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Precipitation, Icing

Revision for “Precipitation, Icing” created on February 22, 2021 @ 19:16:49 [Autosave]

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

<strong>1. General</strong>
Precipitation can severely reduce Visibility (VIS) and can give a false optical illusion during the landing phase. A flooded, contaminated RWY may deteriorate the braking coefficient towards zero (aquaplaning).

<strong>2. Categories of Precipitation</strong>
<ul>
<li style="list-style-type: none;">
<ul>• Vapor – Consists of very small drops of water which form haze, mist, and fog. This form of precipitation reduces the VIS drastically.</ul>
</li>
<li style="list-style-type: none;">
<ul>• Liquid – Forms of precipitation are drizzle and rain.</ul>
</li>
<li style="list-style-type: none;">
<ul>• Frozen – Forms are snow, snow grains, snow pellets, ice pellets, and hail.</ul>
</li>
</ul>
<strong>3. Classification of Precipitation Intensity</strong>
With regard to precipitation, detection thresholds expressed in Millimeters 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>
<tbody>
<tr>
<th>Intensity</th>
<th>Drizzle</th>
<th>Rain</th>
<th>Snow</th>
</tr>
<tr>
<td>Light</td>
<td>&lt;0.1 mm/h</td>
<td>&lt;2.5 mm/h</td>
<td>&lt;1.0 mm/h</td>
</tr>
<tr>
<td>Moderate</td>
<td>0.1 and &lt;0.5 mm/h</td>
<td>2.5 and &lt;10 mm/h</td>
<td>1.0 and &lt;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>
</tbody>
</table>
&nbsp;

<strong>4. Airframe Categories of Icing</strong>
<ul>
<li style="list-style-type: none;">
<ul>• Rime – Thin milky film of frozen vapor.</ul>
</li>
<li style="list-style-type: none;">
<ul>• Frost – Rough, milky, and opaque ice formed by the instantaneous freezing of small water droplets or snow flurries.</ul>
</li>
<li style="list-style-type: none;">
<ul>• Clear ice – Glossy, clear, or translucent ice formed by slow freezing of water droplets.</ul>
</li>
</ul>
Source: ICAO

See also:
<a title="Precipitation, Icing" href="https://flightcrewguide.com/wiki/meteorology/precipitation-icing/">Precipitation, Icing</a>
<a title="Anti-Icing Codes" href="http://flightcrewguide.com/wiki/meteorology/anti-icing-codes/">Anti-Icing Codes</a>
<a title="Winter Operation Definitions" href="http://flightcrewguide.com/wiki/winter-operation-definitions/">Winter Operation Definitions</a>



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February 22, 2021 @ 19:16:49 [Autosave]Captain Bass
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