours ago, M20Doc said:

Those are the internal flame tubes in the muffler.

Wow!  I've stuck an endoscope up into a muffler, but never seen anything like that.  Not good.

[Will.iam]

On 10/17/2022 at 6:01 AM, M20Doc said:

Those are the internal flame tubes in the muffler.

Ok what are internal flame tubes? What should they normally look like and where are they normally suppose to be?

[Greg Ellis]

3 hours ago, Will.iam said:

Ok what are internal flame tubes? What should they normally look like and where are they normally suppose to be?

The first photo are broken flame tubes, bad....  The second photo are repaired flame tubes, good....

[kortopates]

flame tubes/flame arrester damage very possibly caused by afterfire explosion in the exhaust. Multiple ways to accomplish this including from over priming.

[Will.iam]

So is this only a Normally Aspirated engine thing or do turbo charged engine have them too?

[Fly Boomer]

5 hours ago, Will.iam said:

So is this only a Normally Aspirated engine thing or do turbo charged engine have them too?

I can’t think of a turbo with a muffler.  Maybe someone here can.

[A64Pilot]

On 10/17/2022 at 7:16 AM, Shadrach said:

I’ve never seen anything like that in a healthy running engine.I’ve seen flame tubes deteriorate and break off, but never deform like that.  For those of you that are pros, is this something you see occasionally? What’s the root cause?

Normal wear and tear, it’s from a couple things, muffler too close to the engine getting too much heat (think about where it is on a car) crappy build, (light weight materials). Maule’s are worse than any other aircraft I’ve seen so you get used to overhauling a Maule muffler. Usually could maybe twice then it was time for a new one, Maule sells the flame tubes and muffler end caps, so remove the cap replace tubes and cap, pretty simple. Don’t know about a Mooney muff. 

However my experience has been the broken tubes go out the exhaust, and if you continue to fly with broken tubes the exterior walls of the muffler go next, with often bad consequences, CO, fire etc. 

[Guest]

Exhaust parts live a brutal life, at 1400-1500 EGT the pipes glow red.  Install a GoPro in your cowl and go flying, watch the colour change as you lean the mixture.  You’ll have a new respect for how tough your exhaust system really is.  

[GeeBee]

A lot of the high wing Pipers with Lycoming engines have a 50 hour AD requirement to inspect the flame tubes on stock mufflers. That is why most people go to STC mufflers for these airplanes.

[SARNorm]

Nice photos Greg. Thanks.

[carusoam]

20 hours ago, Will.iam said:

So is this only a Normally Aspirated engine thing or do turbo charged engine have them too?

Expect that flame tubes are NA only… as the TC’d birds get no added restriction to the exhaust systems before the TC…  the need for flame tubes goes away after combustion is completed…

At annual the health of the flame tubes is often checked with a video camera going up inside the exhaust pipe…

Broken flame tubes are a common problem for older Mooney mufflers… when they break down… they often redirect the hottest parts of the exhaust towards the muffler’s outer shell….  Which happens to be the inner shell of the heat muff…

When the excess heat causes breaches in the heat muff’s wall… exhaust can easily enter the cabin air supply…

 

Note for 177MC… check the health of the rest of the muffler to avoid any chances of CO entering the cockpit through the heater system…

 

PP thoughts only, My M20C sent its flame tubes somewhere… probably over the Atlantic Ocean…

Best regards,

-a-

[Shadrach]

On 10/19/2022 at 9:52 PM, GeeBee said:

A lot of the high wing Pipers with Lycoming engines have a 50 hour AD requirement to inspect the flame tubes on stock mufflers. That is why most people go to STC mufflers for these airplanes.

Just sent me down the flame tube rabbit hole. Apparently Piper decided that flame tubes are more of a liability than a benefit. I haven’t found a lot of clear literature but it appears that new Comanche exhausts come with empty cans…no cone, tube or baffle of any kind.

[Dialed In]

On 10/18/2022 at 8:51 AM, Will.iam said:

Ok what are internal flame tubes? What should they normally look like and where are they normally suppose to be?

Flame tubes dissipate the heat in our mufflers and aid in the exhaust changing direction so there is not a “blow torch” concentrating on one area of the muffler shell, our shells are thin so they would not take the direct heat coming from the primary exhaust pipes. 
 

On 10/21/2022 at 7:18 AM, Shadrach said:

Just sent me down the flame tube rabbit hole. Apparently Piper decided that flame tubes are more of a liability than a benefit. I haven’t found a lot of clear literature but it appears that new Comanche exhausts come with empty cans…no cone, tube or baffle of any kind.

Do the new comanche’s exhaust change direction or is it essentially a collector that then directs the heat out the exhaust? 

[Shadrach]

2 hours ago, Dialed In said:

Flame tubes dissipate the heat in our mufflers and aid in the exhaust changing direction so there is not a “blow torch” concentrating on one area of the muffler shell, our shells are thin so they would not take the direct heat coming from the primary exhaust pipes. 
 

Do the new comanche’s exhaust change direction or is it essentially a collector that then directs the heat out the exhaust? 

They all hav a collector of some type (2 into 1 or 3 into one). Only the dual exhaust mod for the sixes flows in the same direction. The rest flow into an empty can on opposing sides. The flow then makes an approximately 90° turn to exit the can.

https://awi-ami.com/piper-24-250-comanche-exhaust-system-itemized-parts-list-mapped-image

https://awi-ami.com/piper-24-260-comanche-a-c-exhaust-system-itemized-parts-list-mapped-image

https://awi-ami.com/piper-24-180-comanche-exhaust-system-itemized-parts-list-mapped-image