Manufacturing and maintenance
A, B, C and D checks
Packages of scheduled maintenance, rising in depth from A to D, that an aircraft undergoes at set intervals of flight hours, cycles or calendar time.
Civil aviation from A to Z
Aviation glossary
235terms
10categories
27acronyms explained
2languages
Registration, MSN, ETOPS, livery, slot, probable cause… Aviation has a language of its own, and Vuelopedia's records speak it. Here it is explained term by term, with examples and links to the aircraft, models and airports in the encyclopedia.
Find a term
From A to Z · 235
A
Safety
Accident
Occurrence linked to the operation of an aircraft in which someone is fatally or seriously injured, the aircraft suffers major structural damage or it goes missing.
Safety
Accident investigation authority
Independent state body that investigates aviation accidents and serious incidents to establish what happened and prevent it from happening again.
Operations and flight
ADS-B
Automatic Dependent Surveillance–BroadcastA system in which an aircraft automatically and regularly broadcasts its satellite-derived position, altitude, speed and identity by radio.
The aircraft
Aileron
Movable surface near each wingtip; deflected in opposite directions on the two wings, the ailerons roll the aircraft about its longitudinal axis.
Operations and flight
Air traffic control
The service that keeps aircraft safely apart and orders traffic on the ground and in the air through clearances and instructions passed by radio.
The aircraft
Aircraft family
Group of models from one manufacturer that share a basic design, flight deck and systems while differing in size, capacity or range.
On Vuelopedia
Aircraft key
The unique identifier Vuelopedia gives each aircraft, made up of its model family and serial number, which stays the same when the registration changes.
On Vuelopedia
Aircraft record
The Vuelopedia page devoted to one individual aircraft, bringing together its identity, technical data, operators, flight log and event history.
Registration and rules
Aircraft register
Official record kept by each state of the aircraft entered on it, listing their registration, type, serial number and owner.
On Vuelopedia
Aircraft status
An aircraft's situation according to the available evidence: active, stored, retired, scrapped or, where the evidence is insufficient, unknown.
Airlines and business
Airline
Company that carries passengers, cargo or mail by air for payment, holding an air operator certificate issued by its national aviation authority.
Airlines and business
Airline alliance
Partnership of airlines that coordinate their networks, frequent flyer programmes, lounges and connections to give passengers a joined-up journey.
Airlines and business
Airline group
Holding company that brings several airlines under one owner, with each usually keeping its own brand, operating certificate and airline codes.
Airports
Airport elevation
Height above mean sea level of the highest point of an aerodrome's landing area, given in feet and metres.
Registration and rules
Airworthiness directive
Mandatory instruction issued by an aviation authority to correct an unsafe condition found in a type of aircraft, engine or component.
Airports
Alternate airport
Airport to which an aircraft can proceed if landing at the intended destination becomes impossible or inadvisable, specified in the flight plan.
Operations and flight
Approach
The phase of flight in which the aircraft lines up with the runway and descends along a defined path to the point where the crew decides to land or go around.
Airports
Apron
Area of an airport where aircraft park to board and disembark passengers, load cargo, refuel and receive line maintenance.
The aircraft
APU
Auxiliary Power UnitSmall gas turbine, usually in the tail cone, that supplies electrical power and compressed air when an aircraft's main engines are shut down.
Airlines and business
ASK
Available Seat KilometresMeasure of an airline's capacity: the number of seats available for sale multiplied by the kilometres flown by each, totalled over a period.
The aircraft
Autopilot
System that holds or changes an aircraft's flight path, altitude, heading and vertical speed according to values selected by the crew.
B
Safety
Bird strike
Collision between an aircraft and one or more birds in flight, which happens mostly at low altitude during take-off, initial climb and approach.
Operations and flight
Block time
The total time of a flight, measured from when the aircraft leaves the departure gate until it stops at the arrival gate, including taxiing and any holding.
Registration and rules
Boeing customer code
Two-character code that Boeing assigned to each customer and added to the model designation, as in the 747-436 built for British Airways.
Engines
Bypass ratio
Ratio between the mass of air that flows around a turbofan's core through the outer duct and the mass that passes through the core to be burnt.
C
The aircraft
Cabin classes
Service levels into which an airline divides its cabin, such as first, business, premium economy and economy, each with its own seats and service.
The aircraft
Cabin configuration
Interior layout an operator chooses for its aircraft: seat count, classes, seats per row, seat pitch, galleys and lavatories.
