Powered-gliding/climbing flight

Abstract

A new flight mode in birds that decreases the energy costs is described. This flight mode consists basically of a powered-glide phase and a climb phase. These phases constitute a cycle that is continually performed. The powered-glide phase shows a reduced wing flapping for generating thrust at an intermediate level. Other than a glide with a fixed wing posture, there is an energy support in the powered glide. It is shown that powered-gliding/climbing flight enables a decrease of the energy costs to yield a low fuel consumption. The powered-glide phase is determinative for achieving the decrease of the energy costs. The results based on this effect suggest that powered-gliding/climbing flight shows the lowest fuel consumption per range when compared with other travel flight modes including the flight at constant altitude. It has been found that birds perform continual altitude changes in long-distance flights rather than flying at a constant altitude. There is evidence based on observations and measurements that the descents in these altitude changes take place as powered glides. This suggests that long-distance flights with altitude changes consist of powered-gliding/climbing flight with repeated cycles.

Keywords: Altitude-changing flight mode; Long-distance flight; Low fuel consumption; Powered glide.