Appendix A A-1 APPENDIX A. ABBREVIATIONS AND DEFINITIONS A.1 Abbreviations.
Acronym Description 14 CFR Title 14 of the Code of Federal Regulations 4D Four Dimensional AC Advisory Circular ACARS Aircraft Communications Addressing and Reporting System ACAS Airborne Collision Avoidance System (same as TCAS) ACC Area Control Center ACID Aircraft Identification ADIZ Air Defense Identification Zone ADS Automatic Dependent Surveillance (in older documents published before ADS-B existed, “ADS” generally refers to ADS-C) ADS-B Automatic Dependent Surveillance-Broadcast ADS-C Automatic Dependent Surveillance-Contract AFI African-Indian Ocean Region (per ICAO) AIM Aeronautical Information Manual AIP Aeronautical Information Publication AMU Area of Magnetic Unreliability AMVER Automated Mutual-assistance Vessel Rescue ANP Actual Navigation Performance APR Automatic Positioning Reporting ARTCC Air Route Traffic Control Center ATA Actual Time of Arrival ATC Air Traffic Control ATM Air Traffic Management ATOP Advanced Technologies and Oceanic Procedures ATS Air Traffic Service ATSP Air Traffic Service Provider CAA Civil Aviation Authority CEP Central East Pacific
Appendix A A-2 Acronym Description CFP Computer Flight Plan CPDLC Controller-Pilot Data Link Communications CTA Control Area DME Distance Measuring Equipment DOS Department of State EDTO Extended Diversion Time Operations EFB Electronic Flight Bag ELOS Equivalent Level of Safety ETA Estimated Time of Arrival ETE Estimated Time En Route ETOPS Extended Operations ETP Equal Time Point EWINS Enhanced Weather Information System FAA Federal Aviation Administration FANS 1/A Future Air Navigation System 1/A (1=Boeing; A=Airbus) FDE Fault Detection and Exclusion FIR Flight Information Region FIS Flight Information Services FL Flight Level FLT ID Flight Identification FMC Flight Management Computer FMS Flight Management System FRMS Fatigue Risk Management System GA General Aviation GNE Gross Navigation Error GNSS Global Navigation Satellite System GOLD Global Operational Data Link Document GPS Global Positioning System H2S Hydrogen Sulfide HF High Frequency HLA High Level Airspace
Appendix A A-3 Acronym Description hPa Hectopascal IAP Instrument Approach Procedure IATA International Air Transport Association ICAO International Civil Aviation Organization IFBP In-Flight Broadcast Procedure IFR Instrument Flight Rules ILS Instrument Landing System IMC Instrument Meteorological Conditions inHg Inch of Mercury INS Inertial Navigation System IRS Inertial Reference System LHD Large Height Deviation LNAV Lateral Navigation LOA Letter of Authorization LRC Long Range Cruise LRCS Long-Range Communication System LRNS Long-Range Navigation System MEA Minimum En Route Altitude MEL Minimum Equipment List MHz Megahertz MMEL Master Minimum Equipment List Mode S Mode Select Secondary Radar With Data Link MSpecs Management Specifications NAS National Airspace System NAT North Atlantic NAT HLA North Atlantic High Level Airspace NATO North Atlantic Treaty Organization NAV Navigation NAVAID Navigational Aid NavSpec Navigation Specification
Appendix A A-4 Acronym Description NDA Northern Domestic Airspace NDB Nondirectional Beacon NM Nautical Miles NOAA National Oceanic and Atmospheric Administration NOPAC North Pacific NOTAM Notice to Airmen NWS National Weather Service OAPS Operations Approval Portal System, hosted in the Safety Assurance System (SAS) OCA Oceanic Control Area OESB Oceanic Errors Safety Bulletin OpSpecs Operations Specifications OPSS Operations Safety System, hosted in SAS OROCA Off-Route Obstruction Clearance Altitude OTS Organized Track System PANS Procedures for Air Navigation Services PANS-ATM Procedures for Air Navigation Services—Air Traffic Management (ICAO Doc 4444) PANS-MET Procedures for Air Navigation Services—Meteorology (ICAO Doc 10157) PANS-OPS Procedures for Air Navigation Services—Aircraft Operations (ICAO Doc 8168) PBC Performance-based Communication PBCS Performance-based Communication and Surveillance PBN Performance-based Navigation PI Principal Inspector PIC Pilot in Command PIREP Pilot Weather Report POI Principal Operations Inspector PPO Prior Permission Only QFE Atmospheric pressure at aerodrome elevation (or at runway threshold).
