It’s that time of the year again for airports across the Northern United States and Canada when departing flights receive a coating of orange or green spray, better known as deicing fluid.
Deicing fluid is a hot liquid sprayed onto aircraft before departure to ensure that ice does not form along the wings or horizontal stabilizers, which could lead to a major emergency if any of the control surfaces become inoperative.
Each airport has different de-icing procedures. Some airports have a general deicing area where all aircraft pass through on taxi out and are decided by a common company or by a contractor that the airline has hired. Other airports have aircraft deice at the gate, or while pushed back. Usually this is done by the airline ground staff, or a third party that the airline has hired.
At airports like Denver and Vancouver, common deicing areas are used. Denver has five separate areas with a total of 27 positions for aircraft deicing. Common deicing areas are often set up like a drive through. A deicing truck is positioned on each side while an aircraft pulls into place in between them. It is sprayed from each side and then pulls out of the deicing pad to taxi to the runway. This is often the more efficient deicing setup, as aircraft do not have to wait to push back from their gate until after being deiced, allowing airlines to maintain a normal schedule with their gates.
At Chicago O’Hare, aircraft are deiced at the gate or shortly after pushing back. This makes an already congested airport even more congested. Inbound aircraft have to wait for their gate even longer due to the additional time needed for deicing departing aircraft at the gate. Also, this creates an additional hazard as deicing trucks have to position in between two aircraft and around the other ground workers making deicing aircraft at neighboring gates simultaneously nearly impossible, which can lead to further delays.
While the overall goal of deicing aircraft is to prevent ice from inhibiting the control surface of an aircraft, there are multiple types of deicing fluid for different purposes.
Type I deicing fluid is mainly used to remove ice or snow that has accumulated on an aircraft while parked. Type I is orange in color, and is usually sprayed after a storm has stopped. It is sprayed with a mix of hot water (usually about 8% water and 92% chemical)to effectively melt the accumulated snow and ice off the wing. The temperature when exiting the nozzle of the deicing truck is usually somewhere from 150 to 180 degrees Fahrenheit which creates the steam that is produced during deicing. Type I deicing fluid a short “holdover” time. Holdover time is the time that an aircraft has from the time it is deiced until the time that it must be in the air with anti ice systems on while it is snowing. The holdover time is set by each individual airline, but for type I it is typically somewhere from five to fifteen minutes. If it is still snowing, type I will be sprayed in combination with type II or IV to allow the aircraft a long enough holdover time to taxi and depart without having to be deiced again.
Type IV deicing fluid is green in color. It is much thicker than type I, and is used to prevent the additional accumulation of ice and snow on a wing of an aircraft while it is taxiing to the runway. This is not sprayed on with hot water, but it does contain much more water than type I with about 35% water and 65% chemical. Type IV is sprayed when the storm is still ongoing when a long holdover time is needed as airports typically have limited runway capacity during snowstorms and taxi and takeoff times may be longer than usual. Type IV has a holdover time of up to 80 minutes due to its thicker composition which allows it to stay adhered to the aircraft.
Deicing occurs at an airline’s discretion and is only used when it is absolutely needed because of the cost. Deicing fluid typically runs about 8 to 12 dollars per gallon. For a Boeing 747, 1100 gallons of type I is used along with 250 gallons of type IV, resulting in more than $10,000 in additional expenses.
Featured Image from Wikimedia Commons.
Bottom images from Aeronautics Online editor Max T.