Aviation Dictionary

On this page you will find a searchable and comprehensive alphabetical list of aviation terms. You can help us make it the most comprehensive list in the world. If we have missed anything, click on the ‘send us your word’ button to send us your word, acronym or definition and we will consider adding it to our dictionary.

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Abeam A point or position of the aircraft that is 90 degrees to the left or right of the aircrafts track
Aborted Take A procedure that requires the pilot to bring the aircraft to a stop during the take-off roll.
Above Ground Level (AGL) The distance measured between the aircraft and any part of the ground. A common use for AGL is for parachuting, where the distance to the ground is more important than the distance above mean sea level. Normally, when on the ground, the altimeter is set to 0 feet, which in most cases will not be the current pressure setting that would normally be set on the altimeter to give AMSL.
Above Mean Sea Level (AMSL) The distance above sea level, calculated with the current atmospheric pressure and can be read off of an altimeter. This is normally set on the ground by obtaining the current QNH or pressure for a specific area and can be changed while in flight if a new QNH is obtained.
ACAS Airborne Collision Avoidance System
ACN Aircraft Classification Number
Active Runway The runway that is in use. At an uncontrolled airport, never enter a runway without making a radio call on the CTAF. 
AD Aerodrome
ADC Air Data Computer
ADF Automatic Direction Finder
ADIZ Air Defence Identification Zones
Advection Air moving horizontally
Adverse Yaw An undesirable tendency for an aircraft to yaw about the Normal axis (Vertical axis) in the opposite direction of a roll due to the difference in lift and drag created by each wing.
AEL Aviation English Language
Aerobatics Varying manoeuvres that have abrupt changes in attitude or attitudes exceeding 30 degrees of pitch or more than 60 degrees of bank. Common manoeuvres are loops, rolls and spins.
Aerodrome Any place that can be used for aircraft operations, either on land or on water.
Aerofoil The shape of a cross-sectioned wing or propeller blade designed to give the best lift to drag ratio in flight.
Aeronautical Charts Maps intended for use in aerial navigation. Both airspace boundaries and ground features are marked.
AFCS Automatic Flight Control System
AFM Aircraft Flight Manual
AFOR Area Forecast 
AGL Above Ground Level
AIC Aeronautical Information Circular
Aileron A control surface located near the wing tips and controls the roll around the longitudinal axis. Ailerons move in opposite directions to each other, as one moves up, the other moves down.
AIP Aeronautical Information Package
Aircraft Any powered or unpowered, heavier-than-air type vehicle that is able to oppose the force of gravity in order to fly. Common aircraft examples are hot air balloons, gliders, helicopters and fixed wing aeroplanes.
Aircraft Owners & Pilots Association of Australia (AOPA Australia) is an association representing aircraft owners and pilots. They publish a magazine. https://aopa.com.au/
AIREP Air Report: Typically a weather report given by a pilot in flight
Airservices Australia An Australian Government owned corporation, responsible for providing safe, secure, efficient and environmentally responsible services to the aviation industry within the Australian
Airline Transport Pilot Licence (ATPL) The next step up from a CPL, minimum 1500 hours to your name.  You must have an IFR and multi-engine ratings, most airlines require you to have the theory exams completed before you can apply for an Airline Job
Airmanship The process of using good judgement for the safe outcome of a flight. By continually improving your flying skill set, knowing and obeying the rules, being courteous to other aviators all make up good airmanship. The saying, “Aviate, Navigate, Communicate” is a good airmanship standard and applies to the order in which you manage yourself and your aircraft.
Airspeed The speed an aircraft is flying through the air. Different airspeeds will cause different effects on the controls and the aircraft response rate to a change using the primary controls.
Airspeed Indicator (ASI) An instrument that gives a reading to the pilot on the current speed that the aircraft is doing through the air, measured in knots. This speed is different to Ground Speed.
Air Traffic Control (ATC) A group of highly trained professionals who control the airspace in Controlled Airspace and assist pilots as required to maintain the safety of flights.
Air Taxi A taxi done by a helicopter below 100ft 
AK General aeronautical knowledge
ALA Aerodromes and aeroplane landing areas
ALC Approved load control
ALT Altitude
Altimeter An instrument that gives a reading of height in feet. The setting is based off of a pressure setting, in hectopascals (hPa) and the height shown can vary depending on what reading is required. Common readings will be set for Above Mean Sea Level (AMSL), Above Ground Level (AGL), or can be set for a Flight Level with the standard QNH setting of 1013 hPa.
Altitude A distance measurement showing the height of an object above a reference point.
AMP Aerial application management plan
Amphibian An aircraft that is equipped with retractable wheels for landing on landing, but also has a hull shaped fuselage for landing on water.
Ancillary Controls These are secondary controls which have an effect on the aircrafts direction or altitude, eg: Throttle and Trim
Angle of Attack An angle formed between the wing’s chord and the relative airflow
Angle of Bank This is the angle of the lateral axis of the aircraft to the horizontal plane. In other words, it is the angle of the wings to the horizon when viewed from the rear. If wings are level with the horizon, AoB will be 0 degrees. If the wings are in a vertical position to the horizon, the AoB will be 90 degrees.
Anhedral A downward sloping tendency of the wings, designed for stability. The most common example is the AN-225 or the C-5 Galaxy. Most common on high wing aircraft.
ANP Actual Navigation Performance
AOA Angle of Attack
AOC Air operator’s certificate
AOM Aerodrome operating manual
AP Auto Pilot
Approach Is the intention of flying the aircraft in the final phase of flight to land. An approach can be either an instrument approach for poor weather conditions, or a visual approach if weather conditions permit.
Apron The area on an airport where aircraft are parked, loaded and unloaded with passengers, cargo and fuel. From the apron, aircraft will taxi towards the runway for a take-off via certain taxiways.
APU Auxiliary Power Unit
ARN Aviation Reference Number; your own unique aviation number
ARS Attitude retention system
Artificial Horizon (AH) An instrument that displays an aircraft's position in relation to the horizon and works with a gyroscope.
Aspect Ratio (AR) A ratio between the wing span and wing chord. A high aspect ratio wing will have a high lift value and a lower drag value compared to a lower aspect ratio wing which will have a lower lift and higher drag ratio.
ASI Air speed indicator
AT Auto throttle
ATC Air traffic control
ATIS Automatic Terminal Information Service. This is a continuous broadcast of the current weather which is updated at certain timeframes, or when there is a change in the weather. This is only available at larger aerodromes. Some smaller aerodromes may have an AWIB which is similar to an ATIS 
Atmosphere The layers of gases surrounding the earth or another planet. There are five layers surrounding the Earth, the Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.
ATPL Airline Transport Pilot Licence
ATS Air Traffic Service
Attitude This is the position of the nose of the aircraft in relation to the horizon, ie; being below, level or above the horizon.
AUW All Up Weight
AVADS Auto Voice Activated Decision System
Aviate Flying the aircraft in a safe manner, within the aircrafts limits
AVGAS Fuel used for Piston aircraft. This has a higher octane rating than fuel used for cars
AWIB Aerodrome and Weather Information Broadcast. Similar to an ATIS, the AWIB provides current weather at a particular aerodrome. Used for smaller aerodromes.
AWS Automated Weather Station
Backing Wind An anti-clockwise change in wind direction
BAK Basic Aeronautical Knowledge
Balance This can be referred to as either the Centre of Gravity position which ensures the aircraft is balanced and within its operating limits with weight loading. It could also speak of maintaining sufficient rudder inputs to ensure that the aircraft is flying with the least amount of drag. This can be seen on the Turn and Slip Indicator by looking at the balance ball and ensuring that it is in the middle. If it is off to one side, sufficient rudder needs to be applied and held to keep the ball centred. To help remember which rudder input to use, the saying goes “Step on the ball”. If the ball is off to the right of centre, apply the right rudder. If it is off to the left, apply the left rudder.
Base Leg Part of the aerodrome circuit. This is the second to last leg before turning onto final.
