Definition
A sudden change in wind speed or direction occurring within 2,000 feet of the ground, capable of producing rapid changes in airspeed, lift, and aircraft attitude during takeoff, approach, or landing.
Plain English
A quick shift in wind close to the ground that can throw an aircraft off its expected flight path during the most critical phases of flight.
Context Anchor
Seen in aviation weather forecasts, pilot reports, and airport weather information when wind shear near the ground is expected or reported.
Derivation
"Shear" comes from the Old English sceran, meaning to cut or divide. The wind is described as "shearing" because two adjacent layers of air move in different directions or speeds, as if cut apart from each other.
Why Pilots Care
It poses a serious hazard during takeoff and landing by causing rapid changes in airspeed and altitude.
Grounding Statement
Picture an aircraft climbing after takeoff and suddenly flying from a headwind into much less wind; its airspeed can drop quickly even though the engine power has not changed.
Intuition Check
Do not read “low-level” as “low danger.” In LLWS, “low-level” means near the ground, where sudden wind changes are especially serious.
Example Sentence 1
The ATIS reported LLWS advisories in effect, so the crew briefed a wind shear escape procedure before beginning the approach.
Example Sentence 2
During the preflight briefing, the instructor highlighted LLWS as a key factor in the day's weather conditions affecting departures.