Study of turning takeoff maneuver in free-flying dragonflies: effect of dynamic coupling

Turning takeoff flights of several dragonflies were recorded during which a dragonfly takes off while changing the flight direction at the same time. Center of mass was elevated about 1-2 body lengths. Five of these maneuvers were selected for 3D body surface reconstruction and the body orientation measurement. In oppose to conventional banked turn model, which neglects interactions between the rotational motions, in this study we investigated the strength of the dynamic coupling by dividing pitch, roll and yaw angular accelerations into two contributions: one from aerodynamic torque and one from dynamic coupling effect. The latter term is referred to as Dynamic Coupling Acceleration (DCA). The DCA term can be measured directly from instantaneous rotational velocities of the insect. We found a strong correlation between pitch and yaw velocities at the end of each wingbeat and the time integral of the corresponding DCA term. Generation of pitch, roll and yaw torques requires different aerodynamic mechanisms and is limited due to the other requirements of the flight. Our results suggest that employing DCA term gives the insect capability to perform a variety of maneuvers without fine adjustments in the aerodynamic torque.