Icing Type Definitions MET

For each of the types of icing, you are required to know:

When it forms; How it forms; What it looks like; How difficult it is to dislodge, and; Where it is present.

The summary is as follows:

Clear Ice:

Formed when large supercooled water droplets hit the aircraft surface The drop freezes slowly and spreads back along the surface Forms a clear glaze Difficult to dislodge Present mainly in cumuliform clouds

Rime Ice

Formed when small supercooled water droplets hit the aircraft surface The drop freezes instantaneously Forms a white, opaque substance Relatively straightforward to dislodge Present in cumuliform and stratiform clouds

Hoar frost

Formed when water vapour sublimates directly to ice onto a cold aircraft surface Can form overnight in sub-zero temperatures Forms in clear air Forms a white, opaque substance Relatively straightforward to dislodge