JEPPESEN GENERAL AIRWAY MANUAL (Issue Date 1 JUL 21) - page 30

Definitions in this listing are extracted from the following ICAO documents:
ICAO RULES OF THE AIR, ANNEX 2
PROCEDURES FOR AIR NAVIGATION SERVICES — AIR TRAFFIC MANAGEMENT, PANS-
ATM (Doc 4444)
PROCEDURES FOR AIR NAVIGATION SERVICES — AIRCRAFT OPERATIONS, PANS-OPS
(Doc 8168)

DEFINITIONS

ACCEPTING UNIT/CONTROLLER — Air traffic control unit/air traffic controller next to take con-
trol of an aircraft.
NOTE: See definition of "transferring unit/controller".
ACROBATIC FLIGHT — Manoeuvres intentionally performed by an aircraft involving an abrupt
change in its attitude, an abnormal attitude, or an abnormal variation in speed.
ADS AGREEMENT — An ADS reporting plan which establishes the conditions of ADS data
reporting (i.e., data required by the air traffic services unit and frequency of ADS reports which
have to be agreed to prior to the provision of the ADS services).
NOTE: The terms of the agreement will be exchanged between the ground system and the air-
craft by means of a contract, or a series of contracts.
ADS-C AGREEMENT — A reporting plan which establishes the conditions of ADS-C data report-
ing (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).
NOTE: The terms of the agreement will be exchanged between the ground system and the air-
craft by means of a contract, or a series of contracts.
ADS CONTRACT — A means by which the terms of an ADS agreement will be exchanged
between the ground system and the aircraft, specifying under what conditions ADS reports would
be initiated, and what data would be contained in the reports.
NOTE: The term “ADS contract” is a generic term meaning variously, ADS event contract, ADS
demand contract, ADS periodic contract or an emergency mode. Ground forwarding of ADS
reports may be implemented between ground systems.
ADVISORY AIRSPACE — An airspace of defined dimensions, or designated route, within which
air traffic advisory service is available.
ADVISORY ROUTE — A designated route along which air 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 surface
movement of aircraft.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

929

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

NOTE: The term “aerodrome” where used in the provisions relating to flight plans and ATS mes-
sages is intended to cover also sites other than aerodromes which may be used by certain types
of aircraft; e.g., helicopters or balloons.
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 ELEVATION — The elevation of the highest point of the landing area.
AERODROME TRAFFIC — All traffic on the manoeuvring area of an aerodrome and all aircraft
flying in the vicinity of an aerodrome.
NOTE: An aircraft is in the vicinity of an aerodrome when it is in, entering or leaving an aerodrome
traffic circuit.
AERODROME TRAFFIC CIRCUIT — The specified path to be flown by aircraft operating in the
vicinity of an aerodrome.
AERODROME TRAFFIC ZONE — An airspace of defined dimensions established around an aer-
odrome for the protection of aerodrome traffic.
AERONAUTICAL FIXED SERVICE (AFS) — A telecommunication service between specified
fixed points provided primarily for the safety of air navigation and for the regular, efficient and eco-
nomical operation of air services.
AERONAUTICAL FIXED STATION — A station in the aeronautical fixed service.
AERONAUTICAL GROUND LIGHT — Any light specially provided as an aid to air navigation,
other than a light displayed on an aircraft.
AERONAUTICAL INFORMATION PUBLICATION (AIP) — A publication issued by or with the
authority of a State and containing aeronautical information of a lasting character essential to air
navigation.
AERONAUTICAL MOBILE SERVICE — A mobile service between aeronautical stations and air-
craft stations, or between aircraft stations, in which survival craft stations may participate; emer-
gency position-indicating radio beacon stations may also participate in this service on designated
distress and emergency frequencies.
AERONAUTICAL STATION — 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.
AERONAUTICAL TELECOMMUNICATION SERVICE — A telecommunication service provided
for any aeronautical purpose.
AERONAUTICAL TELECOMMUNICATION STATION — A station in the aeronautical telecom-
munication service.
AEROPLANE — A power-driven heavier-than-air aircraft, deriving its lift in flight chiefly from aero-
dynamic reactions on surfaces which remain fixed under given conditions of flight.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

930

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

AIRBORNE COLLISION AVOIDANCE SYSTEM (ACAS) — An aircraft system based on secon-
dary 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.
AIRCRAFT — 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.
AIRCRAFT ADDRESS — A unique combination of 24 bits available for assignment to an aircraft
for the purpose of air-ground communications, navigation and surveillance.
AIRCRAFT IDENTIFICATION — A group of letters, figures or a combination thereof which is
either identical to, or the coded equivalent of, the aircraft call sign to be used in air-ground com-
munications, and which is used to identify the aircraft in ground-ground air traffic services commu-
nications.
AIRCRAFT OBSERVATION — The evaluation of one or more meteorological elements made
from an aircraft in flight.
AIRCRAFT PROXIMITY — A situation in which, in the opinion of a pilot or air traffic services per-
sonnel, the distance between aircraft as well as their relative positions and speed have been such
that the safety of the aircraft involved may have been compromised. An aircraft proximity is classi-
fied as follows:
Risk of Collision — The risk classification of an aircraft proximity in which serious risk of collision
has existed.
Safety not Assured — The risk classification of an aircraft proximity in which the safety of the
aircraft may have been compromised.
No Risk of Collision — The risk classification of an aircraft proximity in which no risk of collision
has existed.
Risk not Determined — The risk classification of an aircraft proximity in which insufficient infor-
mation was available to determine the risk involved, or inconclusive or conflicting evidence preclu-
ded such determination.
AIR-GROUND COMMUNICATION — Two-way communication between aircraft and stations or
locations on the surface of the earth.
AIR-GROUND CONTROL RADIO STATION — An aeronautical telecommunication station
having primary responsibility for handling communications pertaining to the operation and control
of aircraft in a given area.
AIRMET INFORMATION — 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.
AIRPROX — The code word used in an air traffic incident report to designate aircraft proximity.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

931

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

AIR-REPORT — A report from an aircraft in flight prepared in conformity with requirements for
position and operational and/or meteorological reporting.
AIR-TAXIING — Movement of a helicopter/VTOL above the surface of an aerodrome, normally in
ground effect and at a ground speed normally less than 37 km/h (20 kt).
NOTE: The actual height may vary, and some helicopters may require air-taxiing above 8m (25 ft)
AGL to reduce ground effect turbulence or provide clearance for cargo slingloads.
AIR-TO-GROUND COMMUNICATION — One-way communication from aircraft to stations or
locations on the surface of the earth.
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 practical, between aircraft which are operating on IFR flight plans.
AIR TRAFFIC CONTROL CLEARANCE — Authorization for an aircraft to proceed under condi-
tions specified by an air traffic control unit.
NOTE 1: For convenience, the term “air traffic control clearance” is frequently abbreviated to
“clearance” when used in appropriate contexts.
NOTE 2: The abbreviated term “clearance” may be prefixed by the words “taxi,” “take-off,” “depar-
ture,” “en route,” “approach” or “landing” to indicate the particular portion of flight to which the air
traffic control clearance relates.
AIR TRAFFIC CONTROL INSTRUCTION — Directives issued by air traffic control for the pur-
pose of requiring a pilot to take a specific action.
AIR TRAFFIC CONTROL SERVICE — 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.

