TRANSITION WAYPOINT- The waypoint that defines the beginning of a runway or en route transition on an RNAV SID or STAR. 

TRANSITIONAL AIRSPACE- That portion of controlled airspace wherein aircraft change from one phase of flight or flight condition to another. 

TRANSITIONAL HAZARD AREA (THA)- Used by ATC. Airspace normally associated with an Aircraft Hazard Area within which the flight of aircraft is subject to restrictions. 

(See AIRCRAFT HAZARD AREA.) (See CONTINGENCY HAZARD AREA.) (See REFINED HAZARD AREA.) 

TRANSMISSOMETER- An apparatus used to determine visibility by measuring the transmission of light through the atmosphere. It is the measurement source for determining runway visual range (RVR). 

(See VISIBILITY.) 

TRANSMITTING IN THE BLIND- A transmis- sion from one station to other stations in circumstances where two-way communication cannot be established, but where it is believed that the called stations may be able to receive the transmission. 

TRANSPONDER- The airborne radar beacon receiver/transmitter portion of the Air Traffic Control Radar Beacon System (ATCRBS) which automati- cally receives radio signals from interrogators on the ground, and selectively replies with a specific reply pulse or pulse group only to those interrogations being received on the mode to which it is set to respond. 

(See INTERROGATOR.) (See ICAO term TRANSPONDER.) (Refer to AIM.) 

TRANSPONDER [ICAO]- A receiver/transmitter which will generate a reply signal upon proper interrogation; the interrogation and reply being on different frequencies. 

TRANSPONDER CODES - 

(See CODES.) 

TRANSPONDER OBSERVED - Phraseology used to inform a VFR pilot the aircraft s assigned beacon code and position have been observed. Specifically, this term conveys to a VFR pilot the transponder 

reply has been observed and its position correlated for transit through the designated area. 

TRIAL PLAN- A proposed amendment which utilizes automation to analyze and display potential conflicts along the predicted trajectory of the selected aircraft. 

TRSA - 

(See TERMINAL RADAR SERVICE AREA.) 

TSD- 

(See TRAFFIC SITUATION DISPLAY.) 

TURBOJET AIRCRAFT- An aircraft having a jet engine in which the energy of the jet operates a turbine which in turn operates the air compressor. 

TURBOPROP AIRCRAFT- An aircraft having a jet engine in which the energy of the jet operates a turbine which drives the propeller. 

TURBULENCE- An atmospheric phenomenon that causes changes in aircraft altitude, attitude, and or airspeed with aircraft reaction depending on intensity. Pilots report turbulence intensity according to aircraft's reaction as follows: 

a. Light - Causes slight, erratic changes in altitude and or attitude (pitch, roll, or yaw). 

b. Moderate- Similar to Light but of greater intensity. Changes in altitude and or attitude occur but the aircraft remains in positive control at all times. It usually causes variations in indicated airspeed. 

c. Severe- Causes large, abrupt changes in altitude and or attitude. It usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control. 

d. Extreme- The aircraft is violently tossed about and is practically impossible to control. It may cause structural damage. 

(See CHOP.) (Refer to AIM.) 

TURN ANTICIPATION- (maneuver anticipation). 

TVOR - 

(See TERMINAL-VERY HIGH FREQUENCY OMNIDIRECTIONAL RANGE STATION.) 

TWO-WAY RADIO COMMUNICATIONS FAIL- URE- 

(See LOST COMMUNICATIONS.) 

