Terminal Controller Workstation (TCW)/Tower Display Workstation (TDW)
Displays RADAR data that has been collected by RADAR sensors and processed by
the RADAR Data Processor.
Threshold lights Help approaching aircraft positively identify the beginning of the
operational runway surface at night or during periods of reduced visibility.
Traffic Alert and Collision Avoidance System (TCAS) Airborne collision avoidance
system based on RADAR beacon signals that operates independent of ground-based
equipment.
True Bearing (TB) The relation of an object to the aircraft using true north as the
reference point instead of the aircraft s position.
True Heading (TH) The angle that is expressed with relation to true north.
Variation The angle between magnetic north and true north.
Video Information Distribution System (VIDS) Designed to consolidate, replace,
and automate several ATC systems.
Visual Approach Slope Indicator (VASI) Provides visual descent guidance
information during the approach to a runway.
Warm front Occurs when cold air retreats before an advancing mass of warm air.
Warning area Airspace that contains hazards to nonparticipating aircraft and have
clearly defined dimensions extending 3 miles outward from a coastline.
Wavelength Distance between corresponding points on consecutive waves, or the
distance a wave travels during one cycle.
Wheels-up lights Bar of lights located in the approach area that illuminate the
underside of aircraft preparing for landing.
AI-6
