Pilot/Controller Glossary

VISUAL SEPARATION- A means employed by
ATC to separate aircraft in terminal areas and en route
airspace in the NAS. There are two ways to effect this
separation:
a. The tower controller sees the aircraft involved
and issues instructions, as necessary, to ensure that
the aircraft avoid each other.
b. A pilot sees the other aircraft involved and upon
instructions from the controller provides his/her own
separation by maneuvering his/her aircraft as
necessary to avoid it. This may involve following
another aircraft or keeping it in sight until it is no
longer a factor.
(See SEE AND AVOID.)
(Refer to 14 CFR Part 91.)

VLF-
(See VERY LOW FREQUENCY.)

VMC-
(See VISUAL METEOROLOGICAL
CONDITIONS.)

VOICE SWITCHING AND CONTROL SYSTEM
(VSCS)- A computer controlled switching system
that provides air traffic controllers with all voice
circuits (air to ground and ground to ground)
necessary for air traffic control.
(Refer to AIM.)

VOR- A ground-based electronic navigation aid
transmitting very high frequency navigation signals,
360 degrees in azimuth, oriented from magnetic
north. Used as the basis for navigation in the National
Airspace System. The VOR periodically identifies
itself by Morse Code and may have an additional
voice identification feature. Voice features may be
used by ATC or FSS for transmitting instructions/information to pilots.
(See NAVIGATIONAL AID.)
(Refer to AIM.)

VOR TEST SIGNAL-
(See VOT.)

VORTAC- A navigation aid providing VOR
azimuth, TACAN azimuth, and TACAN distance
measuring equipment (DME) at one site.
(See DISTANCE MEASURING EQUIPMENT.)
(See NAVIGATIONAL AID.)
(See TACAN.)
(See VOR.)
(Refer to AIM.)

VORTICES- Circular patterns of air created by the
movement of an airfoil through the air when
generating lift. As an airfoil moves through the
atmosphere in sustained flight, an area of area of low
pressure is created above it. The air flowing from the
high pressure area to the low pressure areround and
about the tips of the airfoil tends to roll up into two
rapidly rotating vortices, cylindrical in shape. These
vortices are the most predominant parts of aircraft
wake turbulence and their rotational force is
dependent upon the wing loading, gross weight, and
speed of the generating aircraft. The vortices from
medium to super aircraft can be of extremely high
velocity and hazardous to smaller aircraft.
(See AIRCRAFT CLASSES.)
(See WAKE TURBULENCE.)
(Refer to AIM.)

VOT- A ground facility which emits a test signal to
check VOR receiver accuracy. Some VOTs are
available to the user while airborne, and others are
limited to ground use only.
(See CHART SUPPLEMENT U.S.)
(Refer to 14 CFR Part 91.)
(Refer to AIM.)

VR-
(See VFR MILITARY TRAINING ROUTES.)

VSCS-
(See VOICE SWITCHING AND CONTROL
SYSTEM.)

VTA-
(See VERTEX TIME OF ARRIVAL.)

VTOL AIRCRAFT-
(See VERTICAL TAKEOFF AND LANDING
AIRCRAFT.)