Terms and Definitions For RTR/ FRTOL
- Advisory Area. It is a designated area within a flight information region where air traffic advisory service is available.
- Advisory Route. It is a route within a flight information region along which a traffic advisory service is available.
Note. Air traffic control service provides a much more complete service than air traffic advisory service. Advisory areas and routes are therefore not established within controlled airspace, but air traffic advisory service may be provided below and above control areas.
- Aerodrome A defined area on land or water including any buildings, installations and equipment intended to be used either wholly or in part for the arrival, departure and movement of ac.
- Aerodrome Reference Point (ARP). It is a designated geographical location of an aerodrome, normally taken as the geometrical centre of the runways or runway in the case of a single runway aerodrome. The ARP is defined in degrees, minutes and seconds of latitude and longitude.
- Aerodrome Traffic Zone. The airspace extending from an aerodrome to a height of 2000 ft above the level of the aerodrome and within a distance of 1 ½ nm of its boundaries; except any part of that airspace which is within the aerodrome traffic zone of another aerodrome which is notified as being the controlling aerodrome is called the Aerodrome Traffic Zone.
- Aircraft Approach Limitation. The AAL is the lowest height above touchdown point to which a particular type (or mark) of ac may descend on instruments using a specified runway approach aid. From which height a pilot, after transferring from instrument to visual reference, can be expected to recover the ac to the runway centre-line and make a safe landing on the runway, or execute a safe missed approach procedure. The AAL does not take into account local terrain or obstructions.
- Aircraft Classification Number (ACN). The ACN is a number expressing the relative effect of an ac load on a pavement for specified sub-grade strength.
8. Air Defence Identification Zone. Airspace of defined dimensions within which the ready identification, location and control of ac is required.
- Air Report. It is a report passed during the course of a flight in conformity with requirements for position, operational, or meteorological reporting in the AIREP or POMAR forms.
- Air Route. The navigable airspace between two points, identified to the extent necessary for the application of flight rules.
- Air Route Surveillance Radar. It is a long range radar which increases the capability of ATC for handling heavy en-route traffic.
- Air Surveillance Radar. Radar providing position of ac by azimuth and range data without elevation data.
- Air Traffic Advisory Service. Service provided to ensure separation in-so-far as possible between ac which are operating on an IFR flight plan, outside control areas but within advisory routes or advisory areas.
- Air Traffic Control Centre. An organisation established to provide:
- Air traffic control within a control area (where established).
- Flight information service within a flight information region.
- Alerting service for search and rescue within its flight information region.
- Air Traffic Control Clearance. Authorisation for an aircraft to proceed under conditions specified by an air traffic control unit.
- Air Traffic Control Services. A service provided for the purpose of:
- Preventing collisions between ac in the air, and on the manoeuvring area between a/c and obstructions.
- Expediting and maintaining an orderly flow of traffic. Air Traffic Control Services are provided by licensed Air Traffic Controllers. The call sign suffixes, TOWER, APPROACH, GROUND, DIRECTOR, ZONE, and RADAR are used as appropriate.
- Air Traffic Service (ATS). 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.
- Airway. A control area or portion thereof established in the form of a corridor equipped with radio navigational aids.
- Alerting Service. A service provided to notify appropriate organizations regarding ac in need of search and rescue aid, and assist such organizations as required.
- Alternate Aerodrome. An aerodrome specified in the flight plan to which a flight may proceed when it becomes inadvisable to land at the aerodrome of intended landing.
Note. An alternate aerodrome may be the aerodrome of departure.
- The vertical distance of a level, a point or object considered as a point measured from mean sea level (MSL).
- Approach Control. A term used to indicate an air traffic control unit providing approach control service.
- Area Control Centre. A unit established to provide air traffic control service to controlled flights in control area under its jurisdiction.
- ATS Route. A specified route designated for channelling the flow of traffic necessary for the provision of air traffic services.
Note. The term ATS route is used to mean variously, airway, advisory route, controlled or uncontrolled route, arrival or departure route, etc.
- Automatic Terminal Information Service (ATIS). The provision of current, routine information to arriving and departing aircraft by means of continuous and repetitive broadcast throughout the day or specified portion of the day. The transmissions contain weather, QNH, runway is use and any other relevant information.
- The height above ground or water of the base of the lowest layer of cloud below 6,000 meters (20,000’) covering more than half the sky.
- Circling Approach. An approach during which an ac manoeuvres, outside of the 30° arc of the centreline of the active runway, in order to achieve a suitable position from which it can continue with a visual approach.
- Circling Approach Minimum. The circling approach MDH is the lowest authorised height at which a circle-to-land manoeuvre may be carried out following an instrument approach.
- Clearance Limit. The point to which an ac is granted an air traffic control.
