Article 2 Definitions
For the purpose of this Regulation the following definitions shall apply:
1. ‘accuracy’ means a degree of conformance between the estimated or measured value and the true value;
2. ...
Deleted by Commission Implementing Regulation (EU) 2016/1185 of 20 July 2016 amending Implementing Regulation (EU) No 923/2012 as regards the update and completion of the common rules of the air and operational provisions regarding services and procedures in air navigation (SERA Part C) and repealing Regulation (EC) No 730/2006 (Text with EEA relevance).
3. ‘advisory airspace’ means an airspace of defined dimensions, or designated route, within which air traffic advisory service is available;
4. ‘advisory route’ means a designated route along which air traffic advisory service is available;
5. ‘aerobatic flight’ means manoeuvres intentionally performed by an aircraft involving an abrupt change in its attitude, an abnormal attitude, or an abnormal variation in speed, not necessary for normal flight or for instruction for licenses or ratings other than aerobatic rating;
6. ‘aerodrome’ means a defined area (including any buildings, installations and equipment) on land or water or on a fixed, fixed off-shore or floating structure intended to be used either wholly or in part for the arrival, departure and surface movement of aircraft;
7. ‘aerodrome control service’ means air traffic control service for aerodrome traffic;
8. ‘aerodrome control tower’ means a unit established to provide air traffic control service to aerodrome traffic;
9. ‘aerodrome traffic’ means all traffic on the manoeuvring area of an aerodrome and all aircraft flying in the vicinity of an aerodrome. An aircraft operating in the vicinity of an aerodrome includes but is not limited to aircraft entering or leaving an aerodrome traffic circuit;
10. ‘aerodrome traffic circuit’ means the specified path to be flown by aircraft operating in the vicinity of an aerodrome;
11. ‘aerodrome traffic zone’ means an airspace of defined dimensions established around an aerodrome for the protection of aerodrome traffic;
12. ‘aerial work’ means an aircraft operation in which an aircraft is used for specialised services such as agriculture, construction, photography, surveying, observation and patrol, search and rescue, aerial advertisement, etc.;
13. ‘Aeronautical Information Publication (AIP)’ means a publication issued by or with the authority of a State and containing aeronautical information of a lasting character essential to air navigation;
14. ‘aeronautical mobile service’ means a mobile service between aeronautical stations and aircraft stations, or between aircraft stations, in which survival craft stations may participate; emergency position-indicating radio beacon stations may also participate in this service on designated distress and emergency frequencies;
15. ‘aeronautical station’ means a land station in the aeronautical mobile service. In certain instances, an aeronautical station may be located, for example, on board ship or on a platform at sea;
16. ‘aeroplane’ means a power-driven heavier-than-air aircraft, deriving its lift in flight chiefly from aerodynamic reactions on surfaces which remain fixed under given conditions of flight;
17. ‘airborne collision avoidance system (ACAS)’ means an aircraft system based on secondary surveillance radar (SSR) transponder signals which operates independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft that are equipped with SSR transponders;
18. ‘aircraft’ means any machine that can derive support in the atmosphere from the reactions of the air other than the reactions of the air against the earth’s surface;
19. ‘aircraft address’ means a unique combination of 24 bits available for assignment to an aircraft for the purpose of air-ground communications, navigation and surveillance;
20. ‘aircraft observation’ means the evaluation of one or more meteorological elements made from an aircraft in flight;
21. ‘AIRMET information’ means information issued by a meteorological watch office concerning the occurrence or expected occurrence of specified en-route weather phenomena which may affect the safety of low-level aircraft operations and which was not already included in the forecast issued for low-level flights in the flight information region concerned or sub-area thereof;
22. ‘air-ground communication’ means two-way communication between aircraft and stations or locations on the surface of the earth;
23. ‘air-ground control radio station’ means an aeronautical telecommunication station having primary responsibility for handling communications pertaining to the operation and control of aircraft in a given area;
24. ‘air-report’ means a report from an aircraft in flight prepared in conformity with requirements for position, and operational and/or meteorological reporting;
25. ‘ air-taxiing ’ means movement of a helicopter/vertical take-off and landing (VTOL) above the surface of an aerodrome, normally in ground effect and at a ground speed normally less than 37 km/h (20 kts);
Substituted by Commission Implementing Regulation (EU) 2016/1185 of 20 July 2016 amending Implementing Regulation (EU) No 923/2012 as regards the update and completion of the common rules of the air and operational provisions regarding services and procedures in air navigation (SERA Part C) and repealing Regulation (EC) No 730/2006 (Text with EEA relevance).
