Cold weather operations. Preheat?

[Art Tiller]

Hi All,
What are your strategies for preheating your Sonex?
Thanks,
Art

[XenosN42]

I have a OneX with AeroVee, which is hangered. I do fly in the winter.

I use a dragon propane fired heater. https://www.aircraftspruce.eu/engine-parts/engine-preheaters/red-dragon-engine-preheaters.html

I'll preheat if: a) the hanger temperature is below 30F or b) if the over night temperatures have been below 20F for a few nights (engine block is very cold soaked). I use the heater until the oil temperature reaches at least 70F. I always wait for a 70F oil temp before I do the mag check during engine runup/pre-flight. I budget about 15-20 minutes for the pre-heat; perhaps 30 minutes if it's really cold (low 20s) and it has been for a few days.

[GraemeSmith]

I will wrongly intermix the terms "weight" and "viscosity" for oils in the following - but you will get the idea!

Certificated engines usually come with a requirement to preheat if the temperature is 20F or lower.

In the days of single weight oils that turned to jelly in the cold - there used to be an old trick of adding a pint of AvGas per 4 quarts of oil in the sump and pulling the engine through to mix it all and dilute the oil prior to starting. As the oil warmed the AvGas would boil off through the crankcase breather....

Modern multi-weight oils get around this by being thinner in the cold and stay thick in the heat. But even a 20/50 will start to turn to jelly when it gets cold enough.

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To take the AeroVee as an example - I am sure running around the streets of Germany in a VW Bug in the winter - a cold start where it took a while for the oil to warm up and really lubricate was not an issue. Worst that happened was the engine wore out early. In a plane?....

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So I use 32F as my decision point. If the plane has only just got down to that - the engine will start fine. If the plane has been cold soaked overnight and the temperature is just coming up on 32 - I DEFINITELY preheat. A little of "Mr Red Dragon's" breath, gently applied to the sump and allowed to rise up through the engine compartment and contained by an insulated blanket will get the engine toasty in about 30-40 mins while I do a methodical pre-flight. I wait till the front cylinders no longer feel "cold" but they don't need to be hot either. Just enough to not feel like cold metal.

Added benefit - the battery will be warmer and livelier!

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Note - Red Dragon suggest blowing in through the front cowl openings to get the cylinders warm. That's what you will get from a "Winter FBO" that give pre-heats as a service. That works - it's the short cut way of getting a start. But it doesn't take care of the cold oil in the sump and the rest of the metals in the engine. I'm paying for the engine - I'll take my time and gently pre-heat the whole thing. This just yesterday. After preheating use your WARM start procedure. Not a cold start procedure.

Keeping a big extinguisher handy in case you get a bit aggressive with the heat and light something off is a good idea.

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Related Note - MGL's AHRS units do not work well in the cold. They do contain microheaters to get all the electronics up to temperature and tolerance - but can take 20 mins turn on time to do so. Don't depend on your AHRS till the horizon is demonstrably stable after the avionics have warmed up.

[Art Tiller]

20220209_071642.jpg

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This is great information. Thank you.

[mike.smith]

My solution:
https://www.youtube.com/watch?v=4ujF3cdGW5M
I have the extension cord plugged into a "Kasa" Smart Plug so I can turn it on/off from my phone.

I used this before I had a hangar, setting it up the night before flying.

Doing this the night before ensures that not only is the oil warm, but all the metal parts of the engine are warm, saving tremendously on wear during startup and warmup.

[Bryan Cotton]

My preheat needs are modest, because I heat my hangar to 40F, although it often seems to be about 50F in there. I made a duct out of flashing that hooks on the sides of the cowl air exit, and I blow a heater into the duct. I have cowl plugs also. It seems to give me about 10 degrees F temperature rise per hour. I've only used it twice. Once for a test, just for an hour. Today I had it running for two hours before my flight and the oil was about 70F.

[GraemeSmith]

Oh for a hangar.........

[daleandee]

For all you pilots that are pre heating your VWs ...

https://www.youtube.com/watch?v=ABcckOTVqao

[GraemeSmith]

For all you pilots that are pre heating your VWs ...

https://www.youtube.com/watch?v=ABcckOTVqao

HA!

And I bet he didn't have any cabin heat either........

[Bryan Cotton]

I remember that commercial. My dad had a bug. I'm pretty sure it had no external oil filter to blow when the oil was cold! Meanwhile I'm getting weather and waking up, and my preheat should have kicked on 45 minutes ago.