Compressor stall is most likely to occur under which conditions?

Compressor stall is most likely to occur under which conditions?

• A. High power settings, low speed, high angle of attack
• B. Low power settings, high speed, high angle of attack
• C. High power, high speed, low AoA
• D. Low power, low speed

Answer: (C)

The main idea here is flow stability in the compressor. Compressor stall (surge) happens when the airflow through the compressor can’t follow the rotor’s demand and becomes unstable, reversing or breaking up as it passes through the blade passages. This tends to occur when you push the compressor toward the surge boundary on its operating map. Why this combination fits best: at high power settings, the engine demands more air and the compressor is loaded more heavily, loading the blades intensely. When the rotor is turning rapidly (high speed), those loads and any small disturbance in the flow are amplified, making the flow more prone to separation and instability. A relatively low angle of attack means the incoming flow is not entering with a large inclement angle; under these conditions, once a disturbance starts, there’s less inherent swirl or energy in the boundary layer to keep the flow attached, so the instability can develop into a surge. Taken together, high power, high speed, and low AoA place the compressor near its surge limit, where stall is most likely. In scenarios with lower power or lower speed, the compressor isn’t driven as hard and the flow remains within a stable region of the map, so stall is less likely.

The main idea here is flow stability in the compressor. Compressor stall (surge) happens when the airflow through the compressor can’t follow the rotor’s demand and becomes unstable, reversing or breaking up as it passes through the blade passages. This tends to occur when you push the compressor toward the surge boundary on its operating map.

Why this combination fits best: at high power settings, the engine demands more air and the compressor is loaded more heavily, loading the blades intensely. When the rotor is turning rapidly (high speed), those loads and any small disturbance in the flow are amplified, making the flow more prone to separation and instability. A relatively low angle of attack means the incoming flow is not entering with a large inclement angle; under these conditions, once a disturbance starts, there’s less inherent swirl or energy in the boundary layer to keep the flow attached, so the instability can develop into a surge. Taken together, high power, high speed, and low AoA place the compressor near its surge limit, where stall is most likely.

In scenarios with lower power or lower speed, the compressor isn’t driven as hard and the flow remains within a stable region of the map, so stall is less likely.