Gatwick provides more details of the wider swathe of arrivals onto the ILS, from the Arrivals Review
The main reason why Gatwick had to set up the Independent Arrivals Review was the fury and anguish, largely from areas around 10 – 14 miles from the airport, due to changes in 2013 to the distance at which planes joined the ILS (the final straight line flight path onto the runway). NATS and Gatwick had decided, allegedly for safety but in practice to make maximum use of the runway at busy times, to get most planes to join the ILS at 10 nautical miles out, while before that, some joined as close as 7 nm. The concentrated noise over some areas, not previously over-flown, caused unprecedented opposition. The Arrivals Review recommended that the swathe, both east and west of Gatwick, be widened to 8 – 14 nm, and that there should be more fair and equitable distribution of the noise of planes joining the ILS. A large part of the “Final Action Plan” deals with this. It attempts to allay fears that, to save fuel, many planes will try to cut a corner, and concentrate around the 8nm area. It tries to allay fears that there will be concentrated parts of the routes, and that people living relatively near Gatwick – (around 7 – 9nm or so) will suffer unduly from noise of both arrivals and departures. However, Gatwick says it is “not possible to predict precisely the distribution of aircraft within the swathe” and this will be “carefully monitored and reported to the Noise Management Board” which in turn will publish its findings and any conclusions.
Gatwick’s initial response to the Arrivals Review, on 31.3.2016 is at
Gatwick’s Final Action Plan, on the Arrivals Review , on 2.6.2016 is at
Below are some extracts from the Gatwick Arrivals Review “Overview and Final Action Plan” – June 2016 on the issue of the wider arrivals swathes
(Pages 22 – 32)
“That GAL explores with NATS the potential for aircraft to be vectored to be established on the ILS at a minimum of 8nm from touchdown outside of night hours, rather than the current 10nm. This adaptation to vectoring methodology will extend the arrival swathe 2nm further to the west for Runway 26, and east for Runway 08, and will increase the arrivals dispersal to more closely emulate the circumstances prior to 2013 change. Hence the arrival swathe would normally extend from a minimum of 8nm to 14nm, with aircraft joining on a straight in approach when traffic permits”.
GAL accepts this recommendation. Following coordination with airlines, NATS, ANS and the CAA, further analysis and quantification of this proposed change and the expected consequences are now much more fully understood. GAL has been able to confirm that the proposal to widen the arrivals swathe will create a fairer and more equitable distribution of aircraft noise, more closely emulating that experienced by communities prior to 2013. As a part of the implementation process, new monitoring procedures will be developed to quantify the extent and volume of actual flight distribution for regular review by the NMB.
To address the concerns arising from the increased concentration of arrivals that occurred in some locations after a change of radar vectoring methodology in early 2013, the planned adjustment of the present swathe is expected to reduce the concentration of aircraft that resulted from that change. The intended impact of this action is to recreate a greater geographical dispersal of arriving aircraft tracks, so that they are more closely aligned with the arrivals tracks which existed at Gatwick prior to 2013. The benefit is expected to be a reduced concentration of arriving aircraft in the swathe, prior to joining the final approach track, supporting the fairer and more equitable dispersal of aircraft sought by many communities. Because the associated considerations are complex, a more detailed explanation of the issues is provided in the Annex that follows.
1. Complete a thorough analysis of the issues associated with this action item.
2. Assess findings of analysis against feedback from the period of community engagement.
3. GAL to request NATS to utilise the increased swathe from minimum 8nm to 14nm when straight in approach is not applied, for arrivals to both Runway 26 and Runway 08. Responsibility: GAL Complete: May 2016
4. NATS and ANS to complete the associated Safety Case for review and approval by CAA.
5. Confirm planned implementation date
6. The NMB will monitor the impact to verify that the intended fairer and more equitable dispersal is being achieved.
Responsibility: GAL Complete: December 2016
This recommendation is intended to reverse much of the aircraft concentration and noise consequences of the approach stabilisation initiative taken by GAL and NATS in 2013, thereby more closely emulating the distribution of arriving aircraft that occurred previously.
Changes to the Arrivals Joining Point in 2013
The approach stabilisation initiative of 2013, adopted for both safety and operational reasons, extended the daytime ILS final approach minimum joining point of aircraft from 7nm to 10nm from touchdown. The core night time minimum joining point has been located at 10nm (23:30-06:00 local time) since before 2004. The effect of this 2013 change was to concentrate daytime arrivals distribution into a narrower swathe, increasing the number of aircraft above particular areas.
The effect of the reduced dispersal of aircraft tracks is discernible in Figures 4-7 below, which depict the actual arrivals track density for Runway 08 and 26, as measured in the summer of 2012, and contrasted with measurements for the same period in 2015.
Many requests were made to the Independent Arrivals Review by residents seeking to reverse the 2013 change in the Instrument Landing System (ILS) minimum joining point change, which is described in the previous section. Residents making these requests explained that the prior arrangement (with a wider spread of joining points, and more random radar vectors to the ILS final approach track, both east and west of Gatwick) was a much more acceptable means of fairly and equitably dispersing aircraft noise.
The Independent Arrivals Review recommendation
This recommendation calls for an adaptation to NATS radar vectoring methodology to use an ILS joining point located between a minimum of 8nm from touchdown and 14nm, which should, in effect, largely recreate both the locations and the width of the arrival swathes seen at Gatwick before 2013.