(With the runway threshold QFE set in the subscale, your altimeter will read zero on the runway threshold.)
Appendix A A-5 Acronym Description QNE Pressure Altitude (Flight Level), obtained with Standard Pressure
(29.92 inches of mercury (inHg) or 1013.2 hPa) set in the altimeter subscale.
QNH The pressure set on the subscale of the altimeter so that the instrument indicates its height above sea level.
RA Resolution Advisory RAIM Receiver Autonomous Integrity Monitoring RCP Required Communication Performance RD Rapid Decompression RNAV Area Navigation RNP Required Navigation Performance RSP Required Surveillance Performance RVSM Reduced Vertical Separation Minimum SAO Special Area(s) of Operation SAR Search and Rescue SARPs Standards and Recommended Practices (ICAO) SAS Safety Assurance System SATCOM Satellite Communications SATVOICE Satellite Voice SELCAL Selective Calling System SIGWX Significant Weather SLOP Strategic Lateral Offset Procedure SMS Safety Management System SO2 Sulfur Dioxide SOP Standard Operating Procedure SSR Secondary Surveillance Radar SSV Standard Service Volume SUA Special Use Airspace SUPPS Regional Supplementary Procedures (ICAO Doc 7030) SVGM Satellite Voice Guidance Material SWPC Space Weather Prediction Center TAF Terminal Aerodrome Forecast
Appendix A A-6 Acronym Description TAS True Airspeed TCAS Traffic Alert and Collision Avoidance System TIBA Traffic Information Broadcasts by Aircraft TMI Track Message Identifier TSO Technical Standard Order USGS United States Geological Survey UTC Coordinated Universal Time VAAC Volcanic Ash Advisory Center VFR Visual Flight Rules VHF Very High Frequency VMC Visual Meteorological Conditions VONA Volcano Observatory Notice for Aviation VOR Very High Frequency Omnidirectional Range WAT West Atlantic WebOPSS Web-based Operations Safety System, renamed to OPSS in 2025, now hosted in SAS WGS 84 World Geodetic System 1984 A.2 Definitions.
A.2.1 Advisory Airspace. Airspace of defined dimensions, or a designated route, within which air traffic advisory service is available.
A.2.2 Aeronautical Information Manual (AIM). A primary FAA publication whose purpose is to provide the aviation community with basic flight information and ATC procedures for use in the NAS of the United States. The AIM contains items of interest to pilots concerning health and medical facts, factors affecting flight safety, a pilot/controller glossary of terms used in the ATC system, and information on safety and accident and hazard reporting.
A.2.3 Aeronautical Information Publication (AIP) (ICAO). A publication issued by or with the authority of a State and containing aeronautical information of a lasting character essential to air navigation.
A.2.4 Aeronautical Telecommunication Station. An aeronautical station which forms part of a radio telephone network by providing air/ground communications and Flight Information Services (FIS) as an integral part of ATS. Aeronautical telecommunication stations are
Appendix A A-7 also known as international Flight Service Stations (FSS), Aeronautical Radio, or Aeradio Stations, depending on the State providing the service.
A.2.5 Airborne Collision Avoidance System (ACAS) (ICAO). An aircraft system based on 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.
A.2.6 Air Defense Identification Zone (ADIZ). Airspace over land or water, extending upward from the surface, within which the ready identification, location, and control of aircraft are required in the interest of national security.
A.2.7 Air Traffic Advisory Service (ICAO). A service provided within advisory airspace to ensure separation, insofar as practical, between aircraft that are operating on IFR flight plans.
A.2.8 Air Traffic Management (ATM) (ICAO). The dynamic, integrated management of air traffic and airspace including ATS, airspace management, and air traffic flow management—safely, economically, and efficiently—through the provision of facilities and seamless services in collaboration with all parties and involving airborne and ground-based functions.
A.2.9 Air Traffic Management (ATM) System (ICAO). A system that provides ATM through the collaborative integration of humans, information, technology, facilities, and services, supported by air and ground- and/or space-based communications, navigation, and surveillance.
