What function does a stall warning system serve in aircraft?

A stall warning system is designed specifically to alert pilots when they are approaching a stall condition, which occurs when the angle of attack increases to a point where the wings can no longer sustain sufficient lift. This system typically provides an auditory or visual signal to the pilot, serving as a critical warning that allows them to take corrective action before an actual stall occurs. Recognizing the onset of a stall is essential for maintaining control of the aircraft, especially during flight maneuvers that are close to the critical edge of aerodynamic performance.

In contrast, the other options describe functions that are not related to stall warning systems. For instance, monitoring fuel levels is important for flight safety, but it is not the role of a stall warning system to assess fuel quantity. The signaling of successful takeoff and landing is typically managed by different cockpit instruments and indicators. Likewise, while navigating through weather conditions is a critical aspect of flying, it involves various navigation and weather radar systems rather than a stall warning system. Thus, the correct understanding of the function of a stall warning system is to alert pilots as they approach a stall, ensuring they can maintain safety and control of the aircraft.