What does "stalling" a control surface mean?

Stalling a control surface occurs when the airflow over that surface separates, leading to a significant loss of lift or control. This phenomenon typically happens when the angle of attack of the wing or control surface exceeds its critical angle, disrupting the smooth airflow and causing turbulence. When this stall condition occurs, the effectiveness of the control surface diminishes, making it difficult for the pilot to maintain control of the aircraft. Understanding the stall characteristics of a control surface is crucial since it can result in unexpected behavior, particularly during maneuvers that require rapid changes in attitude or altitude. Pilots must be aware of the stall limits to ensure safe flight operations, hence the importance of this concept in flight training and safety protocols.