I just thought of another possible scenario. Somebody might have

attempted to "overhaul"

it by cutting off the the original turbine and welding on another

relatively good

used turbine.

Paul Lamar

I had a failure once where the outer oil seal leaked oil into the

exhaust stream -- crystalization accumulated in the form of a steadily
growing pyramid until finally it became high enough to interfere with

and

stop the turbine.  In the case shown here, it is conceivable that such a
buildup occurred, broke off in a large chunk with the turbine at high

rpms,

causing the failure.  Pure speculation----

Bob

ERuttan wrote:

Bob that's it.

John stated a witness saw a large plume of white smoke when he lost
power, likely the oil seal failed and dumped oil into the exhaust.

The accumulation would have caused the stress right at the seal and
snapped off the turbine right where it broke.

I wonder if we could have a couple of other used turbo shafts x-rayed or

in

some other way imaged before the turbo is returned to service. It sure

would

rule out an existing crack and might reveal some info about the

construction

techniques used.
Dean Head
BKV FL

We have our '91 T2 torn down now.  The turbo unit is sitting on a shelf
waiting it's turn in the parts washer.  If Paul dug through old emailings,
there is a high res pic of the unit, back when we were trying to confirm
whether a casting rough spot was a problem or not.

If someone is in a position to perform the analysis Dean outlines above, we
could loan ours out to be a data point...

Mark & Mark
M-II  N512MM

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