Heathrow ACP for Compton easterly departures – for the first ever, permanent concentrated PBN route possible over Englefield Green

Key Points

  • Heathrow have submitted an ACP (Airspace Change Proposal)2 to the CAA to implement, by 2022, the very first ever permanent PBN (Precision Based Navigation) route, out of Heathrow, on the easterly Compton departure route, affecting Englefield Green, Egham, Virginia Water, etc.
  • The existing Compton SID (Standard Instrument Departure), see Fig. 1, has not been flown for 30 years1
  • Up to June 2014 the flown Compton SID, see Fig. 3, did not impinge on Englefield Green, Egham, Virginia Water, etc. instead flying to the east of the M25 and south of the M3, flying over Addlestone in Runnymede Borough.
  • In June 2014, without public consultation, the flown Compton SID was moved, see Fig. 4, to the west of the M25 and north of the M3, bringing flights over Englefield Green, Egham, Virginia Water and away from previously overflown Addlestone.
  • In December 2018 Heathrow’s proposed ACP (Airspace Change Proposal) SON (Statement of Need) was published2 on the CAA website, with revised SON and preliminary documents published in March 2019 and the potentially affected area, see Fig. 6.
    • Analysis of these documents shows that it is of great benefit to the aviation industry, being the first ever permanent PBN (Precision Based Navigation) out of Heathrow, since the aborted PBN trial flights in 2014.
    • However for communities it could not be more alarming, the 2014 PBN trials created public uproar wherever it was experienced, for up to 30 miles from Heathrow, and in this new proposal a single flight path just 10’s of meters wide would be created, thus concentrating flights, which inhabit a swathe in excess of 10km, to 1000 times those of today, creating a ‘Noise Sewer’ and blighting communities under it permanently, making it unfit for human habitation.

Historical easterly operations Compton SIDs (Standard Instrument Departure) and NPR (Noise Preference Route)

The diagram below shows the existing easterly operations Compton SIDs (Standard Instrument Departure) and NPR (Noise Preference Route). It covers the southern end of Englefield Green from roughly Bond Street southwards – see expanded diagram below, Fig. 2 – but hasn’t been flown for 30 years, according to Heathrow’s ACP submission.

Fig. 1 Existing easterly operations departure Compton SIDs 

Expanding the above figure below to show the extent to which Englefield Green should be affected if the existing Compton SID was adhered to, extending from Bond Street at the southern end of Englefield Green to Virginia Water further south.  

Fig. 2 The expanded diagram shows the extent of the Compton SID on easterly operations within the context of Englefield Green. The swathe or width of an NPR is 3km and as seen above the width covers from Bond Street in Englefield Green to 3km southwards to Virginia Water. 

Compton SID prior to June 2014

As established by an FOI (Freedom of Information) request, the aircraft tracks on the easterly Compton SID prior to June 2014, (which completely avoided Englefield Green, Virginia Water, in fact the majority of Runnymede Borough) where NATS (National Air Traffic Services), without public consultation, altered the flight path bringing it over Englefield Green, see Fig. 4.

Fig.3 The diagram above, obtained by an FOI request, shows the aircraft tracks on the easterly Compton SID prior to June 2014, (completely avoiding Englefield Green, Virginia Water, in fact the majority of Runnymede Borough).

Compton SID post June 2014

Without public consultation NATS altered the Compton SID flight path to directly fly over Englefield Green, Egham, Virginia Water, etc.

Fig. 4 The diagram above shows the post June 2014 tracks that now cross Englefield Green, Egham, Virginia Water, etc. Prior to June 2014 these areas were not affected by the easterly Compton SID, see Fig. 3. 

New Compton SID ACP2 (Airspace Change Proposal) – ID ACP-2018-85

Below is an extract from Heathrow’s ACP powerpoint submission on the CAA website in italics

Step 1a : Assess Requirements

The current Compton (CPT) Departure routes (SIDs) from both runways on easterlies have not been flown for over 30 years. As the number of flights using Heathrow Airport increased, the route became challenging to manage because of their proximity to the Ockham holding stack and the Heathrow Airport arrival flow to the south of the airport.

Fig. 5 The above diagram shows aircraft tracks using the defined easterly Compton SID (superimposed) and NPR for the August – September 2018 period. As can be seen aircraft tracks are not contained in the 3km NPR swathe. This is the norm for the Compton SID after the June 2014 unconsulted change. 

Potentially Affected Area

This area entirely covers Englefield Green and indeed the whole of Runnymede Borough. Currently aircraft are dispersed along a corridor width of 10km or so, see Fig 4. and Fig. 5, providing natural dispersion and non-concentrated flights. As proposed by Heathrow’s ACP, if this corridor is replaced by a single concentrated PBN route 10’s of meters wide, thus concentrating aircraft by a 1000 times, those under this concentrated PBN route area will be living in, what the CAA CEO termed, ‘a Noise Sewer’, effectively unfit for human habitation.

Fig. 6 Easterly Compton ACP Proposal

This is the area which may be affected by this airspace change depending on its development. This area may change as the proposal is developed. (from CAA ACP website) Below in italics is an extract from the ACP documentation



  • Will mean changes to aircraft noise for some communities
  • Possible consultation fatigue and confusion: similar communities for CPT, Expansion and IPA


  • Will significantly reduce the need for controllers to manually direct aircraft
  • Will ensure aircraft fly this route in a more consistent, predictable way
  • Will allow aircraft to stay within the NPR
  • Potential opportunity to explore PBN respite options for SIDs (depending on design principles and technical possibilities)


  • Will likely require a new NPR
  • Limited life-span ~ 4 years. Expansion airspace design will replace this CPT SID in 2026

Community Perspective

As can be seen from an extract of Heathrow’s ACP submission powerpoint (in italics above) the ‘Opportunities’ section, there are considerable benefits for the industry, but the ‘Issues’ section, ‘Will mean changes to aircraft noise for some communities’, characteristically underplays, as always by Heathrow, the price communities will pay of being under, potentially, a single PBN concentrated flight path, with all aircraft travelling along the exact same flight path just 10’s of meters wide, creating a ‘Noise Sewer’ for people blighted under this morally indefensible proposal.

With a single PBN flight path, this will be infinitely worse than existing distributed flight tracks, which in this case currently span some 10km or more in width, i.e. the aircraft will be 1000 times more concentrated than they currently are!!


1  Heathrow ACP submission power point https://airspacechange.caa.co.uk/umbraco/Surface/PublicSurface/DownloadDocument/575

2 CAA Compton SID ACP Website https://airspacechange.caa.co.uk/PublicProposalArea?pID=110

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