12/2/21
Pilot/Controller Glossary
W
WA
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(See AIRMET.)
(See WEATHER ADVISORY.)
WAAS
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(See WIDE-AREA AUGMENTATION SYSTEM.)
WAKE RE
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CATEGORIZATION (RECAT)
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A set
of optimized wake separation standards, featuring an
increased number of aircraft wake categories, in use
at select airports, which allows reduced wake
intervals.
(See WAKE TURBULENCE.)
WAKE TURBULENCE
−
A phenomenon that occurs
when an aircraft develops lift and forms a pair of
counter
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rotating vortices.
(See AIRCRAFT CLASSES.)
(See VORTICES.)
(Refer to AIM.)
WARNING AREA
−
(See SPECIAL USE AIRSPACE.)
WAYPOINT
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A predetermined geographical posi-
tion used for route/instrument approach definition,
progress reports, published VFR routes, visual
reporting points or points for transitioning and/or
circumnavigating controlled and/or special use
airspace, that is defined relative to a VORTAC station
or in terms of latitude/longitude coordinates.
WEATHER ADVISORY
−
In aviation weather
forecast practice, an expression of hazardous weather
conditions not predicted in the Aviation Surface
Forecast, Aviation Cloud Forecast, or area forecast,
as they affect the operation of air traffic and as
prepared by the NWS.
(See AIRMET.)
(See SIGMET.)
WEATHER RECONNAISSANCE AREA (WRA)
−
A WRA is airspace with defined dimensions and
published by Notice to Air Missions, which is
established to support weather reconnaissance/re-
search flights. Air traffic control services are not
provided within WRAs. Only participating weather
reconnaissance/research aircraft from the 53
rd
Weather Reconnaissance Squadron and National
Oceanic and Atmospheric Administration Aircraft
Operations Center are permitted to operate within a
WRA. A WRA may only be established in airspace
within U.S. Flight Information Regions outside of
U.S. territorial airspace.
WHEN ABLE
−
a.
In conjunction with ATC instructions, gives the
pilot the latitude to delay compliance until a
condition or event has been reconciled. Unlike “pilot
discretion,” when instructions are prefaced “when
able,” the pilot is expected to seek the first
opportunity to comply.
b.
In conjunction with a weather deviation
clearance, requires the pilot to determine when he/she
is clear of weather, then execute ATC instructions.
c.
Once a maneuver has been initiated, the pilot is
expected to continue until the specifications of the
instructions have been met. “When able,” should not
be used when expeditious compliance is required.
WIDE-AREA AUGMENTATION SYSTEM
(WAAS)
−
The WAAS is a satellite navigation system
consisting of the equipment and software which
augments the GPS Standard Positioning Service
(SPS). The WAAS provides enhanced integrity,
accuracy, availability, and continuity over and above
GPS SPS. The differential correction function
provides improved accuracy required for precision
approach.
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 deter-
mined 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
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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
PCG W
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