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At-a-glance guide to help you understand the terms used in articles and discussions about aircraft noise.




Arrivals Code of Practice.


Aeronautical Information Publication.

Airbus A320

Small two-engine aircraft, predominantly used for short-haul domestic and European flights. Typically carries 120-130 passengers.

Airbus A380

Large four-engine aircraft, used for long-haul and intercontinental travel. The largest passenger aircraft in service, known as a ‘superjumbo’. Typically carries more than 500 passengers

Airports Commission

Set up by the Government in 2012 to determine the future of airport capacity in the South East of England. The Commission has been tasked with discovering if capacity is needed, and if it is needed, where that capacity should go. The Commission is made up of seven members, chaired by Sir Howard Davies.


Attitudes to Noise from Aviation Sources in England.


Aircraft Noise Monitoring Advisory Committee. The committee is chaired by the Department for Transport and comprises, among others, representatives of the airlines, Heathrow, Gatwick and Stansted airports and airport consultative committees.


Auxiliary power unit. A power unit located on the aircraft.


Air traffic control.


Air Transport White Paper.



British Airports Authority

Balanced approach

An approach to airport noise agreed by governments globally that takes into account the needs and requirements of residents as well as the interests of the aviation industry.

Boeing 747

Large four-engine aircraft, used for long-haul and intercontinental travel, nicknamed the ‘jumbo jet’. Typically carries between 300-400 passengers.

Boeing 777

Large two-engine aircraft, used for long-haul and intercontinental travel. Typically carries 300-400 passengers.

Boeing 787

The Boeing 787 Dreamliner is the newest aircraft operating at Heathrow. Medium-sized two-engine aircraft, which is 60% quieter than the aircraft that it replaces. A very long-range aircraft, it carries around 250 passengers.



Civil Aviation Authority.


Continuous-descent approach.

Cranford Agreement

A verbal agreement made in the 1950s to avoid use of the northern runway for take-offs in an easterly direction over the village of Cranford.



A unit of sound pressure level, adjusted in accordance with the A-weighting scale, which takes into account the increased sensitivity of the human ear at some frequencies.

Decibel (dB)

The decibel is a logarithmic unit of measurement that expresses the magnitude of a physical quantity relative to a specified or implied reference level. Its logarithmic nature allows very large or very small ratios to be represented by a convenient number. Being a ratio, it is a dimensionless unit. Decibels are used for a wide variety of measurements including acoustics, and for audible sound A-weighted decibels (dBA) are commonly used.


Department for Environment, Food and Rural Affairs (UK government).


The Department for Transport is the UK government department responsible for civil aviation including night quotas and environmental standards. The DfT has direct control of noise at Heathrow.


A way of displaying noise averaged over a period. DNL represents noise over a 24-hour period giving a day and night measurement.



Prevailing winds blowing from the east.

Easterly operations

When easterly operations are in effect, planes approach Heathrow over Windsor to the west, and take off towards London. Heathrow switches to easterly operations when the wind is blowing from the east – which it does about 30% of the time


European Civil Aviation Conference.

Engine bypass ratio

The ratio of the amount of air that passes around the outside of the combustion chambers of an aircraft gas turbine to that passing through them


Environmental Research and Consultancy Department of the Civil Aviation Authority.



Fixed electrical ground power.


Flight Evaluation Unit.


Flight Operations Performance Committee.

FlyQuiet programme

The FlyQuiet programme aims to further encourage airlines to use quieter aircraft and to fly them in the quietest possible way. The programme includes the UK's first ever league table that ranks airlines according to their noise performance

Future Airspace Strategy (FAS)

The UK government’s plan to modernise UK airspace by 2020



Ground power unit.



Heathrow Association for the Control of Aircraft Noise. A campaigning organisation that represents people living under Heathrow flight paths, highlighting concerns about issues such as noise and pollution


The Heathrow Airport Consultative Committee is a representative body of local authorities, airport users and interest groups who are consulted by Heathrow and advise the airport on the views of local stakeholders, particularly on issues of airport development, passenger experience and noise

Heathrow Communities Fund

Each year Heathrow donates £750,000 to local community projects through the Heathrow Communities Fund. The fund makes grants to local charitable initiatives that support young people, help protect the environment or encourage sustainable development and eco-education, as well as smaller community-focused projects

Heathrow Noise Forum

The Heathrow Noise Forum was established in January 2014 and brings together representatives from DfT, CAA, NATS, IATA, British Airways, Heathrow, noise pressure group HACAN and local authorities. The forum seeks to foster collaboration in noise management at Heathrow from a range of stakeholders

Hub airport

A hub airport is an airport where local passengers combine with transfer passengers to allow airlines to operate flights to destinations that could not be supported by local demand alone



The International Air Transport Association is a trade association representing 240 of the world’s airlines or 84% of total air traffic. IATA supports many areas of aviation activity and help formulate industry policy on critical aviation issues


International Civil Aviation Organization.


Instrument landing system.




Landing interval

The amount of separation between aircraft on approach


The A-weighted average sound level over the 12 hour day period of 07:00 – 19:00.


