What are the signs of an impending stall?

The signs of an impending stall are best represented by the increased control pressure requirement and an unresponsive aircraft. As an aircraft approaches a stall, it reaches a critical angle of attack where the airflow over the wings becomes turbulent and inefficient. This situation often results in pilots needing to apply more control pressure to maintain the desired flight path, especially when attempting to hold altitude or control the aircraft's pitch.

An unresponsive aircraft can manifest as a lack of response to control inputs, which may indicate that the aircraft is nearing its stall limit. During this phase, pilots may notice that their inputs are less effective in altering the airplane's attitude or maintaining performance, which further signals the onset of a stall. This knowledge is crucial for pilots, as recognizing these signs allows them to take corrective action before an actual stall occurs, thereby enhancing safety and pilot confidence during flight maneuvers.

Other choices, while they may suggest various aircraft issues, do not directly correlate with the aerodynamic conditions leading to a stall. For example, increased fuel consumption and engine vibration, unusual engine sounds, or cockpit lighting changes are not primary indicators of an impending stall, as they relate to different aspects of aircraft performance or maintenance rather than stall conditions.