X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 12 Mar 2009 10:34:24 -0400 Message-ID: X-Original-Return-Path: Received: from elasmtp-dupuy.atl.sa.earthlink.net ([209.86.89.62] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with ESMTP id 3545050 for lml@lancaironline.net; Thu, 12 Mar 2009 09:37:51 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.62; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=EPcowqZj4gQChdMaCC6PE8wRiJGSozoOM1KkNOc5fvelCBPlmhaHc0jCffQTYluu; h=Received:Message-ID:From:To:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE:X-ELNK-Trace:X-Originating-IP; Received: from [216.57.118.63] (helo=ccaselt3) by elasmtp-dupuy.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1Lhl63-00063J-JU for lml@lancaironline.net; Thu, 12 Mar 2009 09:37:15 -0400 X-Original-Message-ID: <050001c9a317$991b7aa0$6501a8c0@nvidia.com> From: "Colyn Case at earthlink" X-Original-To: Subject: Fw: Air Oil Separator Woes X-Original-Date: Thu, 12 Mar 2009 09:36:49 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_04FD_01C9A2F6.119C72D0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da940a4412e6fb685c3b0d0e2236c108b215b350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 216.57.118.63 This is a multi-part message in MIME format. ------=_NextPart_000_04FD_01C9A2F6.119C72D0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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 ------=_NextPart_000_04FD_01C9A2F6.119C72D0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
forwarding for Fred whose email address = changed=20 lately
 

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

 

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

 

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

 

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. 

 

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

 

Hmmmm=85..

 

I wrote ECI who made the = cylinders=20 providing a fairly comprehensive report and asked for guidance.  I = and some=20 friends did a lot of research.  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.  Cause: possibly lousy break in, possibly = cylinders=20 running too cold and thus retaining choke which caused ring flutter, = other=20 possibilities.  All pointed to pulling jugs and inspecting.  = UGH.=20

 

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. 

 

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.   We found our way through the maze with only a = few=20 dead ends. 

 

The problem?  = Captured oil is=20 supposed to drain from the air oil separator to the crankcase via a = pushrod=20 tube.  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  

 

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

 

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.  The rag stayed in the breather discharge line, and did not = even=20 pick up any oil.  The blow by that was occurring was small enough = to seep=20 through the rag without pushing it out the hole.

 

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.  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. 

 

Morals of the story:=20

 

1)     Modern engines = apparently do not=20 need air oil separators.  My old Lycoming 540 sure did!  That = was=20 then.  This is now.

2)     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. 

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

 

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

 

Fred=20 Moreno

------=_NextPart_000_04FD_01C9A2F6.119C72D0--