Definition
A wind shear condition in which an aircraft transitions from a headwind into a tailwind or calm air over a short distance or time, causing a sudden loss of indicated airspeed and lift. The reduction in relative wind over the wings produces a performance loss that, near the ground, can result in undershoot of the intended flight path or runway threshold.
Plain English
The wind that was blowing toward the nose of the aircraft suddenly disappears or reverses, so the aircraft loses airspeed and starts sinking below where it should be.
Context Anchor
Seen in thunderstorm and wind-shear discussions, especially during approach, landing, takeoff, and go-around decisions near convective weather.
Derivation
Shear comes from the Old English sceran, meaning to cut or divide. In aviation, wind shear refers to a sharp change in wind speed or direction across a small distance — as if the wind has been cut from one value to another.
Why Pilots Care
Rapid loss of airspeed can drop the aircraft below stall speed or safe climb performance, demanding immediate corrective action to avoid loss of control.
Grounding Statement
Imagine flying into a steady 20-knot headwind on approach, then within seconds that wind dies to zero — the aircraft suddenly feels 20 knots slower and starts settling.
Intuition Check
Do not read “calm” as automatically safe here. A sudden change from headwind to calm can still make the airplane lose airspeed. “Shearing” does not mean the wind is physically cutting the airplane; it means the wind changes sharply over a short distance.
Example Sentence 1
On final approach through the gust front, the crew experienced a headwind shearing to tailwind or calm and immediately added power to arrest the sink rate.
Example Sentence 2
On short final the headwind shearing to tailwind or calm caused a sudden drop in indicated airspeed, prompting the pilot to execute a go-around.