AIR TRAFFIC CONTROL UNIT — A generic term meaning variously, area control centre,
approach control office or aerodrome control tower.
AIR TRAFFIC FLOW MANAGEMENT (ATFM) — A service established with the objective of con-
tributing to a safe, orderly and expeditious flow of air traffic by ensuring that ATC capacity is uti-
lized to the maximum extent possible, and that the traffic volume is compatible with the capacities
declared by the appropriate ATS authority.
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).

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

932

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

AIR TRAFFIC SERVICES AIRSPACES — Airspaces of defined dimensions, alphabetically desig-
nated, within which specific types of flights may operate and for which air traffic services and rules
of operation are specified.
NOTE: ATS airspaces are classified as Class “A” to “G.”
AIR TRAFFIC SERVICES REPORTING OFFICE — A unit established for the purpose of receiv-
ing reports concerning air traffic services and flight plans submitted before departure.
NOTE: An air traffic services reporting office may be established as a separate unit or combined
with an existing unit, such as another air traffic services unit, or a unit of the aeronautical informa-
tion service.
AIR TRAFFIC SERVICES UNIT — A generic term meaning variously, air traffic control unit, flight
information centre or air traffic services reporting office.
AIRWAY — A control area or portion thereof established in the form of a corridor.
ALERFA — The code word used to designate an alert phase.
ALERTING SERVICE — A service provided to notify appropriate organizations regarding aircraft
in need of search and rescue aid, and assist such organizations as required.
ALERT PHASE — A situation wherein apprehension exists as to the safety of an aircraft and its
occupants.
ALLOCATION, ALLOCATE — Distribution of frequencies, SSR Codes, etc. to a State, unit or
service, Distribution of 24-bit aircraft addresses to a State or common mark registering authority.
ALPHANUMERIC CHARACTERS (Alphanumerics) — A collective term for letters and figures
(digits).
ALTERNATE AERODROME — 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 aero-
dromes include the following:
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 depar-
ture.
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.
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.
NOTE: The aerodrome from which a flight departs may also be an en route or a destination alter-
nate aerodrome for that flight.
ALTITUDE — The vertical distance of a level, a point, or an object considered as a point, meas-
ured from mean sea level (MSL).

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

933

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

APPROACH CONTROL SERVICE — Air traffic control service for arriving or departing controlled
flights.
APPROACH CONTROL UNIT — A unit established to provide air traffic control service to control-
led flights arriving at, or departing from, one or more aerodromes.
APPROACH SEQUENCE — The order in which two or more aircraft are cleared to approach to
land at the aerodrome.
APPROPRIATE ATS AUTHORITY — The relevant authority designated by the State responsible
for providing air traffic services in the airspace concerned.
APPROPRIATE AUTHORITY —

a.

Regarding flight over the high seas: The relevant authority of the State of Registry.

b.

Regarding flight other than over the high seas: The relevant authority of the State having
sovereignty over the territory being overflown.

APRON — A defined area, on a land aerodrome, intended to accommodate aircraft for purposes
of loading or unloading passengers, mail or cargo, fueling, parking or maintenance.
AREA CONTROL CENTRE (ACC) — A unit established to provide air traffic control service to
controlled flights in control areas under its jurisdiction.
AREA CONTROL SERVICE — Air traffic control service for controlled flights in control areas.
AREA MINIMUM ALTITUDE (AMA) — The minimum altitude to be used under instrument mete-
orological conditions (IMC), that provides a minimum obstacle clearance within a specified area,
normally formed by parallels and meridians.
AREA NAVIGATION (RNAV) — 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.
AREA NAVIGATION ROUTE — An ATS route established for the use of aircraft capable of
employing area navigation.
ASSIGNMENT, ASSIGN — Distribution of frequencies to stations. Distribution of SSR Codes or
24-bit addresses to aircraft.
ATIS — The symbol used to designate automatic terminal information service.
ATS ROUTE — A specified route designed for channeling the flow of traffic as necessary for the
provision of air traffic services.
NOTE 1: The term “ATS route” is used to mean variously, airway, advisory route, controlled or
uncontrolled route, arrival or departure route, etc.
NOTE 2: An ATS route is defined by route specifications which include an ATS route designator,
the track to or from significant points (waypoints), distance between significant points, reporting
requirements and, as determined by the appropriate ATS authority, the lowest safe altitude.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

934

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

ATS SURVEILLANCE SERVICE — A term used to indicate a service provided directly by means
of an ATS surveillance system.
ATS SURVEILLANCE SYSTEM — A generic term meaning variously, ADS-B, PSR, SSR or any
comparable ground-based system that enables the identification of aircraft.
NOTE: A comparable ground-based system is one that has been demonstrated, by comparative
assessment or other methodology, to have a level of safety and performance equal to or better
than monopulse SSR.
AUTOMATIC DEPENDENT SURVEILLANCE — BROADCAST (ADS-B) — 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.
AUTOMATIC DEPENDENT SURVEILLANCE — CONTRACT (ADS-C) — 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.
NOTE: The abbreviated term “ADS” contract is commonly used to refer to ADS event contract,
ADS demand contract or an emergency mode.
AUTOMATIC TERMINAL INFORMATION SERVICE (ATIS) — The automatic provision of cur-
rent, routine information to arriving and departing aircraft throughout 24 hours or a specified por-
tion thereof:

– Data link-automatic terminal information service (D-ATIS). The provision of ATIS via data link.
– Voice-automatic terminal information service (Voice-ATIS). The provision of ATIS by means of

continuous and repetitive voice broadcasts.

BALKED LANDING — A landing manoeuvre that is unexpectedly discontinued at any point
below the OCA/H.
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.
NOTE: Base turns may be designated as being made either in level flight or while descending,
according to the circumstances of each individual procedure.
BLIND TRANSMISSION — A transmission from one station to another station in circumstances
where two-way communication cannot be established but where it is believed that the called sta-
tion is able to receive the transmission.
BROADCAST — A transmission of information relating to air navigation that is not addressed to a
specific station or stations.
CEILING — The height above the ground or water of the base of the lowest layer of cloud below
6,000 metres (20,000 feet) covering more than half the sky.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

935

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

CHANGEOVER POINT — 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.
NOTE: Changeover points are established to provide the optimum balance in respect of signal
strength and quality between facilities at all levels to be used and to ensure a common source of
azimuth guidance for all aircraft operating along the same portion of a route segment.
CIRCLING APPROACH — An extension of an instrument approach procedure which provides for
visual circling of the aerodrome prior to landing.
CLEARANCE LIMIT — The point to which an aircraft is granted an air traffic control clearance.
CONTINUOUS CLIMB OPERATION (CCO) — An operation, enabled by airspace design, proce-
dure design and ATC, in which a departing aircraft climbs continuously, to the greatest possible
extent, by employing optimum climb engine thrust and climb speeds until reaching the cruise flight
level.
CONTINUOUS DESCENT FINAL APPROACH (CDFA) — A technique, consistent with stabilized
approach procedures, for flying the final approach segment of a non-precision instrument
approach procedure as a continuous descent, without level-off, from an altitude/height at or above
the final approach fix altitude/height to a point approximately 15m (50 ft) above the landing
runway threshold or the point where the flare maneuver should begin for the type of aircraft flown.
CONTINUOUS DESCENT OPERATION (CDO) — An operation, enabled by airspace design,
procedure design and ATC, in which an arriving aircraft descends continuously, to the greatest
possible extent, by employing minimum engine thrust, ideally in a low drag configuration, prior to
the final approach fix/final approach point.
CODE (SSR) — The number assigned to a particular multiple pulse reply signal transmitted by a
transponder in Mode A or Mode C.
COMPUTER — A device which performs sequences of arithmetical and logical steps upon data
without human intervention.
NOTE: When the word “computer” is used in this document it may denote a computer complex,
which includes one or more computers and peripheral equipment.
CONTROL AREA — A controlled airspace extending upwards from a specified limit above the
earth.
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 aer-
odrome traffic but does not necessarily imply that a control zone exists.
CONTROLLED AIRSPACE — An airspace of defined dimensions within which air traffic control
service is provided in accordance with the airspace classification.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

