Cross Country in Cold Weather

[kitfoxjen]

Hello y'all,

Ok. So if I'm flying across the country in winter, cold weather, how well will the antifreeze protect the Rotax 912ULS engine at night if it gets down into the teens?

Example: I fly all day, land in ColdTown for the night. There is no room inside a hangar to put it inside for the night. It gets down to 15 degrees that night.

The next morning, will it start? What if I don't have pre-heat available?

Ideas?

Thank you

Jen

[N82HB]

Jen,
You might be asking to questions here. The anti-freeze will protect the engine from freezing just like in your car down to the negative digits.

But then will it start is totally different. Starting in cold temps is based on lots of different things. Battery size and spark plug gap play a huge role in how your engine starts in cold weather, every 912 installation seems different.

If you go to your favorite Wal-Mart and buy a travel size hair dryer it will fit in the cowl nicely. It is really hard not to have pre-heat available like this. Nose the airplane up to an outlet and give it 30 to 45 m,ins while having your coffee. I have gone to the airport and plugged in the hair dryer and then ran to breakfast. When I returned the engine and oil were ready to go. Throw something over the cowl (even your coat) and it help even more.

People laugh at my hair dryer until they see it is Genius!
Kelly

[Travm1982]

Hey, Whatever works! I might be wrong because its been a while, but I think its recomended to preheat anytime the temp is below 25 degrees F. That is if the engine is cold/ hasnt been ran for a few hours.

[Esser]

Cold start ups are the hardest thing for any engine.

[Dave S]

Hi Jen,

On the coolant, if it is 100% propylene glycol (Evans Waterless) the melting point/freezing point is -74 degrees F. If it is 50/50 ethylene glycol, the melting point/freezing point is -34 Degrees F. Where people get bit in the butt on freezing point of coolants is if they have a non standard or diluted mixture or don't know what is in the system.

I don't think anyone can tell you if the engine will start or not from a cold soak condition withour pre-heating.

A good strategy is to read the Rotax cold weather operation section of the engine operators manual, get everything up to spec then experiment at different cold temps where you know you can use a pre-heater (the hair dryer is a great improvisation BTW) or have an FBO handy to help with thawing out the plane if it doesn't start. Experimenting will tell you when it will start and when it won't without pre-heating - it's good to know even if it is not your usual procedure.

What a person needs to do is optimize the engine for cold weather operation to improve your chances of a start in the cold.

This means:
1) The correct grade of oil (low or multi viscosity rather than the thick stuff);
2) A battery which is new or at least near new condition with regard to capacity and fully charged (I have a dual electrical system where a cross tie switch throws both batteries on line when I want it) The Rotax has a minimum RPM - it'll never start if the minimum RPM is not met;
3) Be sure both chokes close completely when the cable is pulled to enrich;
4) be sure the correct grade of fuel is on board - with auto gas, summer gas has a higher vapor pressure (volatilizes at a higher temp) and winter gas has a lower vapor pressure (volatalizes at a lower temperature) {I don't know what is available at your location???}
5) Be sure your spark plugs are clean and at the correct gap (Rotax permits a slightly wider gap in cold conditions I believe).
6) Learn and use a correct cold start procedure:
A) Rotate the prop to help ease the initial cranking and help assure the fuel level is up on the carbs
B) Throttle in the correct position
C) If you have a primer use it
D) If you have a boost fuel pump, use it
E) Choke in the correct position
F) Hit the starter switch and be ready to modulate the choke to keep the engine running for the first few seconds and adjust the throttle.
G) If it doesn't start right away or real soon - stop before the battery gets worn down and the engine flooded. If you get a low cranking RPM, it'll flood and won't start anyway. There is a limit and wait time to cool the starter between attempts - good to know that for your particular engine.

Now, with N128DD, I have always had the opportunity to plug in my pre-heater (a modified dairy parlor electric heater) so if it is much below 30 F it gets plugged in. I have always had no problems with cold starts down to 28-30F where I have tried it and I can't honestly say how cold it would have to be to prevent the engine from starting simply because I haven't tried it. The heater and 100" of 12 gauge cord go with if the plane will be left for a long time.

We have had a few chillier days down in the -10 to -15 lately so there is no ambiguity as to whether or not the plane gets pre-heated.

Start or not...it's a matter of increasing your chances down to a point. Ideally we preheat them, as a practical matter a person should have a pretty good idea and that only comes with some experimenting with your particular engine to figure out what that magic temperature is.

Alternatively, a person could get up every 2-3 hours and run the engine if they are really out in the boonies. Also helps retard cool down if you have some kind of cowl blanket and cowl plugs.

Good luck,

sincerely,

Dave S
KF7 Trigear - Flying
912ULS - Warp Drive

[deejayMB]

I worked at a flight school with a fleet of 912-powered Katanas. We plugged them in whenever temps were below freezing (ceramic heaters for cars stuffed in the cowl air exit and engine blankets) and there was an absolute ban on attempting a start below -10F. We used waterless coolant and the Rotax-prescribed oil. The real problem we found was getting the oil temp above 180 in flight (required to boil off the acids formed by combustion.) The oil would develop a murky milky appearance from suspended water droplets and have to be changed more frequently. Being a certified airframe/engine, we had problems getting an effective oil-cooler restriction approved by TC, but it happened before the first winter was over.

[Esser]

The best oil you can use for cold weather is synthetic. The problem is that synthetic oil doesn't scavenge lead so you get dangerous build ups. Shell had this issue back in the 80's. But if you are using auto gas in your flying machine, by all means use synthetic. Your engine will thank you for it. Your cold starts will be much easier and if you ever over heat your engine you don't have to worry about doing an oil change right after.

[Jfquebec]

A long time ago in north of Quebec the guy's land on frozen lake and he flush is oil faster in big metal can,,,and when is ready to start he make a fire and heat is oil to put it faster he can in is engine,broutpoutoupp!,!Take of.....


Jf