Aviation abbreviations

In aviation, abbreviations are not a style but a working tool. Every row gives the expansion the abbreviation is derived from and what it means – radio work and documents use both.

Applicability: mixed – stated per entry in the "Source" column
Rulemaking authority: The canonical abbreviation catalogue of the NorthTrack main app; references per entry
Reviewed by NorthTrack on: 2026-09-13

Where this list comes from
This table is generated from the canonical abbreviation catalogue of the NorthTrack main app. The website and the app read the same source, so the two cannot drift apart. Terms created by users themselves are never published.

A source reference is not a statement of applicability
The "Source" column names where the term is defined or explained – not which rules apply to an actual flight. A few entries cite US glossaries, because that is where the term is clearly defined. For flights in Germany and in the EU, European and national rules apply, not the reference cited.

Weather and altimetry

AIRMET
Expansion: Airmen's Meteorological Information · Meaning: Weather advisory for specified phenomena affecting lower-level operations; product criteria differ by jurisdiction. · Source: FAA AIM Appendix 3 · AIRMET
ASOS
Expansion: Automated Surface Observing System · Meaning: United States automated surface-weather observation system; the actual report may include human augmentation. · Source: FAA AIM Appendix 3 · ASOS; AIM weather-observation section
AWOS
Expansion: Automated Weather Observing System · Meaning: United States automated aerodrome weather-observation system; capabilities vary by installation. · Source: FAA AIM Appendix 3 · AWOS
BECMG
Expansion: Becoming · Meaning: Forecast or trend change group describing a transition to different conditions. · Source: DWD METAR/TAF guide · BECMG
BKN
Expansion: Broken cloud cover · Meaning: Cloud layer covering five to seven oktas; the reported height is not necessarily the same as cloud top. · Source: DWD METAR/TAF guide · cloud amount
BR
Expansion: Mist · Meaning: Present-weather code for mist; visibility criteria differ from FG and may vary by reporting regime. · Source: FAA AIP GEN 3.5 · obscuration codes
CAVOK
Expansion: Cloud and Visibility OK · Meaning: METAR/TAF code used only when the specified visibility, cloud and significant-weather criteria are all met. · Source: DWD METAR/TAF guide · CAVOK criteria
CB
Expansion: Cumulonimbus · Meaning: Deep convective cloud with potentially severe hazards, including turbulence, icing and lightning. · Source: DWD METAR/TAF guide · significant cloud types
DA
Expansion: Density altitude · Meaning: Here: density altitude, pressure altitude corrected for nonstandard temperature. DA can also mean decision altitude in an instrument-approach context. · Source: FAA PHAK · Aircraft Performance
DZ
Expansion: Drizzle · Meaning: Present-weather code for drizzle; intensity may be prefixed by minus or plus. · Source: FAA AIP GEN 3.5 · present-weather codes
FEW
Expansion: Few clouds · Meaning: Cloud layer covering one or two oktas. · Source: DWD METAR/TAF guide · cloud amount
FG
Expansion: Fog · Meaning: Present-weather code for fog; check reported prevailing visibility and local minima. · Source: FAA AIP GEN 3.5 · obscuration codes
FU
Expansion: Smoke · Meaning: METAR/TAF obscuration code for smoke; assess visibility and the actual report. · Source: NWS Surface Weather Observations · present weather table
FZ
Expansion: Freezing · Meaning: METAR/TAF descriptor for freezing phenomena when combined with an applicable weather code, such as FZRA. · Source: NWS Surface Weather Observations · present weather table
GR
Expansion: Hail · Meaning: METAR/TAF precipitation code for hail. Do not confuse it with GS, which has a separate weather-code meaning from groundspeed. · Source: NWS Surface Weather Observations · present weather table
HZ
Expansion: Haze · Meaning: METAR/TAF obscuration code for haze; it is not a cloud-layer code. · Source: NWS Surface Weather Observations · present weather table
IFR
Expansion: Instrument Flight Rules · Meaning: Rules for instrument-flight operations; equipment, qualification and clearance requirements depend on context. · Source: SERA · IFR flight
IMC
Expansion: Instrument Meteorological Conditions · Meaning: Meteorological conditions below the applicable VMC minima. · Source: SERA · instrument meteorological conditions
ISA
Expansion: International Standard Atmosphere · Meaning: Reference atmosphere used for performance and altimetry comparisons; actual conditions may differ. · Source: FAA PHAK · Atmosphere / Aircraft Performance
METAR
Expansion: Aerodrome routine meteorological report · Meaning: A routine coded aerodrome weather observation; check observation time and amendments. · Source: FAA Pilot/Controller Glossary · METAR
