Figure 1: Microraptor model and measurement configurations.

(a) Photograph of the full-scale feathered 3D Microraptor (at Colin Palmer’s house on the Isle of Wight). Inset: main configurations. (b) Free-body diagram of a gliding Microraptor showing forces, moment and flight direction. (c) Measured lift and drag coefficients for the two main configurations. (d) Measured moment coefficient against aerodynamic force coefficient. Blue lines show results for the sprawled configuration, red lines legs down. The palest shades are at a wind tunnel wind speed of 10 m s⁻¹, darkest 20 m s⁻¹ and intermediary shade 15 m s⁻¹. In (c), the lines show the variation of lift and drag coefficients with increasing angle of attack (starting from bottom left at zero angle of attack). Force coefficients are the measured forces shown in the free-body diagram, nondimensionalized on the basis of projected area and dynamic pressure, the conventional approach used in aerodynamic analysis. In (d), the curves show the variation of the pitching moment coefficient and total aerodynamic force coefficient with increasing angle of attack (starting from the left at zero angle of attack). The pitching moment is a measure of the pitch stability. For stable flight, the gradient must be negative; therefore for these results, the models were only flight-stable at large values (>0.6) of total aerodynamic force coefficient.