In the compressor stators case, which vanes are variable?

In the compressor stators case, which vanes are variable?

• A. 3, 4, & 5 are Fixed Compressor Stators
• B. Variable Stage 1 & Stage 2 Vanes
• C. All vanes are Fixed Compressor Stators
• D. Stage 2 only

Answer: (B)

Variable stator vanes are used to keep airflow stable as engine speed and load change. In the compressor of this engine, the first two stages have actuated vanes, so their blade angles can be adjusted to optimize the flow entering the next stage. This helps prevent compressor surge and maintains efficiency across a wide operating range, especially at light throttle where flow conditions are most prone to instability. The later stages use fixed vanes because the flow becomes more predictable at higher pressures and the added complexity of more actuated elements isn’t needed. Therefore, the vanes that remain variable are the Stage 1 and Stage 2 vanes.

Variable stator vanes are used to keep airflow stable as engine speed and load change. In the compressor of this engine, the first two stages have actuated vanes, so their blade angles can be adjusted to optimize the flow entering the next stage. This helps prevent compressor surge and maintains efficiency across a wide operating range, especially at light throttle where flow conditions are most prone to instability. The later stages use fixed vanes because the flow becomes more predictable at higher pressures and the added complexity of more actuated elements isn’t needed. Therefore, the vanes that remain variable are the Stage 1 and Stage 2 vanes.