A/A

Air-to-Air communication or radar mode between aircraft.

A/G

Air-to-Ground communication from aircraft to ground stations.

AAL

Above Aerodrome Level — height measured above the aerodrome elevation.

Abeam

Position 90° to either side of a reference point; used in circuits and navigation.

ABV

Above — used in meteorology and ATC information.

ACAS

Airborne Collision Avoidance System — includes systems such as TCAS.

ACFT

Aircraft.

ACK

Acknowledge — R/T phrase meaning “message received and understood”.

ACN

Aircraft Classification Number — expresses aircraft loading on pavements.

ADF

Automatic Direction Finder — NDB-based radio navigation equipment.

AD

Aerodrome.

ADIZ

Air Defence Identification Zone — airspace requiring identification before entry.

ADM

Aeronautical Decision Making — systematic approach to pilot decision processes.

ADR

Airspace Danger Area — zone where activities may be hazardous to aircraft.

ADS-B

Automatic Dependent Surveillance–Broadcast — aircraft broadcasts GPS-derived position.

AFIS

Aerodrome Flight Information Service — provides information, not clearances.

AFM

Aircraft Flight Manual — official performance and limitation data.

AGL

Above Ground Level — height measured from the surface directly below the aircraft.

AIP

Aeronautical Information Publication — official source of national aeronautical info.

AIS

Aeronautical Information Service — responsible for NOTAMs and aeronautical data.

Alphabet (ICAO Phonetic Alphabet)

The standardized spelling alphabet used in aviation radiotelephony to ensure clarity.

A – Alfa
B – Bravo
C – Charlie
D – Delta
E – Echo
F – Foxtrot
G – Golf
H – Hotel
I – India
J – Juliett
K – Kilo
L – Lima
M – Mike
N – November
O – Oscar
P – Papa
Q – Quebec
R – Romeo
S – Sierra
T – Tango
U – Uniform
V – Victor
W – Whiskey
X – X-ray
Y – Yankee
Z – Zulu

ALS

Approach Lighting System — runway lighting aiding approach alignment.

ALT

Altitude (AMSL) — height above mean sea level.

ALTN

Alternate Aerodrome — backup aerodrome for planning or diversion.

AMSL

Above Mean Sea Level — standard reference for altitude.

AP

Autopilot — automatic flight control system.

APP

Approach Control — ATC unit responsible for arrivals and departures.

APR

Approach Phase — segment of flight before landing.

ASDA

Accelerate-Stop Distance Available — runway length available for aborting takeoff.

ATC

Air Traffic Control — provides clearances and ensures traffic separation.

ATIS

Automatic Terminal Information Service — continuous broadcast of airport information.

ATM

Air Traffic Management — overall management of ATC, flow, and airspace.

ATS

Air Traffic Services — includes ATC, FIS, alerting services.

ATZ

Aerodrome Traffic Zone — controlled airspace surrounding an aerodrome.

AVTUR

Aviation Turbine Fuel — jet fuel such as Jet A / Jet A-1.

BAL

Basic Aerodrome Lighting — minimal lighting system used at small aerodromes.

BC (in METAR)

Patches — used in weather reports to indicate patchy fog or clouds (e.g. BCFG).

BCG

Basic Control Geometry — relates to simple aerodynamics and control surface geometry.

BCN

Beacon — visual or radio navigation beacon at an aerodrome or navaid site.

BECMG (METAR/TAF)

Becoming — gradual weather change expected within the forecast period.

BEM (Basic Empty Mass)

The weight of the aircraft including all basic equipment plus a declared quantity of unusable fuel and oil.

BL (in METAR)

Blowing — used for blowing snow, blowing sand, or blowing dust when raised by wind.

BN

Beacon — sometimes abbreviated in older aviation documentation; same as BCN.

BR

Mist — visibility between 1,000 m and 5,000 m (METAR phenomenon).

BRG

Bearing — direction to or from a station, measured clockwise from north.

BROKEN (BKN)

Cloud coverage of 5–7 oktas; considered a “ceiling” for VFR purposes.

BRT

Bright — descriptor in some light/visibility reports, meaning higher visibility or illumination.

BTL

Below The Line — used in checklists to mark items completed after engine start or other transitions.

BUFR

Binary Universal Form for the Representation of meteorological data — format used for weather exchange.

BUMP

Turbulence bump — informal term referring to sudden turbulence, often light to moderate.

CAA

Civil Aviation Authority — national aviation regulator of a state.

CAS

Calibrated Airspeed — indicated airspeed corrected for position and instrument error.

CAT (turbulence)

Clear Air Turbulence — turbulence occurring in clear air, often near jet streams or strong wind gradients.

CAT (operations)

Category — classification of approach minima (CAT I, II, III) or commercial air transport, depending on context.

CAVOK

Ceiling And Visibility OK — visibility ≥ 10 km, no significant weather, and no clouds below 5000 ft or below the minimum sector altitude (whichever is higher).

CB

Cumulonimbus — large convective cloud associated with thunderstorms, heavy rain, hail and severe turbulence.

CC (in MET)

Cirrocumulus — high-level cloud type consisting of small white patches or ripples.

CDI

Course Deviation Indicator — instrument needle showing lateral deviation from a selected course (VOR/LOC).

CG

Centre of Gravity — point at which the total weight of the aircraft is considered to act; critical for stability and control.

CH

Compass Heading — heading read directly from the magnetic compass, including any deviation error.

CIRRUS (CI)

High-level cloud made of ice crystals, usually wispy; often associated with approaching frontal systems.

CLR

Clear — used in weather reports to indicate absence of significant cloud at or below a given altitude or in vicinity of the aerodrome (depends on local usage).