- Clearway A defined rectangular area on the ground or water under the control of the Appropriate Authority selected or prepared as a suitable area over which an ac may make a portion of its initial climb to a specified height. A clearway should extend laterally to a distance of at least 250 ft on each side of the extended centreline of the runway.
- Control Area. A controlled airspace of defined horizontal dimensions extending upwards from a specified height above the surface of the earth to unlimited unless otherwise indicated.
- Controlled Airspace. A defined airspace in which air traffic control service is provided to aerodrome traffic.
- Controlled Aerodrome. An aerodrome at which air traffic control service is provided to aerodrome traffic.
Note. The term controlled aerodrome indicates that air traffic control service is provided to aerodrome traffic but does not necessarily imply that a control zone exists, since a control zone is required at aerodromes where air traffic control service will be provided to IFR flights, but not at aerodromes where it will be provided only to VFR flights.
- Control Zone. A controlled airspace extending upwards from the surface of the earth.
- Co-ordinate Universal Time (UTC). A combination of International Atomic and Universal Time, which is replacing GMT as the accepted international standard. It is always within 0.5 seconds of Universal Time.
- Current Flight Plan. The flight plan, including changes, if any brought about by subsequent
- Danger Area. An airspace of defined dimensions within which activities dangerous to the flight on ground manoeuvring of ac may exist at specified times.
- Decision Altitude/Height (DA/H). The altitude or height at which a missed approach must be initiated unless the required visual references have been established and the ac is in a suitable position to continue with a visual approach. The DA/DH is applicable while executing an instrument approach with runway approach aids.
Note. Decision Altitude (DA) is referenced to mean sea level (MSL) and Decision Height (DH) is referenced to threshold elevation.
- Distress Message. Emergency message to be used when an ac is threatened by serious or imminent danger and the crew is in need of immediate assistance.
- The vertical position of a point or a level, above, on or affixed to the surface of the earth, measured from mean sea level.
- Engine out Allowance (EOA). EOA is the factor to be added to DH to allow for additional height lost while overshooting with engine(s) out.
- Estimated Time of Arrival (ETA). For IFR flights, the time at which it is estimated that the ac will arrive over a designed point, defined by reference to navigation aids, from which it is intended that an instrument approach procedure will be commenced, or, if no navigational aid is associated with the aerodrome, the time at which the ac will arrive over head. For VFR flights, it is the time at which it is estimated that the ac will arrive over the aerodrome.
- Expected Approach Time. The time at which it is expected that an arriving ac will be cleared to commence an approach for a landing
Note. The actual time of leaving the holding point will depend upon the approach clearance.
- Final Approach. That part of an instrument approach procedure in which alignment and descent for landing are accomplished. It begins at the final approach fix or point and ends at the missed approach point or fix. In a precision approach the final approach is deemed to commence at the glide path intercept point and this has been called the final approach fix or point.
- Flight Information Centre (FIC). A unit established to provide flight information service and alerting service.
- Flight information Region (FIR). Airspace of defined dimensions within which flight information service and alerting services are provided.
- 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 mb (1013.2 hectopascals (hPa) 29.92 inches of mercury), and is separated from other such surfaces by specific pressure intervals.
Notes. A pressure type altimeter calibrated in accordance with the Standard Atmosphere.
- When set to a QNH, altimeter setting will indicate altitude.
- When set to a QFE, altimeter setting will indicate height above the QFE reference datum.
- When set to a pressure of 1013.2 mb (1013.2 hPa, 29.92 ins Hg) the altimeter may be used to indicate flight levels.
- The terms ‘height’ and ‘altitude’ used in Note 1 above indicate altimetric rather than geometric heights and altitudes.
- No altimeter correction is to be applied when setting altimeter to 1013.2 hPa (QNE) to fly the flight levels.
- Flight Plan. Specified information provided to Air Traffic Service Units, relative to the intended flight or portion of a flight of an ac.
- Ground Controlled Approach (GCA). The technique or procedure for talking down an ac during its approach so as to place it in a position for landing during conditions of poor visibility and low cloud ceiling through the use of radar.
- Handover Procedure. The handing over of the control of an ac from one Radar Service Area to another.
- Heading The direction in which the longitudinal axis of an ac is pointed usually expressed in degrees from North (magnetic).
- Height The vertical distance of a level, a point or an object considered as a point, measured from a specified datum.
- Holding Point. A point specifically located, identified by visual or other means in the vicinity of which the position of an ac in flight is maintained in accordance with air traffic control instructions.
- ILS Categories (ICAO)
- (a) ILS Category I. An ILS approach procedure which provides for an approach to a decision height not lower than 200 feet (60m) and a visibility not less than 2400 feet (800m) or a runway visual range not less than 1800 feet (550m).
