Pilot Counsel:

The law on flight into icing

April 1, 2009

John S. Yodice has served as legal counselor to AOPA since 1963.

The FAA has recently issued an interpretation regarding the law on flight into known icing conditions. The law has been unclear for general aviation (noncommercial light aircraft) operations for two reasons. First, there is no specific provision in FAR Part 91 banning flight into known icing conditions (except for large and turbine-powered multiengine airplanes, and fractional ownership program aircraft), and second, the NTSB has sent mixed and confusing signals in its decisions in pilot enforcement cases that were obviously motivated more to find pilot violations than to clarify the law.

What has been clear, and what pilots understand, is that flight into icing conditions about which the pilot actually knows or should reasonably anticipate, is prohibited. It is prohibited more by common sense and self-preservation than the law. And even the legal prohibition does not apply if the aircraft is specifically certificated by the FAA, and equipped, for flight into icing. However, very few light general aviation aircraft have that kind of certification (even if they have anti-ice/deice equipment).

Even though there is no specific provision in Part 91, there are other provisions in Part 91 that indirectly support pilots’ common-sense understanding of the law. The provision that is most applicable, but often obscure, is FAR 91.9(a) that requires compliance with the long list of operating limitations specified in the approved Airplane or Rotorcraft Flight Manual. Among these operating limitations may be the statement that the particular aircraft type is not approved for flight into known icing conditions. Other aircraft may not have such a specific limitation. FAR 91.13(a) prohibits “careless or reckless” flying that the FAA argues includes flight into known or reasonably anticipated icing. Lastly, FAR 91.103 requires a pilot, “before beginning a flight, [to] become familiar with all available information concerning that flight [including] for a flight under IFR or a flight not in the vicinity of the airport, weather reports and forecasts.” That information will include icing, if relevant.

Although much of the written law—though indirect and obscure—is common sense and clearly understood, what has not been clear is the interpretation of the term known icing conditions. As I said in my August 2005 column (“ Pilot Counsel: The Law on ‘Known Icing’”), the NTSB has confused the law by issuing decisions that, if literally applied, could have the effect of unnecessarily grounding many otherwise safe, light general aviation flights. The board has been wont to use arguably relevant forecasts, such as sigmets and pireps to attribute “known” icing conditions to pilots, in order to find violations.

This new FAA interpretation is much more reasonable and practical. It confines “known ice” to “actual ice observed visually to be on the aircraft by the flight crew or identified by on-board sensors. Actual adhesion to the aircraft, rather than the existence of potential icing conditions, is the determinative factor in this definition.”

As for flight into known icing conditions, the interpretation says: “Notwithstanding the references to ‘weather forecasts’ in various NTSB decisions, we [the FAA] emphasize that area forecasts alone are generally too broad to adequately inform a pilot of known icing conditions. Such forecasts may cover a large geographical area or represent too long a span of time to be particularly useful to a pilot.

“The FAA does not necessarily consider the mere presence of clouds (which may only contain ice crystals) or other forms of visible moisture at temperatures at or below freezing to be conducive to the formation of known ice or to constitute known icing conditions. There are many variables that influence whether ice will actually be detected or observed, or will form on and adhere to an aircraft.”

The interpretation offers this guidance: “Pilots should not expose themselves or others to the risk associated with flying into conditions in which ice is likely to adhere to an aircraft. If ice is detected or observed along the route of flight, the pilot should have a viable exit strategy and immediately implement that strategy so that the flight may safely continue to its intended destination or terminate at an alternate landing facility. If icing is encountered by a pilot when operating an aircraft not approved or equipped for flight in known icing conditions, the FAA strongly encourages the submission of pireps and immediate requests to ATC for assistance. Such actions can significantly enhance safety, reduce accidents, and benefit the entire aviation community.”

The FAA articulates this enforcement policy: “Flight which results in the formation of ice on an aircraft is not the sole factor the FAA will use in determining whether enforcement action is warranted in any particular case. In determining whether enforcement action is warranted, the FAA will evaluate those actions taken by the pilot (including both preflight actions and those taken during the flight) to determine if the pilot’s actions were, in fact, reasonable in light of Sections 91.9(a), 91.13(a), and 91.103. The FAA will specifically evaluate all weather information available to the pilot and determine whether the pilot’s preflight planning took into account the possibility of ice formation, alternative courses of action to avoid known icing conditions and, if ice actually formed on the aircraft, what steps were taken by the pilot to exit those conditions.”

John S. Yodice