CNS

Communication, Navigation and Surveillance — collective term for key aviation systems infrastructure.

COP

Changeover Point — point on an ATS route where an aircraft should transfer from one navaid to the next for navigation accuracy.

CPA

Closest Point of Approach — point at which two aircraft or objects will be at minimum separation if their relative tracks are unchanged.

CPL (licence)

Commercial Pilot Licence — licence allowing a pilot to be paid for flying operations within defined limits.

CPT (person)

Captain — pilot in command of the aircraft, with overall responsibility for the flight.

CRS / CRS (course)

Course — intended track over the ground or selected radial on a navaid, expressed in degrees from north.

CTA

Control Area — controlled airspace extending upwards from a specified limit above the ground (higher than a CTR), designed to protect en-route or approach traffic.

CTR

Control Zone — controlled airspace extending upwards from the surface to a specified upper limit around an aerodrome, protecting arriving and departing traffic.

CVR

Cockpit Voice Recorder — records cockpit audio for incident and accident investigation.

DA

Decision Altitude — altitude at which a decision must be made during an instrument approach to continue or go around.

DAH

Directional Aid Height — height reference associated with navigation or approach aids (less common in PPL exams).

DANGER AREA (D)

Airspace where activities dangerous to aviation may take place. Entry may be restricted or require permission.

DCT

Direct — clearance or routing that allows the aircraft to proceed straight to a waypoint without following a published route.

DOM (Dry Operating Mass)

The total weight of the aircraft ready for a specific operation, excluding all fuel and traffic load. Includes crew, crew baggage, catering, and passenger service equipment.

DEPU / DEP

Departure — refers to departing traffic, runway, aerodrome or procedures (e.g. “DEP RWY 03”).

DEW POINT

Temperature at which air becomes saturated and condensation begins; key factor for fog formation and carb icing risk.

DF

Direction Finding — radio technique using bearings from ground stations to locate an aircraft (older but still examinable).

DGA

Danger Area — alternative abbreviation sometimes used interchangeably with D or EPD (varies by country).

DH

Decision Height — height (AGL) at which a decision must be made during an instrument approach. Similar to DA but based on height, not altitude.

DI

Direction Indicator — gyroscopic heading indicator that provides stable heading information unaffected by bank/yaw errors like the magnetic compass.

DIST

Distance — horizontal distance between two points, often used in navigation logs and performance calculations.

DL

Delay — used in flow management or clearances (e.g. “DL due to congestion”).

DME

Distance Measuring Equipment — radio aid providing slant-range distance to a paired ground transponder (often co-located with VOR or ILS).

DNL

Downwind Leg — segment of the circuit flown parallel to the runway in the opposite direction of landing.

DP

Departure Procedure — procedural routing after takeoff; general term (SID if published, or visual departure instructions).

DR

Dead Reckoning — navigation method using heading, time and speed to estimate position without external references.

DSC

Descent — phase of flight during which altitude is reduced; also used in performance tables for rate of descent.

DT

Drift — angle between aircraft heading and track caused by crosswind; corrected through wind-corrected heading.

E (Airspace Class)

Class E Airspace — controlled airspace where IFR traffic is controlled and VFR is permitted without clearance. VFR receives traffic information when possible.

EAT

Expected Approach Time — the time an aircraft is expected to commence approach following a delay or holding pattern.

ECAM

Electronic Centralized Aircraft Monitoring — system that displays aircraft systems status (mainly airliners, rarely in PPL exams but appears in theory).

EDTO

Extended Diversion Time Operations — long-range operation rules for twins (formerly ETOPS). Rare in PPL, but may appear conceptually.

EGPWS

Enhanced Ground Proximity Warning System — advanced terrain-awareness and warning system to prevent CFIT accidents.

ELBA

Emergency Locator Beacon Aircraft — emergency radio beacon transmitting aircraft distress position (modern ELTs use 406 MHz).

ELT

Emergency Locator Transmitter — device activating automatically after an impact to broadcast distress location on 406 MHz and 121.5 MHz.

ENR

En-Route section of the AIP — contains rules and procedures for IFR/VFR operations outside terminal airspace.

EPG

Entry Point Gap — term used in some airspace structures, referring to gaps in entry points (non-critical for PPL).

ETA

Estimated Time of Arrival — predicted time at which the aircraft will reach a specified point or aerodrome.

ETD

Estimated Time of Departure — planned time for departure, used in flight plans and ATC flow management.

ETOPS

Extended-range Twin Operations — older term replaced by EDTO. Not directly PPL-relevant but appears in theory context.

EVS

Enhanced Vision System — infrared/low-light visual system improving situational awareness (advanced GA/IFR).

EW

Empty Weight — weight of the aircraft without usable fuel, passengers, or baggage; important for weight and balance calculations.

FAF

Final Approach Fix — point where the final approach segment of an instrument approach begins.

FAP

Final Approach Point — point used for non-precision approaches where final descent begins (no fix symbol).

FATO

Final Approach and Take-Off Area — defined area for helicopters to complete landing or takeoff.

FBO

Fixed-Base Operator — facility providing general aviation services such as fueling, parking, maintenance, lounges.

FCL

Flight Crew Licensing — EASA/ICAO framework regulating pilot licences, ratings, and medical requirements.

FDR

Flight Data Recorder — device recording technical flight data for investigation purposes (“black box”).

FEW

Few clouds — 1–2 oktas of cloud coverage (METAR cloud amount group).

FIC

Flight Information Centre — provides en-route flight information service and alerting service to pilots.

FIR

Flight Information Region — large airspace region providing ATC, FIS, and alerting services (e.g., Athens FIR).

