6/17/21 

Pilot/Controller Glossary 

b. 

Concerning a precision radar approach (PAR), 

it is the point where the glide path intercepts the 
landing surface. 

(See ICAO term TOUCHDOWN.) 

TOUCHDOWN [ICAO]

−

 The point where the 

nominal glide path intercepts the runway. 

Note: Touchdown as defined above is only a datum 

and is not necessarily the actual point at which the 
aircraft will touch the runway. 

TOUCHDOWN RVR

−

 

(See VISIBILITY.) 

TOUCHDOWN ZONE

−

 The first 3,000 feet of the 

runway beginning at the threshold. The area is used 
for determination of Touchdown Zone Elevation in 
the development of straight-in landing minimums for 
instrument approaches. 

(See ICAO term TOUCHDOWN ZONE.) 

TOUCHDOWN ZONE [ICAO]

−

 The portion of a 

runway, beyond the threshold, where it is intended 
landing aircraft first contact the runway. 

TOUCHDOWN ZONE ELEVATION

−

 The highest 

elevation in the first 3,000 feet of the landing surface. 
TDZE is indicated on the instrument approach 
procedure chart when straight-in landing minimums 
are authorized. 

(See TOUCHDOWN ZONE.) 

TOUCHDOWN ZONE LIGHTING

−

 

(See AIRPORT LIGHTING.) 

TOWER

−

 A terminal facility that uses air/ground 

communications, visual signaling, and other devices 
to provide ATC services to aircraft operating in the 
vicinity of an airport or on the movement area. 
Authorizes aircraft to land or takeoff at the airport 
controlled by the tower or to transit the Class D 
airspace area regardless of flight plan or weather 
conditions (IFR or VFR). A tower may also provide 
approach control services (radar or nonradar). 

(See AIRPORT TRAFFIC CONTROL SERVICE.) 
(See APPROACH CONTROL FACILITY.) 
(See APPROACH CONTROL SERVICE.) 
(See MOVEMENT AREA.) 
(See TOWER EN ROUTE CONTROL 

SERVICE.) 

(See ICAO term AERODROME CONTROL 

TOWER.) 

(Refer to AIM.) 

TOWER EN ROUTE CONTROL SERVICE

−

 The 

control of IFR en route traffic within delegated 
airspace between two or more adjacent approach 
control facilities. This service is designed to expedite 
traffic and reduce control and pilot communication 
requirements. 

TOWER TO TOWER

−

 

(See TOWER EN ROUTE CONTROL 

SERVICE.) 

TRACEABLE PRESSURE STANDARD

−

 The 

facility station pressure instrument, with certifica-
tion/calibration traceable to the National Institute of 
Standards and Technology. Traceable pressure 
standards may be mercurial barometers, commis-
sioned ASOS or dual transducer AWOS, or portable 
pressure standards or DASI. 

TRACK

−

 The actual flight path of an aircraft over the 

surface of the earth. 

(See COURSE.) 
(See FLIGHT PATH.) 
(See ROUTE.) 
(See ICAO term TRACK.) 

TRACK [ICAO]

−

 The projection on the earth’s 

surface of the path of an aircraft, the direction of 
which path at any point is usually expressed in 
degrees from North (True, Magnetic, or Grid). 

TRACK OF INTEREST (TOI)

−

 Displayed data 

representing an airborne object that threatens or has 
the potential to threaten North America or National 
Security. Indicators may include, but are not limited 
to: noncompliance with air traffic control instructions 
or aviation regulations; extended loss of communica-
tions; unusual transmissions or unusual flight 
behavior; unauthorized intrusion into controlled 
airspace or an ADIZ; noncompliance with issued 
flight restrictions/security procedures; or unlawful 
interference with airborne flight crews, up to and 
including hijack. In certain circumstances, an object 
may become a TOI based on specific and credible 
intelligence pertaining to that particular aircraft/ 
object, its passengers, or its cargo. 

TRACK OF INTEREST RESOLUTION

−

 A TOI 

will normally be considered resolved when: the 
aircraft/object is no longer airborne; the aircraft 
complies with air traffic control instructions, aviation 
regulations, and/or issued flight restrictions/security 
procedures; radio contact is re

−

established and 

authorized control of the aircraft is verified; the 
aircraft is intercepted and intent is verified to be 

PCG T

−

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