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Pilot/Controller Glossary 

12/2/21 

TERMINAL-VERY HIGH FREQUENCY OMNI-
DIRECTIONAL 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. 

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.) 

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.) 

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 GLIDESLOPE.) 
(See THRESHOLD.) 

THRESHOLD LIGHTS

 

(See AIRPORT LIGHTING.) 

TIE-IN FACILITY– The FSS primarily responsible 
for providing FSS services, including telecommu-
n i ca t i o n s   s e rv i ce s   fo r   l a n d i n g   f ac i l i t i e 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. 

(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 

PCG T