Llwas - How Does It Work?

Sat Feb 17, 2001 8:36 am

Does anybody know how LLWAS (low level wind shear alerting system) works? How comes the info into the cockpit?

RE: Llwas - How Does It Work?

Sat Feb 17, 2001 11:59 am

Windshear has its greatest effects at low altitudes.

A Low Level Windshear Alert System (LLWAS) basically takes surface
wind measurements at multiple anemometer sensors to detect
windshear and triangulates and pairs the readings. The LLWAS
algorithm uses the filtered wind field values to estimate the true
wind field divergence. This wind and shear information is sent to air traffic controllers in digital or graphic form. LLWAS systems
track and predict windshear in the approach and departure paths
of an airport which allows controllers to anticipate the need to
configure runways before wind shifts occur. LLWAS is designed to issue a Windshear Alert when it estimates an intensity of between 15 and 30 knots and a Microburst Alert when it estimates an intensity in excess of 30 knots.

RE: Llwas - How Does It Work?

Sun Feb 18, 2001 12:54 am

LLWAS alert is given to pilots by the controller via voice communication. The info given are the centerfield wind and the boundary wind.

To have more sophisticated alerts, airports need to have TDWR (Terminal Doppler Weather Radar) , integrated with LLWAS...still done by voice  Smile/happy/getting dizzy. Of course transports have their own windshear detection onboard but that's another story.


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