Didja ever wonder...

[Jay Honeck]

....why our Lycoming engines call for 12 (or 8) quarts of oil, when they blow
out anything over 8 (or 6) quarts?

My old A&P, a real gray head with decades of aviation experience, mentioned
the reason to me in conversation today. Here's the poop:

When Lycoming was certifying these engines, they had to prove that they
could operate them for "x" number of hours at full throttle. (The number
bandied about was in the hundreds of hours, but no one knew for sure.)
Lycoming was not allowed to add oil to the engine during this certification
operation.

Obviously, in order to run at such high power settings for so long, you're
gonna need a lot of oil. Thus, the sump on my O-540 was designed to hold 12
quarts, while the sump on my old O-320 held 8 quarts. This ensured that
they would pass the certification test.

However, since they were certified with these over-sized oil sumps, that
became the only way they could be built and sold. This despite the fact
that anything over 8 and 6 quarts, respectively, ends up painting the belly
of our planes in normal operation...

So now you know...the *rest* of the story.... ;-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Ron Natalie]

"Jay Honeck" > wrote in message news:1EWlb.10391$Fm2.7701@attbi_s04...

> When Lycoming was certifying these engines, they had to prove that they
> could operate them for "x" number of hours at full throttle.

Bull****. Full throttle isn't a certification requirement. There are various endurance runs,
none of which run even at maximum continuous power for the entire run.

The aircraft certification requirements state the that oil capacity must be such as to
provide the maximum consumption at required temperatures for the endurance of the
AIRCRAFT that the engine is installed in. Any oversizing of the tank is hence to
accomodate the range of uses Lycoming envisioned.

> So now you know...the *rest* of the story.... ;-)

Nope.

[Craig Prouse]

Jay Honeck wrote:

> ...why our Lycoming engines call for 12 (or 8) quarts of oil, when they blow
> out anything over 8 (or 6) quarts?

I've got a 9 qt sump. If I fill it to nine, at the end of a short flight
I'll have eight in the sump and one on the belly. If I see eight, I can
expect that after about ten hours I'll have seven.

My POH used to say something to the effect of: fill to 9 qt (or perhaps
they just said full) for "extended" flight, which they defined as some small
number of hours (2-4). This changed in the last revision to the POH, and no
longer does Cessna apply any undue pressure to fill beyond 8 qt. I was
shocked. Pleased, but shocked.

The POH has always stated, do not operate the engine with less than four
quarts in the sump. Now that's a pretty low standard to meet, since I
generally won't fly it with less than seven quarts at takeoff. So I guess
when I retire and ferry the airplane to Hawaii, I shouldn't really need a
means to add oil while in flight. Just lots of gas.

[Roger Long]

On our 172 N, it seems to make a difference what kind of flying we're doing.
Natural level is 5, if we fill to 6 and go on a long flight it will be fine.
Fill to 6 and do a lot of touch and gos or short flights with a lot of take
offs and the first quart will blow out.

An extra quart or two on longer flights thus makes good sense.

--
Roger Long

[Michael 182]

Two comments:

1) I put a m-20 air/oil separator on my 540 - it does a great job reducing
blowby and keeping the belly clean

2) On my 540 the dip stick has a gasket that fits into the top of the oil
check neck. As the dipstick is inserted it pushes the oil down in the check
tube, making the reading about a qt. low. If I remove the gasket and check,
or check after a few hours I get an accurate reading on the amount of oil in
the engine. So, if I fill to 8 qts, which is what my engine can hold, I'll
actually have closer to 9 qts in the engine.

Michael



"Jay Honeck" > wrote in message
news:1EWlb.10391$Fm2.7701@attbi_s04...
> ...why our Lycoming engines call for 12 (or 8) quarts of oil, when they
blow
> out anything over 8 (or 6) quarts?
>
> My old A&P, a real gray head with decades of aviation experience,
mentioned
> the reason to me in conversation today. Here's the poop:
>
> When Lycoming was certifying these engines, they had to prove that they
> could operate them for "x" number of hours at full throttle. (The number
> bandied about was in the hundreds of hours, but no one knew for sure.)
> Lycoming was not allowed to add oil to the engine during this
certification
> operation.
>
> Obviously, in order to run at such high power settings for so long, you're
> gonna need a lot of oil. Thus, the sump on my O-540 was designed to hold
12
> quarts, while the sump on my old O-320 held 8 quarts. This ensured that
> they would pass the certification test.
>
> However, since they were certified with these over-sized oil sumps, that
> became the only way they could be built and sold. This despite the fact
> that anything over 8 and 6 quarts, respectively, ends up painting the
belly
> of our planes in normal operation...
>
> So now you know...the *rest* of the story.... ;-)
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"
>
>

