Anti-Splat "NEWS"! Engine Pre-Heater

rvanstory said:

Question for the brain trust....

Got the Anti Splat oil heater for Christmas. Ordered this thermostatic controlled plug on Amazon.

https://www.amazon.com/gp/product/B015E2UFGM/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1

Is there any issues with setting it up to come on and off with plug even if I have no plans to fly? Plane would be ready "at all times". But, will it hurt anything to have oil heated up (possibly multiple times) without using the plane? I don't want to introduce moisture into engine somehow by doing this.

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I would not recommend doing this. Unless you have an external dry sump type of engine, heating up the sump and letting it cool down without flying it will introduce moisture into the crankcase and potentially cause lots of problems with corrosion.

Vic

Oil heater

How would moisture get in the engine by heating the oil? How is this different than my airplane in the summer going from 60 to 120 degrees every day sitting in the hangar? Just curious.

I think the idea is the top of the engine is cold as the bottom heats up first. The lower engine air picks up more moisture and rises where the colder part is below dew point and water condenses. With ambient temp changes the whole system remains at the same dew point and relative humidity.

That’s the theory. I’m curious to hear real world calamities that befell those who heat their oil too much?

Tanis has done considerable research on this topic with temp and humidity sensors located in the engine. They recommend if you have both sump pad heaters and cylinder heat that preheaters are left on continuously. The entire engine will be above dew point.

They recommend if you only have a sump heater only that you turn it on only if you intend to fly and don't leave it on continuously. If you have sump heat only the upper cylinders will be cold and likely be below the dew point causing condensation. The reason for flying is that you will burn off the moisture that may condense with the sump heat only.

There is a youtube video on this subject produced by Tanis.

Also many recommend that you open your oil dip stick tube cap immediately after landing to let out any moisture produced from the combustion process.

This topic has been beat to death over the past couple of decades. The final answer depends heavily on the climate and conditions in which the aircraft is stored. In my case the RV-6 is in an insulated hangar in north Alabama where very cold temps are short-lived. Therefore I can use just a sump heater 24/7 with a blanket over the cowl and cowl inlets plugged and the entire engine stays warm. Oil and CHTs will be 80F or above anytime during the winter.

I have been using this method since 2000 with no indications of engine stress. My RV-6 thinks it spends the winter in Florida.

Storage in colder temps or on a ramp will indeed need cylinder heaters to maintain total engine warmth. 24/7 heating is ok IF the entire engine is kept warm.

Sam Buchanan said:

This topic has been beat to death over the past couple of decades. The final answer depends heavily on the climate and conditions in which the aircraft is stored. In my case the RV-6 is in an insulated hangar in north Alabama where very cold temps are short-lived. Therefore I can use just a sump heater 24/7 with a blanket over the cowl and cowl inlets plugged and the entire engine stays warm. Oil and CHTs will be 80F or above anytime during the winter.

I have been using this method since 2000 with no indications of engine stress. My RV-6 thinks it spends the winter in Florida.

Storage in colder temps or on a ramp will indeed need cylinder heaters to maintain total engine warmth. 24/7 heating is ok IF the entire engine is kept warm.

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Sam’s practice here is different than the inquiry by the OP. The problem arises from allowing it to cycle on and off. Leaving it on constantly should not be a problem.

Vic

Jetmart said:

Tanis has done considerable research on this topic.
They recommend if you only have a sump heater only that you turn it on only if you intend to fly and don't leave it on continuously.

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Thank you all for your insights. Glenn, that's exactly the type of information I was looking for.

vic syracuse said:

Sam’s practice here is different than the inquiry by the OP. The problem arises from allowing it to cycle on and off. Leaving it on constantly should not be a problem.

Vic

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Not sure about Atlanta, but here in Chicago the ambient temps and dew points cycle pretty good all on their own. Woke up this morning and have frost all over my cars. Technically deposition and not condensation, but same principal. Are you suggesting that is somehow not happening to my airplane engine if I don't have the heater on?

Mother Nature throws us all sorts of temp swings, some as large at 30* in a 24h period and sometimes with pretty radical humidity level changes. While I agree this is not good for what we are trying to avoid, it is happening daily whether we like it or not. Excluding, of course, those lucky folks with climate controlled hangers.

I am not providing a definitive answer here, but do know it is a bunch of complex science to assess the affects of moving ambients and dew points, along with shifting humidity levels and the effects of temp on saturation levels. Whether or not one or all of these changes will produce liquid moisture on a part is a pretty complex calculation and likely varies with each unique mix of variable changes.

For the record, I also feel that cycling a heater on and off is not a good thing to do for the reasons you imply. However, that is pure conjecture on my part and have no research or science to back that up; Just a logical conclusion based upon the limited knowledge that I have.

One thing I do know is if I take 10* air (air can hold very little moisture at this temp) and heat it to 70*, it will still have very little moisture content and therefore little to condense. Here in chicago winter, if I do not add moisture back into the heated air it will be very dry. That air contacting the 10* window pane WILL NOT create condensation, even though well below the typical dew point or 70* air. I will also be getting constant shocks from static buildup. If I turn on the humidifier and start adding moisture back into the air, then yes, I will start producing condensation on the 10* windows, as the supplemental moisture is raising the dew point / RH levels.

A couple of my airport buddies are Michigan snowbirds, fleeing to Florida every winter for 5-6 months. One has a nice C-182, the other a RV-9A. They both use home made heaters under the cowling using simple reptile cage ceramic heating "bulbs". They are placed under the engine on the bottom cowling mounted on a metal heat shield to protect the cowling. The cowling is sealed up and insulated using blankets draped and tied tight to the cowling. I turn them on for them when the weather gets cold up here and I check them every so often making sure they are working. The engines are warm to the touch even in the coldest of winter. The heaters are on 24/7 until they return north. The ceramic bulbs are replaced with new every season.

Great thread! I found it instructive to read the ASA, Tanis, and Reiff FAQs. All three come at the preheat/humidity/corrosion issue from slightly different perspectives and all three cite different scientific resources. But there is some convergence in their conclusions, and as Sam noted, there are different solutions for different climate zones and use cases.