8/15/19 12/31/20  Pilot/Controller Glossary Pilot/Controller Glossary  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  TWO-WAY RADIO COMMUNICATIONS FAIL- URE- (See LOST COMMUNICATIONS.)  TVOR - (See TERMINAL-VERY HIGH FREQUENCY  OMNIDIRECTIONAL RANGE STATION.)  TURN ANTICIPATION- (maneuver anticipation).  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:  (See CHOP.)  (Refer to AIM.)  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.  PCG T-8 