A.2.10 Air Traffic Service (ATS) (ICAO). A generic term meaning variously FIS, alerting service, air traffic advisory service, ATC service, area control service, or approach control service.
A.2.11 Air Traffic Service (ATS) Surveillance System (ICAO). A generic term meaning variously ADS-B, Primary Surveillance Radar (PSR), SSR, or any comparable ground-based system that enables the identification of aircraft. 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.
A.2.12 Alerting Service (ICAO). A service provided to notify appropriate organizations regarding aircraft in need of SAR aid and to assist such organizations as required.
A.2.13 Area Control Center (ACC) (ICAO). A unit established to provide ATC service to controlled flights in CTAs under its jurisdiction. ACCs are the international equivalent of U.S. ARTCC.
A.2.14 Area of Magnetic Unreliability (AMU). For purposes of authorizations for certificated operators, the FAA designates the boundaries of the AMUs as follows:
Appendix A A-8 A.2.14.1 The Northern AMU is the area within 1,000 NM of the Magnetic North Pole but excludes Alaska and its territorial waters. In addition, Canadian Northern Domestic Airspace (NDA) is part of the Northern AMU, as well as the area north of 75° N latitude in the Nuuk (Greenland) flight information region (FIR).
A.2.14.2 The Southern AMU is the area within 1,000 NM of the Magnetic South Pole.
A.2.14.3 As aircraft move towards the Earth’s Magnetic North or South Pole, the horizontal field strength diminishes, and the ability of the compass to accurately sense Magnetic North is reduced. It is generally recognized that when the horizontal magnetic field strength falls below 6,000 nanotesla, the magnetic compass can no longer be considered reliable.
A.2.15 Area Navigation (RNAV) (ICAO). A method of navigation that permits aircraft operation on any desired flightpath within the coverage of ground- or space-based NAVAIDs or within the limits of the capability of self-contained systems or a combination of these.
A.2.16 Automatic Dependent Surveillance (ADS). A surveillance technique in which aircraft automatically provide, via a data link, data derived from onboard navigation and position fixing systems, including ACID, four-dimensional (4D) position, and additional data as appropriate.
A.2.16.1 Automatic Dependent Surveillance-Broadcast (ADS-B) (ICAO). A surveillance system 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.
A.2.16.2 Automatic Dependent Surveillance-Contract (ADS-C) (ICAO). 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. The abbreviated term “ADS contract” is commonly used to refer to ADS event contract, ADS demand contract, ADS periodic contract, or an emergency mode.
A.2.17 Conditional Clearances. A conditional clearance is an ATC clearance given to an aircraft with certain conditions or restrictions, such as changing an FL based on UTC or a specific geographic position. In oceanic and remote continental airspace, this usually involves a restriction to comply with the clearance “BY” or “AT” a certain geographic position or time.
A.2.18 Control Area (CTA) (ICAO). A controlled airspace extending upwards from a specified limit above the Earth.
A.2.19 Controller-Pilot Data Link Communications (CPDLC). A two-way digital communications system that conveys textual ATC messages between controllers and pilots using ground- or satellite-based radio relay stations.
Appendix A A-9 A.2.20 Cross-Checking. Cross-checking is the act of verification. Cross-checking involves matching a set of test data against a set of master data to detect deviations in sequence or content.
A.2.21 Current Flight Plan (ICAO). The flight plan, including changes, if any, brought about by subsequent clearances.
Note: In this AC, we use the term “currently effective route clearance” to refer to the route of flight information in what ICAO Annex 2, Rules of the Air, calls the “current flight plan.”
A.2.22 Dead Reckoning. The navigation of an airplane solely by means of computations based on airspeed, course, heading, wind direction, groundspeed, and elapsed time.
A.2.23 Electronic Flight Bag (EFB). An EFB is any device, or combination of devices, actively displaying EFB applications. EFB applications are categorized as Type A or B and can be hosted on either portable or installed components. A list of EFB applications can be found in the appendices of AC 120-76, Authorization for Use of Electronic Flight Bags.
A.2.24 Erosion of Longitudinal Separation. A loss of required horizontal separation between aircraft operating at the same altitude, on the same oceanic routing, usually due to improper speed control or failure to provide updated voice position reports to ATC in a timely manner on any changes in ETAs in excess of 2 minutes.