[Dale]

In article >,
"Ron Natalie" > wrote:


> Bull****. Full throttle isn't a certification requirement. There are
> various endurance runs,
> none of which run even at maximum continuous power for the entire run.
>
> The aircraft certification requirements state the that oil capacity must be
> such as to
> provide the maximum consumption at required temperatures for the endurance of
> the
> AIRCRAFT that the engine is installed in. Any oversizing of the tank is
> hence to
> accomodate the range of uses Lycoming envisioned.


I believe there is a requirment that the engine must be able to operate
at rated power within allowable temps with only 50% of the oil sump
capacity. If so that might explain why sumps are seemingly "oversized".

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

[Mike Rapoport]

Maybe it obvious to you, but why would you need a lot of oil to run high
power settings?

Mike
MU-2


"Jay Honeck" > wrote in message
news:1EWlb.10391$Fm2.7701@attbi_s04...
> ...why our Lycoming engines call for 12 (or 8) quarts of oil, when they
blow
> out anything over 8 (or 6) quarts?
>
> My old A&P, a real gray head with decades of aviation experience,
mentioned
> the reason to me in conversation today. Here's the poop:
>
> When Lycoming was certifying these engines, they had to prove that they
> could operate them for "x" number of hours at full throttle. (The number
> bandied about was in the hundreds of hours, but no one knew for sure.)
> Lycoming was not allowed to add oil to the engine during this
certification
> operation.
>
> Obviously, in order to run at such high power settings for so long, you're
> gonna need a lot of oil. Thus, the sump on my O-540 was designed to hold
12
> quarts, while the sump on my old O-320 held 8 quarts. This ensured that
> they would pass the certification test.
>
> However, since they were certified with these over-sized oil sumps, that
> became the only way they could be built and sold. This despite the fact
> that anything over 8 and 6 quarts, respectively, ends up painting the
belly
> of our planes in normal operation...
>
> So now you know...the *rest* of the story.... ;-)
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"
>
>

[Ron Natalie]

"Dale" > wrote in message ...

> I believe there is a requirment that the engine must be able to operate
> at rated power within allowable temps with only 50% of the oil sump
> capacity. If so that might explain why sumps are seemingly "oversized".

Bingo.
33.39 (a) The lubrication system of the engine must be designed and constructed so that it wil
l function properly in all flight attitudes and atmospheric conditions in which the airplane is
expected to operate. In wet sump engines, this requirement must be met when only
one-half of the maximum lubricant supply is in the engine.

[Mike Spera]

Jay Honeck wrote:
> ...why our Lycoming engines call for 12 (or 8) quarts of oil, when they blow
> out anything over 8 (or 6) quarts?
>
..stuff snipped

Jay,

Our 0-320 seems happy with 7 on down.

8 to 7 occurs in about an hour or so. 7 to 6 (or 6 to 5 and so on) takes
about 12 hours for each quart drop.

The surprising thing is that they can run with 2!! Well, the manual says
2 is the minimum. Not sure I want to test it out.

Good Luck,
Mike


__________________________________________________ _____________________________
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[G.R. Patterson III]

Jay Honeck wrote:
>
> Obviously, in order to run at such high power settings for so long, you're
> gonna need a lot of oil.

Nonsense. At full throttle, they're gonna blow that oil right out in a few
minutes. You could run my Lycoming for at least 250 hours straight if you
started with 7 quarts, and none of it would be blown out.

George Patterson
You can dress a hog in a tuxedo, but he still wants to roll in the mud.

[G.R. Patterson III]

Dale wrote:
>
> I believe there is a requirment that the engine must be able to operate
> at rated power within allowable temps with only 50% of the oil sump
> capacity. If so that might explain why sumps are seemingly "oversized".

