Page 444 - PPL-engelsk 2025

Principles of flight

Here is an example of a Venturi tube.

Where the airflow is slow, the static air pressure is high.

In the middle, the airflow is

fast, and the static pressure is

low.

This creates the Venturi effect.

We don't fly with tubes on top of our wings, but imagine we cut the top half of

the tube away.

The curved surface that protrudes can be considered the upper surface of a wing.
Low static pressure occurs over the curved surface. This is the reason for the

wonderful phenomenon of "lift."

You can watch a short film about the principle here.

Here is another practical example of Bernoulli's law.

Take a small piece of paper and

blow over it. The paper will lift

because the airflow over the
paper increases, causing the

pressure to drop.

Try it!

Bernoulli's equation says that:

Total pressure = dynamic pressure + static pressure

We get low pressure on the top of the profile and higher pressure on the
underside.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 444