- ILS Category II (Special authorization required). An ILS approach procedure which provides for an approach to a decision height lower than 200 feet (60m) but not lower than 100 feet (30m) and a runway visual range not less than 1200 feet (350m).
- ILS Category III (Special authorization required).
- IIIA An ILS approach procedure which provides for approach with either a decision height lower than 100 feet (30m) or with no decision height and with a runway visual range of not less than 700 feet (200m).
- IIIB An ILS approach procedure which provides for approach with either a decision height lower than 50 feet (15m) or with no decision height and with a runway visual range of less than 700 feet (200m) but not less than 150 feet (50m).
- IIIC An ILS approach procedure which provides for approach with no decision height and no runway visual range limitations.
- Initial Approach. That part of an instrument approach procedure in which the ac has departed an initial approach fix or point and is manoeuvring to enter the intermediate or final approach. It ends at the intermediate fix or, where no intermediate segment is established, at the final approach fix or point.
- Instrument Approach Procedure (IAP). A series of predetermined manoeuvres by reference to flight instrument with specified protection from obstacles from the initial approach fix, or where applicable, from the beginning of a defined arrival 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 (ICAO).
- Intermediate Approach. That part of an instrument approach procedure in which ac configuration, speed and positioning adjustments are made. It blends the initials approach segment into the final approach segment. It begins at the intermediate fix or point and ends at the final fix or point.
- Landing Distance Available (LDA). The length of runway which is declared available and suitable for the ground runs of a landing aircraft. The landing distance available commences at the threshold and in most cases corresponds to the physical length of the runway pavement.
- Load Classification Group (LCG). The bearing strength of a pavement is calculated from the total thickness of the pavement construction and the bearing capacity of the sub grade and is allocated a Load Classification Group Number (LCG) which embraces a range of LCN values. The bands selected are those which group together ac which impose similar levels of stress on the payment.
- Load Classification Number (LCN). The bearing strength of a pavement or runway is defined by a number. This is associated with an indication of the characteristics and type of construction of the pavement; the Indication is given by an ‘I’ value (the radius of relative stiffness) for a rigid pavement, or by an ‘h’ (the thickness for flexible pavements). For those aerodromes for which information is available, and appropriate ‘I’ or ‘h’ values (in cm or inches) for each runway are published in the aerodrome directory of the En Route Supplement. The LCN has been reclassified as the PCN.
- Master Diversion Aerodrome. An Aerodrome with continuous provision of diversion and emergency facilities.
- Minimum Descent height (MDH). The lowest height to which an ac may descend while using an airfield approach aid (as different from a runway approach aid) until the required visual references have been established and the ac is in a suitable position to continue with a visual approach.
- Minimum Flight Level. In order to ensure safe vertical separation between ac flying at the transition altitude and those flying above, the minimum flight level is to be 500 ft above the transition level.
- Minimum Sector Altitude. The lowest altitude which may be used under emergency conditions which will provide a minimum clearance of 300 metres (1000 ft) above all obstacles located in an area contained within a sector of a circle of 25 nautical miles radius centred on a radio aid to navigation.
- Missed Approach Point (MAP). That point in an instrument approach at or before which the prescribed missed approach procedure must be initiated in order to ensure that safe obstacle clearance is accomplished.
- Non-precision Approach. An instrument approach using a procedure which does not employ electronic glide-slope information.
68. Notices to Airmen (NOTAM). A notice containing information concerning the establishment, condition or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel concerned with flight operations
- Obstacle ‘Clearance Altitude / Height’ (OCA/H). The lowest altitude (OCA), or alternatively the lowest height above the elevation of the relevant runway threshold or above the aerodrome elevation as applicable, used in establishing compliance with appropriate obstacle clearance criteria.
- Obstacle Clearance Limit. The height above aerodrome elevation below which the minimum prescribed vertical clearance cannot be maintained either on approach or in the event of a missed approach.
- Operational Air Traffic (OAT). Flights conducted under the control or authority of the military ATS authority.
- Overrun A cleared area beyond the end of the runway to the barrier.
- Pavement Classification Number (PCN). A number expressing the bearing strength of a pavement for unrestricted operations.
- Plan Position Indicator (PPI) Approach. A special type of surveillance radar approach given by the radar controller using the PPI only to assist an ac to the runway.
- Precision Approach. An instrument approach using a facility which provides both azimuth and electronic glide-slope information.
- Precision Approach Radar (PAR). Primary radar equipment used to determine accurately the position in range, azimuth and level of an ac during its approach relative to the selected approach path.
- Prohibited Area. Airspace of defined dimensions, above the land areas of territorial waters of a State, within which the flight of ac is prohibited.