According to the manual that came with my O-320, it will run at rated power
with as little as 2 quarts of oil. Since the sump holds 8 quarts, it would
seem that there isn't a relationship there.

George Patterson
You can dress a hog in a tuxedo, but he still wants to roll in the mud.

[Ron Wanttaja]

On 23 Oct 2003 23:47:43 GMT, Mike Spera > wrote:

>The surprising thing is that they can run with 2!! Well, the manual says
>2 is the minimum. Not sure I want to test it out.

Which leads to something I've been wondering about for quite a while: What
is the true mechanical limit: Oil quantity or oil pressure?

In other words, if I've got only a cup of oil in the airplane but the
pressure gauge shows a level above the lower limit, is the engine going to
be damaged?

(I realize it certainly won't COOL as well...)

Ron Wanttaja

[G.R. Patterson III]

Ron Wanttaja wrote:
>
> Which leads to something I've been wondering about for quite a while: What
> is the true mechanical limit: Oil quantity or oil pressure?

Quantity. The degree depends on the engine, but most aircraft engines have some
components that are lubricated by splash oil churned up by the crankshaft.

> In other words, if I've got only a cup of oil in the airplane but the
> pressure gauge shows a level above the lower limit, is the engine going to
> be damaged?

If you've got only a cup of oil in the plane, you won't have any pressure, but
that's not what you want answered. It's possible for the engine designer to
locate the oil pickup high enough in the sump so that the oil pressure will
drop before the oil level gets low enough to cause damage to the engine. I don't
know that they do so, but it seems to me to be such a good idea that I'd bet
they do.

George Patterson
You can dress a hog in a tuxedo, but he still wants to roll in the mud.

[Wayne]

Sounds like the runway behind you saying. If the oil pickup sucked air
before the oil level was at it's lowest, would't that be wasting the oil
below that line? Other than the cooling of the higher total volume and
whatever splash occurs? A slipping or skidding turn could make it happen
even sooner. Just a thought.
Wayne

>It's possible for the engine designer to
> locate the oil pickup high enough in the sump so that the oil pressure
will
> drop before the oil level gets low enough to cause damage to the engine. I
don't
> know that they do so, but it seems to me to be such a good idea that I'd
bet
> they do.
>
> George Patterson
> You can dress a hog in a tuxedo, but he still wants to roll in the
mud.

[Jay Honeck]

> Maybe it obvious to you, but why would you need a lot of oil to run high
> power settings?

Well, could we not assume that more oil would be used -- in a shorter period
of time -- in an engine running at higher (as opposed to lower) power
settings?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Jay Honeck]

> > I believe there is a requirment that the engine must be able to operate
> > at rated power within allowable temps with only 50% of the oil sump
> > capacity. If so that might explain why sumps are seemingly "oversized".
>
> Bingo.
> 33.39 (a) The lubrication system of the engine must be designed and
constructed so that it wil
> l function properly in all flight attitudes and atmospheric conditions in
which the airplane is
> expected to operate. In wet sump engines, this requirement must be met
when only
> one-half of the maximum lubricant supply is in the engine.

Was their a timed limit for the test runs that proved the engine could
"function properly in all flight attitudes", or did they simply run the
engine until there was only "half of the maximum lubricant supply" left?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Mike Rapoport]

There is no reason for it to do so. Unless it is an oil-fired steam engine.

Mike
MU-2


"Jay Honeck" > wrote in message
news:Jr0mb.13611$Tr4.33739@attbi_s03...
> > Maybe it obvious to you, but why would you need a lot of oil to run high
> > power settings?
>
> Well, could we not assume that more oil would be used -- in a shorter
period
> of time -- in an engine running at higher (as opposed to lower) power
> settings?
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"
>
>

[Jay Honeck]

> There is no reason for it to do so. Unless it is an oil-fired steam
engine.

I'm no mechanic, but I would figure that any given engine uses oil at a more
or less predictable (for that engine) rate.

Therefore, it only seems logical that if you turn the RPMs up, you're going
to use more oil than at a lower power setting. And more gas. And, in turn,
cause more friction and wear, etc...

