Aircraft Anti-Ice and Deicing Systems

Making flight through adverse conditions possible

    Flying in hazardous weather requires aircraft to utilize specialized systems to ensure a safe flight. One such condition is icing conditions. Ice that forms on an aircraft's wings, propellers, control surfaces, or windshield can be extremely detrimental to maintaining proper thrust, lift, and control of the aircraft. There are several methods in which to prevent or remove ice from the surface of an aircraft. Anti-ice systems are designed to prevent or drastically reduce the formation of ice on an aircraft during flight, whereas deicing systems are designed to remove ice that has already formed. Failures of either type of system can have deadly consequences, however certain processes and procedures can be put into place to ensure that doesn't happen.

Anti-Ice

When supercooled water comes into contact with an object, it can immediately freeze. Aircraft utilized anti-icing to prevent the formation of ice on critical surfaces of the aircraft and are designed to be activated prior to entering icing conditions in flight (NASA, n.d.). Anti-icing can be accomplished by heating the surfaces (hot pneumatic air or electrically), or fluid can be used that lowers the freezing point so that ice does not form when supercooled water or ice crystals contact the surface.

Deicing

Aircraft deicing systems are designed to remove ice that may have formed. One common method of deicing is the use of deicing boots that inflate to break up ice formations and dislodge them from various surfaces.

What happens when icing systems fail?

When icing systems either fail or are not activated in icing conditions, ice is likely to form on surfaces that are critical to the aerodynamics of the aircraft. The formation of ice reduces thrust, increases drag, reduces lift, and increases weight. To put into perspective just how detrimental icing can be, see the table below which illustrates the effects icing has on stall speed and drag increase through various instances ranging from "all iced" and "deiced" (Flight Safety Foundation, 2018)

Mitigation

Anti-ice and deicing systems are not effective unless they are fully functional and operate as intended when necessary. To ensure that such systems are operational, they should be regularly tested on the ground. Such system tests should be a part of every aircraft preflight procedure, especially when there is a potential for an aircraft to fly into known icing conditions. Aircraft whose icing systems are not functional should be restricted from flight or, if dispatched with faulty equipment, be restricted from flying into known icing conditions. When icing systems are fully functional, it is also critical that they are activated prior to entering icing conditions.

References

Flight Safety Foundation. (2018, February 27). Discoveries on Ice. https://flightsafety.org/asw-article/discoveries-on-ice/

NASA. (n.d.). In-Flight Icing: Aircraft Design for Icing - Anti-Icing Systems. A Pilot’s Guide to Inflight Icing. https://aircrafticing.grc.nasa.gov/1_1_3_6.html#:%7E:text=The%20anti%2Dicing%20fluid%20runs,on%20propeller%20blades%20and%20windshields.

Stoll, R. (2020, May). UBC ATSC 113 - Aircraft Icing. Weather for Sailing, Flying & Snow Sports. https://www.eoas.ubc.ca/courses/atsc113/flying/met_concepts/03-met_concepts/03g-Icing/index.html