Runway alternation

Runway alternation is a system introduced at Heathrow Airport to alleviate noise disturbance experienced by local residents affected by arriving aircraft on the final approach to land. Its principal advantage is that it provides certainty of periods of relief from aircraft noise for local communities.

During the day, on westerly operations, one runway is used for landings from 07:00 to 15:00 and the other from 15:00 until after the last departure. This arrangement runs for a week from Monday to Sunday and the order is reversed every week. Due to the Cranford Agreement, there is no daytime runway alternation during easterly operations.

At night there is runway alternation on both westerly and easterly operations after the last departure until 06:00. It begins after the last departure in order to coincide with the rotation of the westerly/easterly preference at night. (See direction of operation).

The Department for Transport (DfT) has commissioned an ongoing trial of runway alternation between 06:00 and 07:00 but National Air Traffic Services (NATS) has discretion to make use of the other runway for arrivals when arrival delays building up exceed a given duration. Weather conditions, both locally and encountered en-route by long-haul aircraft, can contribute to the build-up of arrival delays.

Where possible, routine checks and maintenance of runways, adjoining taxiways and associated equipment is planned to coincide with the pattern of runway alternation. However, there will be occasions when alternation has to be suspended, or the pattern modified, to allow maintenance or works of a longer duration, such as resurfacing of runways, to be carried out.

The pattern of runway alternation has to be combined with the rotation of the use of an easterly/westerly preference at night. This makes for a complicated system of runway use, but results in a four-week schedule taking all factors into account. The current schedule is available from the Flight Evaluation Office (Freephone 0800 344 844). At the end of each year the schedule continues in the same pattern without a break.

It is important to note that the system mainly benefits those people living directly under the Instrument Landing Systems (ILSs) and close to the airport where all aircraft will be established on (i.e. using) either of the ILSs. Some other areas only benefit to some degree from runway alternation since they are also overflown by aircraft on their way from the stacks to join the ILS for either runway.

Runway Alternation applies to arriving aircraft only but where possible Air Traffic Control (ATC) use the 'other' runway for departures.

There are occasions when runway alternation needs to be suspended for extended periods, normally to enable maintenance work. This happens rarely and, where it is known in advance, BAA Heathrow gives advance notice to residents.

Whilst every effort is made to ensure that runway alternation operates, there are occasions when, for short periods, unforeseen circumstances mean that changes in the procedure need to be made at short notice.

Occasionally for safety reasons it is necessary for aircraft to land on the runway not scheduled for landings. For example as a result of an aircraft bursting a tyre on touchdown. This means that subsequent aircraft will have to use the other runway until the first aircraft has been moved and the runway checked and cleared of tyre debris. Another example is a medical flight which may be landed 'out of alternation' in order for it to be brought in more quickly.

Landing runway alternation programme for year 2009. (This link will launch a 98KB PDF in a new window.)

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