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I remember hearing about a British airport that had two approaches that were used on alternating weeks. They implemented this pilot project (no pun intended) so that different houses would be overflown each week, giving residents the impression that noise from the airport was reduced. What airport was this?

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Apparently it's called Runway Alteration. The only hits I got were referring to Heathrow airport, so my guess is this is the only airport that uses this procedure.

Actually, the alternation is in two ways: per part of the day, and per week. During week 1, from 06:00 to 15:00 runway 27L is used, and from 15:00 until last departure 27R is used.

The week after this, the things are reversed: From 06:00 to 15:00 runway 27R is used, and from 15:00 until last departure 27L is used. So the people living under the approach of 27L will have noise in the first part of the day in week 1, and during the second part of the day in week 2. See the full programme here.

It is influenced by the six factors below (taken from the same source):

  • Daytime patterns of runway alternation are different to night-time patterns: at night there are only a handful of landings and very few take-offs.
  • Aircraft land and take off into the wind, so the wind direction has a big effect on flight patterns.
  • Government policy currently favours aircraft taking off towards the west. Even when the wind blows from the east, aircraft could still fly in from east and take off towards the west. This is because we have a westerly preference.
  • A historical restriction means that aircraft cannot take off towards the east from the northern runway. This is because of the Cranford Agreement.
  • The hour between 06:00 and 07:00 is the busiest time of the day for arrivals so we are able to use both runways for landings.
  • Occasionally we have to suspend runway alternation for airfield maintenance, in response to bad weather or when air-traffic control want to avoid a build-up of arriving aircraft.

Actually, alternation also occurs for night flights, but then in 4 one-week periods.

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    $\begingroup$ Take-offs from Heathrow are permitted with up to a 5 knot tailwind component (from memory) so runway changes due to wind direction changes are minimised. $\endgroup$ – Simon Oct 19 '15 at 10:35

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