In addition, when traffic conditions permit, aircraft from the east for Runway 26 will join on a straight in approach even further east, and for 08, straight-in further from the west.
The changes made in 2013 were subject to a safety assessment, which precludes a return to the even closer 7nm minimum joining point previously used. An updated safety case is required, for approval by the CAA, before any reduction to the current 10nm ILS joining point can be made. This safety case work is currently underway.
Feedback on this recommendation
A summary of the feedback on this recommendation and the principal issues raised is provided at the end of this Annex. Although feedback to the Independent Arrivals Review regarding the proposed change has been largely positive, a number of concerns were raised. The main issues are set out below, together with a discussion of the points raised.
That aircraft will not use the full width of the swathe as a result of this change, but that aircraft will be concentrated at the 8nm joining point in order to fly the shortest route to the runway and to reduce CO2 emissions.
Concerns have been raised in feedback to Gatwick that aircraft will be concentrated at the minimum joining point and that this will be done to allow aircraft to fly the shortest route to the runway, in order to reduce fuel consumption and CO2 emissions. The concern being that the planned 8nm joining point will create a new concentration of aircraft
Analysis has shown that sustained joining point concentration has not been the case previously, and that it has no basis in actual flight data.
The effect of the 2013 joining point distribution change is illustrated in the chart at Figure 8, which compares the actual distribution of arriving aircraft seen before the joining point change, using 2010 information, with a corresponding analysis of data for 2015. This analysis shows clearly that aircraft were removed from areas closer to the airport in the range between 6nm and 10nm from touchdown, but also shows that aircraft were not concentrated at the 10nm minimum joining distance applied from 2013. The analysis reaffirms that from 2013, a concentration effect has been created further from the airport, which is the background to this recommendation.
The historical aircraft track data shown in Figure 9 further indicates that no such minimum joining point concentration has occurred in any of the years between 2010 and 2015, for either a 7nm or a 10nm minimum joining point, East or West of Gatwick. As can be seen from the analysis, aircraft can and do join the ILS final approach track at multiple distances from touchdown as a result of their flight route and normal traffic patterns.
As to the future, concentration at the minimum 8nm joining point would be contrary to the aim of ‘fair and equitable dispersal’. NATS has confirmed to GAL that in their view, following the proposed change to an 8nm minimum joining point, the arriving aircraft distribution at Gatwick will continue to vary with the traffic patterns, as it has always done. For example, at busy times aircraft tend to join the final approach further from touchdown, something that is expected to continue to be the case. As a consequence, aircraft are not expected to be concentrated at the new minimum joining point. The NMB will, however, need to keep this under review.
Later it adds:
As it is not possible to predict precisely the distribution of aircraft within the swathe, the effects of the change planned for 2016 will be carefully monitored and reported to the Noise Management Board (Imm-18), which in turn will publish its findings and any conclusions.
That the proposal favours communities that are a considerable distance away from the Airport, whilst further disadvantaging those that suffer noise from aircraft below 4,000 ft, and that this is contrary to Government Policy on noise.
In fact, analysis shows that the 2013 change of minimum ILS joining point significantly affected communities further from the airport, by relocating aircraft in the arrivals swathe away from communities closer to the airport. Figure 8 clearly shows the distribution of flights before and after that 2013 change, and the disadvantage of the increased numbers of flights affecting more distant communities.
The Independent Arrivals Review, with a significant level of community input to its Terms of Reference, set out to achieve a fairer and more equitable distribution of aircraft noise through a greater dispersal of aircraft, and thus alleviate the disproportionate concentration that some communities experienced after the 2013 change.
Figures 1 and 2 showed earlier, over which communities arriving aircraft normally descend through 4,000 ft. Figure 3 showed actual aircraft height information related to aircraft distance from touchdown.
Government Policy on aircraft noise has not changed during the period in which aircraft at Gatwick were using the 7nm minimum joining point in 2012 or the 10nm minimum joining point from 2013, and it has not been suggested to us that either of these situations was contrary to Government policy.
A change to the 8nm minimum joining point for aircraft in 2016 is not currently subject to any additional specific Government Policy on aircraft noise, and we conclude therefore that it too is compliant.
That the communities that would be impacted by the 8nm joining point are principally the same ones that already suffer PRNAV on departures
It has been argued that some communities closer to the airport will now be subjected to the overlap of concentrated arrivals around the 8nm joining point, as well as current intense departures below 4,000 ft.
We have explained under Point 1 above why we do not expect arrivals to be concentrated around the 8nm joining point.
In order to address the issue of overlap, an analysis of the implications of any potential for overlap of arrival and departure routes below 4,000 ft has been undertaken. This analysis has set out to verify the extent to which any community located close to the airport might experience the effects of aircraft operating below 4,000 ft, whether arriving or departing. The objective has been to verify whether communities that are affected by arriving aircraft operating below 4,000 ft in the arrivals swathe, will also be potentially affected by departing aircraft operating below 4,000 ft.
Figures 12 and 13 indicate the locations at which both arriving and departing aircraft operate below 4,000 ft. It can be seen that a change to a minimum joining point of 8nm is not expected to relocate significant volumes of arriving aircraft in the swathe to areas experiencing departures at the same altitudes.
The two illustrations below show how arrivals and departures may not affect the same people, or not very much.