What can cause a compressor stall?

A compressor stall occurs when the airflow through the compressor is disrupted, leading to a loss of efficiency and potential malfunction. Foreign object damage is a significant contributor to this phenomenon. When foreign objects enter the engine, they can disrupt the smooth flow of air through the compressor blades. This disruption can cause uneven pressure distribution and stalls at certain operating conditions, particularly at high power settings or during rapid changes in engine performance.

In the context of the other choices, excessive altitude can reduce air density and affect engine performance, but it does not directly cause stalls in the same way that physical disruption from foreign objects does. Excessive weight can impact the overall performance and handling of an aircraft, but again, it does not inherently lead to compressor stalls. Rapid fuel flow, while it can affect combustion dynamics, is not directly linked to the mechanical airflow disruptions caused by foreign objects. Therefore, foreign object damage is the most direct cause of compressor stalls among the options provided.