NOSIG
Expansion: No significant change · Meaning: METAR TREND code indicating no significant change expected in the trend period; not a general all-clear. · Source: DWD METAR/TAF guide · TREND NOSIG
OVC
Expansion: Overcast · Meaning: Cloud layer covering the sky completely at the reported layer. · Source: DWD METAR/TAF guide · cloud amount
PA
Expansion: Pressure altitude · Meaning: Altitude referenced to the standard-pressure setting; a step in density-altitude calculations. · Source: FAA PHAK · Altimetry / Aircraft Performance
PIREP
Expansion: Pilot Weather Report · Meaning: United States term for an in-flight pilot report of observed weather conditions. · Source: FAA AIM Appendix 3 · PIREP
PROB30
Expansion: Probability 30 percent · Meaning: TAF probability group indicating a 30 percent chance of the stated conditions; regional TAF rules differ. · Source: DWD METAR/TAF guide · PROB group
PROB40
Expansion: Probability 40 percent · Meaning: TAF probability group indicating a 40 percent chance of the stated conditions; regional TAF rules differ. · Source: DWD METAR/TAF guide · PROB group
RA
Expansion: Rain · Meaning: Present-weather code for rain, including combinations such as TSRA. · Source: FAA AIP GEN 3.5 · present-weather codes
RVR
Expansion: Runway Visual Range · Meaning: Reported range along a runway from the pilot viewpoint; distinct from general visibility. · Source: EASA EGAST VFR Radiotelephony Guide · RVR
SCT
Expansion: Scattered cloud cover · Meaning: Cloud layer covering three or four oktas. · Source: DWD METAR/TAF guide · cloud amount
SH
Expansion: Showers · Meaning: METAR/TAF descriptor combined with a precipitation code, for example SHRA for rain showers. · Source: NWS Surface Weather Observations · present weather table
SIGMET
Expansion: Significant Meteorological Information · Meaning: Advisory information on specified hazardous en-route weather phenomena; assess area, validity and source. · Source: EASA abbreviations · SIGMET; operational criteria in current meteorological rules
SN
Expansion: Snow · Meaning: Present-weather code for snow; check intensity, visibility and runway condition separately. · Source: FAA AIP GEN 3.5 · present-weather codes
SNOWTAM
Expansion: Snow notice to airmen · Meaning: Special-format aeronautical notice for runway surface conditions under the Global Reporting Format; check current validity. · Source: ICAO Guidance on the Issuance of SNOWTAM · GRF
SPECI
Expansion: Special aerodrome meteorological report · Meaning: An unscheduled aerodrome weather observation issued when specified conditions change; it is not a forecast. · Source: DWD METAR/TAF guide · report types
TAF
Expansion: Terminal Aerodrome Forecast · Meaning: A coded aerodrome forecast with a stated validity period; not an observation. · Source: FAA Pilot/Controller Glossary · TAF
TCU
Expansion: Towering Cumulus · Meaning: Strongly developing cumulus cloud indicating significant convection; assess its evolution. · Source: DWD METAR/TAF guide · significant cloud types
TEMPO
Expansion: Temporary · Meaning: Forecast or trend change group for temporary fluctuations within its stated period; read the applicable product rules. · Source: DWD METAR/TAF guide · TEMPO
TS
Expansion: Thunderstorm · Meaning: Present-weather code for thunderstorm; TS can appear alone or with precipitation codes such as TSRA. · Source: FAA AIP GEN 3.5 · present-weather codes
VFR
Expansion: Visual Flight Rules · Meaning: Rules for flights conducted under visual-flight provisions; weather and airspace requirements still apply. · Source: SERA · VFR flight
VMC
Expansion: Visual Meteorological Conditions · Meaning: Meteorological conditions meeting the applicable visibility and cloud-clearance minima; not identical to permission for VFR. · Source: SERA · visual meteorological conditions
VOLMET
Expansion: Meteorological information for aircraft in flight · Meaning: Broadcast of selected aerodrome weather information for aircraft in flight; availability varies by region. · Source: EASA abbreviations · VOLMET
VRB
Expansion: Variable wind direction · Meaning: In a METAR/TAF wind group, direction is variable rather than a single stated bearing; read the associated speed and full report. · Source: FAA AIP GEN 3.5 · METAR/TAF wind groups
VV
Expansion: Vertical Visibility · Meaning: Reported vertical visibility when the sky is obscured and a normal cloud base cannot be observed. · Source: DWD METAR/TAF guide · vertical visibility
WS
Expansion: Wind shear · Meaning: In a TAF wind-shear group, WS denotes forecast non-convective low-level wind shear; read the complete group for height, direction and speed. · Source: FAA AIP GEN 3.5 · TAF wind-shear group

