What is the function of a stall warning indicator?

The stall warning indicator serves a critical safety function in aircraft by alerting the pilot when the aircraft is approaching a critical angle of attack, which can lead to a stall. A stall occurs when the wings lose lift due to exceeding the critical angle of attack, usually caused by factors such as excessive pitch or insufficient airspeed.

This indicator typically functions through various methods, such as a visual light or an audible alarm, which activates at a predetermined angle of attack. This early warning allows pilots to take corrective action to avoid the stall, such as lowering the nose of the aircraft to reduce the angle of attack and regain altitude or airspeed.

The other options pertain to functions unrelated to stall warnings. For instance, fuel levels and altitude readings are monitored using different instruments specifically designed for those measurements. Similarly, turbulence alerts are provided by other systems that detect aerodynamic disturbances rather than indicating the impending risk of a stall.