Definition
A wake turbulence safety system that monitors weather conditions, particularly winds, near parallel runways and advises air traffic controllers when wake vortices from a leading aircraft are likely to drift into the path of an aircraft on a closely spaced parallel runway. The system was developed to allow safer use of paired parallel approaches and departures by giving controllers real-time information about when reduced wake separation is acceptable.
Plain English
A tool that watches the wind near parallel runways and tells controllers when the swirling air left behind by one aircraft might drift over and affect another aircraft using the next runway.
Context Anchor
Seen in FAA acronym lists and in discussions of wake turbulence awareness and airport traffic operations.
Derivation
Vortex comes from the Latin vortex meaning a whirling mass, the same root as vertex. The name describes what the system tracks: the spinning, tube-shaped wakes of disturbed air that trail behind an aircraft's wingtips.
Why Pilots Care
Helps pilots avoid wake turbulence encounters that can cause loss of control during critical phases of flight.
Intuition Check
Do not read advisory as a casual suggestion. In this context, an advisory is safety-related information meant to help avoid a wake-vortex hazard.
Example Sentence 1
At airports equipped with EVAS, controllers can sometimes reduce the spacing between arrivals on parallel runways when winds make a wake encounter unlikely.
Example Sentence 2
Pilots consult EVAS information when planning arrivals at busy hub airports.