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From: Gary Casey <casey.gary@yahoo.com>
Reply-To: Gary Casey <casey.gary@yahoo.com>
Subject: Re: Oil question for Walter A
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Fred,=0AI too, share your mystification. =A0I think you've stated your obse=
rvation very well. =A0I have heard that on a Lycoming, the oil can get into=
 the gearcase and the gears "pump" the oil up to the top. =A0The top shaft =
- the camshaft - has a slinger that supposedly separates the oil from the b=
lowby. =A0The extra oil from being full gets by the slinger and out it goes=
. =A0I'm not sure I believe that. =A0The Continental has a different breath=
er and oil separator design and the story there is that the oil gets into t=
he crankcase. =A0Yes, I suppose the oil could turn into a foam and therefor=
e rise in level when running. =A0But that has to be balanced by the effect =
of oil drain-back in that there is probably a quart or so of oil "in transi=
t" draining back to the sump. =A0Therefore, while running the oil level wil=
l be significantly lower than with it shut off. =A0The increase in volume d=
ue to foam would have to be substantial. =A0The bottom line is that I'm not=
 sure what
 to believe. =A0One would think that with all of us running these engines w=
e would all know exactly how much oil gets "blown overboard" with a full su=
mp. =A0I'll have to say that after thousands of hours observing mostly Lyco=
ming engines I'm not sure I can tell the difference. =A0Here's a thought, t=
hough: =A0Engines are rarely, if ever, filled exactly to the top since it w=
ould require the addition of a fractional quart of oil. =A0Maybe we look a =
the dipstick, see approximately 11 quarts and then put in a quart. =A0It wi=
ll likely end up at something less than 12 quarts (after all, if it read mo=
re than 11 we wouldn't put in the quart). =A0Then not too many hours later =
we see it is back down to 11 quarts. =A0It didn't burn a quart - it was nev=
er at 12 to begin with. =A0Or?=0A=0AThere is a Lycoming legend that says du=
ring takeoff and landings the engine burns more oil because the nose-up cli=
mb attitude lets oil get back into the gearcase. =A0I propose that the reas=
on for the high oil consumption is the power-off condition during landing. =
=A0In this case the high manifold vacuum draws oil past the=A0intake valve =
guides and=A0rings and during the intake stroke. =A0A lot of engines will b=
urn much more oil at light load than at full load. =A0So the things that af=
fect oil consumption can make up a long list.=0AGary Casey=0A=0AFrom Fred:=
=0A"Everybody"knows that when you put=A0"too much" oil in your aircraft eng=
ine (that is, fill it up to the top level), it will blow oil overboard.=0A=
=A0=0ABut I am mystified after seeing how our engines are constructed.=A0=
=0A=A0=0AOn my Continental IO-550, the oil in the pan can not "see" the cra=
nkshaft spinning overhead because the crank is nearly entirely enclosed by =
the crankcase housing, with only narrow semicircular slits in the casting a=
llowing oil to drain from around the crank and bearings down to the oil pan=
.=A0 So there is very little windage effect possible to disturb the surface=
 of the oil in the sump.=0A=A0=0AThere is a cracked Lycoming 0-360 crankcas=
e in my hangar, and it has narrow slots oriented parallel to the crank cent=
erline through which oil drains to the crankcase so in this design the pros=
pect of windage reaching the oil surface in the crankcase seems remote inde=
ed.=0A=A0=0A=A0Yet, adding two quarts of oil which may raise the=A0oil leve=
l=A0 half an inch on a big engine makes the difference between oil going ov=
erboard=A0or not going overboard.=0A=A0=0AWhy?=A0 What seems obvious is now=
 not so obvious when I think about it and=A0 try to visualize what is going=
 on inside.=0A=A0=0AThe only idea that came up in discussion is that there =
is a layer of oil foam on top of the oil in the sump, and it builds up deep=
 enough to=A0block the drain slots or allow oil foam=A0 to churn around the=
 crankshaft.=A0 That seems like a stretch, except that a friend=A0who used =
to work=A0at Garrett told me he=A0saw a Garrett turbocharger on the test st=
and, and=A0what came out the bottom of the turbo was not oil, but=A0more li=
ke brown mayonnaise that was sucked up by the scavange pump and returned to=
 the engine.=A0 But turbos with bearings at slight negative pressure (and s=
uckng air through seals) are not crankshafts at positive pressure.=A0=A0=0A=
=A0=0AReading about oil foaming ascribes it to water in the oil, an abnorma=
l condition.=A0 Engine oil have anti foaming agents.=A0=0A=A0=0ASo to Walte=
r or anyone: please explain how adding one to two quarts of oil causes oil =
to be blown out?=A0=0A=A0=0AFred Moreno, mystified (as usual)
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<html><body><div style=3D"color:#000; background-color:#fff; font-family:bo=
okman old style, new york, times, serif;font-size:12pt"><div>Fred,</div><di=
v>I too, share your mystification. &nbsp;I think you've stated your observa=