FL

Flight Level — altitude expressed in hundreds of feet based on standard pressure setting (1013 hPa). Example: FL65 = 6,500 ft on standard pressure.

Flaps (Leading & Trailing Edge Devices)

High-lift devices fitted to the wing to increase lift, drag, or stall margin, mainly used during takeoff and landing.

• Plain flap — Simple hinged trailing-edge flap that increases wing camber and lift.
• Split flap — Trailing-edge flap where only the lower surface deflects, producing high drag.
• Slotted flap — Trailing-edge flap with a slot that energizes airflow and delays stall.
• Fowler flap — Trailing-edge flap that moves rearward then downward, increasing both wing area and camber.
• Leading-edge flap — Hinged leading-edge device that increases camber and delays stall.
• Slat — Movable leading-edge device that opens a slot to maintain airflow at high angles of attack.
• Krueger flap — Leading-edge panel that flips forward from the wing underside to increase camber.
• Frise aileron — Trailing-edge device whose leading edge protrudes below the wing when deflected upward, increasing drag on the descending wing and reducing adverse yaw.

FMC

Flight Management Computer — integrated computer managing navigation and performance (airliners/advanced GA).

FM (in TAF)

From — indicates an abrupt change in weather conditions starting at a specific time group in a TAF.

FMCW

Frequency-Modulated Continuous Wave — radar type used in radio altimeters (advanced concept, but appears in exams).

FMS

Flight Management System — integrated navigation and performance system coordinating FMC, autopilot, and sensors.

FO

First Officer — second-in-command pilot assisting the Captain (PIC).

FOD

Foreign Object Debris — objects on the runway/apron that may damage aircraft (critical safety concept).

FPA

Flight Path Angle — vertical angle of ascent/descent relative to horizontal; used in VNAV/advanced avionics.

FPAP

Flight Path Analysis Point — a point used in performance and approach path analysis (rare in PPL).

FPL

Flight Plan — filed document containing route, fuel, persons onboard, and operational intentions of a flight.

FPM

Feet Per Minute — unit for vertical speed (rate of climb or descent).

FQNH / FQFE

QNH/QFE prefixes used in some systems to indicate forecast altimeter settings (non-ICAO standard, low frequency in PPL).

FREQ

Frequency — radio frequency used for ATC, navigation, or communications (e.g. 118.300 MHz).

FRQ

Frequent — used in weather/NOTAM contexts meaning something occurs often.

FSS

Flight Service Station — provides weather briefings, FPL assistance, NOTAM information (more common in US).

GA

General Aviation — all civil aviation operations other than commercial air transport or aerial work.

G/A

Go-Around — discontinued approach followed by climb and rejoining of the circuit or missed approach procedure.

GAFOR

General Aviation Forecast — route-oriented weather forecast for VFR flights (used in many European states).

GBAS

Ground-Based Augmentation System — precision approach system improving GNSS accuracy (advanced but examinable).

GCA

Ground Controlled Approach — radar-based approach guidance provided by a controller (rare today but still tested).

GCI

Ground Controlled Interception — radar vectoring of an intercept aircraft (mostly in military context).

GCL

Ground Control — ATC position responsible for managing traffic on taxiways and aprons (not runways).

GFM

Graphical Forecast for Aviation — visual weather briefing tools (varies by region; conceptually relevant).

GIA

GNSS Integrity Augmentation — systems improving reliability and accuracy of satellite navigation data.

GLD

Glider — aircraft without an engine designed for unpowered flight; appears in airspace and right-of-way rules.

GND

Ground — used in altitude/height reports (e.g., “500 ft GND”) or as ATC frequency abbreviation (“GND 121.9”).

GNSS

Global Navigation Satellite System — generic term for satellite navigation (GPS, Galileo, GLONASS, BeiDou).

GP

Glide Path — vertical guidance angle of an ILS or precision approach (typically 3 degrees).

G/S

Groundspeed — speed of the aircraft relative to the ground, affected by wind; GS = TAS ± wind component.

GS (ILS)

Glide Slope — vertical radio beam component of the ILS providing descent guidance to the runway.

GUST

Sudden, brief increase in wind speed; important for takeoff, landing and Vref adjustments.

HAZ

Hazard — condition or object with potential to cause harm; used in safety and risk assessment contexts.

Hdg / HDG

Heading — direction in which the aircraft nose is pointing, expressed in degrees from magnetic north.

HF

High Frequency — radio band (3–30 MHz) used for long-range communications; less relevant for basic PPL but examinable conceptually.

HFR

High-Frequency Radio — similar to HF, used in long-range aviation and oceanic operations.

HGT

Height — vertical distance of a point measured from a specific datum (usually AGL in aviation terms).

HLDG / HOLD

Holding — predetermined manoeuvre maintaining position over a fix; also refers to ATC instructions to hold short of a runway or point on the ground.

HPA

Hectopascal — unit of pressure used for altimeter settings (QNH, QFE). 1 hPa ≈ 1 millibar.

HR

Hours — time unit used in METAR/TAF groups and NOTAM validity windows (e.g., “HRLY” meaning hourly).

HRZ

Horizon — used in visual references and in attitude interpretation (natural or artificial horizon).

HS

Haze — reduced visibility due to fine dry particles; worse at low sun angles and common in high-pressure weather systems.

HUD

Head-Up Display — system projecting critical flight info onto a transparent screen in the pilot’s line of sight (advanced GA and airliners).

HVY

Heavy — ICAO wake turbulence category for aircraft 136,000 kg or heavier; affects separation minima for smaller aircraft.

IAS

Indicated Airspeed — airspeed shown on the ASI, not corrected for instrument or position error.