26. ‘air traffic’ means all aircraft in flight or operating on the manoeuvring area of an aerodrome;
27. ‘ air traffic advisory service ’ means a service provided within advisory airspace to ensure separation, in so far as practical, between aircraft which are operating on instrument flight rules (IFR) flight plans;
28. ‘ air traffic control (ATC) clearance ’ means authorisation for an aircraft to proceed under conditions specified by an air traffic control unit;
29. ‘air traffic control instruction’ means directives issued by air traffic control for the purpose of requiring a pilot to take a specific action;
30. ‘air traffic control service’ means a service provided for the purpose of:
(a) preventing collisions:
(1) between aircraft; and
(2) on the manoeuvring area between aircraft and obstructions; and
(b) expediting and maintaining an orderly flow of air traffic;
31. ‘air traffic control unit’ means a generic term meaning variously, area control centre, approach control unit or aerodrome control tower;
32. ‘air traffic service (ATS)’ means 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);
33. ‘ air traffic services (ATS) airspaces ’ mean airspaces of defined dimensions, alphabetically designated, within which specific types of flights may operate and for which air traffic services and rules of operation are specified;
34. ‘ air traffic services (ATS) reporting office (ARO) ’ means a unit established for the purpose of receiving reports concerning air traffic services and flight plans submitted before departure;
34a. ‘ air traffic services (ATS) surveillance service ’ means a service provided directly by means of an ATS surveillance system;
Inserted by Commission Implementing Regulation (EU) 2016/1185 of 20 July 2016 amending Implementing Regulation (EU) No 923/2012 as regards the update and completion of the common rules of the air and operational provisions regarding services and procedures in air navigation (SERA Part C) and repealing Regulation (EC) No 730/2006 (Text with EEA relevance).
35. ‘ air traffic services (ATS) unit ’ means a generic term meaning, variously, air traffic control unit, flight information centre, aerodrome flight information service unit or air traffic services reporting office;
36. ‘airway’ means a control area or portion thereof established in the form of a corridor;
37. ‘alerting service’ means a service provided to notify appropriate organisations regarding aircraft in need of search and rescue aid, and assist such organisations as required;
38. ‘ alternate aerodrome ’ means an aerodrome to which an aircraft may proceed when it becomes either impossible or inadvisable to proceed to or to land at the aerodrome of intended landing, where the necessary services and facilities are available, where aircraft performance requirements can be met and which is operational at the expected time of use. Alternate aerodromes include the following:

(a) take-off alternate
an alternate aerodrome at which an aircraft would be able to land should this become necessary shortly after take-off and it is not possible to use the aerodrome of departure;

(b) en-route alternate
an alternate aerodrome at which an aircraft would be able to land in the event that a diversion becomes necessary while en route;

(c) destination alternate
an alternate aerodrome at which an aircraft would be able to land should it become either impossible or inadvisable to land at the aerodrome of intended landing;
39. ‘altitude’ means the vertical distance of a level, a point or an object considered as a point, measured from mean sea level (MSL);
40. ‘approach control service’ means air traffic control service for arriving or departing controlled flights;
41. ‘approach control unit’ means a unit established to provide air traffic control service to controlled flights arriving at, or departing from, one or more aerodromes;
42. ‘apron’ means a defined area, intended to accommodate aircraft for purposes of loading or unloading passengers, mail or cargo, fuelling, parking or maintenance;
43. ‘area control centre (ACC)’ means a unit established to provide air traffic control service to controlled flights in control areas under its jurisdiction;
44. ‘area control service’ means air traffic control service for controlled flights in control areas;
45. ‘area navigation (RNAV)’ means a method of navigation which permits aircraft operation on any desired flight path within the coverage of ground- or space-based navigation aids or within the limits of the capability of self-contained aids, or a combination of these;
46. ‘ATS route’ means a specified route designed for channelling the flow of traffic as necessary for the provision of air traffic services;
47. ‘automatic dependent surveillance — broadcast (ADS-B)’ means a means by which aircraft, aerodrome vehicles and other objects can automatically transmit and/or receive data such as identification, position and additional data, as appropriate, in a broadcast mode via a data link;