A.2.25 Extended Diversion Time Operations (EDTO) (ICAO). Any operation by an airplane with two or more turbine engines where the diversion time to an en route alternate aerodrome is greater than the threshold time established by the State of the Operator.
A.2.26 Extended Operations (ETOPS). An airplane flight operation, other than an all-cargo operation in an airplane with more than two engines, during which a portion of the flight is conducted beyond a time threshold identified in 14 CFR part 121 or 135, that is determined using an approved one-engine-inoperative cruise speed under standard atmospheric conditions in still air.
A.2.27 Fatigue Risk Management System (FRMS) (ICAO). FRMS is a data-driven means of continuously monitoring and managing fatigue-related safety risks, based upon scientific principles and knowledge as well as operational experience that aims to ensure relevant personnel are performing at adequate levels of alertness.
A.2.28 Flight Information Region (FIR) (ICAO). An airspace of defined dimensions within which FIS and alerting services are provided.
A.2.29 Flight Information Services (FIS) (ICAO). A service provided for the purpose of giving advice and information useful for the safe and efficient conduct of flights.
A.2.30 Flight Level (FL) (ICAO). A surface of constant atmospheric pressure which is related to a specific pressure datum (i.e., Standard Pressure—29.92 inHg or 1013.2 hPa) and is separated from other such surfaces by specific pressure intervals.
Appendix A A-10 A.2.31 Flight Operations Officer/Flight Dispatcher (ICAO). A person designated by the operator to engage in the control and supervision of flight operations, whether licensed or not, suitably qualified in accordance with ICAO Annex 1, Personnel Licensing, who supports, briefs, and/or assists the PIC in the safe conduct of the flight.
A.2.32 General Aviation (GA). That portion of civil aviation that does not include scheduled or unscheduled air carriers or commercial space operations.
A.2.33 Global Navigation Satellite System (GNSS) (ICAO). A worldwide position and time determination system that includes one or more satellite constellations, aircraft receivers, and system integrity monitoring, augmented as necessary to support the RNP for the intended operation.
A.2.34 Global Positioning System (GPS). GPS refers to the worldwide positioning, navigation, and timing determination capability available from the U.S. satellite constellation. The service provided by GPS for civil use is defined in the GPS Standard Positioning Service (SPS) Performance Standard. GPS is composed of space, control, and user elements.
A.2.35 Gross Navigation Error (GNE). A GNE is a lateral deviation of 10 NM or more from the aircraft’s cleared route.
A.2.36 High Frequency (HF) Communications. Radio frequencies between 3 and 30 MHz used for air/ground voice communications in overseas operations. HF communications (or, if supported, SATVOICE) capability is required for all IFR operations in controlled airspace when out of the range of VHF communications. If you are in doubt as to the VHF coverage along your intended route of flight, your aircraft should be equipped with HF communications (or SATVOICE, if supported).
A.2.37 High Seas. The seas beyond the 12 NM from the baseline of a shore. Airspace over the high seas is considered international airspace.
A.2.38 Instrument Meteorological Conditions (IMC) (ICAO). Meteorological conditions expressed in terms of visibility, distance from clouds, and ceiling, less than the minima specified for visual meteorological conditions (VMC).
A.2.39 International Civil Aviation Organization (ICAO). ICAO is a specialized agency of the United Nations whose objective is to develop the principles and techniques of international air navigation and to foster planning and development of international civil air transport.
A.2.40 Journey Logbook (ICAO). A record of the flight operation, which should be retained in order to maintain a continuous record of the last 6 months’ operations.
A.2.41 Large Height Deviations (LHD). A deviation from your cleared altitude by 300 feet or more.
A.2.42 Lateral Navigation (LNAV). A function of RNAV equipment that calculates, displays, and provides lateral guidance to a profile or path.
Appendix A A-11 A.2.43 Long-Range Navigation System (LRNS). An electronic navigation unit that is approved for use under IFR as a primary means of navigation. An LRNS must have at least one source of navigational input suitable for oceanic and remote continental navigation, such as an INS or a GPS receiver.
