Cold Weather PreHeating

[Peter R.]

On 1/31/2007 3:31:14 PM, "pgbnh" wrote:

> But anyway, what's the common wisdom on preheating.

I park my aircraft in an unheated t-hangar in central NY state. Normally, I
plug the Tanis heater in when temps get around 40 degrees and I will further
wrap the cowling and cover the prop with an insulated cover when temps are
forecasted to drop below 25 degrees F or so. Keep in mind, though, that this
is a newly overhauled engine and I am simply preserving my investment. :)

One morning a couple of months ago I arrived at my t-hangar to discover that
the plug had somehow pulled out of the socket the previous evening and the
engine was at ambient temperature, somewhere around 36 degrees F.

I did not have the time to wait the three hours for the Tanis heater to warm
the block, so I called my mechanic and asked him if it would hurt the engine
to start at that temperature. This mechanic has 40-years in the business, so
I trusted him when he told me that there would be no harm in starting above
freezing. Being that my engine is a turbonormalized 6 cylinder, it was more
important for me to wait until the oil temperature hit 120 degrees before
applying full power. 36 degrees to 120 is a lot of idling.

Anyway, when I asked him what temperature would be a concern, he opined that
when temperatures dip into the upper 20s or lower, preheating becomes
important to engine health.

Then again, I have seen flight school aircraft started without preheat when
temps were around 0 degrees F, but I have also heard of these same engines
having stuck valves and other complications, so I wouldn't use that as a
guideline.

--
Peter

[pgbnh[_1_]]

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?

[Bob Noel]

In article >, "pgbnh" >
wrote:

> 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).

I use a red dragon preheater. Since I own it I simply take the time
and accept the hassle of preheating anytime below 40 degrees. My
cherokee 140 starts a lot easier.

Doing the preheat was a lot easier when I had a T-hangar, but I still
preheat even though I'm on a crappy tie-down.

--
Bob Noel
Looking for a sig the
lawyers will hate

[Jerry[_2_]]

I believe that Lycoming recommends preheat below 20 degrees to prevent
engine damage..

[Mike Noel]

If you are in even an unheated hangar, the OAT and the engine temperature
can be significantly different. On one of our colder days in Tucson when
the air outside the hangar was 30, a thermometer showed the head fin
temperature to be 45. Of course an aircraft parked outside would have been
a different story.

--
Best Regards,
Mike

http://photoshow.comcast.net/mikenoel

I'm a uniter, not a divider. - GWB, 1999.

"pgbnh" > wrote in message
...
> 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?
>

[Paul kgyy]

Depends on the oil you're using, for one thing. If multi-viscosity, I
wouldn't worry about anything down to 20 or so. Lycoming's web site
says 10F is OK, but my IO360 turns over pretty slowly below 20 - that
might be from a cold battery, though.

I think that a good approach if you live where it's really cold for an
extended period is to have both crankcase pad and electric cylinder
heater. Plug both into one of those cube taps that turns on when the
temp gets below 35F and just leave it on. Moisture does not form if
the engine is evenly heated, so wrapping the cowl is helpful, as is
wrapping the prop and spinner.

[Ross]

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 plug in my preheater when the temperature is less that 40F. It has
about 300 hours on since factory OH. I put a blanket on the cowl and
seal the front openings. I also put a drop light on the rudder pedals to
let the warm air heat the gyros. My plane is in an unheated hangar.

--

Regards, Ross
C-172F 180HP
KSWI

[[email protected]]

We've started our airplanes at ambient temps as low as -25C (-13F)
without preheat, but they sure don't like it. We run Aeroshell 15W50,
and it gets thick at that temperature. The battery loses most of its
cranking power in those conditions.
Big dangers:
1. Cranking too long, overheating the starter, maybe burning it out.
Just replaced one like that. $460. Give up and go home.
2. Priming too much and too long before cranking. The fuel mists into
the intake manifold, but will coalesce onto the manifold walls and run
out into the airbox, creating a fire hazard. Priming too much will
result in a brief run and stop, frosting those cold sparkplugs and
shorting them. Whatever the order of checklist, the prime should
happen immediately before start, not three or four items earlier.
Remember that the vapor pressure of the fuel is really low when it's
cold and won't fire consistently at all. Adding more via the primer
doesn't help, it just increases the flooding problem.
3. Too low or too high revs after start. Too low and the oil won't get
thrown off the crank into the cylinders. Too high and the pump will
cavitate, being unable to suck that thick oil up from the case. Think
McDonalds milkshake. 500-700 RPM works for us. I wouldn't even think
of starting an engine at those temps if it had W100 in it.
4. Idle it for a long time to get the cylinders warmed up and the oil
viscosity down. Taking off on a cold engine is false economy and will
soon enough get you, either financially or fatally.

