Preheating engines: Airplane engines versus auto engines

Jay Honeck wrote:
Matt's answer is right on.

Ah, yes, the annual "Is it necessary to pre-heat?" thread. Soon to
be followed by the "Should I leave it plugged in all the time?"
discussion!

Almost as much fun as the "does it hurt your engine to practice
engine-out approaches."

:-)

Matt

Four questions..

What weight of Oil?

What brand?

How long before the oil pressure came up?

How long since last run?

Preferred answers.

15/50, Aeroshell,less than 15 seconds, less than one week..

4 of 4.. no concern

1, 3 and 4 ...probably no concern

1 and 3, - might see aluminum spike a little in your next oil test

Single weight, brand "X", more than 15 seconds, more than 3 weeks..
Probably should not do this very often...

The above gleaned from others much more capable than I, and I chose
to listen when they speak..

YMMV!

Dave



On Wed, 19 Dec 2007 12:21:28 -0500, "Peter R."
wrote:

This time of year here in the Northeast US I always preheat my Bonanza's
IO520 engine with a Tanis heater and an insulated cowling/prop cover as it
sits in an unheated t-hangar. The result is that the oil temperature at
startup is around 105 degrees F, even if the outside air temperature is as
low as -15 degrees F.

Monday night I arrived at my t-hangar to discover that at some point during

I purchased Fat Albert from an FBO who kept him in an unheated hangar
for 40 years, and never preheated unless it was well below zero
(that's in Farenheit, sonny)... Often it was a 3AM panic call from GM
who needed engine parts delivered to avoid the assembly plant from
shutting down and their truck was already on the way to the airport
with the parts....Load the plane, start the engines, hurry down the
taxiway checking mags while rolling, swing onto the runway, cob the
throttles and go... Elapsed running time from start to takeoff, less
than two minutes for the nearest runway, and perhaps three minutes for
the furthest... HIs engines routinely went to TBO...

While there is nothing wrong with preheat, etc. - there is also
nothing wrong with using synthetic oil and preheating only for extreme
temperatures... The biggest killer of aircraft engines is dry starts
from weeks/months of sitting between starts... Low temperature starts
on a well oiled engine have little to no impact on the wear cycle...
I use 15W50 in the winter and 100W+ in the summer... I do not preheat
unless it is below zero F... My starboard engine has 1700 hours since
factory zero and other than the oil burn being ~ 3 hours to the quart,
it starts and runs like a new engine... The port engine has 900 hours
since a field overhaul and it runs fine...

denny

On Dec 20, 6:04 am, Denny wrote:
The biggest killer of aircraft engines is dry starts
from weeks/months of sitting between starts...


That's one, but there's another bad one: Short flights,
especially in cold weather. byproducts of combustion include water
vapor, and some of that squeezes past the pistons and rings when the
engine is cold (some when it's hot, too, but much less so) and this
vapor condenses in the crankcase and ends up in the oil. If the engine
doesn't get hot enough for long enough, the water isn't boiled off and
will mix slowly with the oil, breaking it down and combining with
sulfur and chlorine and nitrogen to form sulfuric, hydrochloric and
nitric acids. These don't belong in your engine. The stuff that's left
from these reactions forms sludge and clogs up hydraulic lifters and
cakes on the inside of the case and soon enough breaks off and shows
up as scary black guck in the filter. The acids cause dissimilar metal
corrosion between the crank and cam and their bearings, between the
aluminum piston and the steel cylinder and rings, and on valve stems.
Bad. Corroded valve stems break and the engine tries to eat the valve
heads and gets indigestion.
The oil in my little old Continental doesn't get above
120°F on cold days. There's a tank blanket that I need to buy or make
to get it up. I just finished rebuilding the thing to fix corroded
bearings and seized valve lifters.

Dan

On Thu, 20 Dec 2007 08:21:32 -0800 (PST),
wrote:

On Dec 20, 6:04 am, Denny wrote:
The biggest killer of aircraft engines is dry starts
from weeks/months of sitting between starts...


