23 December 2016

Update by Charles Kirwan-Taylor, Corporate Affairs & Sustainability Director

23 December 2016

Charles Kirwan-Taylor

The six month monitoring period of the amendment to the Route 4 Standard instrument Departure (SID) routes came to an end on 26 November 2016. Since that time, we have been collating the remaining data and information and have now forwarded this to the Civil Aviation Authority for consideration.  

Information forwarded to the Civil Aviation Authority incudes:

  • Monthly aircraft track dispersion plots.
  • Monthly aircraft track density plots.
  • Monthly aircraft altitudes maps.
  • Daily ‘METAR’ meteorological information at the aerodrome.
  • Details of operational issues arising from Gatwick Air Traffic Control and London Terminal Control at Swanwick.
  • Details of any operational issues raised by aircraft operators.
  • Plots showing the locations of residents providing feedback.
  • Copies of all feedback received from local communities.

Observations of the amendment

While this amendment has been unpopular in certain communities, our assessment of the route modification is that it has achieved what was required. The majority of aircraft have been restored to flying within the lateral confines of the Noise Preferential Route associated with Route 4 with c. 94% track-keeping compliance while simultaneously providing a degree of dispersal around the route’s turn; something that was particularly requested by the local communities.


For comparative purposes, track-keeping conformance achieved on the ‘conventional’ (i.e. non-R-NAV1) SID during the period May-November 2013 was 92.6%. We are confident that the Route 4 R-NAV1 has delivered improved performance. Following the original R-NAV1 implementation during the period May-November 2015 traffic route conformance dropped to 62.06%. Track-keeping has significantly improved during this monitoring period with conformance reaching 93.95% over the period May-November 2016. In terms of air traffic movements (ATMs) although the number of aircraft flying the route during both periods was around the same – 19,792 (2015) and 19,722 (2016) – this reduced off track aircraft by 6315 ATMs.

Windy day SID

As part of the process to ensure sufficient operational compliance, Gatwick Airport Ltd initially considered whether an alternate R-NAV1 SID design option should be included to be used in periods of strong south-westerly wind conditions. It became clear that such an option, while feasible, could potentially be counterproductive in terms of material noise benefits for the communities overflown. This is because in order to maintain compliance with the parameters of the NPR, aircraft would have to fly at a speed that would require the use of flaps and a thrust setting that was likely to create more noise than would be the case if the aircraft was in a ‘clean’ configuration thus negating any perceived benefit from improved track keeping. This is especially relevant considering the existing levels of compliance are relatively high.

At the present time, we are minded to discontinue the ‘windy day’ SID proposal and have outlined our position on this matter to the CAA. 

Route 4 statistics

During the monitoring period complaints received in respect of Route 4 were as follows:

Number of pieces of email feedback: 16,964
Number of individual email addresses: 1,863


Numbers of email addresses Feedback email nos   Feedback %
50 individuals responsible for                                      5,731 33.78%
100 individuals responsible for                                      7,902 46.58%
250 individuals responsible for                                      11,824 69.70%

Horley overflight

Of the total number of complaints received, 4,858 (29% of the total) from 695 individuals (37% of the total), related to the overflight of Horley, as aircraft were vectored from the SID.

After the adoption of this amendment, levels of vectored traffic leaving Route 4 and over flying Horley increased from historical levels of approximately 1-3% to a high of 8-9%. This is clearly an important issue but one which we consider to be separate from the route design itself. Working closely with NATS this problem has been addressed through a controller education programme as a result of which the number of Horley overflights have progressively declined since the problem was first identified.

For comparison the first 2 weeks of September overflights were measured at 7.36% and 6.67% respectively but the first 2 weeks of December were 0 and 0.71%. We will continue to monitor the numbers of Horley overflights and work with NATS to ensure the highest possible level of compliance.

Making complaints

The dedicated Route 4 email address is no longer monitored and will shortly be closed down therefore should individuals still wish to register noise complaints, they can do so via our dedicated noise complaint tool, Casper.

For those without access to a computer we have a freepost address:

South Terminal
Gatwick Airport
West Sussex RH6 0NP

Information transparency

Route 4 performance data and a summary of feedback received will be available on our website in the early new year.

Finally, the evaluation of the data and the Civil Aviation Authority decision process may take three to four months. I have asked the Civil Aviation Authority to keep me advised of any changes in timescale or in the decision making process in order that I can keep you informed via this blog.