ATC Definitions

Advanced Surface Movement Guidance and Control System	A system providing routing, guidance, surveillance and control to aircraft and affected vehicles in order to maintain movement rate under all local weather conditions within the Aerodrome Visibility Operational level whilst maintaining the required level of safety.
Advisory		A message that serves to warn the controller of actual or anticipated actions that are required to bring a flight back to plan. Advisories are of the following type: time, speed, direction, holding information.
Aerodrome		A defined area (including any buildings, installations, and equipment) intended to be used either wholly or in part for arrival, departure and surface movement of aircraft and operational vehicles.
Aerodrome control service		Air traffic control service for aerodrome traffic.
Aerodrome control tower	A unit established to provide air traffic control service to aerodrome traffic.
Aerodrome Movement		The movement of an aircraft on the movement area.
Aerodrome Visibility Operational Level	The minimum visibility at or above which the declared movement rate can be sustained by an A-SMGCS.
Aeronautical information		Information related to flight safety, air navigation, technical, administrative or legislative matters.
Aeronautical Information Publication		A publication issued by or with the authority of a State and containing aeronautical information of a lasting character essential to air navigation
Air traffic		All aircraft in flight or operating on the manoeuvring area of an aerodrome.
Air traffic advisory service		A service provided within advisory airspace to ensure separation, in so far as possible, between aircraft which are operating on IFR flight plans.
Air traffic control service		A service provided for the purpose of preventing collisions between aircraft and, on the manoeuvring area, between aircraft and obstructions, and expediting and maintaining an orderly flow of traffic.
Air Traffic Management		The Special Committee on FANS described ATM as consisting of a ground part and an air part, both of which are needed to ensure the safe and efficient movement of aircraft during all phases of operation.
Air Traffic Service		A generic term meaning variously, flight information service, alerting service, air traffic advisory service, air traffic control service (area control service, approach control service, or aerodrome control service).
Aircraft operators		This term refer to the aggregate of organisations and people who own and/or operate the equipment, infrastructure, procedures, rules and information used to support their overall mission (to conduct flight operations).
Aircraft separation	Separation is the generic term used to describe action on the part of ATC in order to keep aircraft, operating in the same area, at such distances from each other that the risk of their colliding with each other is reduced. Separations are defined in the vertical and the horizontal planes. Furthermore the horizontal separation is decomposed into the lateral and the longitudinal separations.
Airspace		A continuous volume of defined dimensions.
Airspace region		A defined volume of airspace.
Alert	An indication of an existing or pending situation during aerodrome operations, or an indication of abnormal A-SMGCS operation, that requires attention/action.
Alerting service		A service provided to notify appropriate organisations regarding aircraft in need of search and rescue aid, and assist such organisations as required.
Altitude		The vertical distance of a level, a point, or an object considered as a point, measured from mean sea level.
Approach control office		A unit established to provide air traffic control service to controlled flights arriving at, or departing from, one or more aerodromes.
Approach control service		Air traffic control service for arriving or departing controlled flights.
Approach sequence		The order in which two or more aircraft are cleared to approach to land at the aerodrome.
Apron	A defined area on an aerodrome, intended to accommodate aircraft for purposes of loading or unloading passengers, mail cargo, fuelling, parking or maintenance.
Apron Control Unit	The relevant authority responsible for the provision of Ground Traffic services on the aprons.
Apron Management Service	A service provided to regulate the activities and movement of aircraft, vehicles and personnel on the apron.
Area control service		Air traffic control service for controlled flights in control areas.
Area reminder		A reminder is that is provided whenever a flight enters a particular region of airspace for which area reminders are active (and the flight is eligible). The reminder will include the details of the flight. The reminder is directed at the sector controller that is associated with the specific area reminder.
ATC sector		A defined airspace region for which an associated controller(s) has ATC responsibility.
ATS route		A specified route designed for channelling the flow of traffic as necessary for the provision of air traffic services.
Authorised Movement	An aerodrome movement or vehicle movement authorised by the control authority.
Base turn		A turn executed by the aircraft during the initial approach between the end of the outbound track and the beginning of the intermediate or final approach track. The tracks are not reciprocal.
Conflict (approach)		An aircraft is in conflict with an object (other aircraft, protected airspace or the ground) when it is, or is predicted to be, within pre-defined separation criteria from that object. The separation criteria to not equate to ATC separation standards and may vary depending on the geometry and location of the conflict.
Conflict (aerodrome)	A situation when there is a possibility of a collision between aircraft and/or vehicles.
Conformance monitoring		The process by which the automated ATC system measures and reports on deviations between the actual and expected positions of flights
Constraint point		Any runway, point or fix (expressed in Lat./Long.) that can be defined and described in the system for AMAN metering purposes. For this point rules and requirements could be defined (e.g., interval of flights or holding procedures, etc.).
Control	Application of measures to prevent collisions, runway incursions and to ensure safe, expeditious and efficient movement.
Control area		A controlled airspace extending upwards from a specified limit above the earth.
Control Authority	Air Traffic Control or any other authority providing control services.
