Definition
Small, thin, flat or slightly curved blades mounted on the exterior of an aircraft that pivot freely in the airflow. In angle of attack indicators, vanes align themselves with the relative wind and mechanically or electrically signal the angle between the wing and that airflow to a cockpit display.
Plain English
Tiny moving flaps on the outside of the aircraft that swing to point into the oncoming air. By measuring how they rotate, the aircraft can tell what angle the wing is meeting the air at.
Context Anchor
Seen in angle-of-attack indicator discussions, usually as small sensing pieces mounted where outside airflow can reach them.
Derivation
From the Old English 'fana,' meaning a small flag or banner. The original idea — a flat surface that swings to show wind direction — carries straight over to the aviation use, where the vane points into the relative wind.
Why Pilots Care
Vane position directly drives accurate angle-of-attack and stall-warning information; blockage or damage can remove critical low-speed cues.
Intuition Check
Do not think of vanes here as engine fan blades. In this context, vanes are sensing surfaces in the outside airflow, used to detect the direction the air is coming from.
Example Sentence 1
During the preflight walk-around, the pilot gently checked that the AOA vane on the side of the fuselage moved freely and was not bent.
Example Sentence 2
During preflight the pilot gently moves the AoA vane to confirm it swings freely and is free of ice.