Base Turn The turn onto the base leg of the circuit
BC Patches
BHP Brake Horsepower
Bi lane - An aircraft with two sets of wings, stacked one above the other.
BKN Broken 5-7 Oktas
BL Blowing
Blind Spot A position you are unable to see when performing a lookout, because of parts of the aircraft that may be blocking your view. Eg: A low wing aircraft can block a downwards view to either side of the aircraft
Boundary layer This is the layer of air in the immediate vicinity of the surface of the wing and the air tends to ‘stick’ to this surface. This thickness is several centimetres thick until it reaches the separation point.
BR Mist
Bureau of Meteorology (BOM) this website provides the Australian community with access to weather forecasts, severe weather warnings, radar loops and observations.
Brakes The main way of stopping an aircraft and is most commonly controlled by pushing forward with your toes on the rudder pedals. Some aircraft may have a handbrake style braking system instead of toe brakes.
Brief A portion of time before a flight where you discuss and evaluate all information regarding the upcoming flight. This includes discussing what the objectives of the flight are, the weather conditions, NOTAMS and anything else that may be relevant. 
Buffet Occurs as the aircraft approaches the stall, the airflow that flows over the wings is disturbed and when it reaches the elevator it causes a shaking effect which is felt through the control column. 
BWR Basic Weather Report. A verbal comment on actual weather conditions at a particular aerodrome or place.
CAAP Civil Aviation Advisory Publication
Callsign A combination of either letters or numbers used to identify an aircraft.Normally, the callsign can be seen on the side or tail of the aircraft.
Camber The curve of an aerofoil (wing) from the leading edge to the trailing edge
CAO Civil Aviation Orders include information on technical standards and specifications and are administered by CASA (Civil Aviation Authority) Australia.
Carburetor A component that mixes the air and fuel ratio which then flows to the engine. Carburetors are normally found in older models piston aircraft and newer models generally have a fuel injection system.
CAS Calibrated Air speed
CASA the Civil Aviation Authority of Australia 
CASR 1998 Civil Aviation Safety Regulations 1998
CAT Clear air turbulence
CAVOK Cloud and visibility OK. Visibility 10km or greater and no significant weather
CB Cumulonimbus
CBT Computer-based test
CDFA Continuous descent flight angle
CDI Course deviation indicator
CDP Climb descent procedure
Centre of Gravity (CoG) Is the position on the aircraft where it would balance on a point if it was possible to be suspended at that point. This is calculated by supporting the aircraft on a set of scales and noting the weights shown on each set.
Chart Symbols Symbols found on an aeronautical chart (map)
CHT Cylinder head temperature
Circuit A set pattern flown around a runway, Circuits can be both left hand or right hand, depending on the aerodrome layout and wind direction.
Chord Line An imaginary line drawn from the trailing edge to the leading edge of an aerofoil.
Clearance Obtaining permission to enter controlled airspace from ATC.
Class G Uncontrolled Airspace - no clearances required and no control towers.
Climb A procedure that will cause an intentional gain in altitude usually at a planned rate of climb.
Climb ut - A phase of flight shortly after take-off during which you would retract flaps and gear.
Clock Code A way of identifying the position of yourself or someone else based on the hour positions of a clock. Eg: 12 o’clock will be directly in front of you, 3 o’clock will be 90 degrees to your right. We can also add in high or low to the position, so 12 o’clock high would mean that the other aircraft is directly in front of you, as well as above your altitude. 12 o’clock low would be in front of your position as well as below your altitude.
C of A Certificate of Airworthiness  
Commercial Pilot Licence (CPL) You are a professional pilot and may be paid and will have a minimum 200-250 hours training.  Can be VFR or IFR, choose twin or single engine aircraft, but must be rated in a complex aircraft with Variable Pitch and retractable endorsement (in Australia)
Common Frequency Zones (CFZ) An airspace area which uses the same frequency. Position reports are not mandatory, but it is still good practice to make continual position calls
Communicate Making contact over the radio to other aircraft or ATC.
Compass A device that has a magnetic needle which will point to Magnetic North. In aircraft, a compass can experience variations due to interference from the electrical system and other components within the aircraft and a deviation card can be found which will give the correction for any errors. In the Southern Hemisphere, ONUS is used for compass turns, ONUS being : Overturn North Underturn South
Constant Speed Propeller (CSU) Also known as a variable pitch propeller. The pitch of the propeller blade is able to be changed according to the phase of flight, in order to achieve the most efficiency from the propeller. A fine pitch (high rpm) is used during a take-off while a coarse pitch (low rpm) is used during cruise.
Controlled Airspace The area that requires permission for entry or exit from ATC. Any requests must be made towards ATC for any change to the direction of flight or current altitude. Any instructions issued by ATC must be followed as long as it is safe to do so and by following any instructions, will not break any laws. A pilot can deny a given instruction if he is unable to fulfil the request and may suggest another option that might work for ATC as well.
Convective Turbulence This is low altitude turbulence caused by the sun heating up the earths’ surface. As air moves over a warm surface, it heats up and rises, causing convective currents. Not all air will heat up and rise in a constant manner, and this creates differences in the direction of movement of the air and when flown through, we experience these differences as turbulence.
CP Critical point
CPL Commercial Pilot Licence
CRM Crew resource management
Cross ountry flight - A flight that extends further than 50 nm from the origin airport and may include a landing at a different airport. Can also be referred to as a Nav Flight.
Crosswind This is  a direction of wind that is blowing from any direction other than directly in front of, or directly behind you. With any crosswind in flight, a certain amount of drift needs to be maintained in order for the aircraft to fly in the intended direction.
Crosswind Circuit A circuit flown where the wind is not in line with the runway vector. At some aerodromes with more than one runway, a crosswind circuit may be flown intentionally for practice purposes.
Cruise The phase of flight where the aircraft levels off after a climb, and flies at a level altitude until required to descend to land.
CSU Constant Speed unit
CTA Controlled Airspace
CTAF Common Traffic Advisory Frequency
CTR Control Zone
Cumulonimbus Clouds Formed by powerful updraughts, creating a large, vertical cloud. Associated with large downpours, thunderstorms and hail. The can be formed along frontal lines or anywhere where a significant updraught is formed.
Cumulus Clouds The cotton , puffy clouds generally seen on a fair weather day. These can form into cumulonimbus clouds.
CVR Cockpit voice recorder
DA Density altitude
DALR Dry adiabatic lapse rate
DAME Designated aviation medical examiner
Danger Areas An airspace area which has some form of danger to aircraft. You may enter a danger area, however you will need to take into consideration what danger may be present.
DAP Departure and approach
Debrief A portion of time at the end of a flight that is used to discuss how the flight went, what was done well, what can be improved on etc. As an instructor debriefing a student, this should be done outside the aircraft, away from noise and in a private place as some information may embarrass a student. A solo pilot can debrief himself on a flight to improve on parts that they feel did not meet their expectations. This will improve you as a pilot.
Decision Altitude (DA) A specified altitude in the precision approach, or approach with vertical guidance, at which a missed approach must be initiated if visual reference has not been established. DA is referenced in mean sea level.
Decision Height (DH) A specified height in the precision approach, or approach with vertical guidance, at which a missed approach must be initiated if visual reference has not been established. DH is referenced to the threshold elevation.
Density Altitude (DA) This is the amount of air in a given space above mean sea level (AMSL). In other words, the more dense the air is, the more the amount of air in a given amount of space. Density altitude is pressure altitude corrected for temperature. As density altitude increases, aircraft performance decreases.
Descend A procedure which will cause an intentional loss of altitude usually at a planned rate of descent.
Deviation This is the difference between Magnetic North and the actual direction the compass is pointing to. A difference exists because of interference around the compass which can alter the direction the arrow points to slightly and a correction is noted on a Deviation Card.
Deviation Card A card that is placed near the compass in the aircraft, showing the difference between magnetic north and the direction the compass is pointing, and also showing the correction to use in order to fly the correct compass heading.