Operations and flight
Cabin crew
Crew members responsible for passenger safety in the cabin and for in-flight service, as distinct from the flight crew who fly the aircraft.
Manufacturing and maintenance
Cabin retrofit
The renewal of an in-service aircraft's interior with new seats, entertainment, lighting or a different layout of cabin classes.
Airlines and business
Cabotage
Carriage of passengers or cargo between two points within the same country, traffic that most states reserve for their own airlines and close to foreign carriers.
Registration and rules
Call sign
Name by which an aircraft is identified in radio communications with air traffic control, such as Speedbird or Lufthansa followed by the flight number.
Airlines and business
Cargo airline
Airline dedicated to carrying freight, operating freighter aircraft rather than passenger flights, either on its own account or on behalf of other companies.
The aircraft
Cargo hold
Cargo compartment, usually located beneath the cabin floor, that carries checked baggage, freight and mail on a passenger aircraft.
Registration and rules
Certificate of airworthiness
Document issued by the state of registry to an individual aircraft, confirming that it conforms to its approved design and is in a condition for safe operation.
Airlines and business
Charter airline
Airline selling non-scheduled flights hired by a customer, such as a tour operator, company or government, that books the whole aircraft for a trip.
Registration and rules
Chicago Convention
International treaty signed in 1944 that sets out the principles of international civil aviation and gave rise to ICAO.
Registration and rules
Civil aviation authority
Public body that regulates and oversees a country's civil aviation: it registers aircraft, issues licences and certifies airlines and airports.
Operations and flight
Climb
The phase in which an aircraft gains height after take-off up to its cruising level, following a published departure route and the levels cleared by ATC.
Airlines and business
Codeshare
Agreement under which an airline sells seats, under its own code and flight number, on a flight operated by another carrier.
The aircraft
Combi
Aircraft that carries passengers and cargo together on the main deck, separated by a partition, and fitted with a large cargo door.
Engines
Combustor
Section of a turbine engine where compressed air is mixed with fuel and burnt continuously, producing the hot gases that drive the turbine.
Engines
Compressor
Section of a turbine engine that raises the pressure of incoming air through successive rows of rotating blades and fixed vanes before it reaches the combustor.
Airports
Control tower
Air traffic control unit based at an airport that clears take-offs, landings and ground movements and handles traffic in the immediate vicinity.
Airports
Coordinated airport
Airport where capacity falls short of demand, so landing or taking off there requires a slot allocated by an independent coordinator.
Operations and flight
Cruise
The central and usually longest phase of a flight, in which the aircraft flies level at its most efficient height and speed between the climb and the descent.
Weights and performance
Cruise speed
Speed at which an aircraft flies most of a journey, in level flight at high altitude, chosen to balance fuel burn, time and cost.
Safety
CVR
Cockpit Voice RecorderFlight recorder that captures the pilots’ voices, radio communications and flight deck sounds, from aural warnings to engine noise.
D
Manufacturing and maintenance
Delivery
The handover of a new aircraft from its manufacturer to the customer, an airline or a lessor, after acceptance checks and final payment.
Registration and rules
Deregistration
Cancellation of an aircraft's entry on a state's register, for example because it is exported to another country, withdrawn from use or scrapped.
Operations and flight
Descent
The phase in which an aircraft leaves its cruising level and loses height in a controlled way until the start of the approach to its destination.
Manufacturing and maintenance
Desert storage
The parking of out-of-service aircraft in arid regions, where low humidity slows corrosion and land and space come cheap.
Operations and flight
Diversion
A decision to land at an airport other than the planned destination, because of bad weather, a runway closure, a medical emergency on board or a technical problem.
On Vuelopedia
Documented existence
Vuelopedia's level of evidence based on a freely licensed photograph showing an aircraft's registration on an airframe of the model given in its record.
Airlines and business
Dry lease
Lease of an aircraft alone, without crew or maintenance; the lessee airline flies it with its own staff and under its own operating certificate.
E
Registration and rules
EASA
European Union Aviation Safety AgencyEuropean Union agency responsible for civil aviation safety, which certifies aircraft, engines and components and harmonises rules across Europe.
The aircraft
Elevator
Movable surface on the trailing edge of the horizontal stabiliser that raises or lowers the nose, controlling the aircraft's pitch attitude.
Safety
Emergency landing
Landing made with priority because of an emergency on board, usually at the nearest suitable airport and with rescue services standing by.
