10/5/23 

Pilot/Controller Glossary 

TRANSITIONAL HAZARD AREA (THA)

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 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

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 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

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A transmission 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

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 The airborne radar beacon receiver/transmitter portion of the Air Traffic Control Radar 

Beacon System (ATCRBS) which automatically 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]

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 A receiver/transmitter which will generate a reply signal upon proper interrogation; 

the interrogation and reply being on different frequencies. 
TRANSPONDER CODES

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(See CODES.) 

TRANSPONDER OBSERVED 

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 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

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 A proposed amendment which utilizes automation to analyze and display potential conflicts 

along the predicted trajectory of the selected aircraft. 
TRSA

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(See TERMINAL RADAR SERVICE AREA.) 

TRUST

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(See THE RECREATIONAL UAS SAFETY TEST.) 

TSAS

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(See TERMINAL SEQUENCING AND SPACING.) 

TSD

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(See TRAFFIC SITUATION DISPLAY.) 

TURBOJET AIRCRAFT

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 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

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 An aircraft having a jet engine in which the energy of the jet operates a turbine 

which drives the propeller. 
TURBULENCE

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 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 

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

b. 

Moderate

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 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. 

PCG T

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