With all EV-ornithopters the powered flights often had to be interrupted prematurely because the ornithopters lost their flight stability. Causes include the following:

• Lost of stabilizing force due to changes in the air speed or the angle of climb.
• Lacking practice und nervousness of the pilot.
• Visibility problems because far distance and large turning radius, respectively.

Probably the constantly changing longitudinal dihedral by the wing pitching and twisting has a part of this. In any case, in nearly all EV ornithopter models the horizontal stabilizers were too small after a new design was built.

The unstable forces of a flapping wing by variation of the speed could also duplicated by calculation (please look at the handbook, chapter 8.6).

The stability problems are apparent from the varying presentation of the fuselage in some of the following pictures of a circle flight.

(in succession top down)