Basically, you should use more of everything at a higher power setting, no?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[James M. Knox]

"Ron Natalie" > wrote in
m:

> The aircraft certification requirements state the that oil capacity
> must be such as to provide the maximum consumption at required
> temperatures for the endurance of the AIRCRAFT that the engine is
> installed in. Any oversizing of the tank is hence to accomodate the
> range of uses Lycoming envisioned.

I believe Ron is correct. If I recall correctly, it's a function of
several factors. The engine mfr. sets a maximum allowable oil consumption
rate below which the engine is considered airworthy. [And it's pretty
amazingly high... over a quart per hour for some big bore engines.] The
aircraft mfr. determines the endurance of the aircraft at "rated power"
(which may be 75%, but I believe it's up to the airframe mfr.) by sizing
the fuel tanks for the engine fuel consumption.

The required oil capacity is however much will allow for this flight, at
worst case consumption, with the aircraft ending the flight with "adequate
oil remaining." This "adequate" oil limit may be determined by necessary
cooling under certification requirements (climb at max gross, etc.) or by
the design of the oil pump system (will it still reliably pick up oil at
all normal/utility category flight attitudes).


-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

[Mike Rapoport]

OK, maybe, but you are talking about RPM increases of about 10%. If you are
burning a quart every 10 hours the increased amount wouldn't even show up on
the dipstick.. Also increased power is generally acccompanied by increased
MP and that tends to help the piston rings seal better which reduces oil
comsumption.

Anyway, I suspect that the size of the sump was determined by the fact that
it has to be big enough to cover the bottom of the engine and deep enough to
keep the oil pump pickup covered during normal maneuvers. That would also
explain why the oil capacity on the six bangers is 50% greater than the four
bangers

Mike
MU-2

"Jay Honeck" > wrote in message
news:Sm1mb.15399$HS4.58200@attbi_s01...
> > There is no reason for it to do so. Unless it is an oil-fired steam
> engine.
>
> I'm no mechanic, but I would figure that any given engine uses oil at a
more
> or less predictable (for that engine) rate.
>
> Therefore, it only seems logical that if you turn the RPMs up, you're
going
> to use more oil than at a lower power setting. And more gas. And, in
turn,
> cause more friction and wear, etc...
>
> Basically, you should use more of everything at a higher power setting,
no?
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"
>
>

[Russell Kent]

Ron Wanttaja wrote:

> On 23 Oct 2003 23:47:43 GMT, Mike Spera > wrote:
>
> >The surprising thing is that they can run with 2!! Well, the manual says
> >2 is the minimum. Not sure I want to test it out.
>
> Which leads to something I've been wondering about for quite a while: What
> is the true mechanical limit: Oil quantity or oil pressure?
>
> In other words, if I've got only a cup of oil in the airplane but the
> pressure gauge shows a level above the lower limit, is the engine going to
> be damaged?
>
> (I realize it certainly won't COOL as well...)

I could be completely wrong in my understanding, but:

Unless your engine's oil sump serves as a significant oil cooler (exceedingly
unlikely), the above supposition is incorrect. For a given oil pressure, oil
flow rate through the oil cooler is constant regardless of the oil level.
Cooling effectiveness of a particular oil system is a factor of oil flow rate,
air flow rate (through the cooler), and delta T between engine and OAT.

Russell Kent

[Ron Natalie]

"Jay Honeck" > wrote in message news:By0mb.14915$HS4.56185@attbi_s01...
> > > I believe there is a requirment that the engine must be able to operate
> > > at rated power within allowable temps with only 50% of the oil sump
> > > capacity. If so that might explain why sumps are seemingly "oversized".
> >
> > Bingo.
> > 33.39 (a) The lubrication system of the engine must be designed and
> constructed so that it wil
> > l function properly in all flight attitudes and atmospheric conditions in
> which the airplane is
> > expected to operate. In wet sump engines, this requirement must be met
> when only
> > one-half of the maximum lubricant supply is in the engine.
>
> Was their a timed limit for the test runs that proved the engine could
> "function properly in all flight attitudes", or did they simply run the
> engine until there was only "half of the maximum lubricant supply" left?

No, you fill the engine with half capacity of oil and then run it thorugh the
battery of tests. You're free to put in more oil just as long as it never has
more than half full.

[Ron Natalie]

"Jay Honeck" > wrote in message news:Sm1mb.15399$HS4.58200@attbi_s01...

