Birds flap their wings in order to fly. In the case of an airplane this would have disastrous consequences. Within a few seconds an airplane with flapping wings would be destroyed by huge air forces . What can be done to prevent this from happening?
In research, this catastrophic phenomenon is called "flutter". Flutter are self-excited vibrations of the airfoil structure with exponentially growing amplitudes. Fortunately, they will only occur when exceeding a critical air speed. This critical speed has to be determined in flutter tests. By means of variations in construction of the airfoil the critical speed can be shifted towards higher values thus creating a larger interval of safe flying speeds.