tion very well. &nbsp;I have heard that on a Lycoming, the oil can get into=
 the gearcase and the gears "pump" the oil up to the top. &nbsp;The top sha=
ft - the camshaft - has a slinger that supposedly separates the oil from th=
e blowby. &nbsp;The extra oil from being full gets by the slinger and out i=
t goes. &nbsp;I'm not sure I believe that. &nbsp;The Continental has a diff=
erent breather and oil separator design and the story there is that the oil=
 gets into the crankcase. &nbsp;Yes, I suppose the oil could turn into a fo=
am and therefore rise in level when running. &nbsp;But that has to be balan=
ced by the effect of oil drain-back in that there is probably a quart or so=
 of oil "in transit" draining back to the sump. &nbsp;Therefore, while
 running the oil level will be significantly lower than with it shut off. &=
nbsp;The increase in volume due to foam would have to be substantial. &nbsp=
;The bottom line is that I'm not sure what to believe. &nbsp;One would thin=
k that with all of us running these engines we would all know exactly how m=
uch oil gets "blown overboard" with a full sump. &nbsp;I'll have to say tha=
t after thousands of hours observing mostly Lycoming engines I'm not sure I=
 can tell the difference. &nbsp;Here's a thought, though: &nbsp;Engines are=
 rarely, if ever, filled exactly to the top since it would require the addi=
tion of a fractional quart of oil. &nbsp;Maybe we look a the dipstick, see =
approximately 11 quarts and then put in a quart. &nbsp;It will likely end u=
p at something less than 12 quarts (after all, if it read more than 11 we w=
ouldn't put in the quart). &nbsp;Then not too many hours later we see it is=
 back down to 11 quarts. &nbsp;It didn't burn a quart - it was never
 at 12 to begin with. &nbsp;Or?</div><div><br></div><div>There is a Lycomin=
g legend that says during takeoff and landings the engine burns more oil be=
cause the nose-up climb attitude lets oil get back into the gearcase. &nbsp=
;I propose that the reason for the high oil consumption is the power-off co=
ndition during landing. &nbsp;In this case the high manifold vacuum draws o=
il past the&nbsp;intake valve guides and&nbsp;rings and during the intake s=
troke. &nbsp;A lot of engines will burn much more oil at light load than at=
 full load. &nbsp;So the things that affect oil consumption can make up a l=
ong list.</div><div>Gary Casey</div><div><br></div><div>From Fred:</div><di=
v><span class=3D"Apple-style-span" style=3D"color: rgb(69, 69, 69); font-fa=
mily: arial, helvetica, sans-serif; -webkit-border-horizontal-spacing: 2px;=
 -webkit-border-vertical-spacing: 2px; "><div>"Everybody"knows that when yo=
u put&nbsp;"too much" oil in your aircraft engine (that is, fill it up
 to the top level), it will blow oil overboard.</div><div>&nbsp;</div><div>=
But I am mystified after seeing how our engines are constructed.&nbsp;</div=
><div>&nbsp;</div><div>On my Continental IO-550, the oil in the pan can not=
 "see" the crankshaft spinning overhead because the crank is nearly entirel=
y enclosed by the crankcase housing, with only narrow semicircular slits in=
 the casting allowing oil to drain from around the crank and bearings down =
to the oil pan.&nbsp; So there is very little windage effect possible to di=
sturb the surface of the oil in the sump.</div><div>&nbsp;</div><div>There =
is a cracked Lycoming 0-360 crankcase in my hangar, and it has narrow slots=
 oriented parallel to the crank centerline through which oil drains to the =
crankcase so in this design the prospect of windage reaching the oil surfac=
e in the crankcase seems remote indeed.</div><div>&nbsp;</div><div>&nbsp;Ye=
t, adding two quarts of oil which may raise the&nbsp;oil level&nbsp;
 half an inch on a big engine makes the difference between oil going overbo=
ard&nbsp;or not going overboard.</div><div>&nbsp;</div><div>Why?&nbsp; What=
 seems obvious is now not so obvious when I think about it and&nbsp; try to=
 visualize what is going on inside.</div><div>&nbsp;</div><div>The only ide=
a that came up in discussion is that there is a layer of oil foam on top of=
 the oil in the sump, and it builds up deep enough to&nbsp;block the drain =
slots or allow oil foam&nbsp; to churn around the crankshaft.&nbsp; That se=
ems like a stretch, except that a friend&nbsp;who used to work&nbsp;at Garr=
ett told me he&nbsp;saw a Garrett turbocharger on the test stand, and&nbsp;=
what came out the bottom of the turbo was not oil, but&nbsp;more like brown=
 mayonnaise that was sucked up by the scavange pump and returned to the eng=
ine.&nbsp; But turbos with bearings at slight negative pressure (and suckng=
 air through seals) are not crankshafts at positive
 pressure.&nbsp;&nbsp;</div><div>&nbsp;</div><div>Reading about oil foaming=
 ascribes it to water in the oil, an abnormal condition.&nbsp; Engine oil h=
ave anti foaming agents.&nbsp;</div><div>&nbsp;</div><div>So to Walter or a=
nyone: please explain how adding one to two quarts of oil causes oil to be =
blown out?&nbsp;</div><div>&nbsp;</div><div>Fred Moreno, mystified (as usua=
l)</div></span></div></div></body></html>
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