In a gas turbine engine, what defines a compressor stall?

• A. A minor fluctuation in exhaust temperature during throttle changes.
• B. An incorrect fuel-air mixture causing engine knock.
• C. A condition in an axial-flow compressor in which one or more stages of rotor blades fail to pass air smoothly to the succeeding stages.
• D. A complete shutdown of the engine due to fuel starvation.

Answer: (C)

A compressor stall is a disruption inside an axial-flow compressor where the airflow no longer passes smoothly from one rotor stage to the next. When the flow is distorted or separates off the blade surfaces—often due to high angles of attack, rapid throttle changes, or blade damage—one or more rotor stages fail to transfer air efficiently, causing a drop in pressure rise and unstable operation. This is an internal airflow problem of the compressor, not a symptom of exhaust temperature fluctuations, incorrect fuel-air mixture causing knocking, or fuel starvation shutting down the engine. Therefore, the best description is that one or more stages of rotor blades fail to pass air smoothly to the succeeding stages.