Departure slot		A time frame for departing aircraft in which the aircraft has to be airborne.
Dependent parallel approaches		Simultaneous approaches to parallel or near-parallel instrument runways where radar separation minima between aircraft on adjacent extended runway centre lines are prescribed.
Deviation	Situation where there is a difference between planned and real movement.
ECAC area		The European ECAC area is defined by the geographical boundary of that part of the airspace of the ICAO EUR Region, which is under the jurisdiction of the ECAC Member States.
Eligible flight		A flight for which a flight plan is available and becomes relevant to be considered for AMAN processing.
Error handling	Specification of the number of attempts or retries allowed within a given time period to complete an error free function, transaction or process before a failure is declared.
Estimated time of arrival		For IFR flights, the time at which it is estimated that the aircraft will arrive over that designated point, defined by reference to navigation aids, from which it is intended that an instrument approach procedure will be commenced, or if no navigation aid is associated with the aerodrome, the time at which the aircraft will arrive over the aerodrome.
Expected approach time		The time at which ATC expects that an arriving aircraft, following a delay, will leave the holding point to complete its approach for a landing.
Fail-safe	In this context, a system characteristic such that sufficient redundancy is provided to carry data to the display equipment to permit some component of the equipment to fail without any resultant loss of data displayed.
Fail-soft	In this context, a system characteristic such that the system is so designed that, even if the equipment fail to the extent that loss of some data occur, sufficient data remain on the display to enable the controller to continue operation without assistance of the computer.
Final approach		That part of an instrument approach procedure which commences at the specified final approach fix or point or, where such a fix or point is not specified: at the end of the last procedure turn, base turn or inbound turn of a racetrack procedure, if specified; or at the point of interception of the last track specified in the approach procedure; and ends at a point in the vicinity of an aerodrome from which: landing can be made; or a missed approach procedure is initiated.
Flight		An aircraft, or group of aircraft that are to be considered as a single entity, Known to the ATC system.
Flight data		Combination of surveillance data, flight plan data and other data particular to a flight.
Flight information message	Flight information message given by the controller provides the pilot of a given aircraft with : position of the aircraft in the proximity of the concerned aircraft aircraft type vertical evolution
Flight information service		A service provided for the purpose of giving advice and information useful for the safe and efficient conduct of flights.
Flight level		A surface of constant atmospheric pressure which is related to a specific pressure datum, 1013.2 hectopascals (hPa), and is separated from other such surfaces by specific pressure intervals.
Flight path		The set of positions an aircraft has occupied, is occupying, or is expected to occupy.
Glide path		A descent profile determined for vertical guidance during a final approach.
Guidance	Facilities, information and advice necessary to provide continuous, unambiguous and reliable information to pilots of aircraft and drivers of vehicles to keep their aircraft or vehicles on the surfaces and assigned routes intended for their use.
Heading		The direction in which the longitudinal axis of an aircraft is pointed, usually expressed in degrees from North (true, magnetic, compass or grid).
Height		The vertical distance of a level, a point or an object considered as a point, measured from a specified datum.
Holding point		A specified location, identified by visual or other means, in the vicinity of which the position of an aircraft in flight is maintained in accordance with air traffic control clearances.
Holding position	A specified location, identified by visual or other means, in the vicinity of which the position of an aircraft on ground is maintained in accordance with air traffic control clearances.
Holding procedure		A predetermined manoeuvre which keeps an aircraft within a specified airspace while awaiting further clearance.
Horizontal separation	Lateral separation shall be applied so that the distance between those portions of the indented routes for which the aircraft are to be laterally separated is never less than an established distance to account for navigational inaccuracies plus a specified buffer. This buffer shall be determined by the appropriate authority and included in the lateral separation minima as an integral part of thereof. Lateral separation of aircraft is obtained by geographical separation or different route separation Figure 1: Geographical separation Figure 2 : Different routes separation
Identification		The correlation of a known aerodrome movement or vehicle movement callsign with the displayed target of that aircraft or vehicle on the display of the surveillance system.
Incursion	Situation due to the presence of an unauthorised identified aircraft or vehicle in a runway safety area.
Independent parallel approaches		Simultaneous approaches to parallel or near-parallel instrument runways where radar separation minima between aircraft on adjacent extended runway centre lines are not prescribed.
Initial approach segment		That segment of an instrument approach procedure between the initial approach fix and the intermediate approach fix or, where applicable, the final approach fix or point.
Information error	Prevention of the propagation of hazardous or misleading information.
Instrument approach procedure		A series of predetermined manoeuvres by reference to flight instruments with specified protection from obstacles from the initial approach fix or, where applicable, from the beginning of defined arrival route, to a point from which a landing can be completed and thereafter, if a landing is not completed, to a position at which holding or en-route obstacle clearance criteria apply.
Integrity risk	Probability of an undetected failure, event or occurrence within a given time interval.
Intruder	Unidentified target in a runway safety area.
Intrusion	Situation due to the presence of an intruder.
Letter Of Agreement		An agreement between two adjacent ATC Units that specifies how their respective ATC responsibilities are to be co-ordinated.
