Posted for Frederick Moreno <frederickmoreno@bigpond.com>:

I rose to the bait, John.

Discussions of engine oil loss resurface from time to time here as new
airplanes take to the air.  Causes can sometimes be very puzzling.  At least
that was the case for me since I had three things going on at once and had
to tease them apart and then understand them, a process that took a lot of
time and examination of many dead end hypotheses.   I think we now
understand some the ways for things to go awry.

I have tried to capture all this in a short monograph on 0-550 engine oil
loss mechanisms which I have attached.  It covers the various loss
mechanisms mentioned here in recent emails and adds a few  more mechanisms
to consider.  It also presents some insights to the O-550 series engines
unique breather system and discusses installation errors that can bite you
with an air oil separator.  

While I was trained as a mechanical engineer, I am not a long-experienced
engine guy," so I would ask others with more experience than me to have a
read and let me know of any errors, omissions or topics where a bit more
clarity is needed.   I will then make the necessary revisions, re-post, and
ask Marv to put the monograph in the LML archives so that the information
can be quickly retrieved when this issue arises in the future as it is
almost certain to do so again.

No snide comments about my sloppy drafting or calligraphy

Fly safely,

Fred Moreno




-------Original Message-------

From: John Barrett
Date: 6/11/2012 9:06:32 PM
To: lml@lancaironline.net
Subject: [LML] Re: Oil going overboard

Fred Moreno had a problem early on with his Performance Engine from the
factory with oil loss.  He hopefully will regale us with a repeat of his
story.  My recollection is that he narrowed it down to oil blow by at low
throttle settings on decent.  Essentially the power setting produced less
pressure in the cylinders and the rings, which were either not correct or
the cylinders were not choked appropriately so that this allowed oil to go
overboard.

Not sure if you have the same problem but worth considering.  Fred can tell
you how he diagnosed.

John Barrett

-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Dan
Ballin
Sent: Monday, November 05, 2012 8:40 AM
To: lml@lancaironline.net
Subject: [LML] Oil going overboard

I am flying a Lancair Legacy with an IO-550  10:1 compression - Performance
engine that has been inspected and rebuilt about 60 hrs
ago.   I have had a problem, which I attributed to new cylinder/rings,
with excessive oil consumption.  Initially I was using about a qt an hour
and this improved at about 15 hrs.  Seemed like normal break in.
Then one flight back from the  coast of OR (Sea Level - I fly out of Bend  -
3500 ft), I started losing oil pressure.  When I landed after the hour
flight I had about 5 qts left.  I started with 9.  I attributed it to a
crazy idea I had to hook the breather tube into the exhaust.  I was getting
really tired of cleaning the bottom of the
plane and my hangar floor.   I disconnected it and flew and problem
solved.  Just recently on a trip back East the same thing happened.
Got to Rawlings, Wy 8.5 qts running grat no problems.  Next stop about
1.5 hrs, 2 added qts.  On my way to Kansas City oil pressure dropping slowly
so I diverted and now I was down to 4-5 qts.  After spending the night in
Kansas city and buying a case of oil, I flew back to Bend.  Used 1/2 qt in 6
hrs.

So a few things.  I have a 12 qt oil pan, I have an air/oil separator, I
checked my crank pressure by hooking a pressure gauge to the breather
(before the separator) and it is high somewhere in the 4-5 psi.  I did a
compression check and.

OK so why intermittently dumping from the oil breather?

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