Gleitflug des FlugbeutlersPetaurus breviceps papuanus (Thomas)

Summary

Experiments with models made on thin flat plates were made in front of a wind tunnel in order to determine the relationship between their coefficients of lift and drag (Fig. 2) and the angle of attack as well as their aspects of flow (Fig. 8). The following results were achieved. When the plates were covered on one side with the fur from aPetaurus' flight skin, coefficients of lift at average angles of attack were improved, the critical angle of attack was increased and the characteristics of flow separation were flattened. However, these positive effects were only achieved by physiological orientation of the fur (i.e. placed on the upper surface with fur lying backwards; Fig. 3). The gliding number is improved at very high angles of attack only (Fig. 6). Thus the fur of aPetaurus acts as a lift generator within high (critical) angles of attack, during gliding flight (Nachtigall, 1979). Other natural and synthetic furs show a qualitatively similar, but quantitatively less distinct effect (Fig. 7). The aerodynamic efficiency of a fur coating is due to the boundary layer effects provided by the individual hairs which seem to act as miniature back-flow breaks (Fig. 8,9). The bionic transferability of this effect to technical wings is discussed.