Navigation

ADF
Expansion: Automatic Direction Finder · Meaning: Receiver that displays direction to a suitable NDB; indications require aircraft-heading context. · Source: FAA AIM Appendix 3 · ADF
BRG
Expansion: Bearing · Meaning: Direction of a line to or from a reference point; establish whether the display uses true or magnetic north. · Source: EASA training glossary · BRG / bearing
CDI
Expansion: Course Deviation Indicator · Meaning: Instrument indication of lateral displacement from a selected VOR or navigation course; read its scale in context. · Source: FAA AIM Appendix 3 · CDI
CH
Expansion: Compass Heading · Meaning: Heading read or flown on the magnetic compass after variation and compass deviation are considered. · Source: FAA PHAK · Navigation, compass heading
DEV
Expansion: Compass Deviation · Meaning: Aircraft-specific compass error relative to magnetic north; consult the deviation card. · Source: FAA PHAK · Navigation, deviation
DME
Expansion: Distance Measuring Equipment · Meaning: A radio aid displaying slant-range distance to the ground station, not necessarily horizontal distance. · Source: FAA Pilot/Controller Glossary · DME
GNSS
Expansion: Global Navigation Satellite System · Meaning: Umbrella term for satellite navigation systems and augmentation; check installed equipment approval and integrity. · Source: FAA AIM Appendix 3 · GNSS
GPS
Expansion: Global Positioning System · Meaning: A specific satellite positioning system; GPS capability alone does not establish the aircrafts approved navigation capability. · Source: FAA AIM Appendix 3 · GPS
GS
Expansion: Groundspeed · Meaning: In navigation, speed of the aircraft relative to the ground. In a METAR weather group, GS instead means small hail or snow pellets; read by context. · Source: FAA PHAK · Navigation; NWS Surface Weather Observations · METAR GS
HDG
Expansion: Heading · Meaning: Direction the aircraft points, relative to a stated north reference; unlike track, it need not equal the path over ground. · Source: EASA Aircrew learning objectives · heading (HDG) / track (TRK)
ILS
Expansion: Instrument Landing System · Meaning: A ground-based precision approach guidance system; use the published procedure and equipment requirements. · Source: FAA Pilot/Controller Glossary · ILS
MH
Expansion: Magnetic Heading · Meaning: True heading adjusted for magnetic variation; still before compass deviation. · Source: FAA PHAK · Navigation, variation/deviation
NDB
Expansion: Non-Directional Beacon · Meaning: Radio beacon used with an ADF receiver; verify current service and published limitations. · Source: FAA Pilot/Controller Glossary · NDB
OBS
Expansion: Omni-Bearing Selector · Meaning: Control for selecting a VOR course; interpret together with CDI and TO/FROM indication. · Source: FAA AIM Appendix 3 · OBS
QDM
Expansion: Magnetic bearing to the station · Meaning: Magnetic direction toward a station; in NorthTrack exercises it is the TO counterpart of QDR. · Source: EASA EGAST VFR Radiotelephony Guide · Q codes
QDR
