Exhaust System Inspection, Check this out!

[Walt]

This is what happens when you don't keep an eye on things. It started with a broken exhaust hanger who knows how long ago (which I neglected to get a pic of) and then progressed to a cracked flange. This one was likely only hours away from a compelete seperation

This aircraft has approximately 275 hrs on it!

The Tell tale signs...


A little closer view


Then around the backside....


The crack is approximately 75% of the circumference of the flange, most of it was around the back side not really visible unless you inspect with a mirror.

Moral of story, pull both cowls every oil change and use the opportunity to do a thorough visual inspection with flashlight and mirror. When checking the exhaust system be sure you give it a good tug to check the integrity of the supports.

[db8]

Holly smokes.....Thanks for posting that Walt. Dave

[JonJay]

Another good catch Walt. I would also have a bit of concern over the crack developing exactly along the weld line, not just in the vicinity but exactly following it.
Perhaps Larry or Russ could chime in on that observation.

[lostpilot28]

Hey Walt, do the welds going down the pipe (from the flange) indicate that they've cracked before? I'm guessing so...and wondering why that is. Could it be an indication of an engine that vibrates too much?

[FORANE]

I had the same crack in the same location. We welded it once. It reoccurred but the second time I didn't notice it until I heard what sounded like a shotgun going off immediately followed by the sound of an engine with no muffler shortly followed by a significant drop in EGT on the effected pipe. The pipe completely separated at the flange.

I did not have a faulty hangar but it cracked just the same.

The last time I took it to a friend who does a little metalwork: Gene Fulton of Fulton racing engines.
http://www.fultoncompetition.com/Ful...tion/Home.html
Gene welded 2 support tabs between the flange and the side of the pipe. It has not cracked again.

[LifeofReiley]

Originally Posted by rvmike

Had the same crack happen at 400 hrs and called vetterman. He said that if you don't keep the slip joints lubed (mouse milk ) it will crack because there is no more movement and the weld is the first to go. Gone another 400hrs and no problems

Mike,

You hit the nail on the head!!! and... mouse milk does the trick.

[Bob Kuykendall]

Originally Posted by lostpilot28

Hey Walt, do the welds going down the pipe (from the flange) indicate that they've cracked before? I'm guessing so...and wondering why that is. Could it be an indication of an engine that vibrates too much?

If you're asking about the doubler plates with the holes in them, that's the way the Vetterman pipes come brand new.

[bret]

Look at the gap at 10 and 2 O'clock, Just guessing here but these areas would set up a stress point for vibration work hardening to begin, if the weld was even the vibration load would be spread evenly across the weld-flange...?

[jrs14855]

What kind of exhause hangar?? Attaching the hangar to the airframe puts far more stress on the exhaust than attaching the hangar to the engine. In my opinion there should be symmetrical doublers on both sides of the pipe. This type of failure is common on many types of exhaust. Welding all around a pipe to flange sets up stresses that lead to failure.

[n5lp]

Originally Posted by LifeofReiley

Mike,

You hit the nail on the head!!! and... mouse milk does the trick.

It kind of bugs me when I am suddenly informed that I was supposed to be doing something all these years, when it was not in the documentation. I live in the middle of nowhere.

If you are supposed to put mouse milk on those joints I would expect that to be in the documentation, and it wasn't in mine. I haven't had any problems with my Vetterman exhausts for the past 1,000+ hours and 10+ years, but if I am really supposed to take this action I would like some official notification.