48. ‘automatic dependent surveillance — contract (ADS-C)’ means a means by which the terms of an ADS-C agreement will be exchanged between the ground system and the aircraft, via a data link, specifying under what conditions ADS-C reports would be initiated, and what data would be contained in the reports;
48a. ‘ automatic dependent surveillance — contract (ADS-C) agreement ’ means a reporting plan which establishes the conditions of ADS-C data reporting (i.e. data required by the air traffic services unit and frequency of ADS-C reports which have to be agreed to, prior to using ADS-C in the provision of air traffic services);
49. ‘automatic terminal information service (ATIS)’ means the automatic provision of current, routine information to arriving and departing aircraft throughout 24 hours or a specified portion thereof:
(a) ‘Data link-automatic terminal information service (D-ATIS)’ means the provision of ATIS via data link;
(b) ‘Voice-automatic terminal information service (Voice-ATIS)’ means the provision of ATIS by means of continuous and repetitive voice broadcasts;
50. ‘ceiling’ means the height above the ground or water of the base of the lowest layer of cloud below 6 000 m (20 000 ft) covering more than half the sky;
51. ‘change-over point’ means the point at which an aircraft navigating on an ATS route segment defined by reference to very high frequency omnidirectional radio ranges is expected to transfer its primary navigational reference from the facility behind the aircraft to the next facility ahead of the aircraft;
52. ‘clearance limit’ means the point to which an aircraft is granted an air traffic control clearance;
53. ‘cloud of operational significance’ means a cloud with the height of cloud base below 1 500 m (5 000 ft) or below the highest minimum sector altitude, whichever is greater, or a cumulonimbus cloud or a towering cumulus cloud at any height;
54. ‘code (SSR)’ means the number assigned to a particular multiple pulse reply signal transmitted by a transponder in Mode A or Mode C;
55. ‘competent authority’ means the Civil Aviation Authority;
Art. 2(55) substituted (31.12.2020) by The Air Traffic Management (Amendment etc.) (EU Exit) Regulations 2019 (S.I. 2019/459), regs. 1(2), 296; 2020 c. 1, Sch. 5 para. 1(1)
56. ‘control area’ means a controlled airspace extending upwards from a specified limit above the earth;
57. ‘controlled aerodrome’ means an aerodrome at which air traffic control service is provided to aerodrome traffic regardless whether or not a control zone exists;
58. ‘controlled airspace’ means an airspace of defined dimensions within which air traffic control service is provided in accordance with the airspace classification;
59. ‘controlled flight’ means any flight which is subject to an air traffic control clearance;
60. ‘controller-pilot data link communications (CPDLC)’ mean a means of communication between controller and pilot, using data link for ATC communications;
61. ‘control zone’ means a controlled airspace extending upwards from the surface of the earth to a specified upper limit;
61A. ‘critical area’ means an area of defined dimensions extending around the ground equipment of a precision instrument approach within which the presence of vehicles or aircraft will cause unacceptable disturbance of the guidance signals;
Art. 2(61A) inserted (23.3.2023) by The Aviation Safety and Air Traffic Management (Amendment) Regulations 2022 (S.I. 2022/1235), regs. 1(3), 4(2)
62. ‘cruise climb’ means an aeroplane cruising technique resulting in a net increase in altitude as the aeroplane mass decreases;
63. ‘cruising level’ means a level maintained during a significant portion of a flight;
64. ‘current flight plan (CPL)’ means the flight plan, including changes, if any, brought about by subsequent clearances;
65. ‘danger area’ means an airspace of defined dimensions within which activities dangerous to the flight of aircraft may exist at specified times;
66. ‘data link communications’ mean a form of communication intended for the exchange of messages via a data link;
67. ‘datum’ means any quantity or set of quantities that may serve as a reference or basis for the calculation of other quantities;
68. ‘downstream clearance’ means a clearance issued to an aircraft by an air traffic control unit that is not the current controlling authority of that aircraft;
69. ‘estimated elapsed time’ means the estimated time required to proceed from one significant point to another;
70. ‘estimated off-block time’ means the estimated time at which the aircraft will commence movement associated with departure;
71. ‘ estimated time of arrival (ETA) ’ means 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. For visual flight rules (VFR) flights, the time at which it is estimated that the aircraft will arrive over the aerodrome;
72. ‘expected approach time’ means the time at which ATC expects that an arriving aircraft, following a delay, will leave the holding fix to complete its approach for a landing. The actual time of leaving the holding fix will depend upon the approach clearance;
73. ‘filed flight plan (FPL)’ means the flight plan as filed with an ATS unit by the pilot or a designated representative, without any subsequent changes;