Expansion: Magnetic bearing from the station · Meaning: Magnetic direction outward from a station; reciprocal of QDM. · Source: EASA EGAST VFR Radiotelephony Guide · Q codes
QTE
Expansion: True bearing from the station · Meaning: True bearing of the aircraft from a direction-finding station. In the NorthTrack no-wind exercise it is reciprocal to QUJ; service availability is local. · Source: ENAIRE Spanish AIP GEN 1.7 · VDF/QTE
QUJ
Expansion: True no-wind heading to the station · Meaning: Direction to steer toward a direction-finding station assuming no wind. NorthTrack uses the equivalent true TO bearing in its geometric exercise; actual wind correction is separate. · Source: ENAIRE Spanish AIP GEN 1.7 · VDF/QUJ
RAIM
Expansion: Receiver Autonomous Integrity Monitoring · Meaning: GNSS receiver integrity-monitoring concept; availability alone does not establish approval for a particular procedure. · Source: FAA AIM Appendix 3 · RAIM
RNAV
Expansion: Area Navigation · Meaning: Navigation allowing flight on a desired path within the coverage or capability of the installed system. · Source: FAA AIM Appendix 3 · RNAV
RNP
Expansion: Required Navigation Performance · Meaning: Navigation-performance specification used in performance-based navigation; the published route/procedure and aircraft approval govern use. · Source: FAA AIM Appendix 3 · RNP
SBAS
Expansion: Satellite-Based Augmentation System · Meaning: System augmenting satellite navigation; service area, receiver capability and procedure approval must be checked separately. · Source: FAA AIM Appendix 3 · SBAS
TC
Expansion: True Course · Meaning: Direction of the desired route relative to true north, before wind correction. · Source: FAA PHAK · Navigation, true course/heading
TH
Expansion: True Heading · Meaning: Aircraft nose direction relative to true north after wind correction. · Source: FAA PHAK · Navigation, true course/heading
TO/FROM
Expansion: TO/FROM indication · Meaning: VOR indication of whether the selected course leads toward or away from the station; not an aircraft-heading cue by itself. · Source: FAA Pilot/Controller Glossary · VOR course indication
TRK
Expansion: Track · Meaning: Direction of the actual path over the ground, distinct from aircraft heading when there is drift. · Source: EASA Aircrew learning objectives · heading (HDG) / track (TRK)
VAR
Expansion: Magnetic Variation · Meaning: Angle between true north and magnetic north at a location; use current charted data. · Source: FAA PHAK · Navigation, variation
VDF
Expansion: VHF Direction Finding · Meaning: Direction-finding service using an aircraft radio transmission; reported bearing type matters. · Source: EASA EGAST VFR Radiotelephony Guide · VDF
VOR
Expansion: VHF Omnidirectional Range · Meaning: A radio navigation aid providing azimuth/radial information. · Source: FAA Pilot/Controller Glossary · VOR
WCA
Expansion: Wind Correction Angle · Meaning: Heading correction relative to the desired track for an estimated wind. · Source: FAA PHAK · Navigation / Wind triangle

