Page 450 - PPL-engelsk 2025

Principles of flight

5.3.4 The 4 forces that affect an aircraft during flight

Above, you can see the forces that act on the aircraft during flight (more details

in section 5.5):

- Lift

- Weight

- Drag

- Thrust

Note that the relative wind is 180 degrees opposite to the direction of the

aircraft's movement.

If we reduce the throttle, the aircraft will start moving both downward and

forward, and the forces will look different.

In the diagram here, the thrust is reduced, and the aircraft has changed its
direction of

motion but

maintains the

same position

in the air.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 450