What is the primary cause of aircraft stalls?

The primary cause of aircraft stalls is exceeding the critical angle of attack. The critical angle of attack is the angle between the wing's chord line and the oncoming airflow at which the wing begins to lose lift. When an aircraft exceeds this angle, the airflow separates from the upper surface of the wing, resulting in a significant reduction in lift and the onset of a stall.

Understanding the critical angle of attack is crucial for pilots because stalls can occur at various airspeeds and configurations, not just at low speeds. Additionally, factors such as increased weight or balance issues can make it easier to reach this critical angle, but it is the exceedance of that specific angle that directly leads to a stall condition.

Other factors mentioned, such as loss of engine power, improper weight distribution, and excessive turbulence, can contribute to stall situations or exacerbate the circumstances, but none directly define the stall phenomenon as the critical angle of attack does. The stall is fundamentally a characteristic of aerodynamic behavior relative to airflow over the wing, emphasizing the significance of angle of attack in flight dynamics.