DFDR Digital flight data recorder
DFE Design feature endorsement
Dihedral The upward sloping tendency of the wings which provides lateral stability. This is most common on any low wing aircraft and can be seen when viewing an aircraft from the front.
Displaced Threshold A threshold that has been moved further up the runway. Usually this is done because a portion of the runway is unusable
DME Distance measuring Equipment. This equipment automatically provides the distance between an aircraft and a VOR station. The DME does not send the distance over the ground, but rather the actual distance between the two stations (slant range), so there will generally be a slight difference if comparing to a gps distance
Downwind A position in the aerodrome circuit parallel to the runway in use, but travelling in the opposite direction of intended landing.
Downwind Checks Checks done when on the downwind leg of a circuit. These may vary slightly between different training organisations, but comprise of a BUMFH, BUMPFISH or similar. The purpose of this checklist is to ensure you are ready to land the aircraft, for example, ensuring that your landing gear is down is quite important.
DR Low Drifting
Drag An object moving through air experiences resistance which is known as drag. To overcome drag, aircraft are designed to be streamlined.
Drift This is the difference between where the aircraft is pointing to, to where the actual direction the aircraft is flying or travelling over the ground. This is known as the aircraft heading and aircraft track.
DS Duststorm 
DU Widespread Dust
Dynamic Pressure This is the pressure experienced by any moving object as it passes through the air. On the forwards facing surface of the object, air pressure will build up. Dynamic pressure is = to ½ pV2 (part of the lift formula)
DZ Drizzle
EAS Equivalent air speed
ECT Evening Civil Twilight. This begins when the sun is 6 degrees below the horizon and ends at sunrise
EET Estimated elapsed time
EFATO Engine failure after take-off
EFIS Electronic flight instrument system
EGT Exhaust gas temperature
EICAS Engine indication and crew alerting system
Electronic Flight Bag (EFB) An Electronic Flight Bag (EFB) is an electronic device that hosts applications which allow flight crews to perform functions that were traditionally done using paper products and tools. Two Australian examples are AvPlan and Oz Runways. A US example is Jeppesen Aviator.
Elevation The height of any point on the ground above mean sea level (AMSL). As an example, an aerodrom could be 50 feet AMSL, which means it is 50 feet above the level of the sea.
Elevator The horizontal control surface located on the tail plane and controls the pitch of the aircraft around the lateral axis.
ELR Environmental lapse rate
ELT Emergency Locator Transmitter. A device, which can either be portable or fixed in the aircraft that transmits a signal in the event of an emergency. Depending on the ELT, it may have to be manually turned on, or in most cases will be automatically turned on after some high impact. There is the possibility that a hard landing could activate an ELT. There are specific time periods to test an ELT on 121.5 MHz
Emergency An inflight emergency would mean that the aircraft and/or occupants are in severe danger and a mayday call would be submitted
Engine Failure Is when the engine stops producing power, either due to a loss of fuel or other fluids, or due to mechanical failure. Partial engine failures also occur, and some power may still be available.
EOBT Estimated off-block time. The estimated time that the aircraft moves off the gate to proceed for a departure
EPR Engine pressure ratio
EPT Effective performance time
Equator An imaginary circle that divides the Northern and Southern hemisphere. It is directly in the middle between the North and South pole
Equilibrium This refers to the forces acting upon the aircraft in flight, which would all be in balance. In other words, lift = weight and thrust = drag
ERC En route chart
ERSA En route supplement Australia
ETA Estimated time of arrival
ETD Estimated time of departure
ETI Estimated time interval
ETOPS Extended range twin operations
ETP Equi-time point
Exosphere The outermost layer of the earth’s atmosphere
FAE Flight activity endorsement
FAF Final approach fix
Fatigue The International Civil Aviation Organisation (ICAO) defines fatigue as "A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload." In other words, being fatigued can have a serious effect on the outcome of a flight.
FC Funnel Cloud
FD Flight director
Feather The process of changing the pitch of a propeller so that the chord line of the propeller blade is parallel to airflow. This can only be done on an aircraft with a variable pitch propeller.
FEW 1-2 Oktas
FG Fog
FIA Flight information area
Final The position in the aerodrome circuit just prior to landing. This is where the aircraft is in line with the direction of the runway and pointing towards the runway, normally with the intention of landing.
FIR Flight information region
Firewall A solid fire-resistant part of the airframe which separates the engine compartment from the cockpit.
Fixed Pitch Propeller A propeller which is set to a certain angle for all phases of flight and cannot be changed, unlike a variable pitch propeller.
Fixed Wing Aircraft Helicopters are referred to as Rotary and all other aircraft types are Fixed Wing.
Flapless Landing This is a landing conducted without the use of flaps. A procedure conducted during training to simulate how the aircraft would respond in performance during the landing sequence
Flaps Are located on the inner portion of the wing by the trailing edge and come in many different forms, but essentially serve two main purposes; create more lift which also creates more drag but reduces the stalling speed which enables the aircraft to fly at slower airspeeds.
Flare A manoeuvre or process where the nose of the aircraft is raised slightly just before touching the runway, which prevents the nose wheel from touching the runway first as well as slowing the rate of descent which helps have a smoother landing if done correctly.
FlightAware The world’s largest flight tracking data company and provides over 10,000 aircraft operators and service companies as well as over 12,000,000 passengers with global flight tracking solutions. FlightAware leverages data from air traffic control systems in over 55 countries.
Flightpath The path taken through the air
Flightradar24 A global flight tracking service that provides you with real-time information about thousands of aircraft around the world. Our service is currently available online and for your iOS (iPhone, iPad, iPod Touch) or Android device.
Flight Computer A device with a circular slide rule used to solve aviation related calculations: fuel, wind, distance, speed, conversions and time plus a number of other problem solving features.
Flight Level An altitude that uses a specific pressure datum of 1013.2 hPa. When descending, the altimeter is set from 1013.2 to local area QNH. When ascending through the transition level, the altimeter is set to 1013.2 hPa.
Flight Test A test done in order to gain a pilot licence. This will be done by a certified flight examiner and will usually involve a written test as well as a practical flying test.
Flight Manual Shortened for Aircraft Flight Manual. This is the document which contains all the information regarding the aircraft you are flying and should be familiarised as much as possible and must be carried on every flight.
Float Plane An aircraft that has floats instead of wheels so that it can land on water
Flying Boat An aircraft that is specifically designed for water take offs and landings
FMS Flight management system
Fog A thick cloud formed on the earth's surface which reduces visibility to below VFR flying conditions.
Forced Landing A landing that has to be made due to an engine failure. If you are not near an airfield, then a suitable landing area needs to be found to enable a safe outcome for the aircraft and people on board.
Foreflight flight planning, charts, weather, airport information, flight logging, document management, hazard awareness, and more.
Formation Flying This is a pre-organized part of flight when two or more aircraft fly in close proximity to each other (within 100 ft) and will have a lead aircraft. This is most commonly seen during displays or in military flying.
Four Forces Weight, Lift , Thrust and Drag all act on the aircraft in flight. By adjusting any of these forces, we experience an effect and a change in the aircrafts equilibrium occurs
FSTD Flight simulation training device
FU Smoke
Fuel The highly combustible liquid that burns to create energy to operate an engine. Aviation fuel can be MOGAS , AVGAS or JETA1 and its variants.
Fuel Exhaustion Is when the aircraft runs out of fuel, either from a leak, or not enough being loaded before the flight.
Fuel njected Engine - Unlike a carburetor engine, the fuel and air do not mix until they reach the cylinder.
FZ Freezing
g Gravitational force
GAL Gallon
Glide A power-off descent. In a standard powered aircraft, gliding is practised with the throttle closed to simulate an engine failure.
Glide Approach An approach to an airfield without the use of power. Commonly practised during training to simulate a landing with an engine failure. This is an important part of training because if done incorrectly, the aircraft may land short of the runway or land too far down the runway, both of which could cause significant damage to the aircraft and the occupants inside.
