I've noticed that flights over Richmond (particularly arrivals) seem to have significantly reduced over the last few weeks. This is based on looking at Flightradar, as well as listening to the noise levels overhead.
I believe that Heathrow ATC alternates runways, holding patterns, and directions, but I'm finding it difficult to understand how and when these changes happen.
When do these flight path pattern changes happen, and potentially when will flights overhead Richmond might increase again?
Heathrow has an extraordinarily elaborate runway alternation programme, designed to spread out noise as evenly between its different neighbours as possible.
Daytime runway alternation follows a daily cycle and a fortnightly cycle. Alternation starts at 6am and continues till the last aircraft departs at the end of the day.
- In the morning we use one runway for take-offs and the other for landings. At 3pm – roughly halfway through Heathrow's working day – we swap over
- We continue this morning and evening pattern of runway use for the rest of the week
- The following week we switch completely. What we did in the evening during the previous week, we now do in the morning. And vice versa
Regarding planes over Richmond (which is situated under the approach path to runway 27L):
During the week starting 8th of April, the programme states that 27L was used for landings from 6:00 until 15:00, resulting in a lot of traffic over Richmond during the morning, but little to none in the evening.
During the week starting 15th of April, the programme states that 27L is used for landings from 15:00 until the end of the day.
During the week starting 22nd of April, they will switch over again to land on 27L from 6:00 to 15:00.
You can read much more about the programme here.
ATC will changes runways depending on the direction of the wind. Heathrow has 2 strips:
It is a good thing to land into wind, so if the wind is coming from the east the 09 runways will be used. In London the prevailing wind is more often coming from the southwest, which is why the 27 runways are more often in use. However, historically you'll find that the winds in March and April show a lot more variability, with northeasterly winds much more often, which has been true this year. A wind from the east will mean the 09 runways will be used. Departing airplanes tend to get turned and dispersed relatively quickly, so you'll fewer airplanes taking off over Richmond than on approach.
Richmond is directly under the approach path for 27 Left. Heathrow will often switch the left and right runways in order to reduce the noise impact on local residents. The hold points haven't changed that I know of, but there are several of them and they use different ones depending on the runways in use.
So the combination of wind directions this time of year and the switching of runways means you'll see less airplanes over Richmond this time of year. But never fear, by July the wind will be back to the southwest most of the time.
