Didja ever wonder...

....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"

"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.

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

"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.

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"

"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.

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 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
-----------------------------------------------

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.

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