The impact of frost, ice, and snow on aircraft operations can be significant. Even a layer of 0.4 mm can restrict lift and drag, and ice can also hamper visibility and make it harder for pilots to see and avoid potential hazards, such as:
Deicing is the process whereby snow and ice are removed from a surface of the plane. Commercial deicing is done by mechanical scraping, hydraulic pushing, heated, dry or liquid chemical solutions, or a combination of these methods.
The two primary methods of de-icing are mechanical and chemical.
Mechanical deicing requires the use of a brush or scraper to clear away the frost or ice from the air surface. Chemical deicing, on the other hand, uses a solution that is applied to the aircraft which then affects the bond between the frost or ice and the aircraft surface. Anti-icing is a process of applying chemicals that are deicers to delay the reformation of ice.
Mechanical and chemical deicing have their advantages and disadvantages. Mechanical deicing is generally quicker and more affordable, but less effective during extremely cold temperatures. Chemical deicing takes longer but is effective in all weather conditions.
Electro-Mechanical Expulsion deicing combines anti-icing and deicing measures. Developed by Cox & Company, a manufacturer of electro-thermal systems for marine, aviation, and rail applications, EMEDS is the first ice protection technology to receive FAA certification in 50 years. In 2001, it received FAA certification for use on the Premier 1 business jet manufactured by Raytheon.
The system operates in tandem with other sensors and is triggered automatically once sensors detect ice. First, an electrothermal strip on the back edge of the wing s surface heats it to just above the freezing point, thereby melting the ice.
Other electrokinetic systems heat the leading edge enough to evaporate moisture on contact, preventing it from escaping and refreezing elsewhere as runback ice. These thermal evaporative systems, like those using engine bleed air, require constant high power.
The deicing component of the system includes two sets of elliptical-shaped coils, or rolled circuit boards—one set for the airfoil’s upper portion and one for the lower.
The heating element is installed behind the elevated cooking board of an aircraftskin and a rigid housing. An electric current is sent through one set of coils at a time, and as the current loops through the coil, it flows in one direction and then the opposite, inducing a magnetic field.
The lower and higher ends of the coil then repel, causing the coil from an elliptical to a circular one. The enforced change of the coil’s shape consequently causes the aircraft skin to flex, resulting in the ice’s release.
Jolted with electrical energy pulses that last .0005 second, the coils deliver impact accelerations of over 10,000 Gs to the airfoil skin once a minute, shedding ice as thin as .06 inch.
Despite the high G-load, the impact amplitude — the amount of movement of the aircraft skin — is only about .025 inch. The skin accelerates so rapidly, though, that ice de-bonds as if hit with a hammer.
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Resources: Smithsonian Magazine , Wikipedia
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