74. ‘flight crew member’ means a licensed crew member charged with duties essential to the operation of an aircraft during a flight duty period;
75. ‘flight information centre’ means a unit established to provide flight information service and alerting service;
76. ‘flight information region’ means an airspace of defined dimensions within which flight information service and alerting service are provided;
77. ‘flight information service’ means a service provided for the purpose of giving advice and information useful for the safe and efficient conduct of flights;
78. ‘flight level (FL)’ means a surface of constant atmospheric pressure which is related to a specific pressure datum, 1 013,2 hectopascals (hPa), and is separated from other such surfaces by specific pressure intervals;
79. ‘flight plan’ means specified information provided to air traffic services units, relative to an intended flight or portion of a flight of an aircraft;
80. ‘flight visibility’ means the visibility forward from the cockpit of an aircraft in flight;
81. ‘forecast’ means a statement of expected meteorological conditions for a specified time or period, and for a specified area or portion of airspace;
82. ‘ground visibility’ means the visibility at an aerodrome, as reported by an accredited observer or by automatic systems;
83. ‘heading’ means the direction in which the longitudinal axis of an aircraft is pointed, usually expressed in degrees from North (true, magnetic, compass or grid);
84. ‘height’ means the vertical distance of a level, a point or an object considered as a point, measured from a specified datum;
85. ‘helicopter’ means a heavier-than-air aircraft supported in flight chiefly by the reactions of the air on one or more powerdriven rotors on substantially vertical axes;
86. ‘high seas airspace’ means airspace beyond land territory and territorial seas, as specified in the United Nations Convention on the Law of the Sea (Montego Bay, 1982);
87. ‘IFR’ means the symbol used to designate the instrument flight rules;
88. ‘IFR flight’ means a flight conducted in accordance with the instrument flight rules;
89. ‘IMC’ means the symbol used to designate instrument meteorological conditions;
89a. ‘ instrument approach operation ’ means an approach and landing using instruments for navigation guidance based on an instrument approach procedure. There are two methods for executing instrument approach operations:
(a) a two-dimensional (2D) instrument approach operation, using lateral navigation guidance only; and
(b) a three-dimensional (3D) instrument approach operation, using both lateral and vertical navigation guidance;
90. ‘instrument approach procedure (IAP)’ means 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 a 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. Instrument approach procedures are classified as follows:
(a) non-precision approach (NPA) procedure. An instrument approach procedure designed for 2D instrument approach operations Type A;
(b) approach procedure with vertical guidance (APV). A performance-based navigation (PBN) instrument approach procedure designed for 3D instrument approach operations Type A;
(c) precision approach (PA) procedure. An instrument approach procedure based on navigation systems (ILS, MLS, GLS and SBAS Cat I) designed for 3D instrument approach operations Type A or B;
91. ‘instrument meteorological conditions (IMC)’ mean meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling, less than the minima specified for visual meteorological conditions;
92. ‘landing area’ means that part of a movement area intended for the landing or take-off of aircraft;
93. ‘level’ means a generic term relating to the vertical position of an aircraft in flight and meaning variously, height, altitude or flight level;
94. ‘manoeuvring area’ means that part of an aerodrome to be used for the take-off, landing and taxiing of aircraft, excluding aprons;
94a. ‘ minimum fuel ’ means a term used to describe a situation in which an aircraft's fuel supply has reached a state where the flight is committed to land at a specific aerodrome and no additional delay can be accepted;
95. ‘mode (SSR)’ means the conventional identifier related to specific functions of the interrogation signals transmitted by an SSR interrogator. There are four modes specified in ICAO Annex 10: A, C, S and intermode;
95a. ‘ model aircraft ’ means an unmanned aircraft, other than toy aircraft, having an operating mass not exceeding limits prescribed by the competent authority, that is capable of sustained flight in the atmosphere and that is used exclusively for display or recreational activities;
95b. ‘ mountainous area ’ means an area of changing terrain profile where the changes of terrain elevation exceed 900 m ( 3 000 ft) within a distance of 18,5 km (10,0 NM);
96. ‘movement area’ means that part of an aerodrome to be used for the take-off, landing and taxiing of aircraft, consisting of the manoeuvring area and the apron(s);
