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 certification/calibration traceable to the National Institute of
Standards and Technology. Traceable pressure
standards may be mercurial barometers, commissioned 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.

COURSE.)
FLIGHT PATH.)
ROUTE.)
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 communications; 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