Precipitation can severely reduce Visibility (VIS) and can give a false optical illusion during landing phase. A flooded, contaminated RWY may deteriorate the braking coefficient towards zero (aquaplaning).
<strong>2. Categories of Precipitation</strong>
• Vapor – Consists of very small drops of water which form haze, mist, and fog. This form of precipitation reduces the VIS drastically.
• Liquid – Forms of precipitation are drizzle and rain.
• Frozen – Forms are snow, snow grains, snow pellets, ice pellets, and hail.</ul>
3. Classification of Precipitation Intensity</strong>
With regard to precipitation, detection thresholds expressed in Millimeter per Hour (mm/h) are given for some sensors. The World Meteorological Organization (WMO) reporting thresholds for light, moderate and heavy precipitation are shown in the table below:
<td>0.1 and <0.5 mm/h</td>
<td>2.5 and <10 mm/h</td>
<td>1.0 and <5 mm/h</td>
<strong>4. Airframe Categories of Icing</strong>
• Rime – Thin milky film of frozen vapor.
• Frost – Rough, milky and opaque ice formed by the instantaneous freezing of small water droplets or snow flurries.
• Clear ice – Glossy, clear, or translucent ice formed by slow freezing of water droplets.</ul>
<a href="http://flightcrewguide.com/wiki/meteorology/precipitationicing/" title="Precipitation, Icing">Precipitation, Icing</a>
<a href="http://flightcrewguide.com/wiki/meteorology/anti-icing-codes/" title="Anti-Icing Codes">Anti-Icing Codes</a>
<a href="http://flightcrewguide.com/wiki/winter-operation-definitions/" title="Winter Operation Definitions">Winter Operation Definitions</a>