The U.S. Federal Aviation Administration (FAA) is prohibiting takeoffs with “polished frost” — frost buffed to make it smooth — on the wings, stabilizers and control surfaces of several classes of aircraft.
The new rules are effective on January 30, 2010. There are 57 operators flying 188 aircraft affected by the rule changes. The FAA already prohibits major and regional air carriers from operating with polished frost.
Frost can affect the aerodynamics of wings and control surfaces, and the safest action is to completely remove it. Previous FAA guidance recommended removing all wing frost prior to takeoff, but allowed it to be polished smooth if the aircraft manufacturer’s recommended procedures were followed. But manufacturers never published standards of acceptable smoothness for polished frost, and the FAA has no data to determine exactly how to polish frost to satisfactory smoothness.
The new rules also clarify that affected aircraft must have functioning deicing or anti-icing equipment for flights under Instrument Flight Rules into known or forecast light or moderate icing conditions, or under Visual Flight Rules into known light or moderate icing conditions.