Anti freeze for avgas

[fltcom]

Operation in cold temperatures occaisionally call for the addition of 2% Iso Propyl alcohol to avgas to prevent ice crystallisation of any water content. Has anyone experience of operating in the minus 9 to minus 15 C range, and should we be considering additives at these temperatures? We know the fuel supplied locally does not contain any.

Cheers

Flt

[2Donkeys]

I've used Isoprop through places like Greenland and Iceland, but only because I was then expecting to climb into much colder temperatures above. It was my understanding that the additive was to modify the freezing point of the fuel mix, and had nothing to do with the water (the alcohol and water don't mix anyway). If your tanks are prone to water, you'll find that plugs of ice form over the fuel-drains (inside) which tends to give the game away.

If you are expecting to operate at levels with the OAT is only around 10-15 below, then Isoprop is almost certainly unnecessary.

[fltcom]

Avgas hydrocarbons begin to solidify at different temperatures, as a result there is no specific temperature at at which it freezes, but certain elements will begin to form a sludge as the temperature drops. Avgas specifications dictate that this process will not begin until -58C (-72F) However water content within the fuel (if there is any) will freeze at higher temperatures. Iso propyl alcohol (ethanol) is a substance that will completely mix with water (sorry 2D - you were wrong there) and not only reduces the freezing point but also by default allows it to burn off.

The original question was based on anyones experience of this in arctic conditions, so 2D, did you add your own isoprop? or was it ready mixed with the fuel? If you added it - where did you get it?

Cheers

Flt (GG-33)

[2Donkeys]

FBOs in locations where OAT will be a consideration normally have isoprop available. It is typically poured in by the refueller during the refuelling process.

Flight Services in Reykjavik were the people I had in mind.

[Brooklands]

Iso propyl alcohol (ethanol)

Sorry fltcom, but IsoPropyl Alcohol isn't the same as ethanol: ethanol has two carbon atoms, IPA has three.

Brooklands (I knew that chemistry degree would come in handy one day) :)