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Date: Thu, 12 Mar 2009 10:34:24 -0400
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From: "Colyn Case at earthlink" <colyncase@earthlink.net>
Subject: Fw: Air Oil Separator Woes
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forwarding for Fred whose email address changed lately


-----Original Message-----
From: Frederick Moreno [mailto:frederickmoreno@bigpond.com]=20
Sent: Thursday, 12 March 2009 9:45 PM
To: Lancair Mail (lml@lancaironline.net)
Subject: Air Oil Separator Woes



I now have about 60 hours on my IO-550 in my Lancair IV. =20



We headed off for a big air show near Melbourne, about 1800 miles east.  =
Hot day departure, high power climb to 9500 feet, lots of pork, baggage, =
and fuel on board.  First stop, oil all over the belly.  Uh-oh.   This =
problem had occurred earlier on a few occasions, but with only a few =
drops of oil.  This was a gusher. =20



Did some trouble shooting around the air oil separator, checked lines to =
assure they were clear, cleaned up the mess, added two quarts, put tail =
between legs, turned around and headed home cautiously: lower power =
slower flatter climb, lower cruise manifold pressure and RPM. =20



Arriving home, only a trace of oil caught in the cup of the air oil =
separator gas vent which had previously overflowed and spilled all the =
oil inside the cowl and along the belly.=20



Hmmmm...



I wrote ECI who made the cylinders providing a fairly comprehensive =
report and asked for guidance.  I and some friends did a lot of =
research.  The ECI reply and our research all pointed to excessive blow =
by carrying too much oil to the air oil separator, more than it could =
handle, and when its maximum flow rate for oil return was exceeded, it =
filled and overflowed.  Cause: possibly lousy break in, possibly =
cylinders running too cold and thus retaining choke which caused ring =
flutter, other possibilities.  All pointed to pulling jugs and =
inspecting.  UGH.=20



I returned to the hangar today with some bright and technically astute =
friends and we had about two hours of debate and finally concluded that =
we should first PROVE there was a lot of blow by before turning a single =
cylinder nut. =20



There were a lot of red herrings and a lot of ground tests and finally a =
couple of fairly abusive flight tests to check the fix.   We found our =
way through the maze with only a few dead ends. =20



The problem?  Captured oil is supposed to drain from the air oil =
separator to the crankcase via a pushrod tube.  The drainage is supposed =
to be assisted with a bit of extra air blast to push it along using a =
bit of flow from the top of the cowl. =20



In fact, by pulling tubes one by one and testing, we found that the oil =
was running up the pushrod tube, up the drain tube and INTO the bottom =
of the separator, filling it and finally overflowing it.  It occurs =
primarily at high power high RPM and climb.  The  raised nose decreases =
the drop to the engine and tips the flow into reverse, it appears.  =
Reduce power and lower the nose and the pressure balances change and the =
reverse flow stops. =20



We finally put a rag in the breather line and did a ground full power =
run up (after sinking the bird up to the axles in the grass to keep it =
from skidding away) and there was virtually NO BLOWBY.  The rag stayed =
in the breather discharge line, and did not even pick up any oil.  The =
blow by that was occurring was small enough to seep through the rag =
without pushing it out the hole.=20



We plugged the drain return line feeding into the pushrod tube, put the =
air oil separator oil drain into a cup, and then blasted off on some =
abusive high power sustained climbs to 10,000.  Only a trace of oil was =
captured, and I guess that is to be expected with everything pushed up =
to the firewall and the nose up 12 degrees. =20



Morals of the story:=20



1)     Modern engines apparently do not need air oil separators.  My old =
Lycoming 540 sure did!  That was then.  This is now.