That's one, but there's another bad one: Short flights,
especially in cold weather. byproducts of combustion include water
vapor, and some of that squeezes past the pistons and rings when the
engine is cold (some when it's hot, too, but much less so) and this
vapor condenses in the crankcase and ends up in the oil. If the engine
doesn't get hot enough for long enough, the water isn't boiled off and
will mix slowly with the oil, breaking it down and combining with
sulfur and chlorine and nitrogen to form sulfuric, hydrochloric and
nitric acids. These don't belong in your engine. The stuff that's left
from these reactions forms sludge and clogs up hydraulic lifters and
cakes on the inside of the case and soon enough breaks off and shows
up as scary black guck in the filter. The acids cause dissimilar metal
corrosion between the crank and cam and their bearings, between the
aluminum piston and the steel cylinder and rings, and on valve stems.
Bad. Corroded valve stems break and the engine tries to eat the valve
heads and gets indigestion.
The oil in my little old Continental doesn't get above
120°F on cold days. There's a tank blanket that I need to buy or make
to get it up. I just finished rebuilding the thing to fix corroded
bearings and seized valve lifters.

Dan

as a matter of deep religious significance, once your engine is warm
start the clock and dont land until an hour is up at least.

in the depths of winter remember that some parts of the world need
global warming :-)

now to be serious...
squeezing past the rings probably contributes a millionth of one
poofteenth of a percent to the problem.
when the crankcase cools there is moist external air sucked into the
cavity of the case through the crankcase breather. the moisture
condenses onto the cold internal surfaces of the engine.
can you please factor that into the alchemy above? it probably does
the damage occurring between the poofteenth of your scenario and the
100%.

now if you really want scarey black gunk try taking off the oil
reservoir and cleaning it out.

honestly you must lay awake sleepless at night :-)

Stealth (the O-200 is king) Pilot

On Dec 21, 4:45 am, Stealth Pilot
wrote:

squeezing past the rings probably contributes a millionth of one
poofteenth of a percent to the problem.
when the crankcase cools there is moist external air sucked into the
cavity of the case through the crankcase breather. the moisture
condenses onto the cold internal surfaces of the engine.
can you please factor that into the alchemy above? it probably does
the damage occurring between the poofteenth of your scenario and the
100%.

Nope. We have taken rocker covers off engines immediately
after a runup of a brand-new engine and found copious amounts of water
in them. The blowby of any cold engine is significant. If we briefly
run up an engine that has sat all night in a heated hangar and in our
very dry winter climate, we will find water on the dipstick every
time, with the engine at any point in its life. And the dipstick was
dry beforehand.
We operate on the western Canadian prairies where the air is
drier that where I grew up in south-central BC, which is the northern
tip of the Sonora Desert. We get little rain and snow here. Temps
reach -40C, more typically -20C, no fog and clear skies most of the
winter. It's REALLY dry, and any air sucked into these engines after
shutdown doesn't have enough moisture to make a couple of tears.

Dan

"Stealth Pilot" wrote in message
...
...
now to be serious...
squeezing past the rings probably contributes a millionth of one
poofteenth of a percent to the problem.

Stick your thumb on the crankcase breather and have someone open the
throttle - you will be surprised at the ammount of flow.

--
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.

On 12/19/2007 9:40:19 PM, Dave wrote:

What weight of Oil?

20w-50

What brand?

Exxon Elite

How long before the oil pressure came up?

Within a minute or so, I don't remember now.

How long since last run?

This was Monday, aircraft last flown previous Saturday. Aircraft is flown
twice to three times every week.


--
Peter

20w-50

Close enough



Exxon Elite

Thattle do...

How long before the oil pressure came up?

Within a minute or so, I don't remember now.


Watch this like a hawk on cold starts of any kind...15 secs is
marginal, 10 secs max preferred...

No pressure, shut it down....

How long since last run?


This was Monday, aircraft last flown previous Saturday. Aircraft is flown
twice to three times every week.

2 days since last?

No worries mate!

Fly on.....

(remember, I am not an AME...but I do listen a lot.. fortunate to
have a few near whom I believe to be knowledgeable in this area..
including a reputable engine builder / overhauler..)

Cheers!

Dave

On 12/20/2007 9:15:15 PM, Dave wrote:

Watch this like a hawk on cold starts of any kind...15 secs is
marginal, 10 secs max preferred...

Will pay better attention to this. Thanks.

--
Peter