Page 260 - PPL-engelsk 2025

Meteorology

3.4.5 Mechanical and thermal turbulence

Turbulence can arise in two ways:

- Mechanical turbulence

- Thermal turbulence

3.4.5.1 Mechanical turbulence

Mechanical turbulence forms when air encounters physical obstacles like

mountains, buildings, trees, or other structures, which disrupt the airflow and
create irregularities in the wind's movement.

Mechanical turbulence decreases with height and is strongest in unstable air

(which you'll learn about later). The stronger the wind, the stronger the

mechanical turbulence.

3.4.5.2 Thermal turbulence

Thermal turbulence is caused by the rise of warm air (or the sinking of cold air).

This updraft disturbs the surrounding airflow. The warmer air rises while the

cooler air sinks, creating turbulent airflows.

Thermal turbulence occurs due to uneven heating of the Earth's surface.

Ordinary daily turbulence may be uncomfortable, but in our latitudes, it is not

a significant problem.

Turbulence decreases when flying over water.

Glider pilots love thermal turbulence. They call it "thermic."

Remember to fly early in the morning or in the evening if you want to avoid the

worst turbulence.

3.4.6 CBs and gust fronts

The dangers are easy to spot for small planes flying into clouds, as shown in the

next figure.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 260