a gate printer. In addition, TDLS will emulate the Flight Data Input/Output (FDIO) information within the control tower. 

TERMINAL RADAR SERVICE AREA- Airspace surrounding designated airports wherein ATC provides radar vectoring, sequencing, and separation on a full-time basis for all IFR and participating VFR aircraft. The AIM contains an explanation of TRSA. TRSAs are depicted on VFR aeronautical charts. Pilot participation is urged but is not mandatory. 

TERMINAL VFR RADAR SERVICE- A national program instituted to extend the terminal radar services provided instrument flight rules (IFR) aircraft to visual flight rules (VFR) aircraft. The program is divided into four types service referred to as basic radar service, terminal radar service area (TRSA) service, Class B service and Class C service. The type of service provided at a particular location is contained in the Chart Supplement U.S. 

a. Basic Radar Service- These services are provided for VFR aircraft by all commissioned terminal radar facilities. Basic radar service includes safety alerts, traffic advisories, limited radar vectoring when requested by the pilot, and sequencing at locations where procedures have been established for this purpose and/or when covered by a letter of agreement. The purpose of this service is to adjust the flow of arriving IFR and VFR aircraft into the traffic pattern in a safe and orderly manner and to provide traffic advisories to departing VFR aircraft. 

b. TRSA Service- This service provides, in addition to basic radar service, sequencing of all IFR and participating VFR aircraft to the primary airport and separation between all participating VFR aircraft. The purpose of this service is to provide separation between all participating VFR aircraft and all IFR aircraft operating within the area defined as a TRSA. 

c. Class C Service- This service provides, in addition to basic radar service, approved separation between IFR and VFR aircraft, and sequencing of VFR aircraft, and sequencing of VFR arrivals to the primary airport. 

d. Class B Service- This service provides, in addition to basic radar service, approved separation 

of aircraft based on IFR, VFR, and/or weight, and sequencing of VFR arrivals to the primary airport(s). 

(See CONTROLLED AIRSPACE.) (See TERMINAL RADAR SERVICE AREA.) (Refer to AIM.) (Refer to CHART SUPPLEMENT U.S.) 

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.) 

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.) 

