How cold when you do not preheat engine

The club rental I fly stays plugged in during the winter (parked in covered outside hangar) plus there is an electric heater available to put in thr cockpit during preflight to knock the chill down.

The 152 is parked inside and the electric heater is placed under the cowling to warm up. I'm guessing it doesn't have and oil pan heater but I'm not sure. I never fly it.
 
I don't know why you guys don't preheat at 70*? If your cutoff is 40* and the temp is 39* how long do you preheat? What internal engine temp are you trying to achieve and how do you measure it? Reading about your temp limits and then about some of the preheat methods is downright funny.
 
Stewartb said:
I don't know why you guys don't preheat at 70*? If your cutoff is 40* and the temp is 39* how long do you preheat? What internal engine temp are you trying to achieve and how do you measure it? Reading about your temp limits and then about some of the preheat methods is downright funny.
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Dun worry about it.....It's soo cold where you're at....pre-heating is ineffective. :lol:
 
Fearless Tower said:
Going out and acquiring 300' of extension cords to do a single startup on a 35F day is a bit excessive.
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Well, so is getting nervous about one cold start at 32 when the engine manual says 20 is fine, but the OP seems to be ignoring anything that doesn't fit his preconceived notion of what should happen. :)
 
Checkout_my_Six said:
Don't know....mine is plugged in and blanketed up the night before and is toasty warm in the morning....using just an oil pan heater. The complete engine cell/cowling area is above 70 with an OAT in the teens.
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^^^this^^^
 
blueskyMD said:
True but Lycoming does not have to pay if things get broken down the road.
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Sure, they aren't liable for an individual engine, but they are absolutely liable for the fleet and it seems impossibly unlikely that the engine is going to self destruct if started at 18F. Said another way, the 20F recommendation definition has some engineering tolerance built into it. If you want to preheat below 32F (as we did at my club basically to ensure that our members were in the habit of putting the heater on all winter) then fine. For me it's almost worth it just to have the cabin heat come online instantly. Just don't try and claim it's a safety issue when the manufacturer has had tens of thousands of engines running in alaska for decades and says that 20F is fine.
 
who said anything about this being a safety issue?....it's more of a wear and tear issue....and ease of starting issue.

172andyou said:
Sure, they aren't liable for an individual engine, but they are absolutely liable for the fleet and it seems impossibly unlikely that the engine is going to self destruct if started at 18F. Said another way, the 20F recommendation definition has some engineering tolerance built into it. If you want to preheat below 32F (as we did at my club basically to ensure that our members were in the habit of putting the heater on all winter) then fine. For me it's almost worth it just to have the cabin heat come online instantly. Just don't try and claim it's a safety issue when the manufacturer has had tens of thousands of engines running in alaska for decades and says that 20F is fine.
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Old bush pilots used to bring their batteries and oil inside with them for the night
 
Checkout_my_Six said:
Don't know....mine is plugged in and blanketed up the night before and is toasty warm in the morning....using just an oil pan heater. The complete engine cell/cowling area is above 70 with an OAT in the teens.
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The whole engine block and cylinders are 70+ just from heating the oil pan?
 
paflyer said:
The whole engine block and cylinders are 70+ just from heating the oil pan?
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The whole engine is basically one big conductive heatsink. Heat one part and that heat's going to migrate to all of the other parts eventually. Oil pan heaters can be very effective if they're given enough time to work. They won't heat as fast as a full system with cylinder bands, but they'll do a more than sufficient job in around 6 hours or so (depending on ambient temps).
 
Checkout_my_Six said:
what material is on the outside of the steel cylinder in the choke area?...that's where clearance is lost. :eek:
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There is no "choke" in most aircraft cylinders, and the aluminum head isn't going to crush the steel cylinder much at all when it's cold.