Glider A non-powered heavier-than-air aircraft that maintains flight with the use of high aspect ratio wings.Gliders make exceptional use of mountain waves, thermals and ridges to gain lift.
Glide Ratio The distance an aircraft will move over the ground horizontally versus the altitude lost. A higher glide ratio means the aircraft can glide a further distance than an aircraft with a lower glide ratio with the same amount of altitude lost.
Glide slope A beam transmitted at a set angle (3 degrees) to the ground which provides vertical guidance for an ILS approach at the correct angle to the runway.
G OC - G-induced loss of consciousness
GNSS Global Navigation Satellite System
Go round - This is a procedure of aborting a landing. A go-around is normally a VFR term and a recircuit would normally follow for another landing attempt. 
GPU Ground Power Unit
GPWS Ground Proximity Warning System
GR Hail
Gravity A force which acts towards the centre of the earth. It is measured by acceleration of free falling objects and has an average value of 9.8 m/s2
Ground Effect When an aircraft is flying close to the ground, no more than a wingspan distance away, the air that flows over the wing tips to create wing tip vortices, are unable to fully form and instead, forms a cushion of air which contributes to a slight increase in lift and a reduction of drag.
Groundspeed The speed an aircraft is flying at in relation to the ground and is directly affected by the speed and direction of the wind.
GS Small hail and/or snow pellets
GS Ground speed
G/S Glide slope
Gyroscope A spinning device used for maintaining orientation and angular velocity. A gyroscope is used in a number of aircraft instruments to prevent toppling.
Hangar A large building used to store or park aircraft.
HASELL Checklist for stalling, slow flight, or any other manoeuvre that may cause a sudden loss in altitude. Height Airframe Security Engine Location Lookout
Heading (HDG) The direction the aircraft is pointing. This can be different to the track the aircraft is flying based on wind direction and strength.
Headwind A wind that blows in the opposing direction that the aircraft is travelling. In flight, this decreases the groundspeed. A headwind is crucial for both take-offs and landings and we always land into wind
Helicopter A rotary-wing aircraft which does not require forward motion to create lift, but rather produces lift from the rotation of the rotor blades, which are long, narrow wings that produce lift.
Heliport A defined area designated for helicopter operations for landing and departure.
HF High frequency
High Wing The wing is attached on top of the fuselage. Common examples are C152, C172, ATR 72, AN225
HLS Helicopter landing site
HPAV Horse power available
HPREQ Horse power required
Hold A racetrack type pattern that is flown when an aircraft needs to wait before making an approach, normally so that correct spacing between aircraft can be applied by ATC.
Hot ir Balloon - This is a lighter-than-air aircraft which uses an envelope (bag) to make it buoyant.
Horizon The position where we see the sky meet the ocean in the distance.
Horizontal Stabiliser Also known as the tail plane, this is a  fixed section at the rear of the aircraft that helps prevent excessive pitch. The elevator is connected to the horizontal stabiliser.
Human Factors The process of how we, as humans, complete tasks. The human factor can be both positive and negative towards a flight. If we are well prepared with all relevant documents, have cleaned the windshield, familiarised ourselves with the route we are flying as well as the aerodrome we intend to land at, etc, then this will help us to have the best possible outcome for our flight. If we forget documents, or are unprepared for any reason, this adds a stress to our flight if something occurs that we are not prepared for, which could have a negative outcome for our flight.
HUMS Health usage monitoring system
H-V Height-velocity
Hypoxia A condition that occurs in the human body because of a lack of oxygen. The higher we fly, the less oxygen that is available to us. Smaller aircraft are normally limited to fly below 10 000 feet as no oxygen is carried on board, whereas larger aircraft are pressurised and carry extra oxygen. A sign of possible hypoxia is a blueish sign around the lips and fingernails.
HZ Haze
IAF Initial approach fix
IAL Instrument approach and landing
IAP Instrument approach procedure
IAS Indicated air speed
ICAO International Civil Aviation Organisation
Icing This is a condition where ice builds up somewhere on the aircraft. In piston engined aircraft with a carburettor, icing can form inside the carburettor. Other icing occurs when aircraft are flying in cold conditions through areas with moisture, which can cause ice buildup on the airframe.
ITCZ Inter-tropical convergence zone
IELTS International English language testing system
IFR Instrument Flight Rules.  You may fly through and above clouds and don’t have to see where you are going as you will be using your aircraft instruments to fly and navigate
IFR Arrival A procedure following a set arrival pattern which the aircraft will follow via horizontal and vertical positions to a set point which positions the aircraft for a landing.
IFR Departure A procedure following a set departure pattern which the aircraft will follow which ensures that the aircraft is clear of all terrain while climbing to the cruise altitude.
ILS Instrument Landing System. This is a very accurate instrument approach which gives guidance in both the vertical (glideslope) and horizontal (localizer) planes. The benefits of this system over other navaids is that the minimum altitude for a Missed Approach is much lower than that of an NDB or VOR.
IMC Instrument meteorological  conditions
Inertia The tendency of a body to remain in its current state. In other words, if an aircraft is moving, the tendency is that it will continue moving until a force begins to make it slow down to a stop, or if an aircraft is stationary, it will remain that way until a force is applied to get it moving.
INS Inertial Navigation System
ISA International standard atmosphere
IVSI Instantaneous vertical speed indicator
Jet A1 Aviation fuel used for gas-turbine powered aircraft
Jet Blast The rapid movement of air created by a turbine engine which is very hazardous to anything directly behind the aircraft.
JPT Jet pipe temperature
KDR Knowledge deficiency report
KG Kilogram
KIAS Knots Indicated Airspeed
Knot A measurement of speed. 1 knot = 1 nautical mile (nm/hr) = 1.852 km/hr. Most light aircrafts’ airspeed indicators will show the speed in knots, although there are some that show speed in miles/hr (1 m/hr = 1.6 km/hr) 
LA Landing Area
Laminar Flow The smooth part of the airflow over the wing
Landing Area The part of a movement area for aircraft, that is intended for take-off and landing.
Landing Lights Lights that are on the aircraft that are required to be switched on before landing
LAPT Lookout Attitude Power Trim. The mnemonic for a start to a decent procedure
Lateral Axis The tilting point that runs from wingtip to wingtip. The aircraft will pitch about this axis.
Lateral Stability Stability in the rolling plane around the longitudinal axis, controlled by the ailerons.
Latitude Imaginary lines placed horizontally on the earth which are used as position coordinates, expressed in degrees, minutes and seconds. From the equator to North or South, we have 0 degrees to 90 degrees, with the equator being at 0 degrees. Lines of latitude are parallel to the equator
LB Pounds
LDA Landing distance available
LDP Landing decision point
LDR Landing distance required
L/D Ratio Lift to drag ratio
Leading Edge The front edge of the wing
Lean This is referred to as a lower fuel content in the fuel to air mixture in a piston aircraft. 
Left Hand Circuit All turns conducted in the circuit pattern are left hand 
Lenticular Clouds Round, oval or lens shaped clouds formed on the lee side of a mountain in stable air, indicating mountain waves.
Level The term relating to the vertical position of an aircraft in flight
LG Landing gear
Lift A force that opposes weight. If the lift force is more than the weight force, then the aircraft will climb. If it is less than the force of weight, then the aircraft will descend.
Lift Formula Lift = CL x ½ p V2 (squared) S CL is the co-efficient of lift (AoA) p (rho) is the air density V (velocity) The airspeed S is the surface area of the wing In simple terms, L = AoA x Airspeed
Light Signals Signals used by the control tower to issue instructions to an aircraft if radio communications between the aircraft and tower are not working.
Lighter han-air Aircraft - These are aircraft which are filled with hot air or helium, namely, hot air balloons or airships
Lightning Occurs between -10 to +10 degrees Celsius. Rarely harms aircraft in the air.
