Page 460 - PPL-engelsk 2025
P. 460
Principles of flight
To see how to handle flying behind heavy aircraft that create wingtip vortices,
refer to the operational procedures subject for further explanation or watch the
small videos here.
Induced drag depends on aspect ratio, angle of attack, and wing shape. A lot of
research is focused on creating wings with as little induced drag as possible.
Winglets and wingtip modifications can reduce vortex formation.
5.3.7.3 Ground effect
Ground effect is the reduced aerodynamic drag generated by an aircraft's wings
when they are close to a solid surface.
Flying in ground effect reduces induced drag.
The reduced drag during takeoff can cause the aircraft to "float" when near the
ground and below the recommended climb speed.
But you cannot climb out of ground effect until you reach a safe climb rate! Make
sure to accelerate the aircraft before climbing.
The diagram here shows the effect
of flying in ground effect.
If you fly at one meter altitude in a
Cherokee, it is equivalent to ¼ of
the chord at two meters altitude,
which corresponds to about 1/5 of
the wingspan (0.2).
We can see that this results in a 30%
reduction in induced drag.
Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 460