Aluminum has a coefficient of linear thermal expansion of, IIRC, about .00001255 units per degree F. Steel is a hair over half that. Now, take that cylinder and head and lower their temperature by 40°F and see how much contraction there is. And then figure the amount of expansion at a CHT of 400°F. Is a cold day really a concern here?
 
The outside temperature is not the issue, it is the inside temperature. If it sits overnight at 25F and you arrive in the morning and it is 40F outside, the engine may still be allot colder. The reverse is true as well, if you can get it warmed up before the FBO closes and put a blanket over the engine and maybe the battery, it may not cold soak overnight.
 
paflyer said:
The whole engine block and cylinders are 70+ just from heating the oil pan?
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It works if the engine is covered and the sump is attached to the engine.

Probably less effective with a setup like I have with a separate oil tank located on the other side of the firewall from the engine
 
Dan Thomas said:
There is no "choke" in most aircraft cylinders, and the aluminum head isn't going to crush the steel cylinder much at all when it's cold.

Aluminum has a coefficient of linear thermal expansion of, IIRC, about .00001255 units per degree F. Steel is a hair over half that. Now, take that cylinder and head and lower their temperature by 40°F and see how much contraction there is. And then figure the amount of expansion at a CHT of 400°F. Is a cold day really a concern here?
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sounds like you've worked for either TCM or Lycoming? :eek:
 
My switchover point on when to preheat is just colder than the point that I refuse to be outside doing a preflight. There is such a time as too cold to fly.
 
cgrab said:
The outside temperature is not the issue, it is the inside temperature. If it sits overnight at 25F and you arrive in the morning and it is 40F outside, the engine may still be allot colder. The reverse is true as well, if you can get it warmed up before the FBO closes and put a blanket over the engine and maybe the battery, it may not cold soak overnight.
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How long does it take for the close tolerance areas to heat up?
 
172andyou said:
For me it's almost worth it just to have the cabin heat come online instantly.
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This is really nice. Warm air right after starting up is great. Warms up the cabin quicker and keeps the windows from fogging up.



Wayne

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Checkout_my_Six said:
who said anything about this being a safety issue?....it's more of a wear and tear issue....and ease of starting issue.
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He did. See above his comments about flying at night over hostile terrain. I don't get it either.
 
bradg33 said:
The whole engine is basically one big conductive heatsink. Heat one part and that heat's going to migrate to all of the other parts eventually. Oil pan heaters can be very effective if they're given enough time to work. They won't heat as fast as a full system with cylinder bands, but they'll do a more than sufficient job in around 6 hours or so (depending on ambient temps).
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Don't forget a lot of that heat is also radiating away. Looking at adding Reiff to my engine with sump pad and cylinder bands; you saying that the sump heater is sufficient? Perhaps if it's on all the time... If that's the case I can save hundreds of bucks in parts and labor.
 
paflyer said:
That's gotta take a loooong time, and produce very uneven temps.
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Depends on how cold it is. The sump only heater is plenty sufficient for an airplane kept in a hangar in outside temps 20-30F if you ran it overnight.

If you are in the frigid north or Great Lakes region, you would be best suited with a full Tanis or Reiff preheat setup.
 
paflyer said:
Don't forget a lot of that heat is also radiating away. Looking at adding Reiff to my engine with sump pad and cylinder bands; you saying that the sump heater is sufficient? Perhaps if it's on all the time... If that's the case I can save hundreds of bucks in parts and labor.
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Here's the data from EZ Heat. With 6 hours of pre-heat, the airplane can be outside, with no cover, in damn cold weather and still have hot oil and warm-enough cylinders. Tests show that a cover only gets you about 10 more degrees in general.

http://e-zheat.com/test-results/
 
bradg33 said:
Here's the data from EZ Heat. With 6 hours of pre-heat, the airplane can be outside, with no cover, in damn cold weather and still have hot oil and warm-enough cylinders. Tests show that a cover only gets you about 10 more degrees in general.

http://e-zheat.com/test-results/
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Thanks for the tip, Brad. I owe you a warm beer!
 
