Definition
A set of adjustable vanes positioned at the inlet of a turbine engine compressor that pivot to change the angle at which incoming air strikes the first stage of compressor blades. By varying this angle as engine speed and operating conditions change, VIGVs keep airflow into the compressor smooth and within limits, preventing compressor stall and improving efficiency across a wide range of power settings.
Plain English
Small movable blades at the front of a jet engine's compressor that swivel to direct incoming air at the right angle, so the engine runs smoothly whether it's at idle or full power.
Context Anchor
Seen in turbine engine discussions about compressor airflow, engine acceleration, and avoiding disrupted airflow through the engine.
Derivation
Three plain words doing exactly what they say: 'variable' (adjustable), 'inlet' (the entrance to the compressor), and 'guide vane' (a small fixed or movable blade that steers airflow). Calling it a 'guide vane' rather than just a 'blade' signals that its job is to direct air onto the next set of blades, not to compress the air itself.
Why Pilots Care
They protect the engine from damage, improve fuel efficiency, and allow stable operation from idle to high power.
Grounding Statement
At low and high engine speeds, the compressor needs the incoming air aimed differently, so the VIGV system changes the blade angle to keep the airflow smooth.
Intuition Check
Variable does not mean unpredictable here. It means the vane angle can be adjusted by the engine control system.
Example Sentence 1
As the pilot advanced the throttle, the engine's variable inlet guide vanes repositioned to maintain smooth airflow into the compressor.
Example Sentence 2
During a high-altitude takeoff, the pilot confirmed proper VIGV scheduling before advancing the throttles.