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From: "Marvin Kaye" <marv@lancaironline.net>
Subject: Re: [FlyRotary] More run time, fewer issues
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
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Date: Tue, 16 Mar 2004 00:44:14 -0500
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  > > > The turbo does get very hot and makes some smoke (not a lot) out 
the tail pipe on shut down.  I am wondering if maybe the oil seal is 
leaking.  How much smoke on shut down is normal?  < < < 

We've run the twin-turboed Eagle540 several times now and probably have a 
total of 7 hours of run time between the factory dyno runs and our testing 
runs out on the driveway.  The day after our 3rd run I noticed some drips of 
oil coming from the pilot's side turbo... traced them back to both the turbine 
and compressor sides next to the bearing housing.  The pax side turbo seemed 
ok, so we assumed that there was something amiss with the drippy one on the 
pilot's side.  I removed that turbo and sent it to Turbonetics for an 
inspection... they went through it, declared it to be in tip-top shape and 
sent it back to us.  While it was being checked I changed the oil return 
system to insure that no oil would flow back into the bearing section from the 
scavenge pump by removing the redundant air/oil separator can we had installed 
and moving the check valve between the turbos' outputs and the scavenge pump 
to a location lower than the bearing sections.  The turbo was returned to us, 
reinstalled and we ran the engine again on two separate occasions, both times 
for about 15 minutes.  We now experience a bit of dripping from both turbos... 
nothing horrible, maybe a drop a day from each one.  I called Turbonetics back 
and talked once again to Joe Valenzuela, their head technician and discussed 
the problem.  We were advised that the oil seals in the bearing section more 
closely resemble piston rings than a conventional composite (ie, metal and 
rubber) seal due to the high heat levels involved.  Joe told me that it is 
normal for turbos to leak a bit until they have some hours on them, and that 
it is entirely possible that even after extended run times at normal operating 
temps (we've never gotten there... our MAP has never exceeded about 18" since 
we've had the engine) that there may be a bit of leakage past those piston 
rings.  Sometimes the normal coking process will seal them up, sometimes it 
doesn't.  I'm hoping that our leaks stop once we get into the normal operating 
range, but understand that there are no guarantees. Bummer, huh? 

The worst part of having them leak into the turbine section is that that oil 
gets spewed out the exhaust pipe on startup and makes the airplane an oily 
mess.  Leaks into the compressor aren't as big a deal, as however much of that 
oil makes it through the intercoolers and into the intake stream ultimately 
gets burned off during the combustion process.  Hopefully your seals will coke 
up and stem the flow... give it a couple hours and see what happens.  That's 
what the guys at Turbonetics told me (they're owned by Kelly Aerospace and 
that's what the labels say on both of our Garrett turbos, so I think they know 
from whence they speak) and I thought I'd pass it along to you.  Hang in 
there.

    <Marv>