When hovering in any wind, or in translational flight, the advancing blade is the blade at any point in time that is moving into the oncoming airflow. This blade will generate more lift than the retreating blade on the other side of the aircraft, and so (due to gyroscopic precession), will tend to make the disk tilt up 90 degrees later in its travel. For example, hovering nose into the wind will tend to make the nose rise.
As the retreating blade sees a much slower stream of air, it is prone to stalling as the helicopter's airspeed rises, a condition known as retreating blade stall. Retreating blade stall often defines the top speed of a helicopter.
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