Light Signals Signals used by a control tower in the event of loss of communication between the tower and pilot
Line up Entering the runway for a departure
LLZ Localizer
LMT Local mean time
LNAV Lateral navigation
Load Factor Is the ratio of lift to weight and a measurement of stress or load that is added to an aircraft in flight. It seems as though the aircraft is adding weight, with an increase in load/stress. As an example, a load factor of 2 means that the apparent weight of the aircraft has doubled and this is due to a force applied on the aircraft.
Localizer The beam transmitted along the extended centreline of the runway for an ILS approach
Longitude Imaginary lines placed vertically on the earth which are used as position coordinates, expressed in degrees, minutes and seconds. The datum is at the Greenwich Meridian, which is in England and is at 0 degrees. From there, we can move 180 degrees East and West. All lines of longitude pass through the North and South pole. Lines of longitude are perpendicular (90 degrees) to the equator
Longitudinal Axis An axis from the nose to the tail of an aircraft. The aircraft will roll about this axis.
Lookout A procedure of scanning the surrounding area to ensure no other aircraft are near enough for a collision.
Low Wing Aircraft that have wings attached on the lower part of the fuselage. Common examples are PA32 , B787 , A350
LPAT Lookout Power Attitude Trim. The mnemonic for a start to a climb procedure
LPV Localiser precision with vertical guidance
LRC Long range cruise
LSALT Lowest Safe Altitude. For Visual Flying this is usually 500 feet above the highest terrain on the aircrafts planned flight.
LSB Lower side band
LTE Loss of tail rotor effectiveness
LTR Litre
LVC Live, virtual and constructive (simulators)
MAC Mean aerodynamic chord
MAPt Missed approach point
Magnetic North The direction that a compass needle will point to. This aligns with the earth's magnetic fields and is not in the same position as True North. Magnetic North drifts at a rate of between 9 - 30 miles per year and is currently in the Arctic Ocean between Canada and Russia
Manoeuvring Area The areas of the aerodrome that is used for the surface movement of aircraft associated with take-off and landing, but does not include areas set aside for loading, unloading or maintenance of aircraft.
Mayday A distress call that is sent out by a pilot of either a ship or aircraft and is used to signal a life threatening emergency. Mayday calls have priority over any other radio call
Maximum demonstrated Crosswind Component This is a figure that can be found in the flight manual, detailing the maximum amount of crosswind that the aircraft has been factory tested in and has shown that directional control can still be maintained. It is affected by the size of the rudder, its distance from the CoG and the availability of asymmetric braking 
Maximum Take-Off Weight (MTOW) The maximum weight an aircraft can be at take-off
Maximum Landing Weight (MLW) The maximum weight an aircraft can be at landing. In most light aircraft, this weight will be the same as the MTOW, whereas larger aircraft will have a much lower landing weight then take-off weight.
Magnetic North The direction that a compass needle will point to. This aligns with the earth's magnetic fields and is not in the same position as True North. Magnetic North drifts at a rate of between 9 - 30 miles per year and is currently in the Arctic Ocean between Canada and Russia
MBZ Mandatory Broadcast Zone. An MBZ is established to provide increased protection to aircraft in areas of uncontrolled airspace which may have a high volume of traffic, Position reports are required on the designated frequency at regular time intervals and when at specific reporting points. Lights should also be used when operating in or around high traffic areas
MCT Morning Civil Twilight. This begins when the sun is 6 degrees below the horizon and ends at sunset.
MDA Minimum descent altitude. The minimum altitude for a non-precision approach below which a descent must not be made unless visual reference with the required indicators are acquired.
MDH Minimum descent height. The minimum height above aerodrome level for a non-precision approach below which a descent must not be made unless visual reference with the required indicators are acquired.
Mean Sea Level (MSL) A measurement of your true altitude or elevation above the standard sea level datum.
Mechanical Turbulence This occurs closer to ground level by air moving over buildings, trees or other obstacles, which disrupt a smooth flow of air
Medical A medical certificate issued by a certified aviation doctor
Medium Turn A turn done at a constant bank angle of 30 degrees
MEIR Multi Engine Instrument Rating
MEL Minimum equipment list
Mesosphere The third layer in our atmosphere. The coldest layer and temperature decreases with an increase in height.
Met Meteorology
METAR Routine aerodrome meteorological report, valid for 1 hour
Metar Auto Automated observations provided by an AWS. Produced every 30 mins on the hr and half hr. Will not include cloud type
MF Medium frequency
MI Shallow
Military Operating Areas An airspace area which is generally designated for extensive military operations, including live firing. An entry approval is required and some non-permanent areas may be established and can be found in NOTAMS
Minimum Fuel A term used to describe an aircraft's fuel level where the fuel supply has reached a state where the aircraft is committed to land at a specific aerodrome with no additional delay
Minimum Safe Altitude The lowest altitude round up to the nearest 100ft  which provides the required terrain clearance.
Missed Approach Generally an IFR term used for aborting a landing attempt, possibly because the approach minimas,or visual contact with the runway, lights, or other requirements to land, were not met. Performing a missed approach will lead to further instructions from ATC to reposition for another approach, or continue on towards your alternate.
Mixture This is the ratio of fuel/air which is controlled by the mixture lever. A pilot is able to control the amount of fuel that is mixed with the air and this is useful when climbing to high altitudes where there is less air, which if the pilot does nothing, the mixture will be rich, or have more fuel than required and could lead to rough engine running, so the pilot would lean the mixture. When descending from a high altitude, the pilot would richen the mixture, or increase the amount of fuel to air ratio as there is more air closer to MSL than at altitude. If the pilot forgot to enrich the mixture, the engine could stop because of fuel starvation.
MLS Microwave landing system
MLW Maximum landing weight
MOS Manual of standards
Mountain Waves A disturbance in the airflow on the Lee side of a mountain. Lenticular clouds can show the wave pattern
MP Manifold pressure
MPL Multi-crew pilot licence
MSA Minimum Sector Altitude. The lowest altitude that may be used that will provide a minimum clearance of 1000 ft or 2000 ft above designated mountainous zones, above the highest obstacle located within 25nm of the designated nav aid or aerodrome designation point.
MSL Mean sea level
MTOW Maximum take-off weight
Multi Engine Aircraft An aircraft powered by two or more engines
MZW Mid-zone weight
Navaids Physical navigation devices that are located on the ground that an aircraft can tune into and fly towards. Eg: VOR , NDB , ILS
Navigate Controlling the direction the aircraft is flying
Navigation Lights Red and green lights situated on the wingtips of an aircraft which help identify which direction the aircraft is travelling. The red light is on the left or port side, while the green light is on the right hand side.
NDB A non-directional beacon. A ground based radio station which is used for direction only. This is an older technology and many NDB’s are being removed throughout the world.
NGT Night
NM Nautical mile ( 1 nm = 1.8 km)
Non raffic Side - This refers to the aerodrome circuit based off of the runway centre line. On one side of the centre line, the circuit is flown, while the side without the circuit is referred to as the non-traffic side.
NORDO Non-radio aircraft. Aircraft without a radio can not operate in an MBZ or controlled airspace, unless certain conditions are met
Normal Axis Also called the vertical or yaw axis. The aircraft yaws about this axis and provides directional stability.
Nose Attitude Referred to as the position of the aircraft's nose in relation to the horizon. A high nose attitude indicates that the nose is above the horizon whereas a low nose attitude indicates that the nose is below the horizon.
NOTAM A notice to airmen which provides information on potential safety hazards in areas or routes. As an example, an instrument aid might not be working at a particular aerodrome and this would be shown in the NOTAAM to alert a pilot planning on flying to that aerodrome.
NPA Non precision approach
NSC No significant cloud and no CB or TCU at all
NVFR Nigh visual flight rules
NVG Night vision goggles
NVIS Night vision imaging system
OAT Outside air temperature
OCTA Outside controlled airspace
OEI One engine inoperative
OGE Out of ground effect
OH&S Occupational health and safety
Okta A method used to describe the amount of cloud cover in the sky, divided into eighths ; eg: 8/8 is overcast
Oleo An aircraft shock absorber on the landing system of most aircraft. It is a pneumatic, air-oil hydraulic shock absorber. Some smaller aircraft may have coil springs and both serve to dampen the impact of landing, with the hydraulic system being more effective.
