What is the effect of using variable compressor stator vane angles?

• A. Increases fuel consumption at high altitude
• B. Causes more stall risk
• C. Reduces engine life
• D. Facilitates rapid stall-free accelerations and optimizes fuel consumption at partial power conditions

Answer: (A)

Variable compressor stator vane angles adjust the flow direction entering the compressor stages as engine speed and power settings change. By reorienting the flow, the compressor can maintain a favorable pressure ratio and prevent flow separation across a wide operating range. This improves surge margin and throttle response, so the engine can accelerate quickly without stalling. At partial power conditions, the optimized flow reduces losses from mismatched air and rotor speed, helping to use fuel more efficiently. In flight at high altitude, the lower air density stresses the compressor; the variable vanes help keep the flow stable and efficient under those conditions. In short, changing the vane angles enables rapid, stall-free accelerations and better fuel economy across partial-power and altitude variations.