Demystifying the Deicing Process
So you’re sitting in a plane and it’s snowing out. Everyone is already concerned about flight delays due to the wintry weather, but finally, the plane pushes back, and a collective sigh of relief is heard throughout the cabin. However, just as you start to relax, the captain’s voice comes on over the PA system, and he announces “Well folks, we’re just making a quick stop for deicing, and then we’ll be off.” A few minutes later, you feel as if you are in a car wash for aircraft.
The deicing process may delay departure somewhat, but it is an essential, safe, and ultimately necessary component of cold-weather flying.
When witnessed from afar, the deicing process resembles someone washing a car, albeit at a much larger scale. High-pressure hoses apply aircraft deicing fluid, or ADF, to most flight surfaces of the aircraft, with a focus on the plane’s wings, engines, and tail.
An aircraft’s wings and tail are designed with specific shapes and dimensions to provide appropriate aerodynamics for proper liftoff and flight. When snow and ice build up on a plane, it significantly alters the way that air flows over the surfaces, and this may result in loss of lift and, ultimately, a crash. So while a driver may wash a car for the sake of cleanliness, a pilot makes the decision to deice the aircraft for the safety of everyone on board.
Aircraft deicing fluids are designed to remove buildups of snow, ice, and frost from aircraft so that they may safely takeoff. Currently, four types of ADFs are used for this purpose.
Type I is effective for only a short time, as it tends to come off surfaces not long after being applied. It is typically dyed orange so as to be easily identified.
Type II fluids remain on aircraft longer than Type I, and are shed only when a plane reaches a speed of 124 mph (200 km/hr). Type II fluids are typically used on larger aircraft, and are usually a pale yellow color.
Type III fluids are a mix between Type I and Type II, and are used primarily on slower aircraft. Type III fluids are also usually light yellow.
Type IV fluids are similar to Type II, although they remain on aircraft for a longer period of time. Because of this, Type IV fluids, which are generally dyed green, are increasing in popularity and use over Type II fluids.
According to a study published by NASA in 2008, 9.5% of the total number of fatal commercial aircraft accidents has been due to icing issues. Icing is so dangerous that the U.S. Army has strict regulations about flying in icing conditions, to wit: “…aircraft will not be flown into known or forecast severe icing conditions.” Researchers are constantly looking for new and better ways of making flying under wintry conditions safer for all concerned, but the current system has effectively curtailed accidents and incidents in recent years.
(Photo and video: Accura Media Group)