Dan

[Rip]

According to Lycoming, an even bigger danger is that, at -10 deg. F,
engine tolerances are such that there may be zero, none, nada clearance
between important surfaces, like the crankshaft and it's bearings. The
aluminum case shrinks more than the steel crank, and one start under
those conditions will, not might but will, destroy the engine.

Rip

wrote:
> We've started our airplanes at ambient temps as low as -25C (-13F)
> without preheat, but they sure don't like it. We run Aeroshell 15W50,
> and it gets thick at that temperature. The battery loses most of its
> cranking power in those conditions.
> Big dangers:
> 1. Cranking too long, overheating the starter, maybe burning it out.
> Just replaced one like that. $460. Give up and go home.
> 2. Priming too much and too long before cranking. The fuel mists into
> the intake manifold, but will coalesce onto the manifold walls and run
> out into the airbox, creating a fire hazard. Priming too much will
> result in a brief run and stop, frosting those cold sparkplugs and
> shorting them. Whatever the order of checklist, the prime should
> happen immediately before start, not three or four items earlier.
> Remember that the vapor pressure of the fuel is really low when it's
> cold and won't fire consistently at all. Adding more via the primer
> doesn't help, it just increases the flooding problem.
> 3. Too low or too high revs after start. Too low and the oil won't get
> thrown off the crank into the cylinders. Too high and the pump will
> cavitate, being unable to suck that thick oil up from the case. Think
> McDonalds milkshake. 500-700 RPM works for us. I wouldn't even think
> of starting an engine at those temps if it had W100 in it.
> 4. Idle it for a long time to get the cylinders warmed up and the oil
> viscosity down. Taking off on a cold engine is false economy and will
> soon enough get you, either financially or fatally.
>
> Dan
>

[nrp]

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.

[[email protected]]

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

[[email protected]]

On Feb 2, 4:09 pm, Rip > wrote:
> According to Lycoming, an even bigger danger is that, at -10 deg. F,
> engine tolerances are such that there may be zero, none, nada clearance
> between important surfaces, like the crankshaft and it's bearings. The
> aluminum case shrinks more than the steel crank, and one start under
> those conditions will, not might but will, destroy the engine.
>
> Rip

Here's Lycoming's take on it:
http://www.lycoming.textron.com/main.jsp?bodyPage=support/publications/keyReprints/operation/coldWeather.html

I don't see that they warn about destroying the engine.
Damaging it certainly is likely if care isn't taken. The aluminum case
shrinks at about twice the rate of the steel crank, but the crank's
bearings are steel half-circle shells that are in crush (ends butted
against each other) in the case bores. They will shrink at the same
rate as the crank and prevent the case from binding the crank too
much. Bigger danger in cold weather is running the engine too hard
before the steel cylinder barrels have warmed up; the aluminum piston
can expand enough to cause scuffing as the clearances disappear.
Engine shops see that frequently enough. The two-stroke engines in
ultralights are particulary fussy that way.

IIRC: Coefficient of linear expansion of aluminum is .1244
units per degree F; of steel it's .0655. I'd have to look it up to get
it exact.

[Mike Spera]

> Here's Lycoming's take on it:
> http://www.lycoming.textron.com/main.jsp?bodyPage=support/publications/keyReprints/operation/coldWeather.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

[nrp]

"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?

[Dave Butler]

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

Exactly. Just about everything you read on this subject is folklore and
speculation. There is little data or scientific method.

[[email protected]]

On Feb 5, 8:43 am, Dave Butler > wrote:
> Mike Spera wrote:
> > Until somebody is prepared to take a shiny new engine, cold start it,
> > and immediately tear it down for inspection, we may never know.
>
> Exactly. Just about everything you read on this subject is folklore and
> speculation. There is little data or scientific method.

It might be speculation but it's working for us. When
there is a lack of hard experiential data, you go by your own
experience, being careful not to make large changes. Many folks are
scared to operate engines in climates vastly different from what
they're accustomed to, and that's probably wise. It's not safe to
assume that the thing will behave as usual.

