Flight mechanic and aerodynamic aspects of extremely large dihedral in birds

Flight mechanic and aerodynamic properties resulting from extremely large dihedral which birds can show are treated, with reference made to a realistically modeled wing of a pigeon. For determining the force and moment characteristics, a sophisticated aerodynamic method capable of coping with complex wing geometries is used. It is shown that extremely large dihedral has a significant effect on the lift and drag. This yields a correspondingly great influence on the flight performance in terms of the glide angle and sinking speed, particularly in low speed flight. Furthermore, it is shown that the rolling moment due to sideslip which is an important factor for lateral stability is influenced by extremely large dihedral to a high degree. As an extension to the presented numerical data for the flight performance and lateral stability of the pigeon, an analytical treatment is developed to achieve results of general nature.