2)     If you have enough pressure drop across the engine due to lots of =
ram pressure at the cooling air inlets, a tight fitting plenum, and open =
cowl flaps while climbing to create a lot of suction, the large pressure =
drop created across the engine baffles can screw up the pressure =
distribution in the air oil separator and its various air and oil lines =
causing oil to flow backwards. =20

3)     Be suspicious of oil going overboard.  It may not be blow by at =
all. =20



Other than being shot at and missed, there is nothing quite as =
gratifying as avoiding a premature top overhaul.  Whew.=20



Fred Moreno

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<BODY lang=3DEN-AU vLink=3Dpurple link=3Dblue bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>forwarding for Fred whose email address =
changed=20
lately</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV style=3D"FONT: 10pt arial">
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT></P><FONT =
face=3DArial=20
size=3D3><SPAN style=3D"FONT-SIZE: 12pt; FONT-FAMILY: =
Arial"></SPAN></FONT></DIV>
<DIV class=3DSection1>
<P class=3DMsoNormal><FONT face=3DTahoma size=3D2><SPAN lang=3DEN-US=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">-----Original=20
Message-----<BR><B><SPAN style=3D"FONT-WEIGHT: bold">From:</SPAN></B> =
Frederick=20
Moreno [mailto:frederickmoreno@bigpond.com] <BR><B><SPAN=20
style=3D"FONT-WEIGHT: bold">Sent:</SPAN></B> </SPAN></FONT><FONT =
face=3DTahoma=20
size=3D2><SPAN lang=3DEN-US style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Tahoma">Thursday,=20
12 March 2009</SPAN></FONT><FONT face=3DTahoma size=3D2><SPAN =
lang=3DEN-US=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Tahoma"> </SPAN></FONT><FONT =
face=3DTahoma=20
size=3D2><SPAN lang=3DEN-US style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Tahoma">9:45=20
PM</SPAN></FONT><FONT face=3DTahoma size=3D2><SPAN lang=3DEN-US=20
style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Tahoma"><BR><B><SPAN=20
style=3D"FONT-WEIGHT: bold">To:</SPAN></B> Lancair Mail (<A=20
href=3D"mailto:lml@lancaironline.net">lml@lancaironline.net</A>)<BR><B><S=
PAN=20
style=3D"FONT-WEIGHT: bold">Subject:</SPAN></B> Air Oil Separator=20
Woes</SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3D"Times New Roman" size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">I now have about 60 hours =
on my=20
IO-550 in my Lancair IV.&nbsp; </SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">We headed off for a big =
air show=20
near </SPAN></FONT><FONT face=3DArial><SPAN=20
style=3D"FONT-FAMILY: Arial">Melbourne</SPAN></FONT><FONT =
face=3DArial><SPAN=20
style=3D"FONT-FAMILY: Arial">, about 1800 miles east.&nbsp; Hot day =
departure,=20
high power climb to 9500 feet, lots of pork, baggage, and fuel on =
board.&nbsp;=20
First stop, oil all over the belly.&nbsp; Uh-oh.&nbsp; &nbsp;This =
problem had=20
occurred earlier on a few occasions, but with only a few drops of =
oil.&nbsp;=20
This was a gusher.&nbsp; </SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">Did some trouble shooting =
around the=20
air oil separator, checked lines to assure they were clear, cleaned up =
the mess,=20
added two quarts, put tail between legs, turned around and headed home=20
cautiously: lower power slower flatter climb, lower cruise manifold =
pressure and=20
RPM.&nbsp; </SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">Arriving home, only a =
trace of oil=20
caught in the cup of the air oil separator gas vent which had previously =

