The best indication that an aircraft is approaching a stall is what?

The best indication that an aircraft is approaching a stall is the ineffectiveness of the ailerons and elevator. As an aircraft nears a stall, it experiences a significant loss of lift, leading to a decrease in control effectiveness. The ailerons, which are responsible for controlling roll, and the elevator, which controls pitch, may not respond as expected due to the airflow over these control surfaces becoming disturbed. This lack of control is a critical indicator that the aircraft is nearing its stall angle and is essential for pilots to recognize in order to take corrective action and avoid the stall.

Monitoring and understanding the aircraft's behavior, particularly in terms of control surface responsiveness, is vital for maintaining safe flight operations. Pilots should be attentive to these signs, as they can help prevent dangerous situations where the aircraft may enter a stall unawares.