936

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

NOTE: Controlled airspace is a generic term which covers ATS airspace Classes A, B, C, D and
E as described in Annex 11, 2.6.
CONTROLLED FLIGHT — Any flight which is subject to an air traffic control clearance.
CONTROLLER-PILOT DATA LINK COMMUNICATIONS (CPDLC) — A means of communica-
tion between controller and pilot, using data link for ATC communications.
CONTROL ZONE — A controlled airspace extending upwards from the surface of the earth to a
specified upper limit.
CRUISE CLIMB — An aeroplane cruising technique resulting in a net increase in altitude as the
aeroplane mass decreases.
CRUISING LEVEL — A level maintained during a significant portion of a flight.
CURRENT FLIGHT PLAN (CPL) — The flight plan, including changes, if any, brought about by
subsequent clearances.
NOTE: When the word “message” is used as a suffix to this term, it denotes the content and
format of the current flight plan data sent from one unit to another.
DANGER AREA — An airspace of defined dimensions within which activities dangerous to the
flight of aircraft may exist at specified times.
DATA CONVENTION — An agreed set of rules governing the manner or sequence in which a set
of data may be combined into a meaningful communication.
DATA LINK COMMUNICATIONS — A form of communication intended for the exchange of mes-
sages via a data link.
DATA LINK INITIATION CAPABILITY (DLIC) — A data link application that provides the ability
to exchange addresses, names and version numbers necessary to initiate data link applications.
DEAD RECKONING (DR) NAVIGATION — The estimating or determining of position by advanc-
ing an earlier known position by the application of direction, time and speed data.
DECISION ALTITUDE (DA) OR DECISION HEIGHT (DH) — A specified altitude, or height, in a
3D instrument approach operation at which a missed approach must be initiated if the required
visual reference to continue the approach has not been established.
NOTE 1: Decision altitude (DA) is referenced to mean sea level and decision height (DH) is refer-
enced to the threshold elevation.
NOTE 2: The required visual reference means that section of the visual aids or of the approach
area which should have been in view for sufficient time for the pilot to have made an assessment
of the aircraft position and rate of change of position, in relation to the desired flight path. In Cate-
gory III operations with a decision height the required visual reference is that specified for the par-
ticular procedure and operation.
NOTE 3: For convenience where both expressions are used they may be written in the form “deci-
sion altitude/height” and abbreviated “DA/H.”

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

937

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

DEPENDENT PARALLEL APPROACHES — Simultaneous approaches to parallel or near-paral-
lel instrument runways where ATS surveillance system separation minima between aircraft on
adjacent extended runway centre lines are prescribed.
DETRESFA — The code word used to designate a distress phase.
DESCENT FIX — A fix established in a precision approach at the FAP to eliminate certain obsta-
cles before the FAP, which would otherwise have to be considered for obstacle clearance purpo-
ses.
DESCENT POINT (DP) — A point defined by track and distance from the MAPt to identify the
point at which the helicopter may descend below the OCA/H on a visual descent to the heliport or
landing location.
DIRECT VISUAL SEGMENT (DIRECT-VS) — A visual segment designed as:

a. a leg in a PinS approach, which may contain a single turn, from the MAPt direct to the heli-

port or landing location or via a descent point to the heliport or landing location; or

b. a straight leg from the helicopter or landing location to the IDF in a PinS departure.

DISCRETE CODE — A four-digit SSR Code with the last two digits not being “00.”
DISTRESS PHASE — A situation wherein there is a reasonable certainty that an aircraft and its
occupants are threatened by grave and imminent danger or require immediate assistance.
DME DISTANCE — The line of sight distance (slant range) from the source of a DME signal to
the receiving antenna.
ELEVATION — The vertical distance of a point or a level, on or affixed to the surface of the earth,
measured from mean sea level.
EMERGENCY PHASE — A generic term meaning, as the case may be, uncertainty phase, alert
phase or distress phase.
ESTIMATED ELAPSED TIME — The estimated time required to proceed from one significant
point to another.
ESTIMATED OFF-BLOCK TIME — The estimated time at which the aircraft will commence
movement associated with departure.
ESTIMATED TIME OF ARRIVAL — For IFR flights, the time at which it is estimated that the air-
craft 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
VFR flights, the time at which it is estimated that the aircraft will arrive over the aerodrome.
EXPECTED APPROACH TIME — The time at which ATC expects that an arriving aircraft, follow-
ing a delay, will leave the holding point to complete its approach for a landing.
NOTE: The actual time of leaving the holding point will depend upon the approach clearance.
FILED FLIGHT PLAN (FPL) — The flight plan as filed with an ATS unit by the pilot or a designa-
ted representative, without any subsequent changes.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

938

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

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:

a. at the end of the last procedure turn, base turn or inbound turn of a racetrack procedure, if

specified; or

b. 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:

1. landing can be made; or
2. a missed approach procedure is initiated.

FINAL APPROACH AND TAKE-OFF AREA (FATO) — A defined area over which the final
phase of the approach manoeuvre to hover or landing is completed and from which the take-off
manoeuvre is commenced. Where the FATO is to be used by performance Class 1 helicopters,
the defined area includes the rejected take-off area available.
FINAL APPROACH SEGMENT (FAS) — That segment of an instrument approach procedure in
which alignment and descent for landing are accomplished.
FLIGHT CREW MEMBER — A licensed crew member charged with duties essential to the opera-
tion of an aircraft during flight duty period.
FLIGHT INFORMATION CENTRE — A unit established to provide flight information service and
alerting service.
FLIGHT INFORMATION REGION (FIR) — An airspace of defined dimensions within which flight
information service and alerting service 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 (FL) — 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 spe-
cific pressure intervals.
NOTE 1: A pressure type altimeter calibrated in accordance with the Standard Atmosphere:

a. when set to a QNH altimeter setting, will indicate altitude;
b. when set to a QFE altimeter setting, will indicate height above the QFE reference datum;

c. when set to a pressure of 1013.2 hectopascals (hPa), may be used to indicate flight levels.

NOTE 2: The terms “height” and “altitude,” used in NOTE 1 above, indicate altimetric rather than
geometric heights and altitudes.
FLIGHT PATH MONITORING — The use of ATS surveillance systems for the purpose of provid-
ing aircraft with information and advice relative to significant deviations from nominal flight path,
including deviations from the terms of their air traffic control clearances.
NOTE: Some applications may require a specific technology, e.g. radar, to support the function of
flight path monitoring.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

