Heathrow expansion and aircraft noise
The airport has two main east to west runways. At any one time one runway is used for departures and the other for arrivals. Operations are reversed at around 3pm each day. The pattern is also changed weekly so that the runway used for departures in the mornings one week is used for arrivals in the following week.
This alternation provides considerable relief for residents living close to the airport. Wandsworth residents receive less benefit as an aircraft will still need to cross the borough when lining up to the northern runway.
The system works well when the wind is from the west. Westerly operations mean that landing aircrafts approach Heathrow from the east passing over central London. Departing aircrafts fly out over Windsor.
When the wind is from the east landing aircraft approaches from over Windsor. A departing aircraft will always use the southern runway and depart to the east. Some of these go out directly over Tooting.