Fig. 3. Time traces of aerodynamic force production of the robotic wing throughout the stroke cycle when flapping a single wing (red) and when simultaneously flapping an imaged wing (blue) in close distance to elicit the clap-and-fling maneuver. (A) Total force production, (B) lift force that is equal to the force component in the vertical and (C) drag that is equal to force parallel to the horizontal. The broken lines in A–C indicate aerodynamic force production derived from a conventional analytical model for aerodynamics that solely depends on wing translational velocity and time averaged force coefficients (quasi-steady approach; for more details, see methods in Dickinson et al., 1999). (D) Translational wing motion (purple), the wing's angle of attack (yellow) and heaving motion (green) for a single stroke cycle.