Cold Weather PreHeating

Here's Lycoming's take on it:
http://www.lycoming.textron.com/main...ldWeather.html

I don't see that they warn about destroying the engine.

It is interesting that Lyc only says to expect "minor" wear
abnormalities with improper cold weather starting. That is pretty
watered down compared to some of the gloom and doom stated here and
elsewhere.

Until somebody is prepared to take a shiny new engine, cold start it,
and immediately tear it down for inspection, we may never know.

Good Luck,
Mike

On Feb 2, 3:52 pm, wrote:
We've started our airplanes at ambient temps as low as -25C (-13F)
without preheat, but they sure don't like it.

I'm surprised you got by with that. Must have been a Continental
engine? Lycomings have no crankshaft feature that will sling oil to
the camshaft lobes & most oil pump output has to flow over the relief
valve which has no access to the heat of the engine. It would be
interesting to find out how long it takes a genuine oil fog to
develop, My guess is quite a while.

Another factor is how long an engine has been sitting. A couple of
days is one thing, but if it has been two weeks a few more drops of
camshaft oil would have drained such that the need for preheat has to
be greater.

Having summer 50 weight (100W) oil instead of winter (say SAE 20
weight) is about the same as a 40 degF temperature penalty.

That's my take on it.

On Feb 2, 4:14 pm, "nrp" wrote:
On Feb 2, 3:52 pm, wrote:

We've started our airplanes at ambient temps as low as -25C (-13F)
without preheat, but they sure don't like it.

I'm surprised you got by with that. Must have been a Continental
engine?

Six Lycomings.

Lycomings have no crankshaft feature that will sling oil to
the camshaft lobes & most oil pump output has to flow over the relief
valve which has no access to the heat of the engine. It would be
interesting to find out how long it takes a genuine oil fog to
develop, My guess is quite a while.

Aeroshell 15W50 has the Lycoming-recommended additive to protect
the cam during dry starts. It has served us well.
The cam gets enough splash off the crank once the engine's running.
It's coming off the sides of the main and rod bearings.

Another factor is how long an engine has been sitting. A couple of
days is one thing, but if it has been two weeks a few more drops of
camshaft oil would have drained such that the need for preheat has to
be greater.

We hangar the airplanes every night at 5C. They start just fine at
those temps, six days a week. It's when they sit out at -25C for a few
hours that we have to get really careful, or for a weekend. They will
need preheat if they don't fire and stay running really early in the
attempt. With the frost and ice and snow around here they often need
hangaring anyhow.

We get the full 2000 hours out of them and could go another
500, easily. The compressions are in the mid-to-high 70s when they
come off, and there's no metal in the filters. The secret, I suppose,
is to run them frequently, and not for short 20-minute flights. And
use the Aeroshell with the additive. We had some cam problems before
switching to it. It costs more, but it costs less. Get the idea?

Dan

"Aeroshell 15W50 has the Lycoming-recommended additive to protect
the cam during dry starts. It has served us well.
The cam gets enough splash off the crank once the engine's running.
It's coming off the sides of the main and rod bearings."

Dan -

From what I have seen inside Lycoming engines (and that's not very
many although they are all very similar) a small amount of leaking oil
from crank or rod journals isn't going to impact the cam surfaces very
soon after a really gooey & sticky oil startup. I suspect the cam is
going to have to rely on the residual oil from the last shutdown, for
some time - maybe even minutes for a difficult cold start - until an
oil fog environment is established. Laying a crankshaft next to a
camshaft & looking at the axial alignment of the two, The likely
initial oil splatter patterns look to me like they would miss the cam
surfaces.

A really interesting test would be to cut a hole in the side of a
junkable crankcase and examine the startup spray pattern.

Obviously you are doing something right. We both use the Shell
15W50. I've run counter to one of your "secrets" though in that I've
had a lot of short flights over 31 years to get to 1700 hrs TTSN on a
still solid Lycoming O-320E2D, only being religious about oil
preheats.

Maybe the presence of residual oil is more critical - in which case
the need for preheat would greatly increase for an aircraft sitting
for a few days. Might that jibe with your experience?

pgbnh wrote:
Now that winter has finally arrived in the Northeast, it is time to enjoy
the benefits of cold, dense air. wow - I wish I could see those climb rates
in August.

But anyway, what's the common wisdom on preheating. Granted, in an ideal
world, preheating is probably a good idea anytime it's below 40, but it IS a
pain for those of us who are forced to tie down outside and have no access
to electricity. At what temperature point are you comfortable starting
WITHOUT a preheat? (If it matters, this is for a Lyc IO360 that will start
easily down to about 10 deg).

Any mechanics care to comment on what they have seen happen to engines which
have routinely been started cold?


I have sump heater that will keep the oil warm. I keeps the rest of the
engine moderately warm. I will plug it in when the temp drops below 50.
Sounds a little high? well If I can keep the oil warm and reduce the
stress on the engine components at startup I will. Easier on the starter
ring gear and the case (IO-540).

Michelle (A&P)