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Runway alternation

A system of runway alternation was introduced in the 1970s for aircraft landing during westerly operations (ie when arriving aircraft make their final approach over London) to provide predictable periods of relief from the noise of landing aircraft for communities under the final approach tracks to the east of the airport.

The pattern of alternation has been modified several times since the 1970s and in 1999 was extended to the night period.

The present pattern provides for one runway to be used by landing aircraft from 06:00 until 15:00 and the other runway to be used from 15:00 until after the last departure (normally starting with the midnight hour), after which landing aircraft use the first runway again until 06:00.

However, on Sunday each week the runway used before midnight continues to be used for landings until 06:00. This means early morning arrivals before 06:00 use a different runway on successive weeks and that the runways used by landing aircraft before and after 15:00 also alternate on a weekly basis.

Runway alternation 6am-7am

From 14 August 2000 there has been an ongoing trial of runway alternation between 6am and 7am. It is a trial only and so ATC can still use both runways to land arriving aeroplanes when delays build up. The Department for Transport has not confirmed how long it will run.

Aircraft taking off during westerly operations can use either runway, but most use the runway that is not in use for arrivals.

Runway alternation does not operate in the daytime during easterly operations due to the Cranford Agreement.

The overall pattern of alternation results in a four-week schedule which provides for one runway to be used for arrivals on westerly operations during the day with the rotation of the use of an easterly/westerly preference at night.

The pattern of runway alternation may be suspended by Air Traffic Control if there are sound operational or safety reasons for doing so.

Additionally, maintenance work at the airfield may occasionally mean that adherence to the published programme may not be possible. However, every effort is made to adhere to the alternation programme.

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