97. ‘night’ means the hours between the end of evening civil twilight and the beginning of morning civil twilight. Civil twilight ends in the evening when the centre of the sun’s disc is 6 degrees below the horizon and begins in the morning when the centre of the sun’s disc is 6 degrees below the horizon;
98. ‘obstacle’ means all fixed (whether temporary or permanent) and mobile objects, or parts thereof, that:
(a) are located on an area intended for the surface movement of aircraft; or
(b) extend above a defined surface intended to protect aircraft in flight; or
(c) stand outside those defined surfaces and that have been assessed as being a hazard to air navigation;
99. ‘operating site’ means a site selected by the operator or pilot-in-command for landing, take-off and/or hoist operations;
100. ‘pilot-in-command’ means the pilot designated by the operator, or in the case of general aviation, the owner, as being in command and charged with the safe conduct of a flight;
101. ‘pressure-altitude’ means an atmospheric pressure expressed in terms of altitude which corresponds to that pressure in the Standard Atmosphere, as defined in Annex 8, Part 1 to the Chicago Convention;
102. ‘problematic use of substances’ means the use of one or more psychoactive substances by aviation personnel in a way that:
(a) constitutes a direct hazard to the user or endangers the lives, health or welfare of others; and/or
(b) causes or worsens an occupational, social, mental or physical problem or disorder;
103. ‘prohibited area’ means an airspace of defined dimensions, above the land areas or territorial waters of a State, within which the flight of aircraft is prohibited;
104. ‘ psychoactive substance ’ means alcohol, opioids, cannabinoids, sedatives and hypnotics, cocaine, other psychostimulants, hallucinogens, and volatile solvents, whereas caffeine and tobacco are excluded;
Substituted by Commission Regulation (EU) 2015/340 of 20 February 2015 laying down technical requirements and administrative procedures relating to air traffic controllers' licences and certificates pursuant to Regulation (EC) No 216/2008 of the European Parliament and of the Council, amending Commission Implementing Regulation (EU) No 923/2012 and repealing Commission Regulation (EU) No 805/2011 (Text with EEA relevance).
105. ‘radar’ means a radio detection device which provides information on range, azimuth and/or elevation of objects;
106. ‘radio mandatory zone (RMZ)’ means an airspace of defined dimensions wherein the carriage and operation of radio equipment is mandatory;
107. ‘radio navigation service’ means a service providing guidance information or position data for the efficient and safe operation of aircraft supported by one or more radio navigation aids;
108. ‘radiotelephony’ means a form of radiocommunication primarily intended for the exchange of information in the form of speech;
109. ‘repetitive flight plan’ means a flight plan related to a series of frequently recurring, regularly operated individual flights with identical basic features, submitted by an operator for retention and repetitive use by ATS units;
110. ‘reporting point’ means a specified geographical location in relation to which the position of an aircraft can be reported;
111. ‘restricted area’ means an airspace of defined dimensions, above the land areas or territorial waters of a State, within which the flight of aircraft is restricted in accordance with certain specified conditions;
112. ‘route segment’ means a route or portion of route usually flown without an intermediate stop;
113. ‘runway’ means a defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft;
114. ‘ runway-holding position ’ means a designated position intended to protect a runway, an obstacle limitation surface, or an instrument landing system (ILS)/microwave landing system (MLS) critical/sensitive area at which taxiing aircraft and vehicles are to stop and hold, unless otherwise authorised by the aerodrome control tower;
115. ‘runway visual range (RVR)’ means 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;
116. ‘ safety-sensitive personnel ’ means persons who might endanger aviation safety if they perform their duties and functions improperly, including crew members, aircraft maintenance personnel, aerodrome operations personnel, rescue, fire-fighting and maintenance personnel, personnel allowed unescorted access to the movement area and air traffic controllers;
117. ‘sailplane’ means a heavier-than-air aircraft which is supported in flight by the dynamic reaction of the air against its fixed lifting surfaces, the free flight of which does not depend on an engine, including also hang gliders, paragliders and other comparable craft;
118. ‘secondary surveillance radar (SSR)’ means a surveillance radar system which uses transmitters/receivers (interrogators) and transponders;
118A. ‘sensitive area’ means an area extending beyond the critical area within which the parking or movement, or both parking and movement, of aircraft or vehicles will affect the guidance signal to the extent that it may be rendered as an unacceptable disturbance to aircraft using the signal;
