Page 447 - PPL-engelsk 2025
P. 447
Principles of flight
As seen in the figure on the previous page, the transition point is an area where
the flow changes from laminar to turbulent.
In flight, great efforts are made to avoid turbulent flow.
But turbulent flow does not only have disadvantages. It reduces vortex
formation in the wake. This is why a golf ball has its special surface.
Sailplanes use special tape that is applied to create turbulent flow.
However, it is clear that the initial flow over the aircraft's wings must be laminar.
Therefore, when designing profiles (wings), the goal is to maintain laminar
airflow as far back on the profile as possible, usually 30% with laminar flow.
On a laminar profile, the transition point is 10% farther back on the wing than it
is on a normal profile.
If there is dirt or bumps on the wing, the flow will become turbulent. This will
increase resistance and decrease the lift.
Frost on a wing, in thickness similar to sandpaper, can reduce lift by 30% and
increase drag correspondingly!
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Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 447