939

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

FLIGHT PLAN — Specified information provided to air traffic services units, relative to an inten-
ded flight or portion of a flight of an aircraft.
NOTE: Specifications for flight plans are contained in ICAO Rules of the Air, Annex 2. A Model
Flight Form is contained in ICAO Rules of the Air and Air Traffic Services, PANS-RAC (Doc
4444), Appendix 2.
FLIGHT VISIBILITY — The visibility forward from the cockpit of an aircraft in flight.
FLOW CONTROL — Measures designed to adjust the flow of traffic into a given airspace, along
a given route, or bound for a given aerodrome, so as to ensure the most effective utilization of the
airspace.
FORECAST — A statement of expected meteorological conditions for a specified time or period,
and for a specified area or portion of airspace.
FREE TEXT MESSAGE ELEMENT — Part of a message that does not conform to any standard
message element in the PANS-ATM (Doc 4444).
GBAS LANDING SYSTEM (GLS) — A system for approach and landing operations utilizing
GNSS, augmented by a ground based augmentation system (GBAS), as the primary navigational
reference.
GLIDE PATH — A descent profile determined for vertical guidance during a final approach.
GROUND EFFECT — A condition of improved performance (lift) due to the interference of the
surface with the airflow pattern of the rotor system when a helicopter or other VTOL aircraft is
operating near the ground.
NOTE: Rotor efficiency is increased by ground effect to a height of about one rotor diameter for
most helicopters.
GROUND VISIBILITY — The visibility at an aerodrome, as reported by an accredited observer or
by automatic systems.
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.
HEIGHT ABOVE SURFACE (HAS) — The difference in height between the OCA and the eleva-
tion of the highest terrain, water surface or obstacle within a radius of at least 1.5km (0.8 NM)
from the MAPt in a PinS "Proceed VFR" procedure.
HELIPORT REFERENCE POINT (HRP) — The designated location of a heliport or a landing
location.
HOLDING FIX — A geographical location that serves as a reference for a holding procedure.
HOLDING PROCEDURE — A predetermined manoeuvre which keeps an aircraft within a speci-
fied airspace while awaiting further clearance.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

940

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

HOT SPOT — A location on an aerodrome movement area with a history or potential risk of colli-
sion or runway incursion, and where heightened attention by pilots/drivers is necessary.
HUMAN FACTORS PRINCIPLES — Principles which apply to aeronautical design, certification,
training, operations and maintenance and which seek safe interface between the human and
other system components by proper consideration to human performance.
HUMAN PERFORMANCE — Human capabilities and limitations which have an impact on the
safety and efficiency of aeronautical operations.
IDENTIFICATION — The situation which exists when the position indication of a particular aircraft
is seen on a situation display and positively identified.
IFR — The symbol used to designate the instrument flight rules.
IFR FLIGHT — A flight conducted in accordance with the instrument flight rules.
IMC — The symbol used to designate instrument meteorological conditions.
INCERFA — The code word used to designate an uncertainty phase.
INCIDENT — An occurrence, other than an accident, associated with the operation of an aircraft
which affects or could affect the safety of operation.
NOTE: The type of incidents which are of main interest to the International Civil Aviation Organi-
zation for accident prevention studies can be found at http://www.icao.int/anb/aig
INDEPENDENT PARALLEL APPROACHES — Simultaneous approaches to parallel or near-
parallel instrument runways where ATS surveillance system separation minima between aircraft
on adjacent extended runway centre lines are not prescribed.
INDEPENDENT PARALLEL DEPARTURES — Simultaneous departures from parallel or near-
parallel instrument runways.
INITIAL APPROACH FIX (IAF) — A fix that marks the beginning of the initial segment and the
end of the arrival segment, if applicable. In RNAV applications this fix is normally defined by a fly-
by waypoint.
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.
INITIAL DEPARTURE FIX (IDF) — The terminal fix for the visual segment and the fix where the
instrument phase of the PinS departure begins.
INSTRUMENT APPROACH OPERATIONS — 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 navi-

gation guidance.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

941

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

NOTE: Lateral and vertical navigation guidance refers to the guidance provided either by:

a. a ground-based radio navigation aid; or
b. computer-generated navigation data from ground-based, space-based. sell-contained navi-

gation aid or a combination of these.

INSTRUMENT APPROACH PROCEDURE (IAP) — 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 land-
ing 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:

– Non-precision approach (NPA) procedure. An instrument approach procedure designed for 2D

instrument approach operations Type A.
NOTE: Non-precision approach procedures may be flown using a continuous descent final
approach (CDFA) technique. CDFAs with advisory VNAV guidance calculated by on-board
equipment are considered 3D instrument approach operations. CDFAs with manual calculation
of the required rate of descent are considered 2D instrument approach operations. For more
information on CDFAs, refer to PANS-OPS (Doc 8168), Volume I, Part II, Section 5.

– Approach procedure with vertical guidance (APV). A performance-based navigation (PBN)

instrument approach procedure designed for 3D instrument approach operations Type A.

– 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.
NOTE: Refer to Annex 6 for instrument approach operation types (not published herein).

INSTRUMENT METEOROLOGICAL CONDITIONS (IMC) — Meteorological conditions
expressed in terms of visibility, distance from cloud, and ceiling, less than the minima specified for
visual meteorological conditions.
NOTE 1: The specified minima for visual meteorological conditions are contained in ICAO Rules
of the Air, Annex 2, Chapter 4.
NOTE 2: In a control zone, a VFR flight may proceed under instrument meteorological conditions
if and as authorized by air traffic control.
INTERMEDIATE APPROACH SEGMENT — That segment of an instrument approach procedure
between either the intermediate approach fix and the final approach fix or point, or between the
end of a reversal, racetrack or dead reckoning track procedure and the final approach fix or point,
as appropriate.
INTERMEDIATE FIX (IF) — A fix that marks the end of an initial segment and the beginning of
the intermediate segment. In RNAV applications this fix is normally defined by a fly-by waypoint.
ITP AIRCRAFT — An aircraft approved by the State of the Operator to conduct in-trail procedure
(ITP).

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

942

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

ITP DISTANCE — The distance between the ITP aircraft and a reference aircraft as defined by:

a. aircraft on the same track, the difference in distance to an aircraft calculated common point

along a projection of each other's track; or

b. aircraft on parallel tracks, the distance measured along the track of one of the aircraft using

its calculated position and the point abeam the calculated position of the other aircraft.

NOTE: Reference aircraft refers to one or two aircraft with ADS-B data that meet the ITP criteria
described in 5.4.2.7 (not published herein) and are indicated to ATC by the ITP aircraft as part of
the ITP clearance request.
LANDING AREA — That part of a movement area intended for the landing or take-off of aircraft.
LANDING LOCATION — A marked or unmarked area that has the same physical characteristics
as a visual heliport final approach and take-off area (FATO).
LEVEL — A generic term relating to the vertical position of an aircraft in flight and meaning vari-
ously, height, altitude or flight level.
LOCATION INDICATOR — A four-letter code group formulated in accordance with rules prescri-
bed by ICAO and assigned to the location of an aeronautical fixed station.
LOCALIZER PERFORMANCE WITH VERTICAL GUIDANCE (LPV) — The label to denote
minima lines associated with APV-I or APV-II performance on approach charts.
LOGON ADDRESS — A specified code used for data link logon to an ATS unit.
MANOEUVERING AREA — That part of an aerodrome to be used for the take-off, landing and
taxiing of aircraft, excluding aprons.
MANOEUVERING VISUAL SEGMENT (MANOEUVERING-VS) — PinS visual segment protec-
ted for the following manoeuverers for:
PinS approaches. Visual manoeuver from the MAPt around the heliport or landing location to land
from a direction other than directly from the MAPt.
PinS departures. Take-off in a direction other than directly to the IDF followed by visual manoeu-
ver to join the instrument segment at the IDF.
METEOROLOGICAL INFORMATION — Meteorological report, analysis, forecast, and any other
statement relating to existing or expected meteorological conditions.
METEOROLOGICAL OFFICE — An office designated to provide meteorological service for inter-
national air navigation.
METEOROLOGICAL REPORT — A statement of observed meteorological conditions related to a
specified time and location.
MINIMUM DESCENT ALTITUDE (MDA) OR MINIMUM DESCENT HEIGHT (MDH) — A speci-
fied altitude or height in a 2D instrument approach operation or circling approach below which
descent must not be made without the required visual reference.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