overflowed and spilled all the oil inside the cowl and along the belly.=20
</SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: =
Arial">Hmmmm=85..</SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">I wrote ECI who made the =
cylinders=20
providing a fairly comprehensive report and asked for guidance.&nbsp; I =
and some=20
friends did a lot of research.&nbsp; The ECI reply and our research all =
pointed=20
to excessive blow by carrying too much oil to the air oil separator, =
more than=20
it could handle, and when its maximum flow rate for oil return was =
exceeded, it=20
filled and overflowed.&nbsp; Cause: possibly lousy break in, possibly =
cylinders=20
running too cold and thus retaining choke which caused ring flutter, =
other=20
possibilities.&nbsp; All pointed to pulling jugs and inspecting.&nbsp; =
UGH.=20
</SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">I returned to the hangar =
today with=20
some bright and technically astute friends and we had about two hours of =
debate=20
and finally concluded that we should first PROVE there was a lot of blow =
by=20
before turning a single cylinder nut.&nbsp; </SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">There were a lot of red =
herrings and=20
a lot of ground tests and finally a couple of fairly abusive flight =
tests to=20
check the fix. &nbsp;&nbsp;We found our way through the maze with only a =
few=20
dead ends.&nbsp; </SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">The problem?&nbsp; =
Captured oil is=20
supposed to drain from the air oil separator to the crankcase via a =
pushrod=20
tube.&nbsp; The drainage is supposed to be assisted with a bit of extra =
air=20
blast to push it along using a bit of flow from the top of the cowl.=20
&nbsp;</SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">In fact, by pulling tubes =
one by one=20
and testing, we found that the oil was running up the pushrod tube, =
<U>up the=20
drain tube and INTO the bottom of the separator</U>, filling it and =
finally=20
overflowing it.&nbsp; It occurs primarily at high power high RPM and=20
climb.&nbsp; The&nbsp; raised nose decreases the drop to the engine and =
tips the=20
flow into reverse, it appears.&nbsp; Reduce power and lower the nose and =
the=20
pressure balances change and the reverse flow stops.&nbsp; =
</SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">We finally put a rag in =
the breather=20
line and did a ground full power run up (after sinking the bird up to =
the axles=20
in the grass to keep it from skidding away) and there was virtually NO=20
BLOWBY.&nbsp; The rag stayed in the breather discharge line, and did not =
even=20
pick up any oil.&nbsp; The blow by that was occurring was small enough =
to seep=20
through the rag without pushing it out the hole. </SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">We plugged the drain =
return line=20
feeding into the pushrod tube, put the air oil separator oil drain into =
a cup,=20
and then blasted off on some abusive high power sustained climbs to=20
10,000.&nbsp; Only a trace of oil was captured, and I guess that is to =
be=20
expected with everything pushed up to the firewall and the nose up 12=20
degrees.&nbsp; </SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">Morals of the story:=20
</SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal style=3D"MARGIN-LEFT: 36pt; TEXT-INDENT: =
-18pt"><FONT=20
face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">1)</SPAN></FONT><FONT =
size=3D1><SPAN=20
style=3D"FONT-SIZE: 7pt">&nbsp;&nbsp;&nbsp;&nbsp; </SPAN></FONT><FONT=20
face=3DArial><SPAN style=3D"FONT-FAMILY: Arial">Modern engines =
apparently do not=20
need air oil separators.&nbsp; My old Lycoming 540 sure did!&nbsp; That =
was=20
then.&nbsp; This is now.</SPAN></FONT></P>
<P class=3DMsoNormal style=3D"MARGIN-LEFT: 36pt; TEXT-INDENT: =
-18pt"><FONT=20
face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">2)</SPAN></FONT><FONT =
size=3D1><SPAN=20
style=3D"FONT-SIZE: 7pt">&nbsp;&nbsp;&nbsp;&nbsp; </SPAN></FONT><FONT=20
face=3DArial><SPAN style=3D"FONT-FAMILY: Arial">If you have enough =
pressure drop=20
across the engine due to lots of ram pressure at the cooling air inlets, =
a tight=20
fitting plenum, and open cowl flaps while climbing to create a lot of =
suction,=20
the large pressure drop created across the engine baffles can screw up =
the=20
pressure distribution in the air oil separator and its various air and =
oil lines=20
causing oil to flow backwards.&nbsp; </SPAN></FONT></P>
<P class=3DMsoNormal style=3D"MARGIN-LEFT: 36pt; TEXT-INDENT: =
-18pt"><FONT=20
face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">3)</SPAN></FONT><FONT =
size=3D1><SPAN=20
style=3D"FONT-SIZE: 7pt">&nbsp;&nbsp;&nbsp;&nbsp; </SPAN></FONT><FONT=20
face=3DArial><SPAN style=3D"FONT-FAMILY: Arial">Be suspicious of oil =
going=20
overboard.&nbsp; It may not be blow by at all.&nbsp; </SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">Other than being shot at =
and missed,=20
there is nothing quite as gratifying as avoiding a premature top =
overhaul.&nbsp;=20
Whew. </SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial"></SPAN></FONT>&nbsp;</P>
<P class=3DMsoNormal><FONT face=3DArial size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial">Fred=20
Moreno</SPAN></FONT></P></DIV></BODY></HTML>

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