The aircraft
Empennage
Tail assembly of an aircraft, made up of the horizontal and vertical stabilisers and their control surfaces, providing stability and control.
Manufacturing and maintenance
End of production
The point at which a manufacturer delivers the last example of a type and closes its assembly line, usually once the order backlog has run dry.
Weights and performance
Endurance
Maximum time an aircraft can stay airborne on the fuel it carries, as opposed to range, which measures the distance it can cover.
Engines
Engine core
Central part of a turbofan, essentially the high-pressure compressor, combustor and high-pressure turbine, through which the air that is burnt passes.
Manufacturing and maintenance
Engine overhaul
A visit by an engine to the workshop, after thousands of hours on the wing, to strip it down, inspect it, replace parts and restore its performance.
Manufacturing and maintenance
Entry into service
The date on which a new aircraft type starts carrying fare-paying passengers or revenue cargo with an airline, usually its launch customer.
Operations and flight
ETOPS
Extended-range Twin-engine OperationsRules that let twin-engine aircraft fly routes far from suitable diversion airports, up to a maximum one-engine flying time approved for each aircraft type and airline.
Safety
Evacuation
Rapid, orderly exit of an aircraft’s occupants through the emergency exits, often by escape slide, when staying on board is more dangerous.
On Vuelopedia
Event record
Each significant fact on file in an aircraft's life: an incident, an accident, a period of storage, a return to service or its scrapping.
F
Registration and rules
FAA
Federal Aviation AdministrationUnited States government agency that regulates the country's civil aviation, certifies aircraft and provides air traffic control services.
Engines
FADEC
Full Authority Digital Engine ControlComputer system that controls every aspect of a turbine engine's operation, including fuel flow, starting and limits, based on the thrust lever position.
Engines
Fan
Large bladed rotor at the front of a turbofan that accelerates the incoming air and generates most of the engine's thrust.
Safety
FDR
Flight Data RecorderFlight recorder that continuously logs hundreds of aircraft parameters, such as altitude, airspeed, heading, control positions and engine thrust.
Operations and flight
Ferry flight
A flight without passengers or paying cargo that moves an aircraft to where it is needed: another base, a maintenance shop, a new operator or storage.
Manufacturing and maintenance
Final assembly line
The facility where the major sections of an aircraft, often built at other plants, are joined and its systems installed until it is ready to fly.
Safety
Final report
Document with which an investigation authority closes a case: it reconstructs and analyses the facts, sets out causes and factors, and makes recommendations.
Airports
FIR
Flight Information RegionBlock of airspace of defined dimensions within which flight information and alerting services are provided, under the responsibility of a given state.
Airlines and business
Firm order and option
Ways in which an airline or lessor orders aircraft: a firm order is a binding contract, while an option reserves a delivery slot that can be confirmed later.
Manufacturing and maintenance
First flight
The moment an aircraft leaves the ground for the first time, whether it is the first example of a new type or an individual production airframe.
Operations and flight
First officer
The pilot who shares the controls with the captain, ranks next in the chain of command and usually sits in the right-hand seat of the flight deck.
Airlines and business
Flag carrier
Airline historically identified with a particular country, often founded or part-owned by its government, and representing that country on international routes.
The aircraft
Flap
Movable surface on the trailing edge of the wing that extends to increase lift at low speed during take-off and landing.
Manufacturing and maintenance
Flight cycles
A unit of aircraft use equal to one take-off and one landing; the main measure of fatigue in the fuselage and in many engine parts.
The aircraft
Flight deck
Forward compartment from which the pilots fly the aircraft and manage its systems, navigation and communications.
Manufacturing and maintenance
Flight hours
The time an aircraft, engine or pilot accumulates in flight; one of the basic measures for scheduling maintenance and for recording experience.
Operations and flight
Flight level
An altitude expressed in hundreds of feet and referenced to the standard pressure of 1013.25 hPa, giving aircraft at height a shared vertical reference.
On Vuelopedia
Flight log
A year-by-year summary of an aircraft's activity on Vuelopedia: main airport, most-flown routes, number of flights and periods on the ground.
Registration and rules
Flight number
Combination of an airline code and a number of up to four digits that identifies a particular air service in timetables, tickets and airports.
Operations and flight
Flight plan
Details of a flight filed with air traffic services before departure: aircraft, route, level, speed, estimated times, destination and alternate airports.
Safety
Flight recorders
Crash-protected units that record flight data and flight deck sounds so that investigators can reconstruct what happened during an occurrence.