ICAO

International Civil Aviation Organization — UN agency that sets global standards for aviation safety, airspace, and licensing.

Ident

Identification — used in transponders (“Squawk Ident”) to momentarily highlight the aircraft on radar.

IFR

Instrument Flight Rules — rules for flying by instruments, required in IMC or controlled airspace above certain levels.

ILS

Instrument Landing System — precision approach system providing lateral (localizer) and vertical (glide slope) guidance to runway.

IMC

Instrument Meteorological Conditions — weather conditions below VFR minima requiring IFR flight or special VFR clearance.

IMU

Inertial Measurement Unit — sensor system that detects acceleration and rotation for autopilot and navigation systems (advanced GA).

InHg

Inches of Mercury — alternative unit for altimeter setting used mainly in the US. 1 inHg = 33.8639 hPa.

INS

Inertial Navigation System — autonomous navigation using accelerometers and gyros (advanced but examinable conceptually).

ISA

International Standard Atmosphere — model defining temperature, pressure and density at various altitudes (e.g., +15°C at sea level).

ISOHYET

Line connecting points of equal rainfall — occasionally referenced in meteorology sections of PPL theory.

JAA

Joint Aviation Authorities — former European aviation regulatory body, replaced by EASA. Still appears in legacy documentation and exams.

JET

Jet Engine — turbine engine producing thrust by accelerating exhaust gases; includes turbofan, turbojet, and turboprop variants.

JFIR

Joint Flight Information Region — airspace controlled jointly by more than one state (rare but examinable concept).

JNC

Joint Navigation Chart — en-route chart type used in some ICAO materials (legacy but relevant for navigation principles).

K (Kelvin)

Kelvin — temperature scale used in scientific calculations and atmospheric physics. ISA temperature lapse rates are sometimes expressed in Kelvin.

KIAS

Knots Indicated Airspeed — IAS expressed in knots; primary speed reference for most light aircraft.

KT / KTS

Knot(s) — standard aviation unit of speed. 1 kt = 1 nautical mile per hour = 1.852 km/h.

KW

Kilowatt — unit of power. Used in metric performance tables; 1 kW = 1.34 horsepower.

L

Left — used in circuits and ATC instructions (e.g., “Left-hand circuit”, “Turn left heading 270”).

LAA

Light Aircraft Association — organization supporting recreational flying (mainly UK; general aviation relevance).

LAT

Latitude — angular distance north or south of the equator, measured in degrees; used in navigation coordinates.

LAW

Landing Weight — maximum permissible weight for landing; relevant to performance and aircraft limitations.

LDA

Landing Distance Available — runway length declared available and suitable for landing an aircraft.

LDG

Landing — phase of flight from flare to touchdown; also used in charts (“LDG distance”, “LDG weight”).

LED

Light-Emitting Diode — common in modern aircraft lighting, displays and annunciators.

LF

Low Frequency — radio band (30–300 kHz) used historically for NDBs; still relevant for ADF navigation theory.

LG

Landing Gear — wheels, struts and supports enabling ground operations; can be fixed or retractable.

LH

Left-Hand — used in traffic patterns (circuits), e.g., “Left-hand downwind runway 25”.

LIFR

Low Instrument Flight Rules — visibility < 1 mile and/or ceiling < 500 ft (common US term; sometimes referenced in theory).

LLZ

Localizer — lateral guidance component of the ILS providing course alignment to runway centerline.

LO

Low — used in meteorology and pressure charts indicating a low-pressure system (cyclone).

LOC

Localizer — component of ILS providing horizontal guidance; sometimes used for standalone non-precision LOC approaches.

LOFT

Line-Oriented Flight Training — scenario-based training in simulators (advanced concept but appears in HPL/Human Factors).

Loads (Structural Loads & Factors)

Definitions used in aircraft structural integrity and certification limits.

• Limit Load: Maximum load expected during normal operation (without causing permanent deformation).
• Ultimate Load: Load at which the structure will fail (Limit Load × Safety Factor).
• Safety Factor: Ratio of Ultimate Load to Limit Load — typically 1.5 for certified aircraft.
• Manoeuvre Envelope (V–n Diagram): Graph showing the relationship between airspeed (V) and load factor (n), defining structural limits.

LONG

Longitude — angular distance east or west of the prime meridian; pairs with latitude for coordinates.

LPV

Localizer Performance with Vertical Guidance — high-precision GNSS-based approach comparable to ILS CAT I minima.

LRT

Low Rupture Time — describes specific material properties, sometimes referenced in AGK (Aircraft General Knowledge).

LSALT

Lowest Safe Altitude — minimum altitude ensuring terrain and obstacle clearance on route; extremely important for navigation safety.

M (Mach)

Mach number — ratio of true airspeed to the speed of sound. Mainly relevant in high-speed flight but appears in theory.

MAA

Maximum Authorized Altitude — highest altitude permitted on a particular route segment or airspace area.

MAG

Magnetic — relating to magnetic north; used in magnetic heading, magnetic variation, magnetic track, etc.

Magneto

Engine-driven electrical generator that produces high-voltage pulses for the spark plugs. Most piston aircraft engines use two magnetos for redundancy and better combustion.

Manoeuvre Envelope (V–n Diagram)

A graph showing the relationship between airspeed (V) and load factor (n). Defines the structural load limits and safe operating speeds of the aircraft.

MAP

Missed Approach Point — point in an instrument approach where a missed approach procedure must be initiated if visual references are not acquired.

Masses (Weight Definitions)

Standard mass definitions used in aircraft performance, loading, and certification.

