Turbo Failure

hi Kieth

First do not disassemble the turbo.  I would suggest some trouble shooting first.  Oil puddles may indicate that the oil is not being returned to the oil tank, this will flood the center section and over fill the exhaust and even into the intake.  Remove the oil tank bolt at the bottom of the turbo, it is fitted inside with a screen to trap carbon.  If this is plugged up then you have to clean it and clean the return line to the pump and check for debris from the pump to  the oil tank itself.  

Should this be the problem normally you can simply clean it up and run again to check and see if this solves it.  This could be due to overheated oil (oil coking) or wrong oil used.  

Cheers

Definitely have a look at this video before you do anything.  It specifically discusses what can cause oil to leak from the turbo, and that there really IS no bearing seal, as such.

https://www.rotax-owner.com/en/videos-topmenu/rotax-minute/461-914-turbo-oil

The first thing I would look at is that turbo oil-feed check valve.

Thank you gentlemen,

I believe my 915is turbo is from a different manufacturer than the 914 but I will proceed to check the same elements suggested in the video.  This engine is under 150 hrs and 100LL is being used about 60% of the operating hours.  The engine/turbos should be cooling adequately during low RPM descents and post-landing taxi.  We recently performed an oil change with the recommended syn-oil.  

Ill let you know what I find with fingers crossed.

I performed the recommended repairs as described above and in the video. The check valve did not exhibit any residue however I removed and cleaned the elements as well as flushing the port. The turbo sump did have residue in the screen; all parts have been cleaned. I burned off the excess oil, checked for leaks, replenished the oil to proper levels and elected to fly a couple of laps in the pattern.

A couple days and longer flights later still no leaks. All seems good except I don't have a good explanation of why the significant leak occurred in the first place.

The Turbo bearing is a very loose-fit sleeve bearing that is flooded with Oil.
There is NO Oil Seal.
The oil drips, or more properly, Flows out of the bearing and pours into the sump to be scavaged by the dedicated Turbo Oil pump.
If the sump screen is restricted, the sump will overflow into the exhaust and the oil will get blown out of the exhaust.

It all makes sense.
Dirty Sump Screen = Oily Mess.
This is all part of routine maintenance.