How do birds and bugs that flit through the sky execute precise manoeuvres such as sharp turns and, at the same time, exhibit such stability that crashes seldom occur? Tyson Hedrick of the University of North Carolina at Chapel Hill, and Bo Cheng and Xinyan Deng at the University of Delaware in Newark explain this aerial prowess with a model of 'flapping counter-torque'.
Focusing on low-speed side-to-side turns of 60° or more (see picture, below), the researchers found that flapping fliers of all sizes — from fruitflies to cockatoos — rely on the turning movement itself to create an asymmetry in velocity between the inside and outside wing and end the turn. That is, they don't have to actively put on the brakes to avoid overturning; their wings do it for them.
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Locomotion: Elegant flappers. Nature 458, 811 (2009). https://doi.org/10.1038/458811c
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DOI: https://doi.org/10.1038/458811c
