Page 470 - PPL-engelsk 2025

Principles of flight

5.4.2.1 Twist - geometric and aerodynamic

The upper wing in the figure here shows the root and tip of a wing, where the

root and tip are symmetrical.

Such a design stalls equally over the entire wing.

This can be prevented by:

- geometric twist, where

there is a difference in

the angle of inclination

of the wing root and its

tip (the wing in the

middle).

- aerodynamic twist,

where the profile at the

tip has a different profile than at the root (lower wing) - will also stall at the

root first.

5.4.2.2 Stall strips

The figure here shows the use of stall strips.

In some places on the leading edge of the wing, the so-called strips are placed
close to the body, which

means that when the air

passes over these, the

otherwise laminar airflow will

change to turbulent airflow,

which causes the inner part of

the wing to stall first.

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Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 470