Manufacturing and maintenance
Flight test campaign
The series of test flights through which a manufacturer shows the authorities that a new aircraft type meets the requirements for certification.
The aircraft
Fly-by-wire
Flight control system in which the pilot's inputs travel as electrical signals to computers that move the control surfaces.
Safety
FOD
Foreign Object Debris / Foreign Object DamageAny loose object that does not belong where aircraft operate and could damage them, such as bolts, stones or tools; the term also covers the damage it causes.
Weights and performance
Foot
Imperial unit of length equal to 0.3048 metres, in which civil aviation expresses altitude across most of the world.
The aircraft
Four-engine aircraft
Aircraft powered by four engines, the classic layout for large long-haul airliners before twins took over those routes.
Airlines and business
Freedoms of the air
Set of rights a country grants to foreign airlines to overfly its territory, land there, or carry passengers and cargo to, from and beyond it.
The aircraft
Freighter
Aircraft used solely to carry cargo, with no passenger cabin, a strengthened floor and a large cargo door on the main deck.
Manufacturing and maintenance
Freighter conversion
The rebuilding of a used passenger aircraft as a freighter, with a large side cargo door, a strengthened floor and a cabin stripped to take pallets and containers.
Airlines and business
Frequent flyer programme
Airline loyalty scheme that rewards customers with miles or points redeemable for flights, and with status tiers that bring benefits when travelling.
The aircraft
Fuselage
Main body of an aircraft, carrying the crew, passengers and cargo, to which the wings, tail and landing gear are attached.
G
Airports
Gate
Point in the terminal from which passengers on a flight reach the aircraft, whether by airbridge, on foot across the apron or by bus.
Engines
Geared turbofan
Turbofan with a reduction gearbox between the fan and the turbine that drives it, so that each can turn at its own most efficient speed.
The aircraft
Glass cockpit
Flight deck in which most dial instruments are replaced by electronic screens that combine flight, navigation and systems information.
Operations and flight
Go-around
A manoeuvre in which the pilot abandons an approach or landing, applies power and climbs away to try again or to head for another airport.
Airports
Ground handling
Services an aircraft receives on the ground between flights: passenger handling, baggage, cargo, fuel, cleaning, catering and pushback.
H
Operations and flight
Holding pattern
A racetrack-shaped path that an aircraft flies over a fixed point while waiting for clearance to continue, usually because of congestion or bad weather.
The aircraft
Horizontal stabiliser
Horizontal tail surface that keeps an aircraft stable in pitch and, on most jet airliners, pivots through a few degrees to trim it.
Airlines and business
Hub
Airport where an airline concentrates its flights and times its schedule so that passengers and cargo from many cities can connect with one another.
Airlines and business
Hub-and-spoke
Way of organising an airline network in which most flights start or end at a central airport, where passengers change to reach their destination.
Safety
Hull loss
Accident after which an aircraft is destroyed, goes missing or is so badly damaged that it is not repaired and never returns to service.
I
Registration and rules
IATA
International Air Transport AssociationTrade association representing a large share of the world's airlines, which sets common commercial and operational standards for air transport.
Registration and rules
IATA airline designator
Two-character designator that IATA assigns to an airline and that appears in its flight numbers, tickets and reservations, such as BA for British Airways.
Airports
IATA airport code
Three-letter code that IATA assigns to an airport for use on tickets, timetables and baggage tags, such as LHR for London Heathrow.
Registration and rules
ICAO
International Civil Aviation OrganizationSpecialised agency of the United Nations that sets the standards and recommended practices for international civil aviation.
Registration and rules
ICAO 24-bit address
Unique 24-bit code, written as six hexadecimal characters, that electronically identifies an aircraft in the signals transmitted by its transponder.
Registration and rules
ICAO aircraft type designator
Code of up to four characters that ICAO assigns to each aircraft type for use in flight plans and air traffic control, such as A320 or B738.
Registration and rules
ICAO airline designator
Three-letter designator that ICAO assigns to an aircraft operator for use in flight plans and air traffic control, such as BAW for British Airways.
Airports
ICAO airport code
Four-letter code under the ICAO system that identifies an aerodrome in flight plans, air traffic control and weather reports, such as EGLL for London Heathrow.
Safety
ICAO Annex 13
ICAO’s international standard setting out how civil aviation accidents and incidents are investigated, with the sole aim of preventing future ones.
Safety
Icing
Build-up of ice on an aircraft’s structure, engines or sensors, which reduces lift, increases drag and can corrupt instrument readings.
