Page 319 - PPL-engelsk 2025

Meteorology

3.9.2 Icing formation

Conditions that contribute to ice formation on aircraft include:

- Presence of supercooled water

- Flying in negative temperature conditions

- Flying with a critical wing profile and too high speed

Ice forms on aircraft when the aircraft is hit by supercooled water droplets.

Supercooled droplets can have temperatures as low as minus 25°C, though the

temperature typically ranges from 0°C to minus 12°C.

Below these temperatures, droplets freeze into ice.

For example, when the leading edge of a wing is struck by a supercooled

droplet, the droplet spreads out, and part of it freezes immediately into ice.

The part of the droplet that does not freeze immediately spreads out over the

aircraft and can freeze into ice, depending on the aircraft's surface

temperature.

Small droplets mostly follow the

airflow around the profile, while

larger droplets strike the leading

edge and accumulate as ice.

Regarding the wing profile type, thinner wings collect ice more readily than

thicker ones.

This may sound counterintuitive because the surface area is smaller, but the

airflow is weaker around the thin profile, allowing droplets to penetrate and hit
the wing’s leading edge.

Thin laminar profiles are more sensitive to icing than thick, curved profiles.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 319