What causes the separation of air over the wing during a stall?

The separation of air over the wing during a stall is primarily caused by the angle formed by the wing chord line and the relative wind becoming excessive. When this angle, known as the angle of attack, increases beyond a certain threshold, the airflow can no longer adhere smoothly to the wing’s upper surface. This phenomenon occurs because the increased angle forces the air to travel a longer path, which can disrupt the smooth flow and lead to a condition called flow separation.

As the wing approaches its critical angle of attack, the airflow becomes turbulent and detaches from the wing. This loss of smooth airflow results in a significant decrease in lift, resulting in a stall. Understanding this concept is crucial for pilots, as it emphasizes the importance of managing the angle of attack to maintain effective lift during flight.