Level		A generic term relating to the vertical position of an aircraft in flight and meaning variously, height, altitude, or flight level.
Longitudinal separation	Longitudinal separation shall be applied so that the spacing between the estimated positions of the aircraft being separated is never less than a prescribed minimum. Figure 3: Longitudinal separation
Manoeuvring Area		That part of an aerodrome to be used for the take-off, landing and taxiing of aircraft, excluding aprons.
Metering		It is the calculation of target times (amount of time to lose or to gain) in order to meet scheduled arrival times at a defined constraint point, based on a pre-defined sequence and the arrival interval, i.e., the rate at which the corresponding aircraft will pass through that fix.
Minimum safe altitude		The altitude which is considered to be appropriate for MSAW protection for a specific area.
Missed approach procedure		The procedure to be followed if the approach cannot be continued.
Movement Area	That part of an aerodrome to be used for the take-off, landing or taxiing aircraft, consisting of the manoeuvring area and the apron(s).
Obstacle		All fixed (whether temporary or permanent) and mobile objects, or parts thereof, that are located on an area intended for the surface movement of aircraft and vehicles.
Position		Location of a point or an abject considered as a point (e.g.. aircraft) in 3-D space (x,y,z).
Precision approach radar (PAR)		Primary radar equipment used to determine the position of an aircraft during final approach, in terms of lateral and vertical deviations relative to a nominal approach path, and in range relative to touchdown. Note: precision approach radars are designated to enable pilots of aircraft to be given guidance by radio communication during the final stages of the approach to land.
Prediction horizon		The time interval in which conflicts will be detected.
Procedure turn	A Manoeuvre in which a turn is made away from a designated track followed by a turn in the opposite direction to permit the aircraft to intercept and proceed along the reciprocal of the designated track.
Radar approach		An approach, executed by an aircraft, under the direction of a radar controller.
Radar vectoring		Provision of navigational guidance to aircraft in the form of specific headings, based on the use of radar.
Reminder		A message sent to controllers to remind them of previously planned actions.
Runway		A defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft.
Runway incursion	Any occurrence at an airport involving an aircraft, vehicle, person or object on the runway that creates a collision hazard or results in loss of separation with an aircraft taking off, intending to take off, landing or intending to land.
Runway movement	Any movement of an aircraft on an active runway.
Runway visual range	The range over which the pilot of an aircraft on the centre line of a runway can see the runway surface markings or the lights delineating the runway or identifying its centre line.
Route (approach)		An assigned track from a defined start point to a defined end point.
Route(aerodrome)	An assigned track from a defined start point to a defined end point on the movement area.
Routing (approach)		The planning and assignment of a route to individual aircraft to provide safe, expeditious and efficient movement from its current position to its intended position.
Routing (aerodrome)	The planning and assignment of a route to individual aircraft and vehicles to provide safe, expeditious and efficient movement from its current position to its intended position.
Sector suite		The controller or group of controllers that are associated with an ATC sector.
Sequencing		It is the process of establishing the order of arrival at a constraint point (e.g., FIR exit or IAF) or for a specific runway.
Stand		A designated area on an apron intended to be used for the parking of an aircraft.
System trajectory		The trajectory which represents in the system the latest flow, planning and tactical clearances as input to the system via controller input orders and as amended by system monitoring aids.
Surveillance	A function of the system which provides identification and accurate position information on aircraft, vehicles and unauthorised targets within the required area.
Target		The displayed image of an aircraft, vehicle or other object on the surveillance displays.
Target level of safety	Probability of an accident (fatal or hull loss) during aircraft movement on the aerodrome.
Taxiing		Movement of an aircraft on the surface of an aerodrome under its own power, excluding take-off and landing.
Taxiway		A defined path on a land aerodrome established for the taxiing of aircraft and intended to provide a link between one part of the aerodrome and another.
Terminal control area		A control area normally established at the confluence of ATS routes in the vicinity of one or more major aerodromes.
Trajectory		The flight path of an aircraft with time added (x,y,z,t).
Trajectory prediction		The process of calculating a trajectory of an aircraft, based on a current or proposed plan, weather information, aircraft and flight characteristics data, and other variables.
Track	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.
Threshold	The beginning of that portion of the runway available for landing.
Vehicle Movement	The movement of a vehicle on the movement area.
Vertical separation	Vertical separation is obtained by requiring aircraft using prescribed altimeter setting procedures to operate at different levels expressed in terms of flight levels or altitudes. Figure 4: Vertical separation
Visual approach		An approach by an IFR flight when either part or all of an instrument approach procedure is not completed and the approach is executed in visual reference to terrain.
Wake vortex	Wake vortices are formed every time an airfoil is producing lift. The pressure differential triggers the roll up of the airflow aft of the wing resulting in swirling masses trailing downstream of the wing tips. Viewed from behind the generating aircraft, the wake vortex rotates counter-clockwise. The intensity or strength of the vortex is primarily a function of the aircraft weight and configuration (flap setting, etc.). The strongest vortices are produced by heavy aircraft, flying slowly, in a clean configuration.