[JohnnyB]

Correctly : Fläche

As Col Bruggy already wrote above

Dämpfungsfläche = damping surface
Fläche = surface

Example : Tragfläche = wing

The damping surface is the fixed, non-moving part of the tail/rudder or elevator.
The size ratio of damping surface and rowing depends on the application.
In fast aircraft the rudder is small compared to the attenuation area,
on slow or very moving aircraft (example : aerobatics) is the rudder area correspondingly
larger to produce higher control forces.

Regards,
Rainer