Operations and airspace

AGL
Expansion: Above Ground Level · Meaning: A vertical reference relative to the local ground surface, not mean sea level. · Source: FAA Pilot/Controller Glossary · AGL
AIP
Expansion: Aeronautical Information Publication · Meaning: State publication of aeronautical information of lasting character; use current amendments and supplements. · Source: EASA EGAST VFR Radiotelephony Guide · AIP
ALTN
Expansion: Alternate Aerodrome · Meaning: Flight-plan field for a destination alternate; this does not itself establish alternate-fuel or weather compliance. · Source: EUROCONTROL IFPS Flight Plan Entry · ALTN AERODROME
AMSL
Expansion: Above Mean Sea Level · Meaning: A vertical reference relative to mean sea level; distinct from AGL. · Source: EASA abbreviations · AMSL
ASDA
Expansion: Accelerate-Stop Distance Available · Meaning: Declared take-off run available plus any provided stopway; use the published direction-specific value. · Source: Regulation (EU) 139/2014 · aerodrome definitions / declared distances
BIR
Expansion: Basic Instrument Rating · Meaning: EASA basic instrument rating with specific privileges and minima; not identical to a full IR. · Source: EASA Part-FCL FCL.835 · BIR
CPL
Expansion: Commercial Pilot Licence · Meaning: Pilot licence for commercial privileges subject to aircraft category, ratings and applicable rules. · Source: EASA Part-FCL · CPL
CTA
Expansion: Control Area · Meaning: Controlled airspace extending upward from a specified limit above the surface. · Source: SERA · control area
CTR
Expansion: Control Zone · Meaning: Controlled airspace around an aerodrome; consult the current chart and applicable entry rules. · Source: SERA · controlled airspace / control zone
DOF
Expansion: Date of Flight · Meaning: Date-of-flight indicator in flight-plan other information; follow the applicable filing format. · Source: EUROCONTROL IFPS Users Manual v2.3 · Item 18 DOF/
EET
Expansion: Estimated Elapsed Time · Meaning: Estimated elapsed time in a flight-plan field; distinguish it from ETA, a clock time of arrival. · Source: EUROCONTROL IFPS Flight Plan Entry · total EET
EOBT
Expansion: Estimated Off-Block Time · Meaning: Flight-plan timing field for the estimated time the aircraft leaves the parking position; not the take-off time. · Source: EUROCONTROL IFPS Flight Plan Entry · EOBT
ETA
Expansion: Estimated Time of Arrival · Meaning: Predicted arrival time; specify the reference point and UTC/local basis. · Source: FAA AIM Appendix 3 · ETA
ETD
Expansion: Estimated Time of Departure · Meaning: Predicted departure time, not necessarily actual off-block or take-off time. · Source: FAA AIM Appendix 3 · ETD
ETE
Expansion: Estimated Time En Route · Meaning: Estimated elapsed time along a route or leg; not a clock time. · Source: FAA AIM Appendix 3 · ETE
FIR
Expansion: Flight Information Region · Meaning: Airspace region within which flight information and alerting services are provided. · Source: SERA · flight information region
FL
Expansion: Flight Level · Meaning: Pressure-altitude level referenced to the standard altimeter setting, expressed in hundreds of feet. · Source: SERA · flight level / transition provisions
IR
Expansion: Instrument Rating · Meaning: Rating for instrument-flight privileges within the scope of the licence and aircraft qualification. · Source: EASA Part-FCL · IR
LAPL
Expansion: Light Aircraft Pilot Licence · Meaning: EASA pilot licence with category-specific privileges and limitations; consult current Part-FCL. · Source: EASA Part-FCL · LAPL
LDA
Expansion: Landing Distance Available · Meaning: Declared runway length available and suitable for the landing ground run; it may differ by runway direction. · Source: Regulation (EU) 139/2014 · aerodrome definitions / declared distances
MEL