Maybe in your temps. Try that where it's cold and the cylinders will be frosty. Try it without an engine cover and the oil will barely be warm. Been there, done that. Reiff solved the cylinder problem!
 
Stewartb said:
Maybe in your temps. Try that where it's cold and the cylinders will be frosty. Try it without an engine cover and the oil will barely be warm. Been there, done that. Reiff solved the cylinder problem!
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yup....why bother.....it's just too cold where you're from. :D
 
paflyer said:
Don't forget a lot of that heat is also radiating away. Looking at adding Reiff to my engine with sump pad and cylinder bands; you saying that the sump heater is sufficient? Perhaps if it's on all the time... If that's the case I can save hundreds of bucks in parts and labor.
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After moving to the MW, installed the Reiff and never looked back. Starts like a spring morning every time, with peace of mind...
 
Jeff Cutler said:
After moving to the MW, installed the Reiff and never looked back. Starts like a spring morning every time, with peace of mind...
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Did you just do the sump, or the cylinders as well? There's some info on their site re condensation if you don't do it all.
 
paflyer said:
Did you just do the sump, or the cylinders as well? There's some info on their site re condensation if you don't do it all.
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based on how hot my engine heats with just a sump heater.....I'm having a hard time believing that....and I have the big TSIO-520.
 
Checkout_my_Six said:
well....shoot, you should be able to design them then. ;)
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Never designed an aircraft engine, but did do a lot of design work in a machine shop and had to research much about the properties of various metals. Designing bronze bearings to fit into cast iron, steel, or aluminum housings, for instance, requires knowing what the press fit will do at various temperatures, from -40 to +350F. Get it wrong, and expensive machinery blows up. Also did a bunch of research regarding the use of aftemarket aluminum pistons in air brake compressors, and found that one maker's OEM cast iron pistons were made of cast iron for good reason. Wrote a paper on it and later saw another OEM that was using aluminum pistons switch to cast iron. Wide temperature variations caused excessive crankcase oil escaping into the air when the compressor was unloaded and cool; air brake compressors run constantly with the engine and the intakes are held open once the target pressure is reached. Clearances vary too much with mixed metals.

Enough years of that and you get a feel for certain stuff. The clearance problem at subzero temps, in an engine that sees clearances get bigger as it cools, shouldn't be the concern here. As I said earlier, it's cold oil that the pump can't suck up that's the real danger. And in cold weather, the fuel doesn't vaporize well, so priming has to be done intelligently, and if the engine fires a few times and stops, the water vapor that comes from combustion can sublimate as frost on the sparkplugs and short them so it won't fire anymore. Seen that here in Canada numerous times on really cold engines. Preheating fixes all of that.

And I overhauled my own aircraft engine. Resized the bores using the latest and greatest machinery of the day, 25 years ago. No choke.
 
paflyer said:
Did you just do the sump, or the cylinders as well? There's some info on their site re condensation if you don't do it all.
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Did both the sump and cylinders with the extra pad for the oil cooler, but that wasn't a one size fits all. Had to return it b/c it was too wide to mount between cooler frame.
 
Checkout_my_Six said:
based on how hot my engine heats with just a sump heater.....I'm having a hard time believing that....and I have the big TSIO-520.
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Do you leave the heater on all the time? How frequently do you fly it?
 
Just left Idaho back to California and ended up having to start the engine at around 20F, possibly a little colder. Oil was flowing fine at that temp. The prop was easy to turn. I'm sure I didn't do the engine any favors starting that cold, but I'm not too concerned about it. If I did this more often, I'd invest in preheat, but not for the one time.

Interestingly, what didn't work at first was my GPS and MFD. The KLN 94 required a two minute preheat that it counted down on the screen. The KMD 550 at first just didn't work at all with a blank screen. Later, it complained about failing interfaces. Then, about 15-20 minutes into the flight, it finally decided to start working.
 
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