Page 321 - PPL-engelsk 2025
P. 321
Meteorology
Rime ice forms from small droplets when the water content per cubic meter of
air is low and temperatures are low. The freezing process happens almost
immediately after the droplets hit the profile. The droplets freeze into a porous
ice form, composed of small ice crystals. The ice is whitish and has a texture
similar to frost in a freezer.
Rime ice forms relatively slowly and mainly on
the leading edge of the profile.
Here’s rime ice on a profile and how it affects
the airflow.
Here you can see the leading edge of a wing with
rime ice.
Rime ice doesn’t significantly increase weight, but
its danger lies in the aerodynamic change of the wing profile and in blocking
the openings of the carburetor and instruments.
Rim ice is usually fragile and can be easily removed with de-icing equipment.
Mixed ice, as the name suggests, has characteristics of both clear ice and rime
ice.
Large and small supercooled droplets coexist. The
appearance is whitish, irregular, and rough.
Mixed ice can accumulate quickly and is difficult to
remove.
Mixed ice forms both like clear ice and rime ice. Therefore, it has the harmful
properties of both rime and clear ice!
Here’s mixed ice on a profile and how it
affects the airflow around the profile.
It’s clear that this type of ice is extremely
dangerous!
Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 321
