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Precipitation, Icing

Revision for “Precipitation, Icing” created on October 25, 2013 @ 09:08:27

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Precipitation, Icing
<strong>Precipitation, Icing</strong>

<strong>1. General</strong>
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>
<ul>
• 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>
<strong>

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:

<table>
<tr>
<th>Intensity</th>
<th>Drizzle</th>
<th>Rain</th>
<th>Snow</th>
</tr>
<tr>
<td>Light</td>
<td><0.1 mm/h</td>
<td><2.5 mm/h</td>
<td><1.0 mm/h</td>
</tr>
<tr>
<td>Moderate</td>
<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>
</tr>
<tr>
<td>Heavy</td>
<td>0.5 mm/h</td>
<td>10 mm/h</td>
<td>5 mm/h</td>
</tr>
</table>

<strong>4. Airframe Categories of Icing</strong>

<ul>
• 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>

Source: ICAO

See also:
<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>



Old New Date Created Author Actions
October 25, 2013 @ 09:08:27 Captain Bass
October 25, 2013 @ 09:07:05 Captain Bass
October 25, 2013 @ 09:06:13 Captain Bass
October 25, 2013 @ 08:35:17 Captain Bass
October 25, 2013 @ 08:35:14 [Autosave] Captain Bass
October 25, 2013 @ 08:33:45 Captain Bass
October 6, 2013 @ 12:08:20 Captain Bass
September 19, 2013 @ 07:18:45 Captain Bass
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