Pre-heating concerns this morning

Bonchie

Bonchie

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Bonchie
As you can imagine, we don't get many 20 degree days in the deep south and our plane doesn't have a built in pre-heater like the planes I used to fly up north. Nor do we have a portable one.

It should be around 30 degrees by the time I go but our hanger is open faced. Is the engine typically warmer under the cowl than outside air temp or does all the metal cause it to get even colder in there?

Curious if I should just scrub the next few days or if it's safe to start it.
 
All else being equal (no sun on the cowl for instance) the engine goes to the exact same temp as everything else. Material affects the rate of cooling or heating but everything eventually evens out. The material doesn't make it warmer or cooler.

Personally I never start my engine without preheat under 50... ymmv


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I have an outside air temp sensor in my engine bay (well, the little bay that is around my fuel pump) and nope, the temp there is exactly the same as the outside.
 
Do you have a Lycoming or Continental? Both manufacturers have cold weather starting service instructions.

Long story short, I wouldn't worry about those temps too much. My concern is more how cold soaked is it (in other words, how long was the air temp 20 degrees) than the absolute lowest temperature. An old timer told me to grab the prop and see how easily it rocks back and forth, which seems to be a reasonable indicator for how cold and tight the engine really is.
 
Preheat required when.... Continental-cold soaked below 20*. Lycoming-MOST models, cold soaked below 10*. Both assume you have the appropriate grade of oil for the conditions. Carefully rotating the prop a few times will ease the initial load on the starter and battery.
 
mondtster said:
Do you have a Lycoming or Continental? Both manufacturers have cold weather starting service instructions.

Long story short, I wouldn't worry about those temps too much. My concern is more how cold soaked is it (in other words, how long was the air temp 20 degrees) than the absolute lowest temperature. An old timer told me to grab the prop and see how easily it rocks back and forth, which seems to be a reasonable indicator for how cold and tight the engine really is.
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It's the south, so it was 60 degrees until Thursday night. Been in the 30s during the day and 20s at night since then.
 
Are you running multi-grade?
If you have a way to blanket the cowl even a small electric cube heater will warm the engine nicely in a couple of hours.
 
Stewartb said:
Preheat required when.... Continental-cold soaked below 20*. Lycoming-MOST models, cold soaked below 10*. Both assume you have the appropriate grade of oil for the conditions. Carefully rotating the prop a few times will ease the initial load on the starter and battery.
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It's a 182P.

One of the partners told me to do what you are saying with priming it a couple of shots and turning the prop by hand a couple of times before trying to start it (obviously with the mags and everything turned OFF).
 
No need to prime it to rotate it at those temps unless you're hand propping but I don't guess it'd hurt anything. You are talking about a primer pump, not pumping the throttle, right? When ready to turn the key expect to give it an extra shot or two of primer. if you favor pumping the throttle make sure the prop is turning BEFORE you pump it. Either way cold temps require more fuel to start.
 
Stewartb said:
No need to prime it first at those temps unless you're hand propping but I don't guess it'd hurt anything. You are talking about a primer pump, not pumping the throttle, right? When ready to turn the key expect to give it an extra shot or two of primer. if you favor pumping the throttle make sure the prop is turning BEFORE you pump it. Either way cold temps require more fuel to start.
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Yeah, the primer pump, not the throttle.

If it won't start, it won't start. Not really worried about that and I'm not planning on riding the starter to try to make it start. This is just a leisure flight today. Just didn't want to cause any damage to the engine trying.
 
It should start fine, just remember it'll need more fuel. When cold starting I leave the primer out so I can feed fuel to keep it running but probably not necessary at 20*.
 
Should start fine, but do know that a couple of days is plenty of time to cold soak it. If you regularly start below 50 I'd get a tannis...


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Just trying to exceed TBO. At 1950 hours no problems so I know it can't hurt...


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If you have a CHT you can read the temperature of the cylinders. Most hangars are warmer inside than outside, on a cold day anyway.
 
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I have wondered about the "lag" on temp changes for the engine. That's a big block of metal up there so conduction is going to be pretty slow. Here in northern Arkansas this time of year it's common to have lows in the 20's and highs in the 40's. If it's 25 at 7am and 40 @ 11am I wonder what that core temp of the engine is (esp cylinders) @ 11am. My bet is closer to 25 than 40. Does it matter? I don't know.

I've got an insulated hangar and tend to preheat anything that is 40 or less.
 
Run split weight oil, watch your oil pressure on start up, I don't like to go above 1,000RPM until I have CHTs over 200, but at 30 I'd start her up.
 
I spun the prop a full turn by hand and then cranked it right up.

Carb icing was basically immediate and I had to run it the whole flight but otherwise a pleasant ride. The pitfalls of it being 25 degrees with 60% humidity.
 
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