943

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

NOTE 1: Minimum descent altitude (MDA) is referenced to mean sea level and minimum descent
height (MDH) is referenced to the aerodrome elevation or to the threshold elevation if that is more
than 2m (7 ft) below the aerodrome elevation. A minimum descent height for a circling approach
is referenced to the aerodrome elevation.
NOTE 2: The required visual reference means that section of the visual aids or of the approach
area which should have been in view for sufficient time for the pilot to have made an assessment
of the aircraft position and rate of change of position, in relation to the desired flight path. In the
case of a circling approach the required visual reference is the runway environment.
NOTE 3: For convenience when both expressions are used they may be written in the form “mini-
mum descent altitude/height” abbreviated “MDA/H.”
MINIMUM ENROUTE ALTITUDE (MEA) — The altitude for an enroute segment that provides
adequate reception of relevant navigation facilities and ATS communications, complies with the
airspace structure and provides the required obstacle clearance.
MINIMUM FUEL — The 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.
MINIMUM INSTRUMENT METEOROLOGICAL CONDITIONS AIRSPEED (V

mini

) — The mini-

mum indicated airspeed that a specific helicopter is certified to operate in instrument meteorologi-
cal conditions.
MINIMUM OBSTACLE CLEARANCE ALTITUDE (MOCA) — The minimum altitude for a defined
segment that provides the required obstacle clearance.
MINIMUM SECTOR ALTITUDE (MSA) — The lowest altitude which may be used which will pro-
vide a minimum clearance of 300m (1000 ft) above all objects located in an area contained within
a sector of a circle of 46km (25 NM) radius centered on a significant point, the airport reference
point (ARP) or the heliport reference point (HRP).
MINIMUM STABILIZATION DISTANCE (MSD) — The minimum distance to complete a turn
manoeuvre and after which a new manoeuvre can be initiated. The minimum stabilization dis-
tance is used to compute the minimum distance between waypoints.
MISSED APPROACH HOLDING FIX (MAHF) — A fix used in RNAV applications that marks the
end of the missed approach segment and the centre point for the missed approach holding.
MISSED APPROACH POINT (MAPt) — That point in an instrument approach procedure at or
before which the prescribed missed approach procedure must be initiated in order to ensure that
the minimum obstacle clearance is not infringed.
MISSED APPROACH PROCEDURE — The procedure to be followed if the approach cannot be
continued.
MODE (SSR) — The conventional identifier related to specific functions of the interrogation sig-
nals transmitted by an SSR interrogator. There are four modes specified in ICAO Annex 10 (not
published herein): A, C, S and intermode.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

944

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

MOVEMENT AREA — 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).
MULTILATERATION (MLAT) SYSTEM — A group of equipment configured to provide position
derived from the secondary surveillance radar (SSR) transponder signals (replies or squitters) pri-
marily using time difference of arrival (TDOA) techniques. Additional information, including identifi-
cation, can be extracted from the received signals.
NEAR-PARALLEL RUNWAYS — Non-intersecting runways whose extended centre lines have
an angle of convergence / divergence of 15 degrees or less.
NEXT DATA AUTHORITY — The ground system so designated by the current data authority
through which an onward transfer of communications and control can take place.
NORMAL OPERATING ZONE (NOZ) — Airspace of defined dimensions extending to either side
of a published instrument approach procedure final approach course or track. Only that half of the
normal operating zone adjacent to a no transgression zone (NTZ) is taken into account in inde-
pendent parallel approaches.
NOTAM — A notice distributed by means of telecommunication 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.
NO TRANSGRESSION ZONE (NTZ) — In the context of independent parallel approaches, a cor-
ridor of airspace of defined dimensions located centrally between the two extended runway centre
lines, where a penetration by an aircraft requires a controller intervention to manoeuvre any
threatened aircraft on the adjacent approach.
OBSTACLE ASSESSMENT SURFACE (OAS) — A defined surface intended for the purpose of
determining those obstacles to be considered in the calculation of obstacle clearance altitude/
height for a specific ILS facility and procedure.
OBSTACLE CLEARANCE ALTITUDE (OCA) OR OBSTACLE CLEARANCE HEIGHT (OCH) —
The lowest altitude or the lowest height above the elevation of the relevant runway threshold or
the aerodrome elevation as applicable, used in establishing compliance with appropriate obstacle
clearance criteria.
NOTE 1: Obstacle clearance altitude is referenced to mean sea level and obstacle clearance
height is referenced to the threshold elevation or in the case of non-precision approaches to the
aerodrome elevation or the threshold elevation if that is more than 2m (7 ft) below the aerodrome
elevation. An obstacle clearance height for a circling approach is referenced to the aerodrome
elevation.
NOTE 2: For convenience when both expressions are used they may be written in the form
“obstacle clearance altitude/height” and abbreviated “OCA/H.”
OBSTACLE FREE ZONE (OFZ) — The airspace above the inner approach surface, inner transi-
tional surfaces, and balked landing surface and that portion of the strip bounded by these surfa-
ces, which is not penetrated by any fixed obstacle other than a low-mass and frangibility mounted
one required for air navigation purposes.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

945

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

OPERATIONAL CONTROL — The exercise of authority over the initiation, continuation, diver-
sion or termination of a flight in the interest of the safety of the aircraft and the regularity and effi-
ciency of the flight.
OPERATOR — A person, organization or enterprise engaged in or offering to engage in an air-
craft operation.
PERFORMANCE-BASED COMMUNICATION (PBC) — Communication based on performance
specifications applied to the provision of air traffic services.
NOTE: An RCP specification includes communication performance requirements that are alloca-
ted to system components in terms of the communication to be provided and associated transac-
tion time, continuity, availability, integrity, safety and functionality needed for the proposed opera-
tion in the context of a particular airspace concept.
PERFORMANCE-BASED NAVIGATION (PBN) — Area navigation based on performance
requirements for aircraft operating along an ATS route, on an instrument approach procedure or
in a designated airspace.
NOTE: Performance requirements are expressed in navigation specifications (RNAV specifica-
tion, RNP specification) in terms of accuracy, integrity, continuity, availability and functionality
needed for the proposed operation in the context of a particular airspace concept.
PERFORMANCE-BASED SURVEILLANCE (PBS) — Surveillance based on performance speci-
fications applied to the provision of air traffic services.
NOTE: An RSP specification includes surveillance performance requirements that are allocated to
system components in terms of the surveillance to be provided and associated data delivery time,
continuity, availability, integrity, accuracy of the surveillance data, safety and functionality needed
for the proposed operation in the context of a particular airspace concept.
PILOT-IN-COMMAND — 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.
POINT-IN-SPACE APPROACH (PinS) — An approach procedure designed for helicopters only
that includes both a visual and an instrument segment.
POINT-IN-SPACE DEPARTURE (PinS) — A departure procedure designed for helicopters only
that includes both a visual and an instrument segment.
POINT-IN-SPACE REFERENCE POINT (PRP) — Reference point for the point-in-space
approach as identified by the latitude and longitude of the MAPt.
POSITION INDICATION — The visual indication, in non-symbolic and/or symbolic form, on a sit-
uation display, of the position of an aircraft, airport vehicle or other object.
POSITION SYMBOL — The visual indication in symbolic form, on a situation display, of the posi-
tion of an aircraft, airport vehicle or other object, obtained after automatic processing of positional
data derived from any source,

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

946

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

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.
PREFORMATTED FREE TEXT MESSAGE ELEMENT — A free text message element that is
stored within the aircraft system or ground system for selection.
PRESSURE-ALTITUDE — An atmospheric pressure expressed in terms of altitude which corre-
sponds to that pressure in the Standard Atmosphere.
PRIMARY AREA — A defined area symmetrically disposed about the nominal flight track in
which full obstacle clearance is provided. (See also 

SECONDARY AREA.)