A.2.44 Mach Number Technique. Describes a control technique used by ATC whereby turbojet aircraft operating successively along suitable routes are cleared to maintain appropriate Mach numbers for a relevant portion of the en route phase of flight. The principal objective is to achieve improved utilization of the airspace and to ensure that separation between successive aircraft does not decrease below the established minima.
A.2.45 Master Document. A copy of the operational flight plan, labeled as “Master,” on which the currently effective route clearance is recorded, and which serves as the primary flightcrew reference for updating the progress of the flight. It should list sequentially the waypoints defining the route, the track and distance between each waypoint, and other information relevant to navigation along the cleared track.
A.2.46 Master Minimum Equipment List (MMEL) (ICAO). A list established for a particular aircraft type by the organization responsible for the type design with the approval of the State of Design containing items, one or more of which is permitted to be unserviceable at the commencement of a flight. The MMEL may be associated with special operating conditions, limitations, or procedures.
A.2.47 Minimum Equipment List (MEL) (ICAO). A list that provides for the operation of aircraft, subject to specified conditions, with particular equipment inoperative, prepared by an operator in conformity with, or more restrictive than, the MMEL established for the aircraft type.
A.2.48 Navigation Specification (NavSpec) (ICAO). A set of aircraft and flightcrew requirements needed to support PBN operations within a defined airspace. There are two kinds of NavSpecs:
A.2.48.1 Area Navigation (RNAV) Specification. A NavSpec based on RNAV that does not include the requirement for onboard performance monitoring and alerting, designated by the prefix RNAV (e.g., RNAV 5 or RNAV 1).
A.2.48.2 Required Navigation Performance (RNP) Specification. A NavSpec based on RNAV that includes the requirement for onboard performance monitoring and alerting, designated by the prefix RNP (e.g., RNP 4 or RNP Approach (APCH)).
A.2.49 North Atlantic High Level Airspace (NAT HLA). NAT HLA is that volume of airspace (as defined in ICAO Doc 7030) between FL 285 and FL 420 within the OCAs of Bodo Oceanic, Gander Oceanic, New York Oceanic East, Reykjavik, Santa Maria, and Shanwick, excluding the Shannon and Brest Ocean Transition Areas. Aircraft operators must obtain approval from their State of Registry to operate within NAT HLA.
Appendix A A-12 A.2.50 Notice to Airmen (NOTAM) Domestic/International. 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. NOTAMs are distributed via two methods: telecommunications (Class I Distribution) and other than telecommunications (Class II Distribution).
A.2.51 Oceanic Airspace. Airspace over the high seas. Generally, “oceanic” is included in the airspace designation (e.g., OCA), and direct controller-pilot VHF voice communications are not available. ATC is provided using at least some elements of procedural control in accordance with ICAO.
A.2.52 Oceanic Area Control Center (OACC). An ACC with responsibilities for providing ATS in oceanic airspace. Responsibility for the provisions of ATS is delegated by ICAO to various States based primarily upon geographic proximity and the availability of the required resources.
A.2.53 Offshore/Control Airspace Areas. Airspace designated in international airspace, extending outward from 12 NM from the coast of the United States to the CTA/FIR boundary, in accordance with the criteria in 14 CFR part 71, within which the United States applies domestic ATC procedures.
A.2.54 Performance-based Communication (PBC) (ICAO). Communication based on performance specifications applied to the provision of ATS. An RCP specification includes communication performance requirements that are allocated to system components in terms of communication to be provided and associated continuity, availability, integrity, safety, and functionality needed for the proposed operation in the context of a particular airspace concept.
A.2.55 Performance-based Navigation (PBN) (ICAO). RNAV based on performance requirements for aircraft operating along an ATS route, on an IAP, or in a designated airspace. Performance requirements are expressed in NavSpecs (RNAV specification, RNP specification) in terms of accuracy, integrity, continuity, availability, and functionality needed for the proposed operation in the context of a particular airspace concept.
A.2.56 Performance-based Surveillance (PBS) (ICAO). Surveillance based on performance specifications applied to the provision of ATS. 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.
A.2.57 Pilot in Command (PIC) (ICAO). The pilot designated by the operator, or in the case of GA, the owner, as being in command and charged with the safe conduct of a flight.
A.2.58 Procedural Control (ICAO). Term used to indicate that information derived from an ATS surveillance system is not required for the provision of ATC service.