title: New model of flap-gliding flight.
abstract: A new modelling approach is presented for describing flap-gliding flight in birds and the associated mechanical energy cost of travelling. The new approach is based on the difference in the drag characteristics between flapping and non-flapping due to the drag increase caused by flapping. Thus, the possibility of a gliding flight phase, as it exists in flap-gliding flight, yields a performance advantage resulting from the decrease in the drag when compared with continuous flapping flight. Introducing an appropriate non-dimensionalization for the mathematical relations describing flap-gliding flight, results and findings of generally valid nature are derived. It is shown that there is an energy saving of flap-gliding flight in the entire speed range compared to continuous flapping flight. The energy saving reaches the highest level in the lower speed region. The travelling speed of flap-gliding flight is composed of the weighted average of the differing speeds in the flapping and gliding phases. Furthermore, the maximum range performance achievable with flap-gliding flight and the associated optimal travelling speed are determined.
authors.affiliation: Professor of Flight Mechanics and Flight Control, Institute of Flight System Dynamics, Technische Universität München, Boltzmannstr. 15, 85748 Garching, Germany. Electronic address: sachs@tum.de.
authors.forename: Gottfried
authors.initials: G
authors.lastname: Sachs
mesh_terms: D000465:Algorithms; D000818:Animals; D001696:Biomechanical Phenomena; D001717:Birds / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D005426:Flight, Animal / Q000502:physiology*; D008954:Models, Biological; D014921:Wings, Animal / Q000502:physiology*
keywords: Drag increase due to flapping; Energy saving; Intermittent flight; Travelling cost