FAA Attempts To Define Known Icing Conditions

An FAA draft letter of interpretation seeks public comment by May 3 on the meaning of the term “known icing conditions,” used–but undefined–in the FARs. A June 2006 FAA regional counsel letter defined known icing as existing “when visible moisture or high relative humidity combines with temperatures near or below freezing” and added “flying through clouds at an altitude that is near or below freezing would constitute flight into known icing conditions.” Concern expressed by trade groups prompted the FAA to issue the draft interpretation, which defines known icing as follows: “If the composite information indicates to a reasonable and prudent pilot that he or she will encounter visible moisture at freezing or near freezing temperatures and that ice will adhere to the aircraft along the proposed route and altitude of flight, then known icing conditions likely exist.”