What are signs of a "Compressor Stall"?

A compressor stall occurs when there is a breakdown in the smooth flow of air through the engine’s compressor, often leading to performance issues. Recognizing the signs of a compressor stall is crucial for an effective response to maintain safety and control of the aircraft.

The presence of uncommanded fluctuations in RPM alongside an abnormal engine noise indicates a disruption in the airflow within the engine. This fluctuation in RPM may be accompanied by a rough or screaming sound from the engine, which are clear indications that the compressor is not functioning properly and is indeed stalling. Pilots need to be alert to these symptoms, as they can escalate quickly and may lead to engine failure if not addressed.

The other options describe scenarios that do not align with the manifestations of a compressor stall. For example, a decrease in altitude and speed can result from various factors unrelated to the engine's performance. Steady engine noise and increased RPM might suggest normal operation, while smooth acceleration and reduced fuel consumption imply efficient engine performance. None of these conditions directly indicate a compressor stall, reinforcing why recognizing fluctuating RPMs and abnormal noise is critical for the pilot to identify the issue accurately.