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Winter operations / lowest temperature for starting / preheating methods (merged)

Never really thought about it. The coldest I’ve started is probably about minus 8 and that aircraft on D80. I go for the theory that our aircraft rarely go longer than a week between start ups so (hopefully) there will still be some oil covering the camshaft in the C152.

Does take an age (20 secs) for the oil pressure to get into the green.

At the last Tannkosh, some company was showing an insulated cowling cover with a sleeve connected to a thermostat-controlled electric hot air blower. They claimed to maintain engine at positive temperatures in outside air temperatures below –20°C (don’t remember the exact figure).

LKBU (near Prague), Czech Republic

One problem with all this stuff is that few if any hangars (other than privately owned by pilots) in the UK will let you use it.

And one has to see their point… the fire hazard. Maybe the hazard is very small but one can see where a concern might come from.

We had a thread here recently on doing work in one’s hangar. Some people suggested that it is a problem confined to the UK and could not see why. Then one UK pilot posted that his airport banned it after one owner set his aircraft on fire with a soldering iron which was left unattended. Unfortunately that post was deleted (it went into the wrong thread) and not re-posted… So this concern is real – despite an unwillingness by some to talk about it openly.

If I had my own individual hangar, I could very easily plug in a mains powered heater. A small heater screwed to the sump, say 100 watts (there is such a product) would easily do the job. My wild guess is that a cowled engine, no forced airflow, would have a thermal resistance to ambient of the order of 0.1C/watt so 100W would give you a 10C (10K for the purists ) gain. 200W would probably be OK – the sump is not all that thick (5mm?). But it could also be temperature-limited to say +50C.

Administrator
Shoreham EGKA, United Kingdom

Peter do you think that formula also would work with two 1’000W cartridge heaters stuck up the exhaust pipes :) ?

I think that is a very bad way to heat an engine; the heat would be very localised. During running, there is a lot of airflow under the cowling to prevent the exhaust burning some nearby item.

IMHO screwing a power resistor like this

to the bottom of the engine would be a good way. You would need just two tapped holes, and remove the paint at the interface and use some thermally conductive paste (like for mounting PC processors). The commercial versions are just neater solutions.

Administrator
Shoreham EGKA, United Kingdom

We had a thread here recently on doing work in one’s hangar. Some people suggested that it is a problem confined to the UK and could not see why. Then one UK pilot posted that his airport banned it after one owner set his aircraft on fire with a soldering iron which was left unattended. Unfortunately that post was deleted (it went into the wrong thread) and not re-posted… So this concern is real – despite an unwillingness by some to talk about it openly.

As a data point, my base has around 500 aircraft in hangars, and I’d estimate that 400 of those are regularly serviced or otherwise fiddled with inside the hangar. As far as I know there have been two hangar fires in the last 60 years, one of which was minor (and caused by the occupant) and the other of which was caused by an unmanned jet fighter falling from the sky into the hangars.

PS In the mid-70s, my dad used to start his four cylinder Continental with (ether) starting fluid when it was stored outside in the snow in let’s say -10 C weather. After a while people decided that wasn’t the perfect approach , but it’d been done for decades beforehand.

Last Edited by Silvaire at 03 Feb 17:34

And one has to see their point… the fire hazard

Nonsense! I have never heard of any fire hazard due to electrical heaters, and we use them here all the time 6 months a year (or more).

http://www.aircraftspruce.com/menus/ep/enginepreheaters.html?pageno=1

Get one that heats up the oil (pad or similar). They can be left on 24/7 all year round.

Last Edited by LeSving at 03 Feb 17:57
ENVA ENOP ENMO, Norway

This item:

Incorporates a pressurised fuel burning cooker element (as used by mountaineers to heat their beans) into a duct which feeds the hot air into the cowling. I put it in via the cowl flap. It can burn virtually any liquid fuel, but I have always used Avgas, obviously.

They are manufactured in Alaska, where they are claimed to be effective.

I must say that I have not found it very effective, but if anyone wants mine (I may have two in the garage, I am not sure, but definitely one) they are welcome to try it. Collection from Epsom preferable.

EGKB Biggin Hill

To answer the original question: -10°C is probably the lowest for a piston engine that I would dare. Below that, the battery is not going to be strong enough anyway in most cases, at least if everything is cold soaked. And where ground power is available, there usually also is an engine heater… Our training aeroplanes are parked in the open and on the few days every winter which are colder than -10C, they will be frosted over so badly that defrosting/deicing is going to be a much bigger problem than starting the engine. It’s best to go for a nice breakfast with the student and come back two hours later when the sun has done 80% of the job.

At the home base, usually one can easily arrange something: Ground power, heater, one or two hours in a heated hangar, even if the aircraft owner is not a renter of hangar space. Know somebody who knows someone and everything will be fine. Off homebase is much more difficult, especially at smaller airfields without any kind of facilities. Even with our bizjet operation, in winter we always try to arrange hangarage overnight or at least a couple of hours before departure, everything else is a gamble. The cold-soak limit of “my” Citations is -38°C – the oil is much thinner than piston engine oil, so no factor, but the cabin seals become brittle below that temperature and pressurisation is going to be a problem. But honestly I would not want to try that. After one night in Sweden at -20 … -25C we had big trouble with some systems already.

Last Edited by what_next at 03 Feb 19:13
EDDS - Stuttgart

I have never heard of any fire hazard due to electrical heaters

I tend to agree; I was just trying to get myself into the head of the average risk management (the latest MBA fashion) type around the UK

I must say that I have not found it very effective

I reckon you would need way more energy to heat up a 200kg IO540 lump than a tin of beans.

There is also no way to spread the heat fast enough; if you applied say 100kW to the engine sump, it would melt the sump without doing anything anywhere else. I reckon the most one can apply on the bottom is a few hundred watts, and I will leave it to somebody whose Physics O-Level is more recent to work out how long that would take to raise say 50kg of ally + 150kg of steel, with their respective specific heat capacities, by say 20K.

That’s why the “claimed best” products involve heating the engine at many places, with little heaters screwed all over the place. The installation of that one must be a big job.

Many thanks for the feedback, all… Today my engine was about -2C and started immediately, so I have the one data point!

Administrator
Shoreham EGKA, United Kingdom
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