getting to grips with COLD WEATHER OPERATIONS 寒冷天气运行(9)

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De-icing is a procedure by which frost, ice, slush or snow is removed from the aircraft in order to provide clean surfaces. This may be accomplished by mechanical methods, pneumatic methods, or the use of heated fluids.

De/Anti-icing is a combination of the two procedures, de-icing and anti-icing, performed in one or two steps. A de-/anti-icing fluid, applied prior to the onset of freezing conditions, protects against the build up of frozen deposits for a certain period of time, depending on the fluid used and the intensity of precipitation. With continuing precipitation, holdover time will eventually run out and deposits will start to build up on exposed surfaces. However, the fluid film present will minimize the likelihood of these frozen deposits bonding to the structure, making subsequent de-icing much easier.
Dew point is the temperature at which water vapor starts to condense.
Dry runway: A dry runway is one which is neither wet nor contaminated, and includes those paved runways which have been specially prepared with grooves or porous pavement and maintained to retain .effectively dry. braking action, even when moisture is present.
Fluids (de-icing and anti-icing)
. De-icing fluids are: a) Heated water b) Newtonian fluid (ISO or SAE or AEA Type I in accordance with ISO 11075
specification) c) Mixtures of water and Type I fluid d) Non-Newtonian fluid (ISO or SAE or AEA Type II or IV in accordance with ISO
11078 specification)
e) Mixtures of water and Type II or IV fluid

De-icing fluid is normally applied heated to ensure maximum efficiency
. Anti-icing fluids are: a) Newtonian fluid (ISO or SAE or AEA Type I in accordance with ISO 11075
specification) b) Mixtures of water and Type I fluid c) Non-Newtonian fluid (ISO or SAE or AEA Type II or IV in accordance with ISO
11078 specification)
d) Mixtures of water and Type II or IV fluid

Anti-icing fluid is normally applied unheated on clean aircraft surfaces.
Freezing conditions are conditions in which the outside air temperature is below +3°C (37.4F) and visible moisture in any form (such as fog with visibility below 1.5 km, rain, snow, sleet or ice crystals) or standing water, slush, ice or snow is present on the runway.
Freezing fog (Metar code: FZFG) is a suspension of numerous tiny supercooled water droplets which freeze upon impact with ground or other exposed objects, generally reducing the horizontal visibility at the earth’s surface to less than 1 km (5/8 mile).
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Freezing drizzle (Metar code: FZDZ) is a fairly uniform precipitation composed exclusively of fine drops - diameter less than 0.5 mm (0.02 inch) - very close together which freeze upon impact with the ground or other objects.
Freezing rain (Metar code: FZRA) is a precipitation of liquid water particles which freezes upon impact with the ground or other exposed objects, either in the form of drops of more than 0.5 mm (0.02 inch) diameter or smaller drops which, in contrast to drizzle, are widely separated.
　
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