Do I need to plug in for a 1-hour stop over?

I flew Saturday on a breakfast run. My engine heater is a pad on the oil pan, one on the top of the case, and bands on each cylinder. Plugged in overnight with cowl flaps closed, and cowl plugs in and a thick blanket on. The outside temperature was 18 degrees and the oil temp at startup was 91 degrees. We flew 35 minutes to KUIN, I shutdown and closed the cowl flaps, and installed the cowl plugs. We came back out 90 minutes later and on startup the oil temp was 60 degrees.
 
These would make for a great prop sock. It's that the bay area?
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I adapted a horse blanket. You can buy them off of eBay for 70 bucks. Waterproof nylon with insulation. The prop fits nicely where the tail would go.
 
Stewartb said:
I've preheated more airplanes than most. Two things I've never seen. A preheated engine melt any prop frost, even in close to the hub, and when using my best prop covers I've never recognized any warmth in the prop blades after any amount of preheat, including overnight.
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Very interesting...

Huckster79 said:
Interesting! All my knowledge is theoretical and from reading at this point, i should grab my buddies infered or laser temp gun and do it both ways to see what that says... im always open to an opinion change especially theory vs real world experience..
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That was my first thought too... Time to go dig out the temp gun! Metals have high heat conductivity, so there will likely be more heat loss from the prop than from convection in the cowl, per surface area (and the temp diff, assuming the cowl is blanketed and plugged).

In my hangar, I just use a plain old soft bed blanket on top of my cowl, plus cowl plugs... But I wrap the blanket around two of the three prop blades, and kind of pull it around the top one as much as I can.

I guess what we need to do for this test is to record ambient temps in the hangar for maybe ~12 hours, and measure the temp of the engine and prop blades without having run the heat at all, and then after having the heat on for an extended period.
 
James331 said:
For a hour you’ll be fine.

Or just buy a thick sleeping bag from Walmart and use it was a cowl blanket
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No kidding. That works well. In Alaska, we kept our airplanes warm with sleeping bags and J.C. Whitney electric window heaters!
 
I had a chat with an Alaskan friend who does feel heat in his prop. Turns out he uses a little electric heater with a fan to preheat. With that his accessories get hot long before the engine is ready and that includes the flywheel, so in that scenario heat moves into the prop hub and blades. I use a Reiff system so heat is directed to cylinders and sump only, and the engine is ready to go faster than with hot air so I don’t notice any warmth at the prop. I still have a Little Buddy electric heater and figured to give it a test against the Reiff using my optical thermometer when I find myself with nothing better to do. That won’t be soon!

A good aircraft preheater will put out enough heat to overcome whatever loss a prop might contribute to. I used big puffy engine covers for years but now with the Reiff system doing such a good job I’ve changed to engine covers with half the insulation and half the bulk. There’s no difference in preheat effectiveness.
 
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Stewartb said:
I had a chat with an Alaskan friend who does feel heat in his prop. Turns out he uses a little electric heater with a fan to preheat. With that his accessories get hot long before the engine is ready and that includes the flywheel, so in that scenario heat moves into the prop hub and blades. I use a Reiff system so heat is directed to cylinders and sump only, and the engine is ready to go faster than with hot air so I don’t notice any warmth at the prop. I still have a Little Buddy electric heater and figured to give it a test against the Reiff using my optical thermometer when I find myself with nothing better to do. That won’t be soon!

A good aircraft preheater will put out enough heat to overcome whatever loss a prop might contribute to. I used big puffy engine covers for years but now with the Reiff system doing such a good job I’ve changed to engine covers with half the insulation and half the bulk. There’s no difference in preheat effectiveness.
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I’m sure they will get it warm enough without it wrapped but I do want to heat gun it and see the difference if any. My thought is every degree you get is that much quicker to operating temp- something my c85 doesn’t like to get to when cold out fast at all. I don’t think the prop thing is 200% necessary but feel until I test it every degree is closer to operating temp. Heck I read one guy who preheats at any temp outside in the thought of getting closer to operating temp that much quicker... that’s probably over kill but I get his logic...
 
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Skip Miller said:
Excellent idea! Please do this, and report back!

