How is a stall recognized in flight?

A stall is primarily recognized in flight by experiencing a distinct stall warning or buffet. The aerodynamic stall occurs when the airflow over the wings becomes turbulent and detached, resulting in a significant loss of lift. Most aircraft are designed with built-in warning systems, such as a horn or light that activates at a certain angle of attack, alerting the pilot to the impending stall condition. Additionally, pilots often feel a buffet, a vibration or shaking sensation that indicates the wings are no longer generating sufficient lift. These cues are crucial for a pilot to react promptly and execute stall recovery procedures.

The other options do not provide relevant indicators of a stall. For instance, increases in altitude do not correlate with stall conditions; in fact, they may suggest other flight dynamics at play. The absence of any noise from the aircraft is neither a reliable indicator of a stall nor a typical condition resulting from one, as stalls typically produce a change in sound profile. Lastly, smooth control surface movement does not indicate a stall condition, as stalls usually arise from abrupt or inadequate control inputs combined with excessive airflow angles. Understanding these characteristics helps promote flight safety and effective stall recovery techniques.