• BEM – Basic Empty Mass: Aircraft with all basic equipment plus unusable fuel and oil.
• DOM – Dry Operating Mass: Aircraft prepared for a specific operation excluding fuel and traffic load (crew, equipment, catering included).
• MTOM – Maximum Take-Off Mass: Maximum permissible mass at the start of the takeoff roll.
• MLM – Maximum Landing Mass: Maximum permissible mass at touchdown.
• MZFM – Maximum Zero Fuel Mass: Maximum allowable aircraft mass with no usable fuel onboard.

MDA

Minimum Descent Altitude — lowest altitude to which descent is authorized in a non-precision approach before visual references must be seen.

MDH

Minimum Descent Height — same as MDA but expressed as height above terrain (AGL).

MET

Meteorology — weather information and reports used in aviation (METAR, TAF, SIGMET, etc.).

METAR

Meteorological Aerodrome Report — routine weather report issued at regular intervals for aerodromes.

MF

Medium Frequency — radio band (300–3000 kHz) used historically for NDBs; still relevant in ADF navigation theory.

MHA

Minimum Holding Altitude — lowest altitude at which holding patterns can be safely flown considering terrain and obstacles.

MHz

Megahertz — unit of frequency equal to one million hertz; used for VHF communication and navigation frequencies (e.g., 118.000 MHz).

MILO

Maximum Landing Weight — maximum structural weight permitted for landing; important for performance and limitations.

MIN

Minutes — time unit commonly used in navigation planning, fuel calculations, and ATC instructions (“hold 2 MIN legs”).

MIRL

Medium Intensity Runway Lights — common runway edge lighting system used at many small/medium airports.

MOC

Minimum Obstacle Clearance — minimum required vertical separation between aircraft and obstacles during IFR procedures.

MOCA

Minimum Obstacle Clearance Altitude — ensures obstacle clearance and acceptable navigation signal along a route segment.

MORA

Minimum Off-Route Altitude — provides obstacle clearance for aircraft flying off published airways (typically 1000–2000 ft buffer).

MOSI

Mountain Obscuration — severe reduction in visibility due to clouds or precipitation obscuring terrain; a factor in mountain flying risks.

MOT

Mean Operating Temperature — used in engine and systems performance discussions (advanced concept but appears in AGK theory).

MP (Manifold Pressure)

Manifold Pressure — pressure in the intake manifold of piston engines; used to set power in constant-speed prop aircraft.

MRA

Minimum Reception Altitude — lowest altitude at which an aircraft can reliably receive signals from a given NAVAID on a route segment.

MRVA

Minimum Radar Vectoring Altitude — lowest altitude ATC can assign while providing radar vectors, ensuring obstacle clearance.

MSA

Minimum Sector Altitude — minimum altitude providing at least 1000 ft obstacle clearance within 25 NM of a navigation facility or waypoint.

MSL

Mean Sea Level — standard reference datum for altitudes (e.g., 3500 ft MSL).

MTOW

Maximum Takeoff Weight — maximum structural weight at which the aircraft is certified for takeoff; key performance limitation.

N (North)

North — one of the cardinal directions. Can refer to true north, magnetic north, or grid north depending on context.

NA

Not Available — used in procedures or charts where an approach segment or minimum is not authorized.

NAV

Navigation — general term covering the methods used to determine position and route (dead reckoning, GNSS, VOR, ADF).

NAVAID

Navigation Aid — facility providing guidance to aircraft (VOR, NDB, DME, ILS components, GNSS, etc.).

NB

Northbound — aircraft flying toward the north; used in traffic flow and ATC instructions.

NBD

Non-Directional Beacon — radio navigation aid transmitting a continuous signal used by ADF in aircraft.

NDB

Non-Directional Beacon — standardized ICAO abbreviation for the radio navigation beacon used with ADF equipment.

NM

Nautical Mile — distance unit used in aviation and maritime navigation. 1 NM = 1.852 km = 6076 ft.

NOAA

National Oceanic and Atmospheric Administration — US agency providing weather data used widely in aviation charts and forecasts.

NOTAM

Notice to Airmen / Air Missions — official notice containing time-critical information affecting flight operations, hazards, closures, or procedures.

NPA

Non-Precision Approach — instrument approach without vertical guidance (e.g., VOR, NDB, LNAV-only GNSS).

OAT

Outside Air Temperature — temperature of the air outside the aircraft; important for performance, icing risk, and density altitude.

OBS

Omni Bearing Selector — control on VOR indicators used to select desired radial or course.

OCAS

Outside Controlled Airspace — airspace where most VFR operations occur and fewer ATC services are provided.

OCH

Obstacle Clearance Height — height above the elevation of the runway threshold ensuring obstacle clearance in approach procedures.

OCL

Obstacle Clearance Limit — lowest permitted altitude ensuring obstacle clearance in a given segment of an instrument procedure.

OEI

One Engine Inoperative — performance condition used for multi-engine aircraft calculations and safety margins.

OHP

Overhead Panel — panel located above the pilots containing electrical, lighting, fuel, and system controls (more relevant in larger aircraft).

OIS

Obstacle Identification Surface — sloping surface defining obstacle clearance requirements near runways and procedures.

OM

Outer Marker — marker beacon (now mostly decommissioned) used in ILS approaches indicating the FAF location.

OMB

Outer Marker Beacon — full ICAO term for OM, part of the ILS marker beacon system.

OPA

Other Power-driven Aircraft — ICAO classification for performance categories (e.g., helicopters, gyros, powered gliders).

OPS

Operations — general term referring to flight operations, procedures, and regulatory requirements (EU-OPS, Part-OPS).

PA

Pressure Altitude — altitude read when the altimeter is set to 1013 hPa; used for performance calculations.

PAPI

Precision Approach Path Indicator — four-light system providing visual glide-path information on approach.

