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The Cranford Agreement

What is the Cranford Agreement? - Updated June 2013

The Cranford Agreement is a government agreement made in the 1950s that prevents aircraft from taking off over Cranford from Heathrow's northern runway when the airport is operating on what's known as 'easterly operations'.

Easterly operations occur when the wind blows from the east. Since aircraft always land and take off into the wind, they come in to land from the west (from Windsor) and take off towards the east (towards London) when the wind blows from the east. On average, easterly operations occur 30% of the year, although the proportion of easterly winds vary month to month. 

The Cranford Agreement specifies that departures cannot take off on the northern runway during easterly operations. This means the majority of arriving flights land on the northern runway, and departing flights leave from the southern runway.

Cranford agreement infographich showing percentage split of easterlies and westerlies

What does the Cranford Agreement mean for Heathrow's neighbours?

By favouring one particular community, the Cranford Agreement prevents a more even distribution of aircraft noise around Heathrow. When the wind blows from the east, people who live under the flight path of the southern runway bear the brunt of the noise of departing aircraft. Those living under the approach to the northern runway also get a disproportionate amount of noise from arrivals.

The situation is different when the wind blows from the west, known as 'westerly operations'. Because there are no restrictions, we share the noise of arriving and departing flights equally between the northern and southern runways.

This is done by using one runway for landings and the other for departures, and then swapping over halfway through the day. 'Runway alternation', as it is known, gives residents living under both runway flight paths predictable relief from aircraft noise for half the day.

Although the Cranford Agreement provides relief for residents of Cranford when the wind blows from the east, residents of other areas such as Windsor and the southern parts of Hounslow, get no respite from aircraft noise.

No current alternation on easterlies compared to alternation on westerlies.

The ending of the Cranford Agreement - what happens next?

Aircraft technology has moved on since the Cranford Agreement was drawn up in the 1950s. During take-off, modern aircraft climb higher more quickly. The noise they make is less disruptive to the residents of Cranford than it would have been 60 years ago.

In 2008, the previous government asked residents whether the Cranford Agreement should stay or be abolished.In response to feedback, it announced that the Cranford Agreement would end in 2009. The decision was confirmed by the current government in September 2010.

With the Cranford Agreement gone, we can apply runway alternation throughout the year, no matter which direction the wind blows. But we can't do it straight away. Because Heathrow has developed within the context of the Cranford Agreement, it's not yet geared up to full-time runway alternation. There are too few access taxiways to the northern runway and too few exit taxiways from the southern runway.

To operate runway alternation efficiently, we first have to make changes to Heathrow's taxiways. The building of these taxiways requires planning approval from the London Borough of Hillingdon. We submitted our planning application in May 2013.

What will the ending of the Cranford Agreement mean for Heathrow's neighbours?

Operating runway alternation when the wind blows from the east as well as from the west means we can share the burden of arriving and departing aircraft noise fairly between our neighbours. We can use one runway for take-offs and the other for landings, then swap them over at 3pm each day. 

The ending of the Cranford Agreement does not mean there will be more flights to and from Heathrow. The total number of flights remains the same.

This is what the changes mean for residents. This will only apply when the wind is from the east (approx 30% of the year).

  • Cranford/Heston: introduction of departures from the northern runway taking off towards the east 
  • North Feltham/ southern parts of Hounslow: around 50% fewer departing aircraft using the southern runway to take off towards the east
  • Wraysbury/Old Windsor: more arriving flights using the southern runway from the west 
  • Windsor/Datchet: around 50% fewer arriving aircraft using the northern runway from the west. 

Current and future easterly operations

Mitigating the effects of the changes

 For the majority the ending of the Cranford Agreement will mean less noise from aircraft. For the minority it will mean more. The map opposite shows the difference in noise that various communities will experience when we introduce full runway alternation (when the wind blows from the east). The areas shaded green will see an overall decrease in noise. Those shaded blue will see a small increase in noise.

 As part of our taxiway planning application, we have suggested ways that we can mitigate the effects on residents most affected by changes in operations. This includes the building of a five-metre high acoustic noise barrier at Longford. We're also proposing to provide free double glazing for residents living within a specified zone (known as the 63 decibel leq) who experience an increase in noise of three decibels or more. This is marked as Zone 1 on the map (the dark purple line).

Cranford agreement contour map showing mitigation elegibilty and more versus less noise impact

The Cranford Agreement - June 2013 update (554 KB)
Contour map (2MB)

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