Pilot/Controller Glossary

WIDE AREA MULTILATERATION (WAM)" A distributed surveillance technology which may utilize any
combination of signals from Air Traffic Control Radar Beacon System (ATCRBS) (Modes A and C) and Mode
S transponders, and ADS-B transmissions. Multiple geographically dispersed ground sensors measure the
time-of-arrival of the transponder messages. Aircraft position is determined by joint processing of the
time-difference-of-arrival (TDOA) measurements computed between a reference and the ground stations"
measured time-of-arrival.
WILCO- I have received your message, understand it, and will comply with it.
WIND GRID DISPLAY- A display that presents the latest forecasted wind data overlaid on a map of the ARTCC
area. Wind data is automatically entered and updated periodically by transmissions from the National Weather
Service. Winds at specific altitudes, along with temperatures and air pressure can be viewed.
WIND SHEAR- A change in wind speed and/or wind direction in a short distance resulting in a tearing or
shearing effect. It can exist in a horizontal or vertical direction and occasionally in both.
WIND SHEAR ESCAPE- An unplanned abortive maneuver initiated by the pilot in command (PIC) as a result
of onboard cockpit systems. Wind shear escapes are characterized by maximum thrust climbs in the low altitude
terminal environment until wind shear conditions are no longer detected.
WING TIP VORTICES-
(See VORTICES.)

WORDS TWICE-
a. As a request: "Communication is difficult. Please say every phrase twice."
b. As information: "Since communications are difficult, every phrase in this message will be spoken twice."
WS-
(See SIGMET.)
(See WEATHER ADVISORY.)

WST-
(See CONVECTIVE SIGMET.)
(See WEATHER ADVISORY.)