>
> Therefore, it only seems logical that if you turn the RPMs up, you're going
> to use more oil than at a lower power setting. And more gas. And, in turn,
> cause more friction and wear, etc...

This is a common fallacy that's been proven wrong time and time again, at least
with respect to wear.

> Basically, you should use more of everything at a higher power setting, no?

NO.

[Jay Honeck]

> > Basically, you should use more of everything at a higher power setting,
no?
>
> NO.

Why?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Dan Luke]

"Russell Kent" wrote:
> I could be completely wrong in my understanding, but:
>
> Unless your engine's oil sump serves as a significant oil cooler
(exceedingly
> unlikely),

Why is that unlikely? It seems to me (and I am as confident in my
understanding as you are in yours!), that there would be significant heat
loss from the oil pan. Consider the large delta T between oil and ambient
and the <1 R-value of the metal pan.
--
Dan
C172RG at BFM

[G.R. Patterson III]

Wayne wrote:
>
> Sounds like the runway behind you saying. If the oil pickup sucked air
> before the oil level was at it's lowest, would't that be wasting the oil
> below that line?

No. You *have* to alert the pilot to the fact that the oil level is getting
low enough to cause engine damage or failure. The way that's done is with the
oil pressure gauge. So, you design the system in such a way that the pressure
will fall if the oil gets to that level. Given the size of the sump and the
amount of oil that must be in the various passages of my O-320 when running,
I'd guess that minimum oil level is about 1/4". Probably "wastes" about a quart.

If you wanted to make sure that no oil gets "wasted", then you need to design
a system in which no items are lubricated by splash and use what's known as a
"dry sump" system. My '72 Triumph has one of these.

George Patterson
You can dress a hog in a tuxedo, but he still wants to roll in the mud.

[Mike Weller]

On Fri, 24 Oct 2003 00:50:46 GMT, Ron Wanttaja >
wrote:

>On 23 Oct 2003 23:47:43 GMT, Mike Spera > wrote:
>
>>The surprising thing is that they can run with 2!! Well, the manual says
>>2 is the minimum. Not sure I want to test it out.
>
>Which leads to something I've been wondering about for quite a while: What
>is the true mechanical limit: Oil quantity or oil pressure?
>
>In other words, if I've got only a cup of oil in the airplane but the
>pressure gauge shows a level above the lower limit, is the engine going to
>be damaged?
>
>(I realize it certainly won't COOL as well...)
>
>Ron Wanttaja

From the Lycoming Flyer reprints:

"The phrase_"a minimum safe quantity of 2 quarts per engine"_should be
explained. If the operator checked oil after a flight and found less
than 2 quarts in the engine, it is quite probable that engine damage
has resulted. No flight should be started with only 2 quarts of oil in
the sump."

Mike Weller

[[email protected]]

Jay Honeck > wrote:
:> > Basically, you should use more of everything at a higher power setting,
: no?
:>
:> NO.

: Why?

Don't know about other things, but my oil consumption tends to be *inversely*
proportional to the power setting. A cross-country (400 nm) trip I did last spring at
about 3500' (2500' AGL due to widespread overcast) cost me about 1 qt in 4.5 hours.
Lower power setting and altitude (fixed-pitch prop) seems to cause more vacuum and sucks
oil through the rings. At higher power settings (or high-altitude WOT operation), it's
back to the normal 1 qt in 8-10 hours.

-Cory

--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************

[Russell Kent]

Dan Luke asked:

> Why is that [engine oil pan serving as a significant oil cooler --RAK]
> unlikely? It seems to me (and I am as confident in my understanding as you
> are in yours!), that there would be significant heat loss from the oil pan.
> Consider the large delta T between oil and ambient and the <1 R-value of
> the metal pan.

It is my understanding that the oil pan makes a poor heat radiator (versus a
traditional oil cooler) because:
1. the surface area of the oil cooler is many times that of the pan
2. because the oil cooler has relatively thin tubes, the oil is prevented
from forming a cooled oil boundary layer next to the metal like it can in the
pan
3. because the oil cooler has fins, the air is forced into turbulent
behavior, which precludes the forming of a heated air boundary layer next to
the metal like it can in the pan

I know of some experimenters who have crafted oil pans using aluminum heat
sink extrusions. Their before and after measurements indicated that the
"oil-pan-as-a-cooler" concept wasn't nearly as effective as an oil cooler.
It seems, from empirical data only, that the oil pan's contribution (with or
without fins :-) to cooling is in the single digit percentages: the vast
majority of BTUs (or calories for you S.I. folks) are shed by the oil cooler.