PANS-OPS

Procedures for Air Navigation Services — ICAO rules governing instrument procedure design and obstacle clearance.

PAR

Precision Approach Radar — radar system providing precise glide-path and centerline guidance (military/advanced IFR).

PAX

Passengers — informal abbreviation widely used in operations and manifests.

Pb (Pressure)

Pressure — general symbol for atmospheric or static pressure used in meteorology and performance charts.

PCL

Pilot-Controlled Lighting — system allowing pilots to activate runway lighting via VHF transmissions.

PD (Pilot Deviation)

Pilot Deviation — occurrence where a pilot violates a regulation or ATC instruction (training & safety concept).

PF

Pilot Flying — pilot currently manipulating the controls (opposite of PM, Pilot Monitoring).

PFM

Performance — general performance-related data such as climb rates, takeoff distance, and fuel burn.

PGM

Precipitation Gauge Measurement — used in meteorology to indicate rainfall intensity or accumulation.

PIC

Pilot in Command — pilot responsible for the safe conduct of the flight; holds final authority and responsibility.

PITCH

Longitudinal rotation of the aircraft about its lateral axis; controlled by the elevator.

PNR

Point of No Return — point beyond which the aircraft does not have enough fuel to return to the departure aerodrome.

POB

Persons On Board — required entry in flight plans and operational documentation for emergency services reference.

POH

Pilot’s Operating Handbook — aircraft-specific manual containing procedures, limitations, and performance data.

POT

Potential Temperature — atmospheric thermodynamics term used in advanced meteorology (lightly examinable for PPL).

PPG

Powered Paraglider — type of ultralight aircraft; appears in categorization and airspace rules.

PPL

Private Pilot Licence — licence allowing non-commercial flight in single-engine aircraft under VFR.

PRKG

Parking — stands or apron locations used for aircraft ground operations (e.g., PRKG stand 02).

PROB (MET)

Probability — used in TAF to indicate probability of weather events (e.g., PROB30 means 30% probability).

PS (Pressure Setting)

Pressure Setting — general reference to QNH/QFE/Standard altimeter settings for altitude measurement.

PSR

Primary Surveillance Radar — radar detecting aircraft by reflected radio energy (no transponder required).

PTT

Press-To-Talk — button on the yoke or radio allowing transmission over VHF comms.

QFE

Altimeter setting that reads zero at the airfield reference point (usually runway threshold). Height shown = height above the airfield (AGL).

QFF

Sea-level pressure corrected for actual temperature; used in meteorology, not typically for altimeter setting.

QFU

Magnetic orientation of a runway in whole tens of degrees (e.g., QFU 270 = runway oriented 270° magnetic).

QGH

Controller-assisted approach using radar and radio instructions (similar to talk-down). Mostly historical but appears in theory.

QDM

Magnetic bearing **to** the station from the aircraft (“Go Direct Magnetic”). Used with ADF/NDB navigation.

QDR

Magnetic bearing **from** the station to the aircraft (“Determined Radial”). Reciprocal of QDM ±180°.

QHN

Altimeter subscale setting required to read elevation above mean sea level (less common variant of QNH reference).

QNE

Standard altimeter pressure setting of 1013.25 hPa (29.92 inHg) used to indicate pressure altitude and flight levels above the transition altitude.

QNH

Altimeter setting giving elevation above mean sea level (AMSL). Standard setting used for circuits and approach altitudes at aerodromes.

QRM

Radio interference — signal degraded by man-made noise (e.g., static, equipment interference).

QRU

“Nothing for you” — used to indicate no new information or messages (older radiotelephony code but examinable).

QSY

Change frequency — instruction to change to another radio channel (e.g., “QSY Approach 128.825”).

RA (Runway Ahead)

Runway Ahead — used in runway signage and alerts indicating that a runway is about to be entered.

RA (Radar Altimeter)

Radio Altimeter — measures actual height above terrain (AGL) using radio waves; used for low-level flight and autoland systems.

RAC

Rules of the Air and Air Traffic Services — ICAO procedures governing flight rules and ATC operations.

RAG

Runway Arresting Gear — cables or equipment used to stop military aircraft; noted on airport charts.

RAIM

Receiver Autonomous Integrity Monitoring — GNSS function detecting satellite integrity issues; required for RNAV approaches.

RAP

Runway Alignment Procedure — procedure or alignment used for instrument approaches or localizer intercepts.

RB

Rescue Boat — SAR (Search and Rescue) vessel; appears in emergency procedures documentation and NOTAMs.

RCF

Radiocommunication Failure — complete loss of radio; procedures are detailed in ICAO and national rules.

RDH

Reference Datum Height — height above runway threshold where glide slope signal passes overhead (ILS parameter).

REIL

Runway End Identifier Lights — two flashing white lights at the approach end of a runway to improve recognition.

RFF

Rescue and Fire Fighting — emergency capability category of an aerodrome, based on aircraft size/type.

RH

Right-Hand — used for traffic patterns (e.g., "Right-hand downwind runway 10").

RIA

Radar Information Area — airspace where radar information service is provided but not full ATC control (non-standard, seen in exam theory).

RIME

Rime Ice — rough, milky ice formed in small supercooled droplets; increases drag and decreases lift.

RNAV

Area Navigation — allows aircraft to fly any desired path using GNSS or DME/DME without ground-based tracking.

RO

Runway Occupied — runway is not available for landing/takeoff due to traffic or obstruction; used in operations logs.

ROC

Rate of Climb — vertical speed during climb, usually expressed in feet per minute (fpm).

ROD

Rate of Descent — vertical speed during descent, expressed in feet per minute (fpm).