- Protected Range. Limit of reliability of TACAN, DME and VOR given in nautical miles and thousands of feet. (For example, 200/30000 denotes a protected range of 200 nm upto a height of 30,000 ft).
Note. Civil Authorities use the term Designated Operators Coverage (DOC)
- QFE. Aerodrome pressure corrected for temperature. When set on the altimeter on the ground, the Altimeter should read zero.
- QNH Aerodrome pressure corrected for temperature and adjusted to Mean Sea Level, using the ICAO formula. When set on the altimeter on the ground, the altimeter should read aerodrome elevation.
- Reporting Point. A specified geographical location in relation to which the position of an ac can be reported.
- Rescue Co-ordination Centre. A centre established within an assigned search and rescue area to promote efficient organisation of search and rescue.
- Restricted Area. An airspace of defined dimensions, above the land areas or territorial waters of a State, within which the flight of ac is restricted in accordance with specified conditions.
- Runway Visual Range (RVR). The maximum distance in the direction of take-off or landing at which the runway or the specified lights delineating the runway can be seen from a position on the centre-line at a height corresponding to the average eye-level of the pilot at touchdown.
- Screen Height. The height of an imaginary screen which the ac would just clear when taking-off or landing in an unbaked attitude with the landing gear extended.
- Secondary Surveillance Radar (SSR). Radar used by Air traffic Control Services, Civil and Military, to establish and maintain the identity of ac.
- Shuttle A combination of the holding pattern or procedure coupled with a letdown, that is, maintaining the holding procedure while changing to lower altitude as is common in stacking, or because of hazardous terrain outside the immediate area of the holding facility.
- Sigmet Information. Information prepared by a meteorological watch office regarding the occurrence or expected occurrence of one of the following phenomena:
- Active thunderstorm area.
- Tropical revolving storm.
- Severe line squall.
- Heavy hail.
- Severe turbulence.
- Severe icing.
- Marked mountain waves.
- Widespread sandstorm/dust storm.
- Slope Slope is the tangent of the angle of rise or fall of an aerodrome surface or obstacle profile expressed as a percentage.
- Special VFR Flight. A controlled VFR flight authorized by air traffic control to operate within a control zone under meteorological conditions below the visual meteorological conditions.
- Stop Way A defined rectangular area on the ground at the end of the take-off run available prepared as a suitable area in which an ac can be stopped in the case of an abandoned take-off. A stop way should have the same width as the runway to which it is associated (ICAO).
- Surveillance Radar. Primary radar equipment used to establish the distance and azimuth of all ac within its range.
- Take-off Distance Available (TODA). The length of the take-off run available plus the length of clearway available (if clearway is provided). TODA is not to exceed 1.5 X TORA (ICAO).
- Take-off Flight Path Area. The take-off flight path area commences at the end of TODA, its width at the point of origin is 600 ft and this width increases at the rate of 0.25D to a maximum of 6,000 ft, where D is the distance from the point of origin. It extends to the point beyond which no significant obstructions exist or to a distance of 5.4nm (10km) whichever is the lesser (ICAO).
- Take-off Run Available (TORA). The length of runway declared available and suitable for the ground run of an ac taking-off. This, in most cases, corresponds to the physical length of the runway pavement, (ICAO).
- Terminal Control Area. A control area normally situated at the confluence of ATS Routes in the vicinity of one or more major aerodromes.
- Threshold Crossing Height (TCH). The height of the straight line extension of the glide slope above the runway at the threshold.
- Total Estimated Elapsed Time. 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. For VFR flights, the estimated time required from take-off to arrive over the destination aerodrome.
99. Transition Altitude (TA). The altitude in the vicinity of an aerodrome at or below which the Vertical position of an ac is controlled by reference to altitudes above mean sea level or height above the aerodrome depending on whether QNH or QFE is set on the altimeter.
- Transition Layer. The airspace between the transition altitude and the transition level. The depth of the layer will normally be insignificant, and will in any case never exceed 500 ft.
- Transition Level. The lowest flight level above the transition altitude. It will vary in accordance with the relationship between the QNE and the standard pressure datum.
- The ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent lighted objects by night.
- Wake Turbulence. The term “wake turbulence” is used to describe the effect of the rotating air masses generated behind the wing tips of large jet aircraft, in preference to the term “wake vortex” which describes me nature of the air masses.
- Wake Turbulence Categorisation of Aircraft. Wake turbulence separation minima shall be based on a grouping of aircraft types into three categories according to the maximum .certificated take-off mass as follows:
- Heavy (H). All aircraft types of 136,000 Kg or more.
- Medium (M). Aircraft types less than 136,000 kg, but more than 7000 kg.
- Light (L). Aircraft types of 7000 Kg or less.