The video shows the airflow on a gyrocopter rotorblade while fast flight (IAS 150 km/h with rotor at 320 rpm). While spinning backwards approx. 2m of the inner radius of the blade has a reversed airflow. Note that the blade bends upwards while retreating, because its outer part still produces lift. While spinning forward the airflow creates lift on the whole length of the blade. This explains why the blade bends periodically and the gyrocopter (without roll-trim) tends to tilt to the left (right side blade spins forward) in fast flight. The video was shot with a Gopro Hero 3 with 240 fps.