Expansion: Minimum Equipment List · Meaning: Approved list permitting specified dispatch with inoperative equipment under stated conditions; not universal for every GA aircraft. · Source: FAA Pilot/Controller Glossary · MEL
MSL
Expansion: Mean Sea Level · Meaning: A vertical reference datum. An MSL altitude is measured from mean sea level, not from terrain directly beneath the aircraft. · Source: FAA Pilot/Controller Glossary · MSL altitude
NOTAM
Expansion: Notice to Airmen · Meaning: Time-critical aeronautical information about facilities, procedures or hazards; check official current briefing. · Source: FAA Pilot/Controller Glossary · NOTAM
PAPI
Expansion: Precision Approach Path Indicator · Meaning: A visual approach-slope indicator; follow published local guidance and limitations. · Source: FAA Pilot/Controller Glossary · PAPI
PIC
Expansion: Pilot in Command · Meaning: Pilot designated as responsible for operation and safety of the flight. · Source: EASA Part-FCL · pilot-in-command
POB
Expansion: Persons on Board · Meaning: Number of people aboard, including crew and passengers; confirm the count for the actual flight. · Source: FAA AIM Appendix 3 · POB
PPL(A)
Expansion: Private Pilot Licence (Aeroplanes) · Meaning: EASA private-pilot licence for aeroplanes; ratings and medical requirements are separate. · Source: EASA Part-FCL · PPL(A)
PPR
Expansion: Prior Permission Required · Meaning: Published requirement to obtain permission before using a facility or aerodrome; check who grants it. · Source: EASA Aerodromes FAQ · PPR
QFE
Expansion: QFE pressure setting · Meaning: A setting that indicates zero at a specified aerodrome reference point; availability and usage depend on local procedures. · Source: FAA Pilot/Controller Glossary · QFE; local applicability varies
QNE
Expansion: Standard altimeter pressure setting · Meaning: The standard altimeter setting (1013.2 hPa / 29.92 inHg); transition procedures depend on the applicable region. · Source: FAA Pilot/Controller Glossary · QNE
QNH
Expansion: QNH altimeter setting · Meaning: An altimeter setting used to indicate altitude above mean sea level at the reference conditions; use the current issued value. · Source: SERA · altimeter-setting/ATIS provisions
TA
Expansion: Transition Altitude · Meaning: Published altitude at or below which altitude is referenced to the local altimeter setting; not the same as transition level. · Source: SERA · transition altitude/level
TL
Expansion: Transition Level · Meaning: Lowest usable flight level above the transition altitude under applicable procedures; do not infer it solely from TA. · Source: SERA · transition altitude/level
TMA
Expansion: Terminal Control Area · Meaning: Controlled airspace associated with one or more major aerodromes; consult current chart limits. · Source: SERA · terminal control area
TMZ
Expansion: Transponder Mandatory Zone · Meaning: A designated zone with specified transponder requirements; inspect current published details. · Source: SERA.6005
TODA
Expansion: Take-Off Distance Available · Meaning: Declared take-off run available plus any provided clearway; not automatically the ground-roll distance. · Source: Regulation (EU) 139/2014 · aerodrome definitions / declared distances
TORA
Expansion: Take-Off Run Available · Meaning: Declared runway length available and suitable for an aeroplane ground run during take-off; use the current aerodrome data. · Source: Regulation (EU) 139/2014 · aerodrome definitions / declared distances
UIR
Expansion: Upper Flight Information Region · Meaning: Upper-level flight information region where published; not a separate clearance by itself. · Source: EASA abbreviations · UIR
UTC
Expansion: Coordinated Universal Time · Meaning: Common aviation time reference; retain the date when calculations cross midnight. · Source: FAA AIM Appendix 3 · UTC

