Pilot/Controller Glossary

advisory is no longer depicted on radar, but may still
be a factor.

TRAJECTORY- A EDST representation of the path
an aircraft is predicted to fly based upon a Current
Plan or Trial Plan.

TRAFFIC PATTERN- The traffic flow that is
prescribed for aircraft landing at, taxiing on, or taking
off from an airport. The components of a typical
traffic pattern are upwind leg, crosswind leg,
downwind leg, base leg, and final approach.

(See EN ROUTE DECISION SUPPORT TOOL.)

a. Upwind Leg- A flight path parallel to the
landing runway in the direction of landing.
b. Crosswind Leg- A flight path at right angles to
the landing runway off its upwind end.
c. Downwind Leg- A flight path parallel to the
landing runway in the direction opposite to landing.
The downwind leg normally extends between the
crosswind leg and the base leg.
d. Base Leg- A flight path at right angles to the
landing runway off its approach end. The base leg
normally extends from the downwind leg to the
intersection of the extended runway centerline.
e. Final Approach- A flight path in the direction
of landing along the extended runway centerline. The
final approach normally extends from the base leg to
the runway. An aircraft making a straight-in approach
VFR is also considered to be on final approach.
(See STRAIGHT-IN APPROACH VFR.)
(See TAXI PATTERNS.)
(See ICAO term AERODROME TRAFFIC
CIRCUIT.)
(Refer to 14 CFR Part 91.)
(Refer to AIM.)

TRAFFIC SITUATION DISPLAY (TSD)- TSD is a
computer system that receives radar track data from
all 20 CONUS ARTCCs, organizes this data into a
mosaic display, and presents it on a computer screen.
The display allows the traffic management coordinator multiple methods of selection and highlighting of
individual aircraft or groups of aircraft. The user has
the option of superimposing these aircraft positions
over any number of background displays. These
background options include ARTCC boundaries, any
stratum of en route sector boundaries, fixes, airways,
military and other special use airspace, airports, and
geopolitical boundaries. By using the TSD, a
coordinator can monitor any number of traffic
situations or the entire systemwide traffic flows.

TRAJECTORY MODELING- The automated process of calculating a trajectory.
TRAJECTORY OPTIONS SET (TOS)- A TOS is an
electronic message, submitted by the operator, that is
used by the Collaborative Trajectory Options
Program (CTOP) to manage the airspace captured in
the traffic management program. The TOS will allow
the operator to express the route and delay trade-off
options that they are willing to accept.
TRANSCRIBED WEATHER BROADCAST
(TWEB)- A continuous recording of meteorological
and aeronautical information that is broadcast on
L/MF and VOR facilities for pilots. (Provided only
in Alaska.)
(Refer to AIM.)

TRANSFER OF CONTROL- That action whereby
the responsibility for the separation of an aircraft is
transferred from one controller to another.
(See ICAO term TRANSFER OF CONTROL.)

TRANSFER OF CONTROL [ICAO]- Transfer of
responsibility for providing air traffic control service.
TRANSFERRING CONTROLLER- A controller/
facility transferring control of an aircraft to another
controller/facility.
(See ICAO term TRANSFERRING
UNIT/CONTROLLER.)

TRANSFERRING FACILITY-
(See TRANSFERRING CONTROLLER.)

TRANSFERRING UNIT/CONTROLLER [ICAO]-
Air traffic control unit/air traffic controller in the
process of transferring the responsibility for
providing air traffic control service to an aircraft to
the next air traffic control unit/air traffic controller
along the route of flight.
Note: See definition of accepting unit/controller.

TRANSITION-
a. The general term that describes the change from
one phase of flight or flight condition to another; e.g.,
transition from en route flight to the approach or
transition from instrument flight to visual flight.
b. A published procedure (DP Transition) used to
connect the basic DP to one of several en route