Definition
A warning issued by air traffic control or generated by airport sensors when a sudden change in wind speed or direction has been detected near the airport, particularly along the approach or departure path. The alert tells pilots that conditions exist which could cause a rapid loss of airspeed, lift, or controllability during takeoff or landing.
Plain English
A heads-up that the wind near the airport is shifting suddenly enough to be dangerous for aircraft taking off or landing.
Context Anchor
Seen in instrument weather flying, airport weather systems, air traffic control warnings, and cockpit alerts during takeoff or landing in changing weather.
Derivation
‘Shear’ comes from the Old English sceran, meaning to cut or divide. The wind is being ‘cut’ into layers moving at different speeds or directions, and the alert warns you that you are about to fly through that cut.
Why Pilots Care
Uncorrected wind shear can produce rapid loss of airspeed and altitude at low altitude, creating an immediate risk of stall or controlled flight into terrain.
Grounding Statement
Picture an airplane close to the runway flying from one moving block of air into another that is moving a different speed or direction.
Intuition Check
A wind shear alert is not just a general warning that it is windy. It means the wind may change suddenly in a way that can immediately affect the airplane.
Example Sentence 1
Tower issued a wind shear alert for the approach end of runway 27, so we held short and waited for conditions to improve.
Example Sentence 2
ATC broadcast a wind shear alert for the approach end of runway 27L due to a nearby thunderstorm.