PRIMARY RADAR — A radar system which uses reflected radio signals.
PRIMARY SURVEILLANCE RADAR (PSR) — A surveillance radar system which uses reflected
radio signals.
PROBLEMATIC USE OF SUBSTANCES — 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.

PROCEDURAL CONTROL — Term used to indicate that information derived from an ATS sur-
veillance system is not required for the provision of air traffic control service.
PROCEDURAL SEPARATION — The separation used when providing procedural control.
PROCEDURE ALTITUDE/HEIGHT — A specified altitude/height flown operationally at or above
the minimum altitude/height and established to accommodate a stabilized descent at a prescribed
descent gradient/angle in the intermediate/final approach segment.
PROCEDURE TURN — A manoeuvre in which a turn is made away from a designated track fol-
lowed by a turn in the opposite direction to permit the aircraft to intercept and proceed along the
reciprocal of the designated track.
NOTE 1: Procedure turns are designated “left” or “right” according to the direction of the initial
turn.
NOTE 2: Procedure turns may be designated as being made either in level flight or while
descending, according to the circumstances of each individual procedure.
PROFILE — The orthogonal projection of a flight path or portion thereof on the vertical surface
containing the nominal track.
PROHIBITED AREA — An airspace of defined dimensions, above the land areas or territorial
waters of a State, within which the flight of aircraft is prohibited.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

947

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

PSR BLIP — The visual indication, in non-symbolic form, on a situation display of the position of
an aircraft obtained by primary radar.
PSYCHOACTIVE SUBSTANCES — Alcohol, opioids, cannabinoids, sedatives and hypnotics,
cocaine, other psychostimulants, hallucinogens, and volatile solvents, whereas coffee and
tobacco are excluded.
RACETRACK PROCEDURE — A procedure designed to enable the aircraft to reduce altitude
during the initial approach segment and/or establish the aircraft inbound when the entry into a
reversal procedure is not practical.
RADAR — A radio detection device which provides information on range, azimuth and/or eleva-
tion of objects.
RADAR APPROACH — An approach, in which the final approach phase is executed under the
direction of a controller using radar.
RADAR CLUTTER — The visual indication on a situation display of unwanted signals.
RADAR CONTACT — The situation which exists when the radar position of a particular aircraft is
seen and identified on a situation display.
RADAR SEPARATION — The separation used when aircraft position information is derived from
radar sources.
RADIOTELEPHONY — A form of radio communication primarily intended for the exchange of
information in the form of speech.
RECEIVING UNIT/CONTROLLER — Air traffic services unit/air traffic controller to which a mes-
sage is sent.
NOTE: See definition of "sending unit/controller".
REMOTE PILOT — A person charged by the operator with duties essential to the operation of a
remotely piloted aircraft and who manipulates the flight controls, as appropriate, during flight time.
REMOTE PILOT STATION — The component of the remotely piloted aircraft system containing
the equipment used to pilot the remotely piloted aircraft.
REMOTELY PILOTED AIRCRAFT (RPA) — An unmanned aircraft which is piloted from a remote
pilot station.
REMOTELY PILOTED AIRCRAFT SYSTEM (RPAS) — A remotely piloted aircraft, its associated
remote pilot station(s), the required command and control links and any other components as
specified in the type design.
REPETITIVE FLIGHT PLAN (RPL) — A flight plan related to a series of frequently recurring, reg-
ularly operated individual flights with identical basic features, submitted by an operator for reten-
tion and repetitive use by ATS units.
REPORTING POINT — A specified geographical location in relation to which the position of an
aircraft can be reported.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

948

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

REQUIRED COMMUNICATION PERFORMANCE (RCP) — A set of requirements for air traffic
service provision and associated ground equipment, aircraft capability, and operations needed to
support performance-based communication.
REQUIRED NAVIGATION PERFORMANCE (RNP) — A statement of the navigation perform-
ance accuracy necessary for operation within a defined airspace.
NOTE: Navigation performance and requirements are defined for a particular RNP type and/or
application.
RESCUE COORDINATION CENTRE — A unit responsible for promoting efficient organization of
search and rescue service and for coordinating the conduct of search and rescue operations
within a search and rescue region.
RESCUE UNIT — A unit composed of trained personnel and provided with equipment suitable for
the expeditious conduct 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 aircraft is restricted in accordance with certain speci-
fied conditions.
REVERSAL PROCEDURE — A procedure designed to enable aircraft to reverse direction during
the initial approach segment of an instrument approach procedure. The sequence may include
procedure turns or base turns.
RNP TYPE — A containment value expressed as a distance in nautical miles from the intended
position within which flights would be for at least 95 per cent of the total flying time.
EXAMPLE: RNP 4 represents a navigation accuracy of plus or minus 7.4 km (4 NM) on a 95 per-
cent containment basis.
RPA OBSERVER — A trained and competent person designated by the operator who, by visual
observation of the remotely piloted aircraft, assists the remote pilot in the safe conduct of the
flight.
RUNWAY — A defined rectangular area on a land aerodrome prepared for the landing and take-
off of aircraft.
RUNWAY-HOLDING POSITION — A designated position intended to protect a runway, an obsta-
cle limitation surface, or an ILS/MLS critical/sensitive area at which taxiing aircraft and vehicles
shall stop and hold, unless otherwise authorized by the aerodrome control tower.
NOTE: In radiotelephony phraseologies, the expression “holding point” is used to designate the
runway-holding position.
RUNWAY INCURSION — Any occurrence at an aerodrome involving the incorrect presence of
an aircraft, vehicle or person on the protected area of a surface designated for the landing and
take-off of aircraft.
RUNWAY VISUAL RANGE (RVR) — 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 iden-
tifying its centre line.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

949

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

SAFETY MANAGEMENT SYSTEM (SMS) — A systematic approach to managing safety, includ-
ing the necessary organizational structures, accountabilities, policies and procedures.
SAFETY-SENSITIVE PERSONNEL — Persons who might endanger aviation safety if they per-
form their duties and functions improperly including, but not limited to, crew members, aircraft
maintenance personnel and air traffic controllers.
SECONDARY AREA — A defined area on each side of the primary area located along the nomi-
nal flight track in which decreasing obstacle clearance is provided. (See also 

PRIMARY AREA)

