Quota Count system
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Quota Count is a system used by London's Heathrow, Gatwick, and Stansted airports to limit the amount of noise generated by night-time aircraft movements.
[edit] Description
From 1962 until 1993, operations at Heathrow were subject to a simple limit on the number of aircraft movements that were allowed to take place during the night period.
In 1993 a new Quota Count system was introduced based on aircraft noise certification data. Each aircraft type is classified and awarded a quota count (QC) value depending on the amount of noise it generated under controlled certification conditions. The quieter the aircraft the smaller the QC value. Aircraft are classified separately for landing and take-off.
Aircraft were originally divided into six QC bands from 0.5 to 16, but following a review by the Department for Transport[1] a seventh category - Quota Count 0.25 - was added in March 2007.[2]
| Noise Classification | Quota Count |
|---|---|
| 84 - 86.9 EPNdB | 0.25 |
| 87 - 89.9 EPNdB | 0.5 |
| 90 - 92.9 EPNdB | 1 |
| 93 - 95.9 EPNdB | 2 |
| 96 - 98.9 EPNdB | 4 |
| 99 - 101.9 EPNdB | 8 |
| Greater than 101.9 EPNdB | 16 |
The Quota Count doubles with each increase of 3 dB because this corresponds to an approximate doubling of perceived noise level. This is due to the logarithmic nature of the decibel.
Airports operating the system have a fixed quota for each of the summer and winter seasons. As each night-time aircraft movement takes place, an amount of this quota is used depending on the classification of the aircraft. For example, the Boeing 747-400 is classed as QC/2 on arrival, while a Boeing 777-300 is rated QC/1. The quieter 777 therefore uses up the airport's noise quota at half the rate of the 747, thus providing airlines with an incentive to operate quieter types of aircraft.
Subject to some limited carry-over provisions, when the airport's quota has been fully used up, no more night-time movements are allowed to take place. In practice, the airport spreads the quota so that it is used evenly across the season.
The quotas allocated to each airport operating the system are gradually reduced year-on-year in order to achieve long-term reductions in the impact of night-time aircraft noise. (e.g. [1])
London Heathrow Airport prohibits aircraft noiser than QC/2 to operate at night. As this is more stringent than the ICAO's Chapter 4 limits, QC/2 has become a de facto aircraft noise standard.
The Quota Count system has been adapted for use in Madrid and Brussels.
[edit] Notes and references
- ^ National Air Traffic Services (02-2003). "Review of the Quota Count (QC) System used for Administering the Night Noise Quotaa at Heathrow, Gatwick and Stansted Airports". Retrieved on 2007-10-28.
- ^ National Air Traffic Services (02-02-2007). "London Heathrow, London Gatwick and London Stansted Airports Noise Restrictions Notice 2007". Retrieved on 2007-10-28.
