5 and is in agreement with previously broadcasted live recording 6, 7, 8. This observation was confirmed from the live recordings also reported in ref. During the M-shape the arm opens up further into the horizontal plane and the primary feathers are aligned with the axis of the bird to form an M-shaped planform when viewed from the top. In C-shape the arms are slighly untucked, creating a cavity between the body and the primary feathers, which are oriented vertically. 4) and the M-shape (the focus of this manuscript). The success of the attack largely depends on the manoeuvrability during the second phase of the stoop, when the bird 1 starts to pull out from the dive, while undergoing two important morphological transformations, namely the cupped-wing shape (C-shape, detail presented in ref. Within the initial phase of the stoop it adopts a ‘teardrop’ shape (T-shape) where the wings are folded and feathers tucked in a streamlined shape, which is intuitively the lowest drag configuration. While soaring, the falcon first climbs with the wings completely stretched out to increase lift, collected from vertical columns of rising air known as ‘thermals’ 3. Diving from high altitude is necessary to build-up such speeds. These findings could help in improving aircraft performance and wing suits for human flights.ĭuring stoop, peregine falcon ( Falco peregrinus), can dive at 39 ms −1 1 to 51 ms −1 2, making it the world’s fastest animal. A vortex pair with a sense of rotation opposite to that from conventional planar wings interacts with the main wings vortex to reduce induced drag, which would otherwise decelerate the bird significantly during pull-out. The stronger wing and tail vortices provide extra aerodynamic forces through vortex-induced lift for pitch and roll control. These vortices enhance mixing for flow reattachment towards the tail. Both experiments and simulations on life-size models, derived from field observations, revealed the presence of vortices emanating from the frontal and dorsal region due to a strong spanwise flow promoted by the forward sweep of the radiale. Here we demonstrate that the superior manoeuvrability of peregrine falcons during stoop is attributed to vortex-dominated flow promoted by their morphology, in the M-shape configuration adopted towards the end of dive. The peregrine falcon ( Falco peregrinus) is known for its extremely high speeds during hunting dives or stoop.
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