ROP

Rich of Peak — mixture setting where fuel mixture is richer than peak exhaust gas temperature (EGT). Used for cooling and engine protection.

RPM

Revolutions Per Minute — rotation speed of propeller or engine crankshaft; primary power indication in fixed-pitch prop aircraft.

RR

Rapid Runway (or Rapid Exit) — fast-exit taxiway enabling aircraft to vacate the runway quickly after landing.

RS (Runway Slope)

Runway Slope — slope percentage affecting takeoff/landing performance (positive = uphill in direction of travel).

RTF

Radiotelephony — two-way voice communication between pilots and ATS, governed by ICAO phraseology rules.

RWY

Runway — defined rectangular area on land aerodromes prepared for takeoff and landing of aircraft.

SAR

Search and Rescue — service responsible for assisting aircraft in distress and coordinating rescue activities.

SAT

Static Air Temperature — true ambient air temperature; important for performance and TAS calculations.

SBAS

Satellite-Based Augmentation System — improves GNSS accuracy (e.g., EGNOS) enabling LPV approaches.

SC

Stratocumulus — mid-level cloud layer with lumpy structure; possible drizzle and turbulence.

SCT

Scattered — METAR cloud coverage term indicating 3–4 oktas of cloud.

SELCAL

Selective Calling — alerts the aircraft when ATC wants to contact them, avoiding constant HF/VHF monitoring (airline-level).

SIGMET

Significant Meteorological Information — urgent weather warning for turbulence, icing, thunderstorms, volcanic ash, etc.

SKC

Sky Clear — METAR term indicating no clouds detected below the reporting system limit.

SLP

Sea Level Pressure — METAR code showing pressure reduced to mean sea level.

SMC

Surface Movement Control — ATC function managing taxiways and apron traffic (not runways).

SN

Snow — METAR code indicating falling snow; affects visibility and runway braking.

SOFT FIELD

Takeoff/landing technique used on grass or soft surfaces to reduce rolling resistance and prevent sinking.

SOP

Standard Operating Procedure — step-by-step procedures used for consistency and safety.

SPECI

Special Weather Report — METAR issued when significant weather changes occur between regular observations.

SPD

Speed — a general term referring to IAS, TAS, GS, or vertical speed depending on context.

Speeds (V-Speeds)

Standardized performance speeds used in aircraft operation. Each V-speed has a precise definition and operational limit.

• V — Velocity / Speed.
• Va — Maneuvering speed: maximum speed at which full control deflection will not damage the aircraft.
• Vd — Design dive speed: maximum design test speed (never to be reached in normal operations).
• Vx — Best angle of climb speed (maximum height gain per horizontal distance).
• Vy — Best rate of climb speed (maximum height gain per unit of time).
• Vs — Stall speed in clean (no flaps) configuration.
• Vr — Rotation speed (speed at which the pilot initiates pitch-up for takeoff).
• Vno — Normal operating speed: top of the green arc on the airspeed indicator.
• Vne — Never exceed speed: red line on the airspeed indicator; structural danger above this speed.
• Vfe — Maximum flap extension speed.
• Vlo — Maximum landing gear operating speed (gear movement).
• Vle — Maximum landing gear extended speed (gear down and locked).
• Vra — Rough air (turbulence) penetration speed.
• Vso — Stall speed in landing configuration (full flaps, gear down).
• Vmd — Speed for minimum drag (maximum lift-to-drag ratio).
• Vmp — Speed for minimum power required (maximum endurance).
• Vbg — Best glide speed (maximum glide distance).
• Vref — Reference landing speed.
• Vapp — Final approach speed.

SQUAWK

Transponder code assigned by ATC for identification (e.g., Squawk 7000, Squawk 7700, Squawk Ident).

SR

Sunrise — operational reference time used in lighting rules and VFR day definitions.

SS

Sunset — operational reference time; in many countries night begins 30 minutes after SS.

STAR

Standard Terminal Arrival Route — published IFR arrival procedure guiding aircraft toward an airport.

STOL

Short Takeoff and Landing — aircraft or procedures requiring minimal runway length.

TA (Transition Altitude)

Altitude at or below which vertical position is referenced to local QNH. Above TA pilots set standard 1013 hPa.

TAS

True Airspeed — actual speed of the aircraft through the air mass; important for navigation and flight planning.

TAXI

Movement of an aircraft on the ground under its own power, excluding takeoff and landing runs.

TCH

Threshold Crossing Height — height at which the aircraft crosses the runway threshold during an instrument approach.

TDM

TDM (Time Division Multiplexing) — digital signal technique used in some radio navigation systems.

TDZ

Touchdown Zone — first 3,000 ft (or first third) of runway intended for landing. TDZ lighting assists visual reference in low-visibility operations.

TEMP (MET)

Temperature — general term used in METAR, TAF and performance calculations (e.g., high temp → reduced performance).

THM

Track to Hold Magnetically — magnetic track flown in a holding pattern, ensuring correct alignment with wind correction.

THR

Throttle / Thrust — general term for engine power control or thrust output from engines.

TMA

Terminal Control Area — controlled airspace around major airports where arriving and departing traffic is managed by ATC.

Traffic Load

The total weight of passengers, baggage, and freight carried on the aircraft.

TUC (Time of Useful Consciousness)

The length of time an individual can act effectively after oxygen supply is lost, before incapacitation occurs.

TODA

Takeoff Distance Available — length of runway plus any clearway available for takeoff run calculations.

TOGA

Takeoff/Go-Around — throttle setting providing maximum power for takeoff or go-around maneuvers.

TORA

Takeoff Run Available — length of runway declared available for the ground run during takeoff.

TRK

Track — actual path of the aircraft over the ground; differs from heading due to wind.

