Aircraft Icing Training - Courses
All of your questions regarding icing are answered in the above link. Its a fantastic resource and its completely free. In short, if the SAT is between +2 and -20c and there is visible moisture in the atmosphere, then an airframe can accrete icing. The only limiting factor on the cold side is -40c. From a legal standpoint what are known icing conditions.? Well if you fly into visible moisture below the forecast freezing level, ie cloud, FZFG, FZRA, supercooled large droplets, ice pellets etc and your in a non de-iced aircraft and an accident results. The likely candidate who will inform you of the legalities would more than likely be your insurance company if you survive of course. Its also right as whirly mentions that snow isnt considered as icing conditions in flight (explained in the course relating to temp at which snow exists) but snow on an aircraft on the ground is a different issue and certainly would be considered a danger as snow insulates and a layer of snow on the aircraft on the ground could leave the airframe covered in a coating of ice. Any snow/ice should be removed prior to flight. I have known some people who thought, ah the snow will blow off when I start to roll? It most certainly would but what it left behind would certainly diminish the aerodynamic properties of said aircraft and the POH figures could be severely out.