Pilot/Controller Glossary

TERMINAL-VERY HIGH FREQUENCY OMNIDIRECTIONAL RANGE STATION (TVOR)- A
very high frequency terminal omnirange station
located on or near an airport and used as an approach
aid.
(See NAVIGATIONAL AID.)
(See VOR.)

TERRAIN AWARENESS WARNING SYSTEM
(TAWS)- An on-board, terrain proximity alerting
system providing the aircrew "Low Altitude
warnings" to allow immediate pilot action.
TERRAIN FOLLOWING- The flight of a military
aircraft maintaining a constant AGL altitude above
the terrain or the highest obstruction. The altitude of
the aircraft will constantly change with the varying
terrain and/or obstruction.

TF-
(See TERRAIN FOLLOWING.)

TFDM-
(See TERMINAL FLIGHT DATA MANAGER.)

TGUI-
(See TIMELINE GRAPHICAL USER
INTERFACE.)

THAT IS CORRECT- The understanding you have
is right.
THA-
(See TRANSITIONAL HAZARD AREA.)

THREE-HOUR TARMAC RULE" Rule that relates
to Department of Transportation (DOT) requirements
placed on airlines when tarmac delays are anticipated
to reach 3 hours.
360 OVERHEAD-
(See OVERHEAD MANEUVER.)

THRESHOLD- The beginning of that portion of the
runway usable for landing.
(See AIRPORT LIGHTING.)
(See DISPLACED THRESHOLD.)

(See GLIDESLOPE.)
(See THRESHOLD.)

THRESHOLD LIGHTS-
(See AIRPORT LIGHTING.)

TIE-IN FACILITY" The FSS primarily responsible
for providing FSS services, including telecommuni ca ti on s se rv i ce s fo r la nd in g f ac il it ie s o r
navigational aids located within the boundaries of a
flight plan area (FPA). Three-letter identifiers are
assigned to each FSS/FPA and are annotated as tie-in
facilities in the Chart Supplement U.S., the Alaska
Supplement, the Pacific Supplement, and FAA Order
JO 7350.9, Location Identifiers. Large consolidated
FSS facilities may have many tie-in facilities or FSS
sectors within one facility.

yutsrpon

TETRAHEDRON- A device normally located on
uncontrolled airports and used as a landing direction
indicator. The small end of a tetrahedron points in the
direction of landing. At controlled airports, the
tetrahedron, if installed, should be disregarded
because tower instructions supersede the indicator.
(See SEGMENTED CIRCLE.)
(Refer to AIM.)

THRESHOLD CROSSING HEIGHT- The
theoretical height above the runway threshold at
which the aircraft"s glideslope antenna would be if
the aircraft maintains the trajectory established by the
mean ILS glideslope or the altitude at which the
calculated glidepath of an RNAV or GPS approaches.

(See FLIGHT PLAN AREA.)
(See FLIGHT SERVICE STATION.)

TIME-BASED FLOW MANAGEMENT (TBFM)-
A foundational Decision Support Tool for
time-based management in the en route and terminal
environments. TBFM"s core function is the ability to
schedule aircraft within a stream of traffic to reach a
defined constraint point (e.g., meter fix/meter arc) at
specified times, creating a time-ordered sequence of
traffic. The scheduled times allow for merging of
traffic flows, efficiently utilizing airport and airspace
capacity while minimizing coordination and
reducing the need for vectoring/holding. The TBFM
schedule is calculated using current aircraft estimated
time of arrival at key defined constraint points based
on wind forecasts, aircraft flight plan, the desired
separation at the constraint point and other
parameters. The schedule applies spacing only when
needed to maintain the desired separation at one or
more constraint points. This includes, but is not
limited to, Single Center Metering (SCM), Adjacent
Center Metering (ACM), En Route Departure
Capability (EDC), Integrated Departure/Arrival
Capability (IDAC), Ground-based Interval
Management-Spacing (GIM-S), Departure
Scheduling, and Extended/Coupled Metering.
TIME-BASED MANAGEMENT (TBM)- A
methodology for managing the flow of air traffic