Figure 2: Velocity-averaged aerodynamic performance of sprawled and legs down configurations.

The forces are divided by the square of wind tunnel airspeed, thus allowing more direct comparisons between configurations of different projected areas than would be the case for conventional non-dimensional lift and drag coefficients. (a) Speed-specific Lift-Drag polar. It is apparent from this graph that the sprawled configuration (blue) produces more lift than legs down (red), a result obscured in Fig. 1c. (b) Glide ratio against speed-specific aerodynamic force coefficient. The glide ratio is the ratio of lift:drag and is a measure of the glide angle. The higher the glide ratio, the shallower the glide angle. (c) Speed-specific moment coefficient against speed-specific force coefficient. Stable flight points occur where the pitching moment curve gradients are negative and the moment is zero. The graphs (b) and (c) share a common x axis; therefore, the stable flight points have been projected from (c) to (b) to determine the corresponding glide ratios. Although the sprawled configurations are capable of producing a higher glide ratio than legs down, the stability limit means that legs down actually achieves stable flight at a higher glide ratio. (d) Glide velocities and glide performance for the stable points. (e) Glide trajectories for the points in the stable regime. The curves show calculated flight paths for animals leaping from an elevated perch, flying at the aerodynamic conditions taken from the stable flight points. The legs down configuration initially falls further in order to build up a greater steady flight speed; therefore, for flights from heights of <15 m the sprawled configuration has the greater range. From heights of 2 m or more, legs down gives the greater range.