One might think that the success of air cooled cylinders would indicate that
an air cooled oil pan would work. But sometimes it useful to remember that
thermal transfer is a function of (among other things) delta T, and that the
delta T between the oil (at around 200 degF) and air (at 80 degF) isn't
nearly as high as the delta T between a cylinder (at around 350 degF) and air
(at 80 degF). This is the same reason that water-cooled engine's radiators
have much greater surface area that the air cooled engine's cylinder fins:
the water temperature is limited to about 220 degF (+/- depending on system
pressure and coolant chemistry).

When trying to transfer heat, there's one fundamental thing to remember:
transfer rate goes as delta T times contact area

For our purposes, the oil-to-air delta T is (relatively) fixed, so the only
thing we can work on is the contact area. Oil coolers, radiators, evaporator
and condenser coils all strive to package the largest contact area into a
fixed (small) volume. Increasing the flow rate of either the air (fly
faster) or the oil (higher pressure pump?) can improve the flow rate by
increasing the effective delta T at the oil cooler, but doing so is a
"diminishing returns" problem: the waste heat generated by the engine is
linearly proportional to the HP produced, but heat transferred isn't
increasing linearly.

Russell Kent

[TripFarmer]

Hey Jay,

You know what engine I've got (O-540) and I try to keep it at 10.5 quarts.
When it gets to 9.5 I add a quart. This happens about every 10 hours. Are you
telling me that I can run maybe 9 and maybe not need to add as often?


Trip



In article <1EWlb.10391$Fm2.7701@attbi_s04>, says...
>
>...why our Lycoming engines call for 12 (or 8) quarts of oil, when they blow
>out anything over 8 (or 6) quarts?
>
>My old A&P, a real gray head with decades of aviation experience, mentioned
>the reason to me in conversation today. Here's the poop:
>
>When Lycoming was certifying these engines, they had to prove that they
>could operate them for "x" number of hours at full throttle. (The number
>bandied about was in the hundreds of hours, but no one knew for sure.)
>Lycoming was not allowed to add oil to the engine during this certification
>operation.
>
>Obviously, in order to run at such high power settings for so long, you're
>gonna need a lot of oil. Thus, the sump on my O-540 was designed to hold 12
>quarts, while the sump on my old O-320 held 8 quarts. This ensured that
>they would pass the certification test.
>
>However, since they were certified with these over-sized oil sumps, that
>became the only way they could be built and sold. This despite the fact
>that anything over 8 and 6 quarts, respectively, ends up painting the belly
>of our planes in normal operation...
>
>So now you know...the *rest* of the story.... ;-)
>--
>Jay Honeck
>Iowa City, IA
>Pathfinder N56993
>www.AlexisParkInn.com
>"Your Aviation Destination"
>
>

[Edward Todd]

In article >,
(TripFarmer) wrote:

> Hey Jay,
>
> You know what engine I've got (O-540) and I try to keep it at 10.5 quarts.
> When it gets to 9.5 I add a quart. This happens about every 10 hours. Are
> you
> telling me that I can run maybe 9 and maybe not need to add as often?
>
>
> Trip
>
>
>


Hello Trip,

So how is that partnership working out? I'm wondering if I need to start
looking in that direction. Renting enough to where a partnership may
work out now.

Edward Todd
(T-town)

[Wayne]

I agree that the oil volume and pressure will be higher when the level
of the oil is closer to the level of the pump than if it has to draw it up a
long way, but disagree that moving the pickup tube up will help. The
pressure of the oil keeps the bearing from contacting the crank, rods etc...
if the level gets to the point that the pump actually sucks air, damage will
be done, whether it shows right away or not.

The placement of the end of the pickup tube doesn't make any difference
at all to the oil pressure unless it draws air. The level of the oil as
compared to the height of the pump is what makes the difference, that is
until it does suck air. That may not be what you are saying though.