-Skip
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Will do, may be a minute, I got caught in bad spot getting my TW endorsement, all but done- so close was told if all runways were grass I’d have it and we should do one or two more times out then my instructor got called in for knee surgery... the other guy who’s around here that not only instructs but flies TW himself is going to finish me up but has another job so I’m grounded until he has a break in his schedule.

Once signed off I could do a couple variations over a couple different days and track the data...I will definitely share once done
 
Stewartb said:
I use a Reiff system so heat is directed to cylinders and sump only, and the engine is ready to go faster than with hot air so I don’t notice any warmth at the prop.

A good aircraft preheater will put out enough heat to overcome whatever loss a prop might contribute to.
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I also use a Reiff, and like them a lot. Cheaper and better than Tanis IMO (bands vs. screw-in single point heat, no need for funky CHT probes, etc)

However, my concern isn't that the heat lost through the prop will somehow cool the engine too far - My concern is that the crankshaft may lose enough heat through the prop to be below the dewpoint inside the case, leading to condensation, which would be bad.
 
Okay, but I only preheat before flying. Condensation goes away at normal operating temps.
 
flyingcheesehead said:
I also use a Reiff, and like them a lot. Cheaper and better than Tanis IMO (bands vs. screw-in single point heat, no need for funky CHT probes, etc)

However, my concern isn't that the heat lost through the prop will somehow cool the engine too far - My concern is that the crankshaft may lose enough heat through the prop to be below the dewpoint inside the case, leading to condensation, which would be bad.
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That seems like a valid concern for those that leave it on all the time... or being in a spot like myself that warmed it up for my last flight to finish my endorsement which got cancelled- so I’ve chosen to leave it plugged in vs letting it cool through dew point again... so wasn’t my intention to leave it on but understand doing what I’m doing is lesser of 2 evils-I’m hoping wrapped up like it is no part of its reaching dee point..
 
For an hour, no. Unless it's extremely extremely cold or there's a lot of wind blowing it will be fine. I might throw in the cowl plugs. If you want to understand why feel how warm your dipstick is before you depart- that's how much heat your pre-heater put into the engine. Now when you go do your lunch stop, check the oil again before you leave, I bet it will be significantly warmer. This is a fairly basic but effective way to gauge how warm an engine is before starting up.

As for when pre-heat is required my experience with a Piper Archer and it's Lycoming O-360 was that it was hard to impossible to get started below freezing without it. YMMV.
 
Just finished my $40 closed loop engine dehumidifier, going to add that to cut down on corrosion worries. I get that its debated if they help, but for $40 over the years I'll gamble it. Plus I like dining room table engineering things... One 60 gallon aquarium pump, an oil/water/particulate filter for air compressor, a few fittings from hardware store, two rubbermaid left overs containers, and a bag of silica gel kitty litter, is all I had to buy, had some old compressor hose laying around and a tube of silicone to seal things up.

Not trying to divert a preheating discussion but not totally unrelated. I also feel its important as I haven't been able to get my temp up to 180 since we picked her up last month, 150 is best I can get. Going to tape up the prop side of the front cowl vents until I can manufacture replicas of the winterization kit Cessna sold for em to see if that helps a bit. But been concerned preheating it when flying hasn't been able to get it to 180 for the last 10 or 12 hours of flight...
 
Huckster79 said:
Just finished my $40 closed loop engine dehumidifier, going to add that to cut down on corrosion worries. I get that its debated if they help, but for $40 over the years I'll gamble it. Plus I like dining room table engineering things... One 60 gallon aquarium pump, an oil/water/particulate filter for air compressor, a few fittings from hardware store, two rubbermaid left overs containers, and a bag of silica gel kitty litter, is all I had to buy, had some old compressor hose laying around and a tube of silicone to seal things up.
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Cool. Would love to see a thread on the build.
 
flyingcheesehead said:
Cool. Would love to see a thread on the build.
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I will do that, I'll let you know when I do. It was crazy simple... The airflow is pretty low but Im not sure thats a bad thing with using desiccant to pull the humidity out, fast moving air may not get exposed to the silica long enough to do much... And lets face it not tons of cubic feet of air inside an airplane engine. I will do a thread on it...
 
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