How can a pilot best detect the approach of a stall?

A pilot can best detect the approach of a stall through the ineffectiveness of the ailerons and elevator. As an aircraft approaches a stall, the airflow over the wings becomes increasingly disrupted, which results in a loss of lift. This condition also affects the control surfaces; both ailerons and elevator may become less responsive or ineffective, signaling to the pilot that the aircraft is approaching a stall condition.

During this time, pilots will notice that any attempts to maneuver the aircraft using the ailerons may not yield the expected changes in direction, and the elevator's ability to control pitch will be compromised. Recognizing these changes in control effectiveness is critical for a pilot, as they can act on this information to prevent an actual stall.

While visual observations, instrument readings, and engine noise can contribute to a pilot's overall situational awareness, they may not provide the immediate feedback necessary to detect the onset of a stall as effectively as the response of the control surfaces.