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Aeronautical Information Manual (AIM), page 723

5/26/16
12/10/15

W
WA-
(See AIRMET.)
(See WEATHER ADVISORY.)
WAAS-
(See WIDE-AREA AUGMENTATION SYSTEM.)

WAKE TURBULENCE- Phenomena resulting from
the passage of an aircraft through the atmosphere.
The term includes vortices, thrust stream turbulence,
jet blast, jet wash, propeller wash, and rotor wash
both on the ground and in the air.
(See AIRCRAFT CLASSES.)
(See JET BLAST.)
(See VORTICES.)
(Refer to AIM.)
WARNING AREA-

(See SPECIAL USE AIRSPACE.)

WAYPOINT- 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 area forecast, as they
affect the operation of air traffic and as prepared by
the NWS.
(See AIRMET.)
(See SIGMET.)
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

Pilot/Controller Glossary

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 determ-
ined by joint processing of the time-
difference-of-arrival (TDOA) measurements com-
puted 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.)


PCG W-1

Page 723 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   722 -- Page 723 -- 724