The day, evening, night level. Lden is a logarithmic composite of the Lday, Levening, and Lnight levels but with 5 dB(A) being added to the Levening value and 10 dB(A) being added to the Lnight value.


Equivalent sound level of aircraft noise in dBA, often called equivalent continuous sound level. For conventional historical contours this is based on the daily average movements that take place in the 16 hour period (07:00 – 23:00 LT) during the 92-day period 16 June to 15 September inclusive.


The A-weighted average sound level over the four-hour evening period of 19:00 – 23:00.


The A-weighted average sound level over the eight-hour night period of 23:00 – 07:00.




Formerly known as National Air Traffic Services Ltd, NATS is licensed to provide en-route air traffic control for the UK and the Eastern part of the North Atlantic, and also provides air traffic control services at several major UK airports including Heathrow, Gatwick and Stansted.

Noise Action Plan

We are required by EU law to produce a five-year plan setting out proposals for how we will tackle noise. Our current Noise Action Plan was published in 2011

Noise exposure contour

A noise contour is a line on a map that represents equal levels of noise exposure. Aircraft noise maps, which show lines joining points of equal noise, are a powerful tool for illustrating the impact of aircraft noise around airports. The Environmental Research and Consultancy Department (ERCD) of the Civil Aviation Authority developed the UK civil aircraft noise contour model, ANCON, which calculates the contours from data describing aircraft movements, routes, noise generation and sound propagation. The number of annual flights, aircraft types and flight tracks are critical inputs to the contour model.

Noise mitigation

A set of strategies to reduce noise pollution or to reduce the impact of that noise


Noise preferential route.


Noise and Track Keeping monitoring system. The NTK system associates radar data from air traffic control with related data from both fixed (permanent) and mobile noise monitors at prescribed positions on the ground.



Performance Based Navigation (PBN)

A broad range of technologies that are moving aviation away from a ground-based navigation towards relying more on the performance and capabilities of equipment on board the aircraft


Perceived noise level is measured in PNdB. Its measurement involves analyses of the frequency spectra of noise events as well as the maximum level.


Planning Policy Guidance.


Quieter Homes programme

Pilot scheme that ran throughout 2013. Under the pilot, residents were offered full funding for customised noise insulation improvements based on an assessment by an independent noise appraisal expert


Quota Count – the basis of the London airports night restrictions regime.


Runway alternation

At Heathrow during periods of westerly operations, one runway is used by landing aircraft between 7am and 3pm and the other for departures. Arrivals and departures then switch to the other runway from 3pm to the last departure. The pattern alternates on a weekly basis. For example, one week flights will land on the southern runway in the morning and the northern runway in the afternoon. The following week, flights will land on the northern runway in the morning and the southern runway in the afternoon. There is also a runway alternation pattern for flights during the night



Sound exposure level. The level generated by a single aircraft at the monitoring point. This is normalised to a one-second burst of sound and takes account of the duration of the sound as well as its intensity.


Standard Instrument Departure route.


Start-of-roll: The position on a runway where aircraft commence their take-off runs.


Secretary of State.

Summer Leq

Equivalent sound level of aircraft noise in dB(A), often called equivalent continuous sound level. For conventional historical contours this is based on the daily average movements that take place in the 16-hour period (from 7am to 11pm LT) during the 92 day period from 16 June to 15 September inclusive

Sustainable Aviation

A UK aviation industry initiative aiming to set out a long-term strategy for the industry to address sustainability issues.


Taking Britain Further

Heathrow’s revised third runway proposal


Route used by aircraft moving to and from the runway to their allocated parking stand


Tactically Enhanced Arrivals Measures refers to using both runways simultaneously for arrivals to clear major backlogs of flights waiting to land


Heathrow Airport Terminal 5.



Variable landing charges

Heathrow’s landing charges are varied according to how noisy aircraft are. This is to encourage airlines to use their quietest aircraft. For example, the noisiest type of aircraft operating at Heathrow pays ten time more than the quietest aircraft.

Vortex strike

A vortex is a circulating current of air generated by planes. It can sometimes strike and damage the roofs of houses located under a flight path. Pitched roofs with loose-laid tiles are prone to vortex damage



A map-based tool that allows people to track specific flights on specific days in relation to where they live

Webtrak My Neighbourhood

A map-based tool that gives a general overview of where planes fly and to see how the distribution of flights changes over time


Prevailing winds blowing from the west

Westerly operations

Around Heathrow the wind usually blows from the west. Because aircraft must land into the wind, the majority of aircraft arrive from the east (over London) and take off towards the west (over Berkshire/Surrey). This is known as westerly operations

Westerly preference

Aircraft usually land and take-off into the wind. A westerly preference is operated at Heathrow, which means that during periods of light easterly winds (up to 5 knots), aircraft will often continue to land in a westerly direction making their final approach over London. The westerly preference was introduced in the 1960s to reduce numbers of aircraft taking off in an easterly direction over London, i.e. over the most heavily populated side of the airport