Dan

[Dave Butler]

wrote:
> On Feb 5, 8:43 am, Dave Butler > wrote:
>> Mike Spera wrote:
>>> Until somebody is prepared to take a shiny new engine, cold start it,
>>> and immediately tear it down for inspection, we may never know.
>> Exactly. Just about everything you read on this subject is folklore and
>> speculation. There is little data or scientific method.
>
> It might be speculation but it's working for us. When
> there is a lack of hard experiential data, you go by your own
> experience, being careful not to make large changes. Many folks are
> scared to operate engines in climates vastly different from what
> they're accustomed to, and that's probably wise. It's not safe to
> assume that the thing will behave as usual.

Don't mean to discount your experience. Experience is good. Yours is
most probably more extensive than mine.

[[email protected]]

On Feb 4, 1:19 pm, "nrp" > wrote:
> "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?

That would be wise. I wish someone would certify a simple
preoiler for these engines. There's a system operated by an electric
oil pump, but it seems to me that an accumulator that stored oil from
the system while the engine was running, and released it via a
solenoid controlled by the pilot immedialtely before start, would be
better and lighter. It could include a small electric heating element
that would warm the oil in it, and would inject oil into the galleries
as well as into a couple of spray nozzles that would fog the inside of
the case with the warmed, thin oil.
Even better would be a drilled camshaft that would have small
oil ports in the lobes, or even right next to the lobes, to get the
lifter faces wet.

Dan

[David Lesher]

writes:


> That would be wise. I wish someone would certify a simple
>preoiler for these engines.

I rather liked the idea of something that you stuck down
the dipstick hole and oh, blew compressed air in, I guess;
in any case spraying oil here there & everywhere...

[Not to say it would work, but it sounds intriguing...]

Hmm; how about a spiral shaft that you spin on a drill?
The end dips into the pan....
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

[[email protected]]

On Feb 5, 11:46 am, David Lesher > wrote:
> writes:
> > That would be wise. I wish someone would certify a simple
> >preoiler for these engines.
>
> I rather liked the idea of something that you stuck down
> the dipstick hole and oh, blew compressed air in, I guess;
> in any case spraying oil here there & everywhere...
>
> [Not to say it would work, but it sounds intriguing...]
>
> Hmm; how about a spiral shaft that you spin on a drill?
> The end dips into the pan....
> --
> A host is a host from coast to
> & no one will talk to a host that's close........[v].(301) 56-LINUX
> Unless the host (that isn't close).........................pob 1433
> is busy, hung or dead....................................20915-1433

The Lycoming has some of narrow slots in the bottom of the case under
the camshaft, and below that is the oil pan. The idea is to keep
engine vibration from throwing too much oil up into the rotating
machinery, while allowing the oil flung off the crank to drain. The
oil fog might have some difficulty reaching the camshaft, and cold oil
won't fog much, anyway.
Too much oil mist or spray overwhelms the oil control rings on the
piston. They can't scrape it all off at the piston speeds encountered
at higher RPM, and begin to float on it. The oil gets into the
combustion chamber and is burned, making smoke, using a lot of oil,
and carboning things up too much. It's just one reason worn-out
engines will use more oil; the bearings get looser and allow more oil
past them, which is then thrown into the cylinder. The oil pump is
made about four times larger than necessary to allow for this
increased flow as the engine wears. Early on, the excess is dumped
through the relief valve back into the case, but as things get old the
relief valve passes less and less until it's shut altogether, and now
you'll see the oil pressure start to drop.

Dan

[Capt. Geoffrey Thorpe]

> wrote in message
oups.com...

<...> Even better would be a drilled camshaft that would have small
> oil ports in the lobes, or even right next to the lobes, to get the
> lifter faces wet.
>
> Dan
>

http://www.firewallforward.com/firewall_forward_web_page_011.htm

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Michelle P]

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)

[[email protected]]

On Feb 8, 5:42 pm, "Capt. Geoffrey Thorpe" <The Sea Hawk at wow way
d0t com> wrote:
> > wrote in message
>
> oups.com...
>
> <...> Even better would be a drilled camshaft that would have small
>
> > oil ports in the lobes, or even right next to the lobes, to get the
> > lifter faces wet.
>
> > Dan
>
> http://www.firewallforward.com/firewall_forward_web_page_011.htm

I suppose these guys have a patent on that cam so that Lycoming
can't use the idea in factory-new or O/H engines without paying big
royalties for it. It's about time someone did it, though. Glad to see
it's available. Lycoming should have done it themselves a long time
ago. Surely it's not because they didn't think of it.

Dan