SECONDARY RADAR — A radar system wherein a radio signal transmitted from a radar station
initiates the transmission of a radio signal from another station.
SECONDARY SURVEILLANCE RADAR (SSR) — A surveillance radar system which uses trans-
mitters / receivers (interrogators) and transponders.
SEGREGATED PARALLEL OPERATIONS — Simultaneous operations on parallel or near-paral-
lel instrument runways in which one runway is used exclusively for approaches and the other
runway is used exclusively for departures.
SENDING UNIT/CONTROLLER — Air traffic services unit/air traffic controller transmitting a mes-
sage.
NOTE: See definition of "receiving unit/controller”.
SHORELINE — A line following the general contour of the shore, except that in cases of inlets or
bays less than 30 NM in width, the line shall pass directly across the inlet or bay to intersect the
general contour on the opposite side.
SIGMET INFORMATION — Information issued by a meteorological watch office concerning the
occurrence or expected occurrence of specified en-route weather and other phenomena which
may affect the safety of aircraft operations.
SIGNAL AREA — An area on an aerodrome used for the display of ground signals.
SIGNIFICANT POINT — A specified geographical location used in defining an ATS route or the
flight path of an aircraft and for other navigation and ATS purposes.
NOTE: There are three categories of significant points: ground-based navigation aid, intersection
and waypoint. In the context of this definition, intersection is a significant point expressed as radi-
als, bearings and/or distances from ground-based navigation aids.
SITUATION DISPLAY — An electronic display depicting the position and movement of aircraft
and other information as required.
SLUSH — Water-saturated snow which with a heel-and-toe slap-down motion against the ground
will be displaced with a splatter; specific gravity: 0.5 up to 0.8.
NOTE: Combinations of ice, snow and/or standing water may, especially when rain, rain and
snow, or snow is falling, produce substances with specific gravities in excess of 0.8. These sub-
stances, due to their high water/ice content, will have a transparent rather than a cloudy appear-
ance and, at the higher specific gravities, will be readily distinguishable from slush.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

950

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

SNOW (on the ground) —

a. Dry snow. Snow which can be blown if loose or, if compacted by hand, will fall apart upon

release; specific gravity: up to but not including 0.35.

b. Wet snow. Snow which, if compacted by hand, will stick together and tend to or form a snow-

ball; specific gravity: 0.35 up to but not including 0.5.

c. Compacted snow. Snow which has been compressed into a solid mass that resists further

compression and will hold together or break up into lumps if picked up; specific gravity: 0.5
and over.

SPECIAL VFR FLIGHT — A VFR flight cleared by air traffic control to operate within a control
zone in meteorological conditions below VMC.
SSR RESPONSE — The visual indication, in non-symbolic form, on a situation display, of a
response from an SSR transponder in reply to an interrogation.
STANDARD INSTRUMENT ARRIVAL (STAR) — A designated instrument flight rule (IFR) arrival
route linking a significant point, normally on an ATS route, with a point from which a published
instrument approach procedure can be commenced.
STANDARD INSTRUMENT DEPARTURE (SID) — A designated instrument flight rule (IFR)
departure route linking the aerodrome or a specified runway of the aerodrome with a specified
significant point, normally on a designated ATS route, at which the enroute phase of a flight com-
mences.
STANDARD MESSAGE ELEMENT — Part of a message defined in the PANS-ATM (Doc 4444)
in terms of display format, intended use and attributes.
STANDARDIZED FREE TEXT MESSAGE ELEMENT — A message element that uses a defined
free text message format, using specific words in a specific order.
NOTE: Standardized free text message elements may be manually entered by the user or prefor-
matted.
STOPWAY — A defined rectangular area on the ground at the end of take-off run available pre-
pared as a suitable area in which an aircraft can be stopped in the case of an abandoned take-off.
SURVEILLANCE RADAR — Radar equipment used to determine the position of an aircraft in
range and azimuth.
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 inten-
ded to provide a link between one part of the aerodrome and another, including:
Aircraft Stand Taxilane — A portion of an apron designated as a taxiway and intended to pro-
vide access to aircraft stands only.
Apron Taxiway — A portion of a taxiway system located on an apron and intended to provide a
through taxi route across the apron.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

951

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

Rapid Exit Taxiway — 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 taxi-ways and
thereby minimizing runway occupancy times.
TERMINAL ARRIVAL ALTITUDE (TAA) — The lowest altitude that will provide a minimum clear-
ance of 300m (1000 ft) above all objects located in an arc of a circle defined by a 46km (25 NM)
radius centered on the initial approach fix (IAF), or where there is no IAF on the intermediate fix
(IF), delimited by straight lines joining the extremity of the arc to the IF. The combined TAAs asso-
ciated with an approach procedure shall account for an area of 360 degrees around the IF.
TERMINAL CONTROL AREA (TMA) — A control area normally established at the confluence of
ATS routes in the vicinity of one or more major aerodromes.
THRESHOLD (THR) — The beginning of that portion of the runway usable for landing.
TIME DIFFERENCE OF ARRIVAL (TDOA) — The difference in relative time that a transponder
signal from the same aircraft (or ground vehicle) is received at different receivers.
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.
TOUCHDOWN — 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.
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 (true, magnetic or grid).
TRAFFIC AVOIDANCE ADVICE — Advice provided by an air traffic services unit specifying
manoeuvres to assist a pilot to avoid a collision.
TRAFFIC INFORMATION — 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.
TRANSFER OF CONTROL POINT — 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.
TRANSFERRING UNIT/CONTROLLER — Air traffic control unit/air traffic controller in the proc-
ess of transferring the responsibility for providing air traffic control service to an aircraft to the next
air traffic control unit/air traffic controller along the route of flight.
NOTE: See definition of "accepting unit/controller”.
TRANSITION ALTITUDE — The altitude at or below which the vertical position of an aircraft is
controlled by reference to altitudes.
TRANSITION LAYER — The airspace between the transition altitude and the transition level.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

952

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

TRANSITION LEVEL — The lowest flight level available for use above the transition altitude.
UNCERTAINTY PHASE — A situation wherein uncertainty exists as to the safety of an aircraft
and its occupants.
UNMANNED FREE BALLOON — A non-power-driven, unmanned, lighter-than-air aircraft in free
flight.
NOTE: Unmanned free balloons are classified as heavy, medium or light in accordance with spec-
ifications contained in ICAO Rules of the Air, Annex 2, Appendix 5.
VECTORING — Provision of navigational guidance to aircraft in the form of specific headings,
based on the use of an ATS surveillance system.
VERTICAL PATH ANGLE (VPA) — Angle of the published final approach descent in baro-VNAV
procedures.
VFR — The symbol used to designate the visual flight rules.
VFR FLIGHT — A flight conducted in accordance with the visual flight rules.
VISIBILITY — Visibility for aeronautical purposes is the greater of:

a. the greatest distance at which a black object of suitable dimensions, situated near the

ground, can be seen and recognized when observed against a bright background;

b. the greatest distance at which lights in the vicinity of 1000 candelas can be seen and identi-

fied against an unlit background.

NOTE 1: The two distances have different values in air of a given extinction coefficient, and the
latter b) varies with the background illumination. The former a) is represented by the meteorologi-
cal optical range (MOR).
NOTE 2: The definition applies to the observations of visibility in local routine and special reports,
to the observations of prevailing and minimum visibility reported in METAR and SPECI and to the
observations of ground visibility.
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.
VISUAL MANOEUVERING (CIRCLING) AREA — The area in which obstacle clearance should
be taken into consideration for aircraft carrying out a circling approach.
VISUAL METEOROLOGICAL CONDITIONS (VMC) — Meteorological conditions expressed in
terms of visibility, distance from cloud, and ceiling equal to or better than specified minima.
NOTE: The specified minima are contained in ICAO Rules of the Air, Annex 2, Chapter 4.
VISUAL SEGMENT DESCENT ANGLE (VSDA) — The angle between the MDA/H at the
MPAt/DP and the heliport crossing height.
VISUAL SEGMENT DESIGN GRADIENT (VSDG) — The gradient of the visual segment in a
PinS departure procedure. The visual segment connects the heliport or landing location with the
initial departure fix (IDF) minimum crossing altitude (MCA).

