Flight Paths11/2015


As the representative for TDC at Gatcom (Gatwick Consultative Committee), I feel it is incumbent upon me to draw a line under the vexed subject of flight paths (concentration v dispersal), as it does not appear to me, that anyone else is going to clarify the position in words that are understood by everyone.

This is a very, very brief synopsis of what has occurred concerning change of flight paths relating solely to departures at Gatwick.

For many years, aircraft have used land based navigational methods to track their course and direction. This consisted of land based "beacons" which transmitted radio beams (to all 360 degrees of the compass) which aircraft would pick up on their instruments and then fly "down" those radio beams, hence the development of S.I.D's (Standard Instrument Departures) and N.P.R's (Noise Preferential Routes) . These are routes that are coincident with SID's, covering a specified distance and altitude from the airport.

At Gatwick Airport there are several N.P.Rís, which cover the departure routes of aircraft leaving for different parts of the world. Up until 2013, aircraft leaving Gatwick were (in theory and where practicable) obliged to fly along the centre line of those NPR's. However, because of the mix of aircraft, all with differing flight capabilities, plus other factors such as weather conditions etc., it meant that not all aircraft could fly down this central line. To overcome the possibility of aircraft literally wandering about somewhere near this centre line, over a period of time a "corridor/swathe " of airspace measuring 3 kilometres wide was added to the NPR's to ensure that aircraft flew within those swathes. People came to accept that this was the area in which aircraft could lawfully/legitimately fly.

This meant that residents on the ground living under these N.P.R's would know quite specifically that they could expect to see and hear aircraft moving along within the swathes, dependant upon the flight characteristics of the aircraft and other factors such as weather conditions. This meant that there was a wide difference of where aircraft flew within those swathes. The offshoot of that situation was that all those living under the NPRís equitably shared the noise impact.

Coming down the track are major changes to airspace usage across the whole spectrum of flying, associated in part, with the use of Sat Nav style technology. This technology does away with the use of land-based beacons and enables aircraft to fly more accurately within the NPR's. With that in mind, in 2013 Gatwick Airport decided that they would become the vanguard for this new type of air navigation technology particularly on their departure routes. Initially the trials only involved a very small number of NPR's and because many aircraft at that time were not able to utilise the new technology, the number of actual flights were minimal.

However, in 2014 it was decided that all aircraft using Gatwick would have to use the new style navigational technology which was referred to as P-RNav (Precision Area Navigation). At the same time there was an airspace change consultation which involved the CAA (Civil Aviation Authority), seeking views and comments from across the broad spectrum of the community which included "the community (whatever that meant)", aircraft manufactures, airlines, airport and associated groups/users as to the impact of this new technology. During the trial and certainly once the full implementation of the new system was introduced, residents under the NPR's became acutely aware of an increase in noise and frequency of over flying.


Why was that?

Because the ability of aircraft to fly enhanced flight paths by using this new technology, it resulted in there being a massive concentration of aircraft flying down what could be best be described as a single track (the original single line SID/NPR). This became known as "concentration".

Beforehand, because of the vagaries of land based navigation, aircraft flight characteristics et al, aircraft could be frequently seen and heard to be flying down the NPR on different paths but still within the 3 kilometre swathe. This was known as "dispersal".

Concern was raised at Gatcom about the perceived problems resulting from "concentration" of flights and Gatwick issued a written undertaking in 2013 that should the trials and new technology result in their being a worsening impact on residents caused by "concentration", they (Gatwick) would revert back to the original NPR's , thus re-introduce  "dispersal". At the time, that undertaking satisfied the public.

As part of the airspace change procedure, the CAA were obliged to undertake a P.I.R (Post Implementation Review) of the whole change that had occurred with the introduction of P-RNav now referred to as PBN (Performance Based Navigation) . The public were invited to participate in that process and a massive number of complaints/responses were received by the CAA, which highlighted the negative impact caused by the "concentration" of the flight paths.

Several attempts were made to get the re-assurance of Gatwick that their commitment in writing made, concerning the return to the old NPR's would be honoured, but each time the response was one of vagueness caused by the