TS (Thunderstorm)

Thunderstorm — significant weather phenomenon involving lightning, severe turbulence, hail, icing, strong winds, and downdrafts.

TSO

Technical Standard Order — FAA minimum performance standard for parts and equipment used in aircraft.

TWR

Tower — ATC unit responsible for aerodrome control, including runways and circuit traffic (“Tower Control”).

U/S

Unserviceable — equipment or system that is not functioning and must not be used. Often seen in NOTAMs, checklists, and aircraft logs.

UHF

Ultra High Frequency — 300 MHz to 3 GHz. Used by military aviation and some ground-based systems; not standard for civilian VHF comms.

UKL

Upper Kilometres — measurement used in meteorology for upper-air wind and temperature observations (less common but examinable).

ULM

Ultralight / Microlight — lightweight aircraft category with reduced regulatory requirements; relevant in European airspace rules.

UTC

Coordinated Universal Time — the aviation standard time reference for all flight planning, ATC, and weather reports. Equivalent to Zulu time (Z).

VASIS

Visual Approach Slope Indicator System — older visual glide-path aid, predecessor of PAPI. Uses pairs of red/white lights to indicate correct approach angle.

VDF

VHF Direction Finding — ground station determines bearing to/from an aircraft using VHF transmissions. Produces QDM/QDR bearings (e.g., “Steady, steady…”).

VDL

VHF Data Link — digital communication system using VHF frequencies; basis of CPDLC in some regions.

VELOCITY

Vector quantity describing speed with direction. Used heavily in navigation, wind triangle, and performance calculations.

VF

Flap limiting speed — maximum speed at which flaps can safely be extended to a specific position (variant of Vfe).

VFR

Visual Flight Rules — regulations allowing flight with visual reference to terrain and horizon, requiring minimum visibility and cloud clearance.

VHF

Very High Frequency — 118.000–136.975 MHz band used for civil aviation voice communication and some navigation systems (e.g., ILS, VOR).

VMC

Visual Meteorological Conditions — weather conditions meeting or exceeding VIS & cloud separation minima for VFR flight. Basis for where/when VFR is permitted.

VNAV

Vertical Navigation — automated or advisory vertical flight path computed by the FMS/GNSS. Mostly IFR but appears in modern avionics even for GA.

VNO

Maximum structural cruising speed — top of the green arc; normal operations must stay below this except in smooth air.

VOR

VHF Omnidirectional Range — radio navigation aid providing bearings (radials) from the station. Used with CDI/HSI for en-route and approach guidance.

VORTAC

Combined VOR and TACAN station giving both VOR radials and military DME distances — widely used in en-route charts.

VR

Rotation Speed — speed at which the pilot initiates pitch-up for takeoff. Determined by performance charts and aircraft weight.

VSI

Vertical Speed Indicator — cockpit instrument showing climb/descent rate in feet per minute (fpm).

W/V

Wind/Velocity — METAR/TAF shorthand for reporting wind direction and speed (e.g., 180/10KT).

WAAS

Wide Area Augmentation System — U.S. version of SBAS improving GNSS accuracy for LPV and RNAV approaches.

WDI

Wind Direction Indicator — usually a windsock showing surface wind direction and approximate strength at an aerodrome.

WGS-84

World Geodetic System 1984 — global reference coordinate system used for GPS and ICAO charts.

WI

Within — used in NOTAMs and procedures to specify distance limits (e.g., “WI 5 NM of VOR”).

WIND SHEAR

Sudden change in wind speed or direction over a short distance. Critical near the ground; can cause severe loss of airspeed on approach or departure.

WINTEM

Wind and Temperature Chart — upper-air forecast providing wind direction, speed, and temperature at various altitudes.

WIP

Work In Progress — aerodrome or runway work indicated in NOTAMs; may restrict taxiways, runways or aprons.

WPT

Waypoint — defined geographic position used in RNAV/GNSS navigation, flight plans, and approaches.

WS

Wind Shear — METAR/TAF weather code indicating low-level wind shear or vertical shear hazards.

XA

Executive Airport code used in some regional documentation or ICAO references; rare but occasionally seen in materials.

XCVR

Transceiver — combined transmitter and receiver used in aircraft radios (e.g., VHF COM transceiver).

XFMR

Transformer — electrical device used to step voltage up or down; appears in AGK/aircraft electrical system diagrams.

XL

Extra Long — used occasionally in runway/taxi descriptions and airport documentation to denote extended length.

XTK

Cross Track Error — lateral deviation from the planned path in RNAV/GNSS navigation systems.

X (Runway Closed)

Large white “X” marking — indicates a runway or taxiway is closed and must not be used for takeoff, landing, or taxiing.

YD

Yaw Damper — automatic system that reduces unwanted yaw oscillations (“Dutch roll”). More common in larger aircraft but appears in AGK theory.

YOKE

Primary flight control used to manipulate ailerons (roll) and elevator (pitch). Equivalent to a control stick in some aircraft.

YVR

Vancouver International Airport ICAO code context (uncommon in theory but appears in some global chart examples).

YAW

Rotation of the aircraft around the vertical axis, controlled by the rudder. Yaw control is essential for coordinated turns and crosswind corrections.

Z (Zulu Time)

Zulu Time — global aviation standard time equal to UTC. Used in all flight plans, NOTAMs, METARs, TAFs, and ATC coordination.

ZFW

Zero Fuel Weight — aircraft weight excluding usable fuel; important limitation for structural load and mass & balance.

ZULU APPROACH

Specific instrument approach procedure identified by the suffix “Z” (e.g., RNAV (GNSS) Z RWY 34). Indicates a variant of an approach with different minima or guidance.