What flaps setting activates the stall warning horn?

The activation of the stall warning horn is closely tied to the angle of attack and configuration of the aircraft during flight. Specifically, in many multi-engine airplanes, the stall warning system is designed to alert pilots when the aircraft is approaching a critical angle of attack, which can happen sooner with certain flap configurations due to increased lift and changes in airflow over the wings.

In the context of the question, the flaps setting that activates the stall warning horn is linked to the configurations most likely to bring the aircraft closer to its stalling angle. Typically, when flaps are extended to greater degrees, such as 25 and 40, the stall warning is activated at a higher airspeed compared to flaps up (0) or a lower flap setting like 10. This is because the additional lift generated by the flaps alters the aerodynamic characteristics, causing the critical angle of attack for stall to be reached at a different point.

Therefore, when the flaps are set to 25 and 40, the stall warning horn is engaged anticipating the increased risk of stall that may occur due to the altered aerodynamic profile that comes with fully deploying the flaps. This feature is integral for maintaining safety during flight operations, especially in configurations where the aircraft is close to its