Departures

How do aircraft take-off from the airport

Heathrow

By Heathrow

Published 9th July 2018

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On average there are around 650 departures from Heathrow each day, but how do they happen and who decides which routes they go on? Below we explore how aircraft are directed and managed on Heathrow departure routes, which were set in the 1960s by Government.

The first departure is around 06:00 and the last scheduled departure is at 22:50.

Departure routes

Aircraft taking off from Heathrow follow pre-defined routes, known as Standard Instrument Departures routes (SIDs). The choice of SID used is decided by the airline and is predominately dictated by the destination of the aircraft.

Due to the fact that all aircraft perform differently and may be affected by weather conditions which can cause them to drift left or right, there will be some variation as to where different aircraft will fly relative to the centreline of the SID.

For this reason, when the SIDs were designed in the 1960s by the Department for Transport (DfT), the Government set corridors, known as Noise Preferential Routes (NPRs), which extend 1.5 kilometres either side of the SID route centreline.

There are 6 NPRs on easterly and westerly operations (more information on wind direction can be found here).

Aircraft don’t have to follow the centreline of the SID precisely, they just have to be within the 3km wide NPR up to 4,000ft. Under government rules, once aircraft reach an altitude of 4,000ft, NATS air traffic controllers can direct planes off the departure route towards a more direct heading to their destination. This is known as vectoring.

Track keeping

Track keeping (how well aircraft stay within the NPR up to 4,000ft) on Heathrow’s departure routes is very high overall, with about 95% of all departures staying within the published routes.

The exception is the Compton route – a departure route used during periods of easterly operations that heads west. Track keeping compliance is much lower on this route, and has been for many years. Both the DfT and CAA are well aware of this.

We monitor how well planes stick to these routes and we publish data on track keeping on a daily basis on our Operational Data website and quarterly and yearly in our Flight Performance reports.

Who decides which flight takes with departure route?

The choice of which of the six departure routes aircraft take is a decision for airlines. It is dictated primarily by the destination of the flight but there are a number of other factors that influence this too including international situations, the availability of the route and the route charges. Heathrow has no power to dictate which route the airline takes.

Rules on aircraft height

The Department for Transport set rules regarding the height of aircraft on departure. The rules state that:

  • After take-off aircraft must reach 1000ft at 6.5km from ‘start of roll’ (the departure);
  • After passing this point the aircraft shall maintain a gradient of climb not less than 4% to an altitude of not less than 4000ft, and
  • Aircraft must stay within the departure route (NPR) to 4,000ft.

Bigger aircraft such as the Airbus A380s will climb more slowly compared with smaller aircraft such as an A319 or A320, and therefore they may be lower than a smaller aircraft in the same position.

The climb rates will vary because aircraft climb at different rates depending on factors such as the type of aircraft, weather conditions or how fully laden they are. For example, bigger aircraft such as the Airbus A380s will climb more slowly compared with smaller aircraft such as an A319 or A320, and therefore they may be lower than a smaller aircraft in the same position.

Aircraft not following a departure route

On occasions planes are directed to take a different route by Air Traffic Control the air traffic controller or to leave the NPR below 4,000ft. This could be for a number of reasons such as thunderstorms, severe weather conditions or another aircraft such as a police helicopter that is flying within the departure route.


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Late running departures

Although there is not an imposed ban on planes landing or taking off at night, the Government places tight restrictions on the number of flights that can operate at night.

Generally speaking there are no scheduled departures between 23:00 and 06.00 but we know there are times when flights do departure late causing disruption to the local communities. To address this, we have made it one of the steps to tackle as part of our Blueprint for Noise Reduction.

In our Noise Blueprint we’ve outlined 10 practical steps we’re taking to make Heathrow quieter.

Unfortunately sometimes extreme weather conditions can also have an impact on our operations which can mean that the number of departures that are able to take off each hour has to be reduced for safety reasons.

The knock-on effect of this means that the normal schedule is significantly impacted and in order for us to recover from the disruption, some departures are allowed to operate later than usual. In exceptional circumstances like this, we have to be granted dispensation by the DfT in order to operate flights during these hours.

Noise limits on departure

There are set noise limits for departing aircraft. The Government set the limits and the noise is measured at fixed monitors around Heathrow. Departures are continually monitored and if an aircraft creates more noise than is allowed, the airline is fined.

Heathrow is getting quieter. Despite double the number of aircraft movements since the 70’s, noise has reduced almost 10 fold.

In October 2014, we introduced increased noise fines for aircraft that that break the noise limits. The below table shows the previous penalties along with and the new increased fines:

Daytime Shoulder Night
Existing From 27 Oct 2014 Existing From 27 Oct 2014 Existing From 27 Oct 2014
0.1 to 3.0dBA excess = £500 £500 per dBA excess 0.1 to 3.0dBA excess = £500 £1500 per dBA excess 0.1 to 3.0dBA excess = £500 £4000 per dBA excess
More than 3.0dBA excess = £1000 More than 3.0dBA excess = £1000 More than 3.0dBA excess = £1000

The money that is collected is distributed via the Heathrow Community Fund to a range of community projects in areas affected by the airport’s operations.

As a result of the rules and incentives already in place, aircraft flying in an out of Heathrow are on average 15% quieter than the other planes flying in the fleets of the same airlines at other world airports.

See our Community investment page for details of the grant schemes we offer.

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Heathrow

By Heathrow

Published 9th July 2018