Art. 2(118A) inserted (23.3.2023) by The Aviation Safety and Air Traffic Management (Amendment) Regulations 2022 (S.I. 2022/1235), regs. 1(3), 4(3)
119. ‘SIGMET information’ means information issued by a meteorological watch office concerning the occurrence or expected occurrence of specified en-route weather phenomena which may affect the safety of aircraft operations;
120. ‘signal area’ means an area on an aerodrome used for the display of ground signals;
121. ‘significant point’ means a specified geographical location used in defining an ATS route or the flight path of an aircraft and for other navigation and ATS purposes;
122. ‘special VFR flight’ means a VFR flight cleared by air traffic control to operate within a control zone in meteorological conditions below VMC;
123. ‘strayed aircraft’ means an aircraft which has deviated significantly from its intended track or which reports that it is lost;
124. ‘surveillance radar’ means radar equipment used to determine the position of an aircraft in range and azimuth;
125. ‘taxiing’ means movement of an aircraft on the surface of an aerodrome or an operating site under its own power, excluding take-off and landing;
126. ‘taxiway’ means 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, including:
(a) Aircraft stand taxilane means a portion of an apron designated as a taxiway and intended to provide access to aircraft stands only.
(b) Apron taxiway means a portion of a taxiway system located on an apron and intended to provide a through taxi route across the apron.
(c) Rapid exit taxiway means a taxiway connected to a runway at an acute angle and designed to allow landing aeroplanes to turn off at higher speeds than are achieved on other exit taxiways thereby minimising runway occupancy times;
127. ‘territory’ means the land areas and territorial waters adjacent thereto under the sovereignty, suzerainty, protection or mandate of a State;
128. ‘threshold’ means the beginning of that portion of the runway usable for landing;
129. ‘total estimated elapsed time’ means:
(a) for IFR flights, the estimated time required from take-off to 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 destination aerodrome, to arrive over the destination aerodrome;
(b) for VFR flights, the estimated time required from take-off to arrive over the destination aerodrome;
129a. ‘ toy aircraft ’ means an unmanned aircraft designed or intended for use, whether or not exclusively, in play by children under 14 years of age;
130. ‘track’ means 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);
131. ‘traffic avoidance advice’ means an advice provided by an air traffic services unit specifying manoeuvres to assist a pilot to avoid a collision;
132. ‘traffic information’ means information issued by an air traffic services unit to alert a pilot to other known or observed air traffic which may be in proximity to the position or intended route of flight and to help the pilot avoid a collision;
133. ‘transfer of control point’ means a defined point located along the flight path of an aircraft, at which the responsibility for providing air traffic control service to the aircraft is transferred from one control unit or control position to the next;
134. ‘transition altitude’ means the altitude at or below which the vertical position of an aircraft is controlled by reference to altitudes;
135. ‘transition level’ means the lowest flight level available for use above the transition altitude;
136. ‘transponder mandatory zone (TMZ)’ means an airspace of defined dimensions wherein the carriage and operation of pressure-altitude reporting transponders is mandatory;
137. ‘unidentified aircraft’ means an aircraft which has been observed or reported to be operating in a given area but whose identity has not been established;
138. ‘unmanned free balloon’ means a non-power-driven, unmanned, lighter-than-air aircraft in free flight;
139. ‘VFR’ means the symbol used to designate the visual flight rules;
140. ‘VFR flight’ means a flight conducted in accordance with the visual flight rules;
141. ‘visibility’ means visibility for aeronautical purposes which is the greater of:
(a) the greatest distance at which a black object of suitable dimensions, situated near the ground, can be seen and recognised when observed against a bright background;
(b) the greatest distance at which lights in the vicinity of 1 000 candelas can be seen and identified against an unlit background;
142. ‘visual meteorological conditions’ mean meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling, equal to or better than specified minima;
143. ‘VMC’ means the symbol used to designate visual meteorological conditions.
144. ‘with the surface in sight’ means with the flight crew being able to see sufficient surface features or surface illumination to enable the flight crew to maintain the aircraft in a desired attitude without reference to any flight instrument.
Art. 2(144) inserted (20.5.2021) by The Aviation Safety (Amendment) Regulations 2021 (S.I. 2021/10), regs. 1(3), 2(2)