Kinematic and aerodynamic response of locusts in sideslip

Effects of the sideslip angle on the wing kinematics and the aerodynamic forces and moments generated by the locusts were investigated in a low-speed wind tunnel. Three live locusts (Schistocerca americana) were tested at tunnel speeds of 0, 2, and 4 m/s at three body angles of attack (0°, 3°, and 7°) and three sideslip angles (0°, -10°, and -20°). A sensitive custom-built microbalance was used to measure the forces and moments. The balance was synchronized with high-speed video system recording the wing kinematics. It was observed that the nose down pitching moment increases with the angle of attack increase. This is an indication of active and/or passive mechanisms restoring the body orientation in the vertical plane and providing pitch stability of locusts. The side airflow generates a large side force and positive rolling moment. In response to the oncoming side wind, the locust executes larger-amplitude flapping motion on the windward wings. Changes in kinematic parameters of locust wings are similar to those observed in dragonfly during the right-turn maneuver. However, the yawing moment increases with the sideslip angle increase indicating yaw stability. This could be due to the weathercock stability, since about two thirds of locust's body length and legs lie behind its center of mass.