Nature’s example is technically realised by the so-called self actuating flaps. After the proof of positive influence of self actuating flaps had been shown, the technical realisation on the motor glider Stemme S10 has been worked out in excessive tests and optimisations in the wind tunnel, up to the performance of free-flight tests with self actuating flaps. Flight tests showed, the tested self actuating flaps are working reliable at all speeds. An improvement in flight performance as well as a reduction of the stall speed (i.e. lift increase) has been confimed.