Orbit A procedure normally used to generate spacing between aircraft. An orbit is simply a turn at a constant altitude and a constant AoB in your current position. It is NOT the same as a hold.
OVC Overcast 8 Oktas
Overbanking The tendency of an aircraft to want to increase its angle of bank, or continue to roll into the turn on its own, because of the differing amounts of lift created on both wings during the turn
Overhead A position fix directly over a point; ie overhead an airfield means that you are directly above that airfield
Overhead Join A procedure for aircraft to join an aerodrome circuit safely. This is normally done at a minimum of 500 feet above the circuit height with a descent to circuit height on the non-traffic side of the aerodrome circuit. It is important to be familiar with the specific aerodrome plates as the circuit direction can be either left hand or right hand based on the wind direction, aerodrome layout for noise control over populated areas, terrain, or other operational requirements 
Overshoot This is when the aircraft runs off the end of the runway, which could be either on take-off or landing.
PAL Pilot-activated lighting
Pan-Pan An emergency distress call that is urgent, but for the time being does not pose any life threatening danger. A  pan-pan can be upgraded to a mayday
PAPI Precision approach path indicator
Parachute Landing Area An area established to want pilots of potential parachutists falling in a particular area. Extreme care is needed when operating near any parachuting activity as they can be hard to spot, and may also land at the incorrect designated spot, may drift over a runway or may be in the general flight path of an aircraft on landing or take-off.
PBN Performance based navigation. For aircraft operating along an ATS route, instrument approach procedure or in designated airspace for area navigation based on performance requirements
PCN Pavement classification number
PEC Pressure error correction
PF Pilot flying
PIF Private instrument flight
PIFR Private IFR rating
PIO Pilot induced oscillation
PIC Pilot In Command is the pilot who is responsible for the safe operation of the aircraft.
Pitch The rotational movement of the aircraft across the lateral axis and is controlled by the elevator.
Pitot tatic System - A system that provides the pressure instruments with the required pressure to operate.
Pitot Tube A pipe-like object that is forward facing and has a small inlet where air can pass through and can be brought to rest. This creates total pressure and is sent to the ASI
PL Ice Pellets
PM Pilot monitoring
PNR Point of no return
PO Dust/Sand whirls
POH Pilot operating handbook
Power Lever Also referred to as a Thrust lever or Throttle lever and is the primary way a pilot controls the amount of fuel that is supplied to the engine.
Power Sandwich This occurs during a turn when load factor is being introduced. As the load factor increases, there is an increase in stall speed. While in a turn, drag is increased, which effectively decreases airspeed. The power sandwich occurs between the decrease in airspeed and increase in stall speed, because power needs to be added to combat the increased drag to maintain a margin over the stall speed. To calculate a new stall speed with an increased load factor, we can use √g x stall speed = new stall speed with increased load factor.
PPL Private Pilot Licence
PR Partial (covering part of the aerodrome)
PRD Prohibited, Restricted, Danger area
Precipitation Any form of moisture that is released from the atmosphere. Examples are: dew, frost, hail, rain , snow and other similar variants and they form by condensation and fall under gravity.
Pre-flight Briefing A period of time before a flight that the pilot spends preparing for the flight. This can be looking at weather reports and NOTAMS, calculating weight and balance, submitting flight plans and anything else required on the day.
Pre-flight Inspection An inspection of the aircraft that is done before flight, to make sure that the aircraft is airworthy and has enough fuel and oil for the flight.
Pressure In aviation, pressure is the atmospheric pressure which is measured in Hectopascals (Hpa). Pressure can have a major effect on aircraft performance and is directly related to temperature.
Pressure Altitude The altitude displayed on the altimeter when it is set to the standard ISA pressure of 1013 Hpa or 29.92 in mg. This setting is only used above the transition altitude.
Pressure Instruments There are three primary pressure instruments,VSI, ASI and altimeter
Primary Controls These are the main controls that are used to manoeuvre the aircraft. They are the Ailerons, Elevator and Rudder.
Private Pilot Licence (PPL) Allows you to fly for fun and for your own business anywhere in Australia in an aircraft up to 5400kg
Prohibited Area An area of airspace which you may not enter
Propeller A device that is fitted to the front of a piston aircraft and is turned by the engine to create a propulsive force which creates either a pulling or pushing force, which enables the forward movement of an aircraft. Propellers can be either Fixed Pitch or Variable Pitch and have a minimum of 2 blades but could have as many as 14!
Propeller Clearance The distance from the tip of the propeller to the ground. 
PUS Permissible unserviceability
QFE A pressure setting which indicates the height above the reference elevation when set on the altimeter subscale
QNH A pressure setting that shows height above sea level when the QNH value is set on the altimeter.
QRH Quick reference handbook
RA Rain
RA Resolution advisory
Radar A radio detection device that provides information on range,azimuth and elevation of objects
Radio A transmitting and receiving device that allows pilots to communicate with other pilots, ATC or any other ground based person who has a device of their own. The correct frequency needs to be selected on both radios in order for communication between both parties involved.
RAF Relative airflow
RAIM Receiver autonomous integrity monitoring
Ramp Weight This is MTOW plus additional taxi fuel which allows you to taxi from your parked position to your take-off position, so that by the time you take-off, you have the maximum fuel available for your flight if MTOW fuel is required.
Rate 1 Turn A standard turn of 3 degrees/sec. A full 360 degree turn will take 2 minutes.
Recreational Aviation Australia (Limited) A self administering Australian organisation on behalf of CASA that is responsible for FTS Flight training schools operating in the Recreational Flight Training Sector, and flying standards for its members.
Recreational Pilot Certificate (RPC) Allows you to fly a Recreational Light Sport Aircraft up to 600kg.
Recreational Pilot Licence (RPL) You are not allowed to be paid for flying but you can take a passenger if you have a Passenger Endorsement and this allows you to fly single engine aircraft up to 1500kg
REIL Runway end identification lights. Very high intensity light projectors located on either side of the runway centreline.
Relative AirFlow It is the airflow that is created from a moving object, flowing in the opposite direction the that objects direction of travel
Retractable undercarriage Landing gear is the undercarriage of an aircraft and may be used for either takeoff or landing. Some aircraft have retractable undercarriages, which fold away during flight to reduce drag.
Restricted Area An airspace area that you may not enter unless prior approval has been gained by the designated administering authority.
RFM Rotorcraft flight manual
Rich This is referred to as a higher fuel content in the fuel to air mixture in a piston aircraft. 
Right Hand Circuit All turns conducted in the circuit are right hand
Right of Way The law which says who needs to give way in the event of a potential collision. When two aircraft are heading directly towards each other, both aircraft will make a right hand turn to avoid the oncoming traffic. Powered aircraft will give way to non-powered aircraft.
RMI Remote magnetic indicator
RNAV Route navigation. A method of navigation which permits aircraft to follow any desired path within the coverage of navigation aids or self-contained aids.
RNP Required navigation performance
ROC Rate of climb
ROD Rate of descent 
Roll A movement around the longitudinal axis that is controlled by the ailerons
Rolling This is either the movement around the longitudinal axis or can be referred to as the beginning of the take-off where the aircraft starts moving.
Rotary aircraft Not a fixed wing aircraft but one that uses rotor blades, i.e. a helicopter.
RPL Recreational Pilot Licence
RPM Revolutions per minute
RRPM Rotor rpm
RT Radio transmission
Rudder The vertical control surface on the tail plane and controls the yaw of the aircraft around the normal axis.
Runway The surface that aircraft use to take-off or land. Different materials are used for runway surfaces, the most common being bitumen or grass. Runways are graded based on their strength and ability to hold the weight of aircraft without breaking or sinking. This grade is shown on the aerodrome charts which also gives the size of the runway and the runway designator, along with other important information.
