Originally Posted by HN39
At -40 °C there was no liquid water to cause icing of the airframe.
- incorrect. Liquid water can and does exist in the atmosphere at temperatures well below -40 as super-cooled water drops or normal drops carried aloft by rising air, hence the need to be aware of what is under you before you elect NOT to use engine anti-icing. The statement is a myth based on the meteorological fact that at temperatures below -40 air cannot
normally contain significant concentrations of water droplets or water vapour.