i know that it is not good to run rc car engines in cold weather. is this also true for model engines on airplanes/helis? if so how cold before it gets damaged? This will help me decide choose what plane/ engine to buy. thank you

Only thing that gets damaged is that you get cold.

If you can get them started and let them warm up a little before removing the glow plug heat, they actually like cold weather

As the weather gets colder, you have to open the needle valve a little to allow for the denser air

There's nothing wrong with running them in cold weather. Snowmobile engines are air cooled and they run in the wintertime--you ever heard anyone say NOT to run a snowmobile engine in the spring, when temps are warmer?

You will have to adjust the high speed needle to flow more fuel. Cold air is more dense, and therefore the engine will actually run better. You'll need more fuel to get the mixture correct. I even run my low speed needle about 1/4 turn richer in the winter.

How cold do you consider "cold"?

I've noticed that my engines don't throttle well when the temps get down into the 20's or lower, so I wrap some alum. (the real, metal foil ) duct tape around the cyl. I also go from (just an example ) an O.S. #8 to an A3 and from 10% to 15% nitro...along with the obligatory needle adjustments.

If I am shooting touch and go landings and the throttle is pulled back for a while, the engine will cool down to the point where it does not want to throttle up...and I'm thinking that could also be carb ice.

I have used a somewhat disposable engine (.46 Pro or FX ) but a ringed engine would be better I think...and I would not use an ABC/N etc. type that I really cared about during winter...JMO.

Some of the engines that I have run in the cold have seemed to exhibit more wear, and sooner, than the other engines that have never seen the cold, but that's really difficult to determine for sure.
(that's where I think a ringed engine might be better...if there was distortion caused by uneven heating/cooling around the cyl. the ringed engine might be slightly more "forgiving" than an ABx type? )

Few people fly around here (Finland) in the cold and when it is cold it is VERY cold, i.e. like -16 to -26 deg.C is the temp. most
likely in Dec-Jan-Feb. I have given up to fly duringthose months. Still the more "friendly" cold months of March-April and then
Oct-Nov the temperatute is +/- 5 even +/-10 deg and then flying is quite OK if the there is sunshine and low humidity.

Problems with Engine: - have to lower the oil contents otherwise you cannot turn it even by hand, nitro is not so needed.
In this cases I wash the engine with 10-20 cc pure methanol and then use even 20% castor oil fuel. But the real big
PROBLEMS are in the Battery, Glue joints and Plastics, which when give up to the cold would result in a bad crash
just like that - no "visible" reasons, it was just ... cold enough.

For battery the solution seems to be either NiCd, or any other type+voltage stabilizer; I use NiMH and 6V regulators
which in fact leads to the need to fly with 8 cells (10V) in order to have room for the voltage going down due
to temperature and the voltage drop over the regulators; this I have "nicely tested" together with the whole
radio+servos in my frizer to temperatures down to -26 deg.C and works fine.

Well, as it was said, take care for your fingers and hands - they can get badly damaged.

I ran into this for the first time this last weekend. I have a GMS .32 that ran like a top everytime I took it out this summer. Mid-30s this winter wreaked havoc on it and once I increased the richness it was again happy. There was no way it was going to run with that summer setting.

somegeek

The air-fuel ratio for gasoline is close to 14:1

With methanol it is somewhere on down around 5 or 6:1. What ever it is, it is significantly different than gasoline.

Therefore with a greater density of the air will mean more significance with the amount of fuel when you are running methanol.

Nitro methane makes this phenomena even more noticeable because it has a air-fuel ratio below 2:1.

http://www.smokemup.com/tech/fuels.php

I think part of the theory is that in cold weather the cylinder is so cold it causes too tight of an interference fit with the piston on an ABC engine. I don't believe that it happens enough to be detrimental to the wear of the engine, since it heats up to operating temperature fairly quickly.

A more real problem is just getting the engine to start in cold weather, especially larger displacement glow engines. We have discussed that here on RCU in the past, and several recommended using a little Naptha (Zippo lighter fluid) to get the initial start up. Others suggested using a higher nitro blend in the winter months.

Back 40 years ago I would use the zippo fluid to prime a engine. It just takes a little.

It would start on the first flip.

Watch your fingers.

It is 18 degrees outside right now. A heat wave from yesterday. I have not considered going flying.

I'm with you on that. Every year I plan to buy some skis for one of my planes and promise to fly off snow, and every year I realize I don't like cold weather enough to spend much time in it. Oh well.[:-]