Radiotelephony

ADS-B
Expansion: Automatic Dependent Surveillance–Broadcast · Meaning: Surveillance technology broadcasting aircraft-derived position and other data; equipment mandates vary by region. · Source: FAA AIM Appendix 3 · ADS-B
AFIS
Expansion: Aerodrome Flight Information Service · Meaning: Here the European aerodrome service, distinct from an ATC clearance. In FAA usage AFIS may mean Automatic Flight Information Service. · Source: EASA EGAST VFR Radiotelephony Guide · AFIS
ATC
Expansion: Air Traffic Control · Meaning: Service that controls applicable aircraft movements and issues clearances within its responsibility. · Source: SERA · air traffic control service
ATIS
Expansion: Automatic Terminal Information Service · Meaning: A regularly updated terminal information broadcast or data-link service; verify the current information and local procedures. · Source: SERA.9010 · ATIS
AZF
Expansion: General radiotelephony certificate · Meaning: German certificate for radiotelephony in German and English under VFR and IFR. · Source: Bundesnetzagentur Flugfunk FAQ · Zeugnisarten
AZF E
Expansion: General radiotelephony certificate E · Meaning: German certificate for radiotelephony in English under VFR and IFR. · Source: Bundesnetzagentur Flugfunk FAQ · Zeugnisarten
BZF
Expansion: German radiotelephony certificate (restricted) · Meaning: German aviation radiotelephony qualification family; scope differs by certificate type. · Source: Bundesnetzagentur · Flugfunkzeugnisse
BZF E
Expansion: Restricted radiotelephony certificate E · Meaning: German certificate for radiotelephony in English under VFR. · Source: Bundesnetzagentur Flugfunk FAQ · Zeugnisarten
BZF I
Expansion: Restricted radiotelephony certificate I · Meaning: German certificate for radiotelephony in German and English under VFR; verify current privileges. · Source: Bundesnetzagentur Flugfunk FAQ · Zeugnisarten
BZF II
Expansion: Restricted radiotelephony certificate II · Meaning: German certificate for radiotelephony in German within Germany under VFR. · Source: Bundesnetzagentur Flugfunk FAQ · Zeugnisarten
CTAF
Expansion: Common Traffic Advisory Frequency · Meaning: United States-designated frequency for traffic advisories at an airport; it is not automatically a tower or clearance frequency. · Source: FAA AIM Appendix 3 · CTAF; AIM 4-1 airport advisory practices
FIS
Expansion: Flight Information Service · Meaning: Information useful for safe and efficient flight; receiving FIS does not itself constitute an ATC clearance. · Source: SERA · flight information service
PTT
Expansion: Press To Transmit · Meaning: Radio control that keys the transmitter while pressed; listen and verify the selected frequency before transmitting. · Source: EASA EGAST VFR Radiotelephony Guide · microphone technique
RMZ
Expansion: Radio Mandatory Zone · Meaning: A designated zone with specific radio-communication requirements; inspect current published details. · Source: SERA.6005
SSR
Expansion: Secondary Surveillance Radar · Meaning: Surveillance system using aircraft transponder replies; code and mode requirements depend on airspace and instructions. · Source: EASA EGAST VFR Radiotelephony Guide · SSR
UNICOM
Expansion: UNICOM aeronautical advisory station · Meaning: United States nongovernment air/ground station that may provide airport information; it does not issue ATC clearance merely by being UNICOM. · Source: FAA AIM 4-1 · Information Provided by Aeronautical Advisory Stations
XPDR
Expansion: Transponder · Meaning: Common panel abbreviation for the aircraft transponder; set assigned code/mode as instructed. · Source: Garmin AXIS Pilot Guide · XPDR equipment label