RVR Runway visual range. Equipment installed at an aerodrome which gives the visibility values based on the equipment. The equipment consists of 3 transmissometers located adjacent to the TDZ (touchdown zone), MID (mid-point) and END (stop-end)
RVSM Reduced vertical separation minima
SA Sand
SALR Saturated adiabatic lapse rate
SAR Search and rescue
SARTIME Search and rescue time
SARWATCH Search and rescue watch
SAS Stability augmentation system
SCT Scattered 3-4 Oktas
Separation Point The point on the wing where the boundary layer lifts off the wing surface.
Seven S’s Size, Surface, Shape, Slope, Stock, Sun, Surrounds
SG Snow Grains
SH Showers
Shifting An abrupt change in wind direction.
Shutdown The process of switching off the engines either in flight, or on the ground
SID Standard instrument departure
Sideslip An intentional slip that the pilot induces by using cross controls in order to lose altitude and increase the rate of descent and lose more altitude in a short amount of time.
SIGMET A weather report issued for any significant meteorological conditions that may be present; lightning , severe turbulence , volcanic ash etc
SIGWX Significant weather
Sink A condition where the aircraft feels like it is losing lift and has an increased rate of descent. This can normally be felt during landing where a smooth descent rate is set up and some windshear is experienced, causing a small, sudden drop in altitude.
SEA Single Engine Aeroplane - an aircraft powered by only one engine.
SKC Sky Clear
Skid A condition where the aircraft is yawing away from the intended flight path or is yawing into a turn without the use of roll.
Slat Is a device on the leading edge of the wing that opens up to form a slot
Slip A slip is a condition where the aircraft starts slipping inwards or sideways towards the lower wing. A slip can occur during an uncoordinated turn, or during an intentional side slip to offset a cross wind or to increase drag to increase the aircraft's rate of descent. Both of these slips are caused by cross or uncoordinated flight  controls in roll and yaw.
Slipstream A corkscrew pattern of air behind the propeller which is caused by the acceleration of the air from the propeller.
Slope Refers to the incline of the runway. Normally, most runways have a slight slope of +- 2 degrees. This means that one end of the runway has a slightly higher elevation than the other. Some runways may have a much larger slope and would be a one direction runway because you shouldn’t take-off with a large up slope or land with a large down slope.
Slot Create a pathway for air to flow over a wing to re-energize the airflow over the wing
Slow Flight An attitude of flying where the aircraft is at a high AoA and a low airspeed (1.2Vs). This can be useful for VFR pilots in poor visibility, but more commonly is experienced near any phase of flight that may operate near the stall.
SN Snow
SOP Standard operating procedure
Solo a first solo flight is when the student pilot is deemed ready to fly without an instructor on board.  
Spacing This can be referred to with the distance between aircraft, where in controlled airspace, ATC will ensure sufficient spacing between aircraft, while in uncontrolled airspace, the pilot needs to ensure sufficient spacing between other aircraft. Spacing can also be referred to as the correct distance between the downwind leg and the runway. This spacing is usually conducted at circuit altitude, and where the runway ‘intersects’ part of the airframe in the line of sight of the pilot. The purpose of correct spacing is to ensure that circuits are not flow too wide so that in the event of an engine failure during any part of the circuit, the aircraft is still able to return to the runway to conduct a landing.
Span Also called the wingspan, this is the total distance from wing tip to wing tip
Speci A special aerodrome report issued off the hour.They are prepared when some weather element changes significantly. An improvement of weather conditions must last for at least 10 minutes before a Speci detailing the improvements is issued.
Spin An aggravated stall where one wing produces more lift than the other,which, if not corrected, causes a continuation of roll while the aircraft is stalled. A spin can be either intentional or unintentional and has four phases. If practised correctly, it can be a safe manoeuvre to perform.
Spiral Dive This is a steep descending turn, with a rapidly increasing airspeed because of an excessively nose-down attitude and is generally caused by over-banking.
SQ Squall
Squawk A four digit code which is put into the transponder
SS SAndstorm
SSB Single side band
SSR Secondary surveillance radar
Stall Is a loss of lift that occurs as the wing passes the critical angle. It is NOT an engine stall. There are several factors which can affect a stall or cause a stall to occur at varying airspeeds.
Stagnation Point This is the point where there is no air movement on the wing and is in the area on the leading edge of the wing and can vary slightly based on AoA or relative airflow.
STAR Standard arrival route
Static Pressure The standard pressure on any surface in the atmosphere without any compounding effect, A standard ISA day has a static pressure of 1013.25 hPa and this decreases at 1 hPa / 27 feet of altitude that is gained. Static pressure is supplied to the ASi, VSi and Altimeter.
Static Vents Vents on the surface of the aircraft, placed in a location that will give the most accurate reading with minimal changes as the aircraft experiences changes in roll, pitch or yaw.
Steep Turn A turn done at a constant angle of bank of 45 degrees
Storm A change in the atmosphere where wind speeds can reach 48-55 knots. Typically associated with strong gusty winds, lightning and precipitation.
Straight and Level (S&L) The phase of flight that makes up the majority of all flight. This is achieved by flying in a given direction at a constant altitude. The attitude of the aircraft can vary significantly based on the speed at which S&L is being maintained.
Stratosphere The second layer closest to the Earth's surface. The ozone layer can be found here
Streamlining The process of minimising the frontal face of an object thus reducing drag
Strobe Lights White lights situated on the wingtips of an aircraft that constantly flash
Strut A structural component that is common on high wing Cessna aircraft. The strut adds strengthening to aircraft structure.
Student Pilot A person who has not yet gained a pilot licence, but may be able to fly solo if they hold a current medical and have met the requirements for a solo flight.
S-Turn A snake-like turn of two half circles. Commonly used on final approach as a means of losing altitude if the aircraft position is too high
Surface Refers to the type of material used for the runway. Runways that need to accomodate large aircraft, need a certain amount of strength factor and are normally made of bitumen (tar), and smaller runways for smaller aircraft are most commonly grass, but can also be crushed shells, gravel and packed sand.
Surface Wind The direction and speed of the wind measure a few metres above the surface.
SMS Safety Management System. A system designed to identify hazards lower and manage risk for organisations, groups and businesses.
TA Traffic advisory
TAF Terminal aerodrome forecast. Issued 1 hour before validity and are valid for 24 hrs. Issued 4 times per day
Tailwind The wind direction that is coming from behind the aircraft and moving in the same direction as the aircraft. This increases the aircrafts groundspeed.
Takeoff Distance The total distance it takes for the aircraft to start rolling, to the point of 50 ft in height.
TAS True air speed
TAT Total air temperature
Taxi Any time the aircraft is moving under its own power on the ground. Directional control is achieved by using the rudder pedals while the control column is used to prevent the wind from raising a wing in strong winds.
Taxiway The areas the aircraft is permitted to move between the runway and apron
TCAS Traffic collision avoidance system
TCU Towering Cumulus
TEM Threat error management
Temperature The measure of how hot or cold something is. Temperature can greatly affect the performance of aircraft. The standard sea level temperature is 15 degrees Celsius.
Temporary Hazards Temporary special use airspace that may have some form of hazard to the pilot. These can be found in Supplements or NOTAMS
Terminal A building within the airport where passengers go to depart a flight, or arrive from a flight which can be made up of several gates where the aircraft can park
TGT Turbine gas temperature
Thermosphere The fourth layer in the earth's atmosphere which lies between the mesosphere and exosphere.
THP Thrust horsepower
Threshold The beginning portion of the runway which is useable for landing
Throttle Lever Also referred to as a Thrust lever or Power lever and is the primary way a pilot controls the amount of fuel that is supplied to the engine.
Thrust A force that opposes drag and is created with engine power. If thrust is more than drag, the airspeed will increase and if it is less than drag then the airspeed will decrease.
Thrust Lever Also referred to as a Throttle lever or Power lever and is the primary way a pilot controls the amount of fuel that is supplied to the engine.
Thunderstorm A storm which is extremely hazardous for aircraft. Severe turbulence is associated with the massive Cumulonimbus cloud, both inside the cloud and below it. Severe icing can be experienced within the cloud as well as hail, which can damage an aircraft.