Think about it this way. If you have a straw sticking out of the top of
a glass of water by one inch and below the water level one inch as well and
take a drink, it takes the same amount of suction to get a drink as it would
if the straw went all the way to the bottom ( not counting the drag). On the
other hand, if you were to keep drinking, the short straw would suck air and
stop delivering any water while the full legnth straw would continue to flow
although it would require more suction. It would have to overcome the weight
of the amount of soda in the straw to the level of the water.

So you would see the decrease in pressure gradually instead of the total
lack of flow and major needle swing. I have spent many hours pumping liquids
from one tank to another, I am a certified waste water treatment plant
operator.

This is a very hard thing to explain for me with by typing. reminds me
of the discussion about the fly in the cockpit and whether of not his weight
would show up before he landed on the dash..... Or only while landed. Makes
good hangar talk though.
Wayne

> No. You *have* to alert the pilot to the fact that the oil level is
getting
> low enough to cause engine damage or failure. The way that's done is with
the
> oil pressure gauge. So, you design the system in such a way that the
pressure
> will fall if the oil gets to that level. Given the size of the sump and
the
> amount of oil that must be in the various passages of my O-320 when
running,
> I'd guess that minimum oil level is about 1/4". Probably "wastes" about a
quart.
>
> If you wanted to make sure that no oil gets "wasted", then you need to
design
> a system in which no items are lubricated by splash and use what's known
as a
> "dry sump" system. My '72 Triumph has one of these.

[G.R. Patterson III]

Wayne wrote:
>
> I agree that the oil volume and pressure will be higher when the level
> of the oil is closer to the level of the pump than if it has to draw it up a
> long way, but disagree that moving the pickup tube up will help.

I think you do not understand my point. If you move the pickup screen up in
the pan, you will cause the pump to start sucking air when there is still a
fair amount of oil in the pan. If you set the pickup screen level to the point
at which there is barely enough oil to provide the necessary splash lubrication,
you will ensure that the oil pressure gauge will show a drop in pressure at the
point at which you can expect damage to your engine if you run it further. What
happens is that the needle will start to bounce as the pump begins to suck air.
That tends to get your attention.

If you set the pickup screen level lower than this, it is possible for the
engine to seize due to lack of lubrication without the oil pressure gauge
providing any warning to the pilot.

George Patterson
You can dress a hog in a tuxedo, but he still wants to roll in the mud.

[Mike Rapoport]

"Wayne" > wrote in message
...
> I agree that the oil volume and pressure will be higher when the level
> of the oil is closer to the level of the pump than if it has to draw it up
a
> long way, but disagree that moving the pickup tube up will help. The
> pressure of the oil keeps the bearing from contacting the crank, rods
etc...
> if the level gets to the point that the pump actually sucks air, damage
will
> be done, whether it shows right away or not.

A small nit: It is not oil preasure that prevents metal to metal contact,
it is the oil's film strenth

Mike
MU-2

[Jay Honeck]

> You know what engine I've got (O-540) and I try to keep it at 10.5 quarts.
> When it gets to 9.5 I add a quart. This happens about every 10 hours.
Are you
> telling me that I can run maybe 9 and maybe not need to add as often?

Yep. Anything over 9 (or even 8) quarts is just blowing out the breather
tube...
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Les Gawlik]

Year ago, there was a fascinating article in Scientific American about the
physics of a journal bearing. The film strength of the "wedge" of oil that
is forced between the crank and the babbit shell as the crank rotates has an
effective pressure on the order of thousands of pounds per square inch.
That is how you can avoid metal to metal contact with 60 to 100 pounds per
square inch of oil pressure in an engine that is developing forces clearly
in excess of that.

Les

"Mike Rapoport" > wrote in message
nk.net...
>
> "Wayne" > wrote in message
> ...
> > I agree that the oil volume and pressure will be higher when the
level
> > of the oil is closer to the level of the pump than if it has to draw it
up
> a
> > long way, but disagree that moving the pickup tube up will help. The
> > pressure of the oil keeps the bearing from contacting the crank, rods
> etc...
> > if the level gets to the point that the pump actually sucks air, damage
> will
> > be done, whether it shows right away or not.
>
> A small nit: It is not oil preasure that prevents metal to metal contact,
> it is the oil's film strenth
>
> Mike
> MU-2
>
>