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Glossary

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

A

AIP
Aeronautical Information Publication.
ACOP
Arrivals Code of Practice.
ANASE
Attitudes to Noise from Aviation Sources in England.
ANMAC
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.
APU
Auxiliary power unit. A power unit located on the aircraft.
ATC
Air traffic control.
ATWP
Air Transport White Paper.

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C

CAA
Civil Aviation Authority.
CDA
Continuous-descent approach.

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D

dB(A)
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.
DEFRA
Department for Environment, Food and Rural Affairs (UK government).
DfT
Department for Transport (UK government).

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E

ECAC
European Civil Aviation Conference.
ERCD
Environmental Research and Consultancy Department of the Civil Aviation Authority.

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F

FEGP
Fixed electrical ground power.
FEU
Flight Evaluation Unit.
FLOPC
Flight Operations Performance Committee.

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G

GPU
Ground power unit.

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H

HACC
Heathrow Airport Consultative Committee.

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I

ICAO
International Civil Aviation Organization.
ILS
Instrument landing system.

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L

Lday
The A-weighted average sound level over the 12 hour day period of 07:00 – 19:00.
Lden
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.
Leq
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.
Levening
The A-weighted average sound level over the four-hour evening period of 19:00 – 23:00.
Lnight
The A-weighted average sound level over the eight-hour night period of 23:00 – 07:00.

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N

NATS
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 contour
Map contour line indicating noise exposure in dB for the area it encloses.
NPR
Noise preferential route.
NTK
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.

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P

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

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Q

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

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S

SEL
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.
SID
Standard Instrument Departure route.
SOR
Start-of-roll: The position on a runway where aircraft commence their take-off runs.
SoS
Secretary of State.
Sustainable Aviation
A UK aviation industry initiative aiming to set out a long-term strategy for the industry to address sustainability issues.

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T

T5
Heathrow Airport Terminal 5.

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