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

953

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

VISUAL SURVEILLANCE SYSTEM — An electro-optical system providing an electronic visual
presentation of traffic and any other information necessary to maintain situational awareness at
an aerodrome and its vicinity.
VMC — The symbol used to designate visual meteorological conditions.
WAYPOINT — A specified geographical location used to define an area navigation route or the
flight path of an aircraft employing area navigation. Waypoints are identified as either:
Fly-By Waypoint — A waypoint which requires turn anticipation to allow tangential interception of
the next segment of a route or procedure, or
Flyover Waypoint — A waypoint at which a turn is initiated in order to join the next segment of a
route or procedure.

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

DEFINITIONS

954

INTERNATIONAL CIVIL AVIATION ORGANIZATION -- DEFINITIONS

Air Traffic Control

International Civil Aviation

Organization - Flight Procedures

Extracted from ICAO Document 8168, Volume I - Sixth Edition - Procedures for Air Naviga-
tion Services - AIRCRAFT OPERATIONS, Flight Procedures and from ICAO Document
8168, Volume III - First Edition - Procedures for Air Navigation Services - AIRCRAFT OPER-
ATIONS, Aircraft Operating Procedures, herein known as PANS-OPS.

GENERAL

1.1  This section describes operational procedures and outlines the parameters on which the cri-
teria of ICAO Document 8168, Volume II - Construction of Visual and Instrument Flight Proce-
dures, are based, so as to illustrate the need for pilots to adhere strictly to the published proce-
dures.
1.1.1  With the exception of this introductory material, paragraphs have been extracted in whole
or in part from PANS-OPS. The PANS-OPS paragraph numbers are used beginning with Part I.

STATE PAGES - RULES AND PROCEDURES

1.2.1  On RULES AND PROCEDURES pages, any differences to the latest PANS-OPS are
explained under the subtitle “Flight Procedures”.

1

1.2

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

FLIGHT PROCEDURES

956

FLIGHT PROCEDURES - (DOC 8168) AIR TRAFFIC CONTROL

Extracted from ICAO Document 8168, Volume I - Sixth Edition - Procedures for Air Naviga-
tion Services - AIRCRAFT OPERATIONS, Flight Procedures, herein known as PANS-OPS.

GENERAL REQUIREMENTS

GENERAL

1.1.1  Procedures contained in PANS-OPS assume that all engines are operating. Development
of contingency procedures is the responsibility of the operator.
1.1.2  Procedures depict tracks or bearings. The pilot should attempt to maintain the track or
bearing by applying corrections to heading for known wind.
1.1.3  All examples of calculations in this document are based on an altitude of 600 m (2000 ft)
above mean sea level (MSL) and a temperature of international standard atmosphere (ISA)
+15°C unless otherwise stated.
NOTE: Detailed specifications for instrument approach procedure construction, primarily for the
use of procedures specialists, are contained in PANS-OPS, Volume II.

OBSTACLE CLEARANCE

Obstacle clearance is a primary safety consideration in the development of instrument flight pro-
cedures. The criteria used and the detailed method of calculation are covered in PANS-OPS,
Volume II. However, from the operational point of view it is stressed that the obstacle clearance
applied in the development of each instrument procedure is considered to be the minimum
required for an acceptable level of safety in operations.

AREAS

1.3.1  Where track guidance is provided in the design of a procedure, each segment comprises a
specified volume of airspace, the vertical cross-section of which is an area located symmetrically
about the centre line of each segment. The vertical cross-section of each segment is divided into
primary and secondary areas. Full obstacle clearances are applied over the primary areas reduc-
ing to zero at the outer edges of the secondary areas (see Figure II-1-1-1).
1.3.2  On straight segments, the width of the primary area at any given point is equal to one-half
of the total width. The width of each secondary area is equal to one-quarter of the total width.
1.3.4  The minimum obstacle clearance (MOC) is provided for the whole width of the primary
area. In the secondary area, MOC is provided at the inner edges reducing to zero at the outer
edges.
NOTE: Areas for RNP AR Procedures are described in the Required Navigation Performance
Authorization Required (RNP AR) Procedure Design Manual (Doc 9905).

USE OF FLIGHT MANAGEMENT SYSTEM (FMS)/AREA NAVIGATION

(RNAV) EQUIPMENT IN CONVENTIONAL PROCEDURES

1.4.1  Where FMS/RNAV equipment is available, it may be used to fly conventional procedures
provided:

1

1.1

1.2

1.3

1.4

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

FLIGHT PROCEDURES

957

FLIGHT PROCEDURES - (DOC 8168) - GENERAL REQUIREMENTS

a. the procedure is monitored using the basic display normally associated with that procedure;

and

b. the tolerances for flight using raw data on the basic display are complied with.

1.4.2  Lead radials are for use by non-RNAV-equipped aircraft and are not intended to restrict
the use of turn anticipation by the FMS.

TURNING POINTS

The turning point (TP) is specified in one of two ways:

a. at a designated facility or fix - the turn is made upon arrival overhead a facility or fix; or
b. at a designated altitude - the turn is made upon reaching the designated altitude unless an

additional fix or distance is specified to limit early turns (departures and missed approach
only); or

c. at a designated waypoint - turns in performance-based navigation (PBN) procedures may be

either fly-by, fly-over or constant radius arc to a fix (RF). See Figures II-1-1-2, II-1-1-3 and
II-1-1-4.

PROTECTION AREA FOR TURNS

Speed is a controlling factor in determining the aircraft track during the turn. The outer boundary
of the turning area is based on the highest speed of the category for which the procedure is
authorized. The inner boundary caters for the slowest aircraft.
NOTE: For more information about the construction of protected areas for turns, see Attachment
A - Procedure Design Principles.

COLD TEMPERATURE CORRECTION

1.7.1  Temperatures lower than those of the standard atmosphere result in the actual altitude of
an aircraft being lower than that indicated by the barometric altimeter. As a consequence, the
MOC actually achieved could be lower than the prescribed MOC. In order to prevent this, the pilot
shall correct for low temperatures. The pilot is responsible for any necessary cold temperature
corrections to all published minimum altitudes/heights in both conventional and PBN procedures.
This includes:

a. the altitudes/heights for the initial and intermediate segment(s);
b. the decision altitude/height (DA/H) or minimum descent altitude/height (MDA/H); and

c. subsequent missed approach altitudes/heights.

1.7.2  The final approach path vertical path angle (VPA) on a 3D approach operation which is
based on barometric vertical navigation (baro-VNAV) criteria is safeguarded against the effects of
low temperature by the design of the procedure. This will ensure that the effective VPA at the min-
imum temperature published on the chart will not be less than 2.5° and has been obstacle
assessed. By applying the cold temperature correction to this procedure type the nominal VPA
will actually be flown. This can be achieved by manual application of the correction by the pilot, or

1.5

1.6

1.7

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

FLIGHT PROCEDURES

958

FLIGHT PROCEDURES - (DOC 8168) - GENERAL REQUIREMENTS

in some cases where certified systems are used, through automatic application of the correction
by an FMS.
NOTE: For more information on the use of automated systems for temperature compensation,
see the Performance-based Navigation (PBN) Manual (Doc 9613).

Figure II-1-1-1. Relationship of minimum obstacle clearances in primary and secondary

areas in cross-section

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

FLIGHT PROCEDURES

959

FLIGHT PROCEDURES - (DOC 8168) - GENERAL REQUIREMENTS

Figure II-1-1-2. Fly by waypoint (WP1)

INTERNATIONAL CIVIL AVIATION ORGANIZATION -

FLIGHT PROCEDURES

960

FLIGHT PROCEDURES - (DOC 8168) - GENERAL REQUIREMENTS