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Ground deicing of aircraft is commonly performed in both commercial and general aviation.
Additional recommended knowledge
Deicing fluids come in a variety of types, and are typically composed of ethylene glycol or propylene glycol, along with other ingredients such as thickening agents, wettening agents, corrosion inhibitors, and colored, UV-sensitive dye. Propylene Glycol is more common due to the fact it is less toxic than ethylene glycol.
The Society of Automotive Engineers publishes standards (SAE AMS 1428 & AMS 1424) for four different types of aviation deicing fluids:
Deicing fluids containing thickeners (types II, III, and IV) are also known as anti-icing fluids, because they are used primarily to prevent icing from re-occurring after an initial deicing with a type I fluid.
Deicing fluids are typically sold in concentrated form and diluted with water according to the ambient weather conditions. The freezing point of undiluted fluid is typically about -30 °C. Adding water reduces the freezing point, with a minimum of -55 °C being reached at a dilution of 75% fluid and 25% water. Further dilution raises the freezing point again. The dilution of deicing fluid is carefully done in order to minimize costs while maintaining safety.
Deicing fluid performance is measured by holdover time, which is the length of time an aircraft can wait after being treated prior to takeoff. Holdover time is influenced by the ambient temperature, wind, precipitation, humidity, aircraft skin temperature, and other factors. For Type I fluids, the holdover time is only about five to 15 minutes, so the aircraft has to take off right away or else wait to be deiced again. Type IV fluids generally provide a holdover time between 30 and 80 minutes.
The toxicity of deicing fluids is an environmental concern, and research is underway to find less toxic alternatives. For example, the US Air Force Research Laboratory (AFRL) is currently studying a chemical known as METSS ADF-2. Other strategies can be used to minimize the environmental impact such as collecting used fluid and using the maximum dilution consistent with safety.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Deicing_fluid". A list of authors is available in Wikipedia.|