The Atmosphere
Movement in the Atmosphere
Atmospheric Stability
Localised Winds
Clouds
Fronts
Visibility and Fog
Aircraft Icing
Thunderstorms
Altimetry
Weather Reports and Forecasts
Practice Exam

Rime Ice

When small water droplets below 0°C hit the aircraft, they freeze almost instantly. This causes some air to be trapped inside the ice, which makes it look milky, opaque, and rough. This is known as Rime Ice.

Rime ice is fairly brittle because of the air trapped inside, making it easier for it to break away from the aircraft.

Photo Credit: FAA

These small water droplets are most commonly found in clouds, which means rime ice typically forms on the leading edges of aircraft as you fly through clouds with temperatures below 0°C.

Rime Ice:

Freezes instantly
Is easy to remove because of the air in it
Usually only forms on leading edges
Can stack in peculiar formations
Has a powder, milky, granular appearance

Below are pictures from an icing experiment in an aircraft manufacturer’s testing lab. Large quantities of rime ice can be seen built up along the leading edge in the ‘after’ photo.