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5.Mixed Ice

Rime and clear ice frequently occur together and combine the most dangerous
characteristics of both types. mixed with snow, ice particles, or small hail, the mixed ice
becomes If the liquid drops are rough, whitish, and irregularly shaped.

6. Frost

a. Frost is a very thin type of ice caused by the condensation of water vapor directly into ice
on surface objects whose temperatures are below freezing. It is' similar in appearance to a
thin layer of snow. It is the same type of ice that forms on a car's windows when the tem-
perature falls below freezing and there is moisture in the air.

b. Thin metal structures are especially likely surfaces on which frost will form. Frost does not
change the shape of a wing but its roughness destroys the smoothness of the surface and
affects the flow of air across the wing's surfaces. The changing of the airflow over the surface
results in decreased lift. A thick layer of hard frost on aircraft structures wil1 increase the
minimum speed at which the air- craft can continue to fly by 5% to 10%.

7. Icing Intensity

The military and civilian aviation groups and the National Weather ice have agreed to use a
standard classification system to report the intensity of icing. The system uses four
classifications of icing: trace, light, moderate, and severe.