Aircraft icing for general aviation and others

This is a partial reprint of an article previously published in ASL 03/2005. —Ed.

Transport Canada wishes to maintain a high level of awareness within the civil aviation community of the hazards of flying with ice and snow adhering to the critical surfaces of an aircraft, and of flying into icing conditions. This article is primarily aimed at the general aviation pilot, but indeed applies to all pilots who fly in our tough climate.

A very small amount of roughness—in thickness as low as 0.40 mm (1/64 in.), caused by ice, snow, or frost—disrupts the airflow over the lift and control surfaces of an aircraft. The consequence of this roughness is severe loss of lift, increased drag, and impaired manoeuvrability, particularly during the take-off and initial climb phases of flight. Ice can also interfere with the movement of control surfaces or add significantly to aircraft weight, as well as block critical aircraft sensors. There is no such thing as an insignificant amount of ice.

Aircraft operating from smaller regional airports are generally de-iced by company personnel, or in some cases, by the pilot of the aircraft, using a pressure sprayer containing an approved de-icing fluid. Aircraft must be de-iced shortly prior to takeoff. When operating under icing conditions from remote sites, aircraft operators are responsible for carrying the appropriate anti-icing and de-icing equipment on board the aircraft or storing the equipment at the airport. If conditions are too severe, pilots are prohibited from attempting a takeoff.

In all aviation operations, the pilot-in-command (PIC) has the ultimate responsibility of determining if the aircraft is in a condition for safe flight.

Ground de-icing and anti-icing procedures vary greatly depending primarily on aircraft type, the type of contamination accumulation on the aircraft, and the freezing point depressant (FPD) or de-/anti-icing fluid type. Pilots should become familiar with the applicable Canadian Aviation Regulations (CARs) and Standards, as well as the procedures recommended by the aircraft manufacturer in the pilot operating handbook (POH), aircraft flight manual (AFM), maintenance manual, and, where appropriate, the aircraft service manual. As well, they should comply with all company operations manual provisions.

Acceptable fluids—A list of acceptable de-icing and anti-icing fluids is included on the Transport Canada website in the Transport Canada Holdover Time (HOT) Guidelines. If reliable holdover times are to be achieved, only acceptable fluids that are stored, dispensed, and applied in accordance with the manufacturers' instructions can be used. The acceptable fluids have undergone laboratory testing to quantify their protection and to confirm aerodynamic acceptability.

Proper fluid coverage is absolutely essential for proper fluid performance. It is imperative that the personnel applying the fluid are properly trained and that a consistent fluid application technique is utilized.

For more information on the guidelines for aircraft in ground icing conditions, you can refer to TP 14052. You will find information on application methods, liquid types, and more.