Abstract
Wind tunnel tests conducted on a model based on the long-eared bat Plecotus auritus indicated that the positioning of the tail membrane (uropatagium) can significantly influence flight control. Adjusting tail position by increasing the angle of the legs ventrally relative to the body has a two-fold effect; increasing leg-induced wing camber (i.e., locally increased camber of the inner wing surface) and increasing the angle of attack of the tail membrane. We also used our model to examine the effects of flying with and without a tail membrane. For the bat model with a tail membrane increasing leg angle increased the lift, drag and pitching moment (nose-down) produced. However, removing the tail membrane significantly reduced the change in pitching moment with increasing leg angle, but it had no significant effect on the level of lift produced. The drag on the model also significantly increased with the removal of the tail membrane. The tail membrane, therefore, is potentially important for controlling the level of pitching moment produced by bats and an aid to flight control, specifically improving agility and manoeuvrability. Although the tail of bats is different from that of birds, in that it is only divided from the wings by the legs, it nonetheless, may, in addition to its prey capturing function, fulfil a similar role in aiding flight control.
Highlights
In recent years it has become established that bird tails have important effects upon their flight
The CL and CD produced by the bat model with a tail membrane follow similar general trends with body angle and leg angle (Figure 3A and B)
An ANCOVA (Figure 4A) confirmed that CL increased with both leg angle (b) and changed with bat model configuration, and the incremental change in CL with leg angle differed between the model configurations
Summary
In recent years it has become established that bird tails have important effects upon their flight. Bird tails are known to produce lift during flight [1,2]. Sufficient flight stability is essential for all flying animals and bird tails are thought to be a key component for overall flight stability [5,6,7]. Bird tails are thought to be important for flight control, during takeoff and landing when the tail is fanned out and the angle of attack increased, augmenting lift production, improving manoeuvrability and possibly reducing wing stall [8,9]. Relatively little research has investigated the aerodynamic function(s) of a bat’s tail membrane (uropatagium). For example bats seem to generate more complex aerodynamic wakes than birds [14]
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