What effect do flight control surfaces have during a stall?

During a stall, flight control surfaces can indeed cause loss of control. This is primarily because a stall occurs when the angle of attack exceeds a critical limit, leading to a dramatic decrease in lift and a potential increase in drag. Control surfaces such as ailerons, elevators, and rudders become less effective or can even produce opposite effects when airflow over the wings is disrupted during a stall.

For instance, if a pilot attempts to use ailerons to recover from a stall, it may exacerbate the situation by increasing the angle of attack on the wing that is still lifting, potentially leading to a spin. Similarly, using the elevator incorrectly can contribute to further stall by causing a greater angle of attack. Therefore, during a stall, rather than enhancing control or stability, the flight control surfaces can significantly impair the aircraft's controllability and safety.

This understanding highlights the importance of managing the angle of attack and recognizing stall conditions, as relying on control surfaces inappropriately during a stall can lead to serious loss of control.