Aircraft

AFM
Expansion: Aircraft Flight Manual · Meaning: Approved aircraft flight manual containing limitations and operating data for the aircraft. · Source: FAA PHAK · Aircraft Documents
AHRS
Expansion: Attitude and Heading Reference System · Meaning: Solid-state attitude/heading reference for compatible avionics; exact sensors and failure indications are equipment-specific. · Source: EASA Aircrew Subject 022 · AHRS learning objectives
CAS
Expansion: Calibrated Airspeed · Meaning: Indicated airspeed corrected for instrument and position errors; it is not true airspeed. · Source: FAA PHAK · Flight Instruments
CG
Expansion: Center of Gravity · Meaning: Point at which aircraft mass may be treated as concentrated for balance calculations; stay within approved limits. · Source: FAA PHAK · Weight and Balance
EFB
Expansion: Electronic Flight Bag · Meaning: Electronic cockpit information device/application; suitability, currency and backup requirements depend on operation and equipment. · Source: FAA AC 91-78A · Use of Electronic Flight Bags
ELT
Expansion: Emergency Locator Transmitter · Meaning: Aircraft emergency beacon intended to aid search and rescue; registration and inspection requirements apply. · Source: FAA AIM Appendix 3 · ELT
IAS
Expansion: Indicated Airspeed · Meaning: Airspeed read from the indicator before instrument/position corrections. · Source: FAA PHAK · Flight Instruments
MLW
Expansion: Maximum Landing Weight · Meaning: Maximum permitted landing weight where specified by the aircraft documentation; not necessarily equal to MTOW. · Source: FAA PHAK · Weight and Balance
MTOM
Expansion: Maximum Take-Off Mass · Meaning: Certified maximum mass for take-off; EASA commonly uses mass terminology, and aircraft documents control actual limits. · Source: EASA Part-FCL · maximum take-off mass
MTOW
Expansion: Maximum Take-Off Weight · Meaning: Weight-language counterpart often seen in FAA or aircraft documents; check the particular aircraft limitation. · Source: FAA PHAK · Weight and Balance
OAT
Expansion: Outside Air Temperature · Meaning: Ambient air temperature outside the aircraft; use the aircraft-specific measurement and performance procedure. · Source: FAA AIM Appendix 3 · OAT
POH
Expansion: Pilots Operating Handbook · Meaning: Aircraft operating handbook; confirm applicability to the specific aircraft and approved limitations. · Source: FAA PHAK · Aircraft Documents
SEP
Expansion: Single-Engine Piston · Meaning: Aeroplane class-rating designation; privileges depend on the licence and current rating. · Source: EASA Part-FCL · SEP class rating
TAS
Expansion: True Airspeed · Meaning: Speed through the air mass, distinct from groundspeed. · Source: FAA PHAK · Flight Instruments / Navigation

NorthTrack learning terms – not official terminology

Please keep these apart
The abbreviations below belong to NorthTrack's own teaching model for the 1-in-60 navigation geometry. They are not official definitions and do not appear in this form in regulations or in the Aeronautical Information Publication. They are set out separately here so they are not mistaken for regulated terminology.

CA
Expansion: Closing Angle · Meaning in the NorthTrack learning model: In the NorthTrack 1:60 exercise, an approximate angle to regain the route over a chosen remaining distance.
CTS
Expansion: Correction To Steer · Meaning in the NorthTrack learning model: In the NorthTrack exercise, the signed combination of track-error correction and closing angle; confirm actual navigation independently.
CWC
Expansion: Crosswind Component · Meaning in the NorthTrack learning model: NorthTrack calculator shorthand for the wind component across a selected runway or track; the component is a standard concept, but CWC is an app label.
HWC
Expansion: Headwind Component · Meaning in the NorthTrack learning model: NorthTrack calculator shorthand for the wind component opposing motion along the selected track.
TE
Expansion: Track Error · Meaning in the NorthTrack learning model: In the NorthTrack 1:60 exercise, the angle inferred from cross-track displacement over distance flown.
TWC
Expansion: Tailwind Component · Meaning in the NorthTrack learning model: NorthTrack calculator shorthand for the wind component aiding motion along the selected track.

Where the remaining abbreviations are explained

Weather codes such as CAVOK, TEMPO, BECMG or SHRA: on the METAR and TAF pages.
Warnings: SIGMET and SNOWTAM.
Airspace: CTR, TMA, RMZ and TMZ.
Licence abbreviations such as LAPL, PPL, IR or BIR: in the Training and licensing section.

The full catalogue, with search and English explanations, is available in the NorthTrack app. Open the NorthTrack app

Official sources

NorthTrack General Aviation: The canonical abbreviation catalogue of the NorthTrack main app – Terminology reviewed 2026-09-13. Open source (retrieved 2026-09-13)