Operations and flight
IFR and VFR
Instrument Flight Rules / Visual Flight RulesTwo sets of flight rules: visual flight rules (VFR), under which pilots navigate and avoid traffic by looking outside, and instrument flight rules (IFR), based on instruments and ATC.
Airports
ILS
Instrument Landing SystemGround-based radio guidance system that leads an aircraft both laterally and vertically to the runway, allowing landings in very poor visibility.
Airports
ILS categories
Classification of ILS approaches by minimum decision height and visibility, from CAT I to CAT III, which allows aircraft to land in dense fog.
Safety
Incident
Occurrence, other than an accident, associated with the operation of an aircraft that affects or could affect the safety of operation.
Airlines and business
Integrator
Express delivery company that controls the whole chain, from collection to delivery, with its own aircraft and sorting hubs, offering a door-to-door service.
J
Airports
Jet bridge
Enclosed, movable walkway linking the terminal to an aircraft door so that passengers can board and disembark without crossing the apron.
Engines
Jet fuel
Petroleum-based fuel used by the turbine engines of civil aircraft; the most common grades are Jet A-1 and, in the United States, Jet A.
Operations and flight
Jet stream
A narrow band of very strong westerly winds at high altitude in the mid-latitudes, which shortens or lengthens flights depending on whether they fly with it or against it.
Airlines and business
Joint venture
Agreement in which two or more airlines run a set of routes together and share revenue or profit, acting as a single business in that market.
The aircraft
Jumbo jet
Popular nickname for the Boeing 747, the first wide-body airliner, sometimes applied to other very large passenger aircraft.
K
Weights and performance
Knot
Unit of speed used in aviation and at sea, equal to one nautical mile per hour, which is exactly 1.852 km/h.
L
Operations and flight
Landing
The final phase of flight in which the aircraft crosses the runway threshold, touches down on its main gear and slows to taxi speed.
The aircraft
Landing gear
Assembly of legs, wheels, shock absorbers and brakes that supports an aircraft on the ground and absorbs landing loads; on most airliners it retracts in flight.
Airlines and business
Launch customer
First airline or operator to order a new aircraft model in sufficient numbers for the manufacturer to commit to launching the programme.
Airlines and business
Lessor
Company that owns aircraft and rents them out to airlines for years at a time in return for regular payments, without operating them itself.
Registration and rules
Line number
Number showing the order in which an aircraft left its type's assembly line; a convention used mainly by Boeing alongside the serial number.
On Vuelopedia
Live position
The current position of an aircraft in flight, shown in its record from the ADS-B signals it transmits and that ground receivers pick up.
The aircraft
Livery
Paint scheme and markings that identify an aircraft's operator: colours, name, logo and often a distinctive design on the tail.
Airlines and business
Load factor
Share of the capacity offered that is actually sold; for passengers, revenue passenger kilometres divided by available seat kilometres over a flight or period.
Airlines and business
Low-cost carrier
Airline built around keeping costs down to sell cheap fares: a single aircraft type, high aircraft utilisation, one cabin class and extras charged separately.
M
Weights and performance
Mach number
Ratio of an aircraft's speed through the air to the speed of sound in that air; Mach 1 means flying at exactly the speed of sound.
Safety
Mayday and pan-pan
Standard radio calls for declaring an emergency: ‘mayday’ signals grave or imminent danger, ‘pan-pan’ an urgent situation that needs no immediate help.
Weights and performance
MLW
Maximum Landing WeightMaximum weight at which an aircraft is certified to land, determined mainly by the strength of the landing gear and the airframe.
Manufacturing and maintenance
MRO
Maintenance, Repair and OverhaulThe industry and range of work that keeps aircraft airworthy: line maintenance, heavy checks, engine overhauls and component repairs.
Registration and rules
MSN
Manufacturer Serial NumberSerial number assigned by the manufacturer to each aircraft which, unlike the registration, stays with it unchanged for its entire life.
Weights and performance
MTOW
Maximum Take-Off WeightMaximum weight at which an aircraft is certified to begin its take-off, including structure, crew, passengers, cargo and fuel.
Weights and performance
MZFW
Maximum Zero Fuel WeightMaximum permitted weight of an aircraft with all its payload, crew and passengers on board, excluding the usable fuel in its tanks.
N
Engines
Nacelle
Streamlined housing around an aircraft engine that brings together the air intake, access cowlings, thrust reverser and exhaust nozzle.
