Definition
A variable inlet guide vane is a movable, angle-adjustable vane positioned at the inlet of a turbine engine compressor that directs incoming airflow onto the first stage of compressor blades at the correct angle for the engine's current operating conditions. By rotating to change their pitch, VIGVs control how the air strikes the compressor, helping prevent compressor stalls across a wide range of power settings, airspeeds, and altitudes.
Plain English
A set of small, angled blades at the front of a jet engine's compressor that can pivot to steer incoming air onto the spinning compressor blades at the right angle. The angle changes automatically as engine conditions change, so the airflow always meets the blades smoothly.
Context Anchor
Seen in turbine engine discussions, especially when learning how compressor stalls are prevented during power changes.
Derivation
Three plain words doing exactly what they say: 'variable' means the angle can be changed, 'inlet' means at the entry to the compressor, and 'guide vane' means a small fixed-shape blade that steers airflow. Together: a steering blade at the engine inlet whose angle can be varied. Knowing this makes the term self-explanatory in flight manuals.
Why Pilots Care
They reduce the likelihood of compressor stall during acceleration, deceleration, and high-altitude operation, protecting engine performance and safety.
Analogy
A VIGV works a little like adjustable slats in an air vent. The slats do not create the air; they aim it in the direction it needs to go.
Intuition Check
Do not think of a VIGV as a fan blade that pulls air through the engine. It is a guide surface that changes angle to aim the incoming air.
Example Sentence 1
The variable inlet guide vanes adjust automatically during throttle changes to keep airflow into the compressor smooth and prevent a stall.
Example Sentence 2
The maintenance check confirmed the variable inlet guide vanes responded correctly to the engine control system during a stall-margin test.