TIT Turbine inlet temperature
TMG Track made good
TODA Take off distance available
TODR Take off distance required
TOEFL CBT Test of English as a foreign language computer-based test
TOEFL IBT Test of English as a foreign language internet-based test
TOEFL PB Test of English as a foreign language paper-based test
TOEIC Test of English for international communication
Torque A force that attempts to rotate the aircraft, rather than the propeller. This force is noticed on take-off in a single, piston engine aircraft when throttle is increased. You will notice that the aircraft begins yawing and the correct rudder input needs to be applied to maintain centreline
Touch and Go Normally only done while training in the circuit, this is the process of conducting a normal landing, followed by a normal take-off, without stopping in between.
TR Track
Track The path over the ground that the aircraft is flying. This can vary to the aircrafts heading based on the direction of the wind
Traffic Any other aircraft within your vicinity
Transition Altitude (TA) This is the altitude where aircraft switch between using local or area QNH settings to Flight levels using the ISA setting of 1013 hPa
Transition Level The lowest flight level available for use above the transition altitude. This layer will differ between countries.
Trailing Edge The rear edge of the wing
Transponder A transponder is a piece of radio equipment in the aircraft that picks up and automatically responds to an incoming signal. Also the pilot can use to  input various codes which ATC can view and track. The code that the pilot inputs is either a generic code , given directly from ATC or is the standard emergency codes if required
Transponder Code The four digit code inserted into the transponder.
Trend A forecast which is attached to Metar Auto reports. A trend will supersede a TAF
Trim Most often referred to when ‘trimming’ the aircraft using a trim wheel inside the aircraft. In smaller aircraft, a movable trim tab is located on the elevator and can be manually adjusted in flight to balance out small pitching forces. There can also be a fixed trim tab, normally on the rudder which can only be adjusted on the ground. In larger aircraft, the rudder will also have a movable trim tab. 
Tri-Plane An aircraft with three sets of wings, stacked on top of each other.
Troposphere The first layer closest to the earth which has the majority of the atmosphere’s mass. It is wider at the equator than it is at the poles.
True North The geographic North Pole which is determined by an imaginary line drawn through the Earth to find the Northernmost point. It is not in the same position as Magnetic North.
TS Thunderstorm
TTF Trend type forecast
Turbulence This is the ‘bumpiness’ that is experienced during a flight. This can be caused by a number of different sources and can range from light to severe. Different forms of turbulence are; Mechanical turbulence, Wind-shear turbulence, Convective turbulence and Wake turbulence.
Turns Are controlled by a co-ordinated use of the ailerons and the rudder. As a turn begins, the weight vector is no longer directly opposite to the weight vector and we begin to lose altitude, so some backpressure (slight pitch up) needs to be applied to maintain altitude.
Turn & Slip Indicator A gyroscopic instrument which measures the rate at which the aircraft turns as well as the direction that it is turning and gives an indication whether the turn is a balanced turn.
TWS Take off warning system
UAS Undesired aircraft states
UHF Ultra high frequency
Uncontrolled Airspace This is Class G airspace where ATC does not have control over the movements of any aircraft. There are no clearances required and no control towers.
USB Upper side band
UTC Universal time coordinate
V1 The speed beyond which take-off should no longer be aborted. In other words, if V1 is reached, then you as the pilot are committed to the take-off. An aborted take-off after V1 will mean that there is not enough runway available to safely bring the aircraft to a stop
Va Design manoeuvring speed. Below this speed, the aircraft will stall before experiencing any structural failure if full application of any flight controls is experienced. Above Va and the aircraft may experience significant structural damage before stalling.
VA Volcanic Ash
Vacate Leaving the runway and joining a taxi way
Variable Pitch Propeller A propeller which has the ability to change its pitch in flight, either automatically or manually by the pilot,  which reduces drag and increases performance
VASI Visual approach slope indicator
VC Vicinity
Veering wind A clockwise change in wind direction
Vertical Stabiliser Used to provide directional stability. The rudder is attached to the vertical stabiliser
Vfe Maximum flap extended speed
VFR Visual Flight Rules. You may only fly when you can actually see where you are going.
VFR Transit Lanes A pathway through a control zone or control area that has specific altitude requirements which aircraft can fly through without obtaining a clearance.
Vfto Final take-off speed
VHF Very high frequency
VIS Visibility
Visibility The ability to clearly see an object at a certain distance. The minimum visibility required for VFR flight is 5km and when obtaining weather reports, either before your flight or via an ATIS, the visibility for a specific period of time will be displayed or given in the weather report.
Visual Departure A departure by an IFR flight when either part or all of an instrument procedure is not completed and the departure is executed based on visual reference to terrain.
Visual Reference Continuous reference to either land or water
Vle Maximum landing gear extended speed
Vlo Maximum landing gear operating speed
VMC Visual meteorological conditions
Vmca Minimum control speed in the air
Vmcg Minimum control speed on the ground
Vmo Maximum operating speed
VNAV Vertical navigation
Vne Never exceed Speed
Vno Normal Operating Speed
Volcanic Hazard Zones Areas of airspace designated around a volcano. These have special conditions and the size of the area can change based on the volcanic alert level. Entering a VHZ has specific requirements.
VOLMET Meteorological information for aircraft in flight
VOR A ground based radio station which is used for navigation by pilots who have a VOR receiver in the aircraft. A VOR transmits radials from the station.
Vr Rotate speed
Vso Stall speed - flaps extended
Vs1 Stall speed - clean 
VS Vertical speed
VSI Vertical speed indicator
Vso Stall speed in landing configuration
VTC Visual terminal chart
VTOSS Take-off safety speed
Vx Best angle of climb speed
Vy Best rate of climb speed
WAAS Wide area augmentation system
WAC World aeronautical chart
Wake Turbulence Turbulence caused by the air flowing around the wings of an aircraft. The larger the aircraft, the greater the wake turbulence. If you are flying in a small aircraft following a larger aircraft, wake turbulence can flip a smaller aircraft over and cause significant damage. On landing, it is important to note where the larger aircraft touches down on the runway, and you should then land further down the runway. On take-off, the position the larger aircraft leaves the ground should be noted and a smaller aircraft should be off the ground before that position.
Weathercock The tendency for the aircraft to veer into the direction of the wind
Weather Radar Radar equipment in aircraft which sends out a signal of pulses and is reflected back if it hits a cloud containing rain.
Weight and Balance A calculation performed to ensure the aircraft is within its take off and landing limitations. This calculation ensures the aircraft is within its weight limits as well as within the Centre of Gravity envelope
White Arc Found on the airspeed indicator, this shows the operational flap range in knots for your aircraft.
Wind The movement of air from one position to another. In the Southern Hemisphere, wind moves clockwise around a low and anti-clockwise around a high and the opposite is true for the Northern Hemisphere.
Wind Gradient The gradual increase or decrease in wind strength. From a higher altitude to the earths’ surface, the wind gradient gradually decreases
Windshear Either a significant horizontal or vertical change in wind speed or direction. This can be extremely dangerous, especially at low levels when landing as a sudden change in wind velocity may cause a loss in lift and could result in an aircraft landing short of the runway. This has caused many accidents, from light aircraft, to large jets.
Windsock A device found on an airfield that shows the direction that the wind is blowing. Some may be illuminated and can also vary in size which would show a different wind strength. When a pilot is deciding on which runway to use, they will look at the windsock to confirm the wind direction.
Windmilling This is a condition when a propeller is no longer turned by the power produced by the engine, but rather from the air flowing over the blades
Wingspan The distance from one wingtip to the other wingtip
W/V Wind velocity
Wx Weather
Yaw A turning or twisting movement around the normal (vertical) axis, controlled with rudder.
ZFW Zero fuel weight
Zulu Universal time, more commonly referred to as UTC (Co-ordinated Universal Time). UTC 0 is based in England on the Greenwich Meridian. The time was originally called GMT (Greenwich Mean Time)

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