Meeting Abstract
Fossils intermediate to theropod dinosaurs and modern birds show well-developed flight feathers on both fore- and hindlimbs that indicate aerodynamic function. To test the biomechanical functionality of these transitional structures, we evaluated flight performance of a robotic model with forewings of two sizes activated over a range of wing flapping kinematics. The robot was launched at fixed height via catapult with the wings either held in fixed position laterally, or when flapping at different combinations of three wingbeat frequencies and three stroke amplitudes. Wing length, for all frequency-amplitude combinations, was the most important parameter in determining horizontal distance travelled and total time aloft. Wingbeat frequency and stroke amplitude contributed positively and equivalently to horizontal distance and total time aloft, when compared to fixed-wing gliding. Rudimentary wing flapping at low frequencies and amplitudes thus improves aerodynamic performance for gliders at physical scales relevant to the origins of vertebrate flight. In combination with recent paleontological findings of four-winged avian precursors, these results further buttress the hypothesis of an aerial origin for flapping flight in birds.
