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Work with Ivo Ros (PNAS 2011) & collaborators at Harvey Mudd College recently shows that during slow flight pigeons turn much like a helicopter, with the net aerodynamic force having a fixed orientation with respect to the bird's body (blue vector cone +8 deg during downstroke; red vector cone during upstroke). Thus, pigeons mainly reorient Faero by banking (rolling) into the turn. Surprisingly, pigeons generate significant upstroke lift ( ~27% of downstroke lift) through their wingtip reversal upstroke, originally noted by RJH Brown (1963). These results were obtained by combining 3D kinematics obtained from 5 high-speed video cameras with a detailed mass-distribution model of the pigeons to track movements of the pigeon's center of mass over time.
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