Icing conditions

In aviation, icing conditions are atmospheric conditions that can lead to the formation of water ice on an aircraft. Ice accretion can affect the external surfaces of an aircraft – in which case it is referred to as airframe icing – or the engine, resulting in carburetor icing, air inlet icing, or more generically engine icing. These phenomena do not necessarily occur together. In aviation, icing conditions are atmospheric conditions that can lead to the formation of water ice on an aircraft. Ice accretion can affect the external surfaces of an aircraft – in which case it is referred to as airframe icing – or the engine, resulting in carburetor icing, air inlet icing, or more generically engine icing. These phenomena do not necessarily occur together. Not all aircraft, especially general aviation aircraft, are certified for flight into known icing (FIKI) – that is icing conditions certain or likely to exist, based on pilot reports, observations, and forecasts. In order to be FIKI-certified, aircraft must be fitted with suitable ice protection systems. Icing conditions exist when the air contains droplets of supercooled liquid water; icing conditions are characterized quantitatively by the average droplet size, the liquid water content and the air temperature. These parameters affect the extent and speed that characterize the formation of ice on an aircraft. Federal Aviation Regulations contain a definition of icing conditions that some aircraft are certified to fly into. So-called SLD, or supercooled large droplet, conditions are those that exceed that specification and represent a particular hazard to aircraft. Qualitatively, pilot reports indicate icing conditions in terms of their effect upon the aircraft, and will be dependent upon the capabilities of the aircraft. Different aircraft may report the same quantitative conditions as different levels of icing as a result.