Definition
A ground-based system installed at certain airports that detects sudden changes in wind speed or direction near the surface and alerts air traffic controllers, who then pass the information to pilots. It uses a network of wind sensors placed around the airport perimeter and on the airfield. When the system detects a meaningful difference between the wind at one sensor and the wind at others, it identifies a possible wind shear or microburst and triggers an alert specifying the affected runway and the nature of the wind change.
Plain English
A network of wind sensors around an airport that watches for sudden, dangerous shifts in the wind near the ground and warns controllers so they can warn pilots taking off or landing.
Context Anchor
Seen in wind shear discussions, airport weather information, and warnings from air traffic control near takeoff or landing.
Why Pilots Care
Low-level wind shear can produce abrupt losses of airspeed and altitude during the most critical phases of flight; LLWAS gives pilots advance warning so they can go around or delay departure before the hazard is encountered.
Grounding Statement
LLWAS is a warning system for sudden wind changes near the ground, especially around runways.
Intuition Check
“Low-level” does not mean a low level of danger. Here it means the wind shear is close to the ground, where takeoff and landing leave little room to recover.
Example Sentence 1
Tower advised an LLWAS alert on runway 27, with a 20-knot loss reported on final approach.
Example Sentence 2
Before takeoff the captain checked that the departure runway had no current LLWAS warnings.