The aircraft
Narrow-body
Airliner with a single cabin aisle and typically four to six seats per row; the most common type on short and medium-haul routes.
Registration and rules
Nationality prefix
Opening letters or digits of a registration that show the country in which an aircraft is registered, such as G for the United Kingdom or N for the United States.
Weights and performance
Nautical mile
Unit of distance used in air and sea navigation, equal to exactly 1,852 metres and corresponding approximately to one minute of arc of latitude.
O
Safety
Occurrence
Umbrella term for any safety-related event in aviation, covering everything from a minor incident to an accident.
Weights and performance
OEW
Operating Empty WeightWeight of an aircraft ready for service, with crew, equipment and the necessary fluids, but without passengers, cargo or usable fuel.
Airlines and business
On-time performance
Share of flights that depart or arrive within a set margin of their scheduled time, usually meaning less than 15 minutes late.
Engines
Open rotor
Turbine engine whose large blades spin in the open air without a casing, achieving a very high bypass ratio and lower fuel burn than a turbofan.
Airlines and business
Operator and owner
Distinction between the operator, the airline that flies an aircraft and is responsible for its operation, and the legal owner, often a lessor or a bank.
On Vuelopedia
Operator history
The time-ordered sequence of airlines that have operated an aircraft, with the registration it carried with each and, where known, its owner.
Manufacturing and maintenance
Order backlog
The aircraft firmly ordered from a manufacturer but not yet delivered; it shows how many years of production lie ahead.
P
Weights and performance
Passenger capacity
Number of passengers an aircraft can carry, which varies with the cabin layout chosen by the airline and is capped by a certified maximum.
Weights and performance
Payload
Weight of everything that earns revenue on a flight, namely passengers and their baggage, cargo and mail, excluding the aircraft, crew and fuel.
Weights and performance
Payload-range diagram
Chart showing how much payload an aircraft can carry over each distance, revealing the trade-off between payload and fuel within the maximum take-off weight.
Operations and flight
Phases of flight
The stages into which a flight is divided, from leaving one gate to arriving at the next: taxi, take-off, climb, cruise, descent, approach and landing.
Operations and flight
Pilot in command
The pilot designated as ultimately responsible for the operation and safety of a flight; at an airline this is the captain, who normally sits in the left-hand seat.
Engines
Piston engine
Internal combustion engine in which pistons, driven by burning a mixture of air and fuel, turn a crankshaft that drives the propeller.
Airlines and business
Point-to-point
Network model in which an airline flies directly between the cities it serves, rather than funnelling connections through a central hub airport.
Safety
Preliminary report
First official document of an accident investigation, setting out the facts established in the opening weeks without drawing conclusions about causes.
Manufacturing and maintenance
Preserved aircraft
A retired aircraft kept intact for its historical value, in a museum, on public display or, in some cases, in flying condition.
The aircraft
Pressurisation
System that keeps the air pressure inside an aircraft higher than outside, so that passengers and crew can breathe normally at high altitude.
Safety
Probable cause
Investigation finding that identifies the event, or combination of events and conditions, that most likely led to an occurrence.
Engines
Propeller
Set of blades with an aerofoil section that, as it rotates, accelerates a large mass of air rearwards to produce thrust for piston and turboprop aircraft.
Manufacturing and maintenance
Prototype
An early example of a new aircraft type, built to prove the design on the ground and in the air before the type is certified.
Operations and flight
Pushback
The manoeuvre in which a tug pushes an aircraft backwards away from the gate, since airliners do not normally reverse under their own power.
Engines
Pylon
Structure that attaches an engine to the aircraft, usually beneath the wing, and carries its thrust as well as fuel lines, wiring and bleed air ducts.
R
Weights and performance
Range
Maximum distance an aircraft can fly without refuelling with a given load, while keeping the fuel reserves required by regulations.
Registration and rules
Re-registration
Change of an aircraft's registration, common when it moves to another country or operator; its serial number, by contrast, never changes.
The aircraft
Regional aircraft
Smaller passenger aircraft, typically with about 30 to 100 seats, designed for short routes and airports with modest traffic.
Airlines and business
Regional airline
Airline flying short, thinner routes with regional aircraft, often linking smaller cities to the hubs of the major carriers.
Registration and rules
Registration
Combination of letters and numbers that identifies an aircraft with the state in which it is registered and must be painted on its exterior.
Manufacturing and maintenance
Retirement
The permanent removal of an aircraft, or of a whole type, from an operator's fleet, whether for sale, conversion, preservation or scrapping.
Manufacturing and maintenance
Return to service
An aircraft's return to operation after storage, repair or maintenance, once it has been confirmed as fit to fly.
Airlines and business
RPK
Revenue Passenger KilometresMeasure of airline traffic: the number of fare-paying passengers carried multiplied by the distance, in kilometres, that each of them flies.
The aircraft
Rudder
Movable surface hinged to the back of the fin that swings the nose left or right, controlling the aircraft in yaw.
Airports
Runway
Rectangular surface at an aerodrome prepared for aircraft to take off and land, identified by its magnetic orientation.
Airports
Runway designation
Two-digit number painted at each end of a runway giving its magnetic heading in tens of degrees, with L, C or R added where runways are parallel.
Safety
Runway excursion
Event in which an aircraft leaves the runway surface during take-off or landing, either off the side or past the end.
Safety
Runway incursion
Incorrect presence of an aircraft, vehicle or person on the protected area of a surface designated for the landing and take-off of aircraft.
Airports
Runway surface
Material a runway is built from, such as asphalt, concrete, gravel or grass, which determines the aircraft and weights it can accept.
Airports
Runway threshold
Beginning of the part of a runway usable for landing, marked with white longitudinal stripes and green lights visible to aircraft on approach.
S
Engines
SAF
Sustainable Aviation FuelJet fuel made from renewable or waste sources that can be blended with conventional kerosene and reduces carbon dioxide emissions over its life cycle.
Safety
Safety recommendation
Proposal from an investigation authority, based on lessons from an occurrence, to prevent future accidents, with no presumption of blame or liability.
Airlines and business
Sale and leaseback
Deal in which an airline sells an aircraft to a lessor and immediately leases it back, so that it can keep flying the aircraft without interruption.
Airports
Scheduled service
Flight or series of flights operated to a published timetable, open for sale to the public and repeated systematically between two or more points.
Manufacturing and maintenance
Scrapping
The dismantling of a retired aircraft to recover its usable parts and recycle the rest of the structure for its materials.
Safety
Serious incident
Incident whose circumstances indicate there was a high probability of an accident, and which is therefore formally investigated with the same rigour as an accident.
Registration and rules
Service bulletin
Document in which the manufacturer of an aircraft, engine or component recommends an inspection, improvement or modification to its operators.
Weights and performance
Service ceiling
Highest altitude at which an aircraft can operate normally, set either by its ability to keep climbing or by the limit fixed in its certification.
Manufacturing and maintenance
Service life
The period of use, measured in cycles, flight hours and years, over which the manufacturer has shown that an aircraft's structure withstands fatigue.
The aircraft
Slat
Movable leading-edge surface that moves forward to open a slot, letting the wing reach a higher angle of attack before it stalls.
Airports
Slot
Permission to land or take off at a congested airport on a given date and time, or a departure time allocated to manage the flow of air traffic.
Engines
Specific fuel consumption
Amount of fuel an engine burns for each unit of thrust or power it produces over a given time; the standard measure of engine efficiency.
The aircraft
Spoiler
Hinged panel on the upper wing surface that rises to spoil lift and add drag, helping the aircraft descend, slow down or roll.
Operations and flight
Squawk code
A four-digit number, each digit from 0 to 7, that air traffic control assigns to a flight and the transponder transmits to identify it on radar screens.
Manufacturing and maintenance
Storage
The status of an aircraft that stops flying for a time and is parked under a preservation programme while its future is decided.
Safety
Substantial damage
Damage or failure that adversely affects an aircraft’s structural strength, performance or flight characteristics and would normally require major repair.
The aircraft
Swept wing
Wing whose edges angle backwards from the fuselage to delay compressibility effects, allowing an aircraft to cruise closer to the speed of sound.
T
The aircraft
T-tail
Tail layout in which the horizontal stabiliser sits on top of the fin, so that seen from the front or rear the assembly forms a letter T.
Operations and flight
Take-off
The phase in which an aircraft accelerates along the runway to rotation speed, raises its nose and climbs away to a safe height above any obstacles.
Weights and performance
Take-off distance
Distance an aircraft needs from the start of its take-off run until it reaches a reference height above the runway, normally 35 feet for transport aircraft.
Safety
TAWS
Terrain Awareness and Warning SystemOnboard system that gives pilots visual and aural alerts when the aircraft’s flight path brings it dangerously close to terrain or obstacles.
Operations and flight
Taxiing
Movement of an aircraft on the ground under its own power between the apron and the runway, along taxiways and following instructions from ground control.
Airports
Taxiway
Paved route linking the runways with the apron and other parts of an airport, along which aircraft move on the ground under their own power.
Safety
TCAS
Traffic Alert and Collision Avoidance SystemOnboard system that interrogates the transponders of nearby aircraft and, if it detects a collision risk, tells the pilots to climb or descend.
Airports
Terminal
Airport building where passengers check in, pass through controls, wait for their flight, board and collect their baggage on arrival.
Engines
Thrust
Force produced by an engine as it accelerates air or exhaust gas rearwards, pushing the aircraft forward in reaction.
Engines
Thrust reverser
Engine mechanism that, after touchdown, redirects part of the airflow forwards to help slow the aircraft on the runway.
Operations and flight
Transponder
An on-board device that answers secondary radar interrogations with an identity code, its altitude and, in Mode S, a unique 24-bit address.
Engines
Turbine
Set of bladed wheels that extracts energy from the hot combustion gases to drive the engine's compressor, fan or propeller.
Engines
Turbofan
Jet engine in which a large front fan drives air around the core, producing most of the thrust with greater efficiency and less noise.
Engines
Turbojet
Jet engine in which all the intake air passes through the compressor, combustor and turbine before leaving the nozzle as a high-speed jet.
Engines
Turboprop
Gas turbine engine that drives a propeller through a reduction gearbox, with the propeller rather than the exhaust producing almost all the thrust.
The aircraft
Twin-engine aircraft
Aircraft powered by two engines, now the dominant layout in airline service thanks to the reliability of modern engines.
Registration and rules
Type certificate
Document in which an aviation authority declares that the design of an aircraft, engine or propeller model meets the applicable airworthiness requirements.
U
The aircraft
ULD
Unit Load DeviceStandardised container or pallet in which baggage and freight are consolidated so they can be loaded onto an aircraft as a single unit.
Operations and flight
Ultra-long-haul flight
A non-stop flight of exceptional length, usually more than 16 hours, which needs very long-range aircraft and augmented crews who take turns to rest.
V
Operations and flight
V1, VR and V2
Reference speeds calculated for every take-off: V1, the decision speed; VR, the rotation speed; and V2, the safety speed for climbing with an engine out.
The aircraft
Variant
Version of an aircraft model that keeps the basic design but changes features such as length, engines, range or intended role.
On Vuelopedia
Verification seal
A mark showing that an aircraft's identity (registration, serial number and model) has been checked against the official register of its civil aviation authority.
Airports
VOR
VHF Omnidirectional RangeGround-based radio aid transmitting on VHF that lets an aircraft determine which radial, or magnetic bearing from the station, it is on.
W
Operations and flight
Wake turbulence
Swirling air left behind an aircraft as it generates lift; its strength depends mainly on weight, and it dictates the spacing of the aircraft that follow.
Airlines and business
Wet lease
Arrangement in which one airline hires another's aircraft together with its crew, maintenance and insurance, while the lessor operates it under its own certificate.
The aircraft
Wide-body
Airliner with two cabin aisles and usually seven to ten seats per row in economy; the dominant type on long-haul routes.
Safety
Wind shear
Sudden change in wind speed or direction over a short distance, which is most dangerous close to the ground during take-off and approach.
The aircraft
Wing
Surface that generates the lift needed for flight; on airliners it usually also holds much of the fuel and carries the engines.
Weights and performance
Wing area
Plan-view area of an aircraft's wings, usually including the portion that passes through the fuselage, used as the reference for lift calculations.
Weights and performance
Wing loading
Ratio of an aircraft's weight to the area of its wings, usually expressed in kilograms per square metre; it shapes take-off, landing and ride quality.
The aircraft
Winglet
Near-vertical extension at the wingtip that weakens the tip vortex, cutting induced drag and with it the aircraft's fuel burn.
Weights and performance
Wingspan
Distance between the outer tips of an aircraft's wings, measured from tip to tip and including winglets or other wingtip devices.
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How this glossary is made
The definitions are written by Vuelopedia's editorial team on the basis of ICAO standards, the rules of civil aviation authorities and manufacturers' technical documentation. They are written so that any curious reader can follow them and no professional will find anything wrong in them.
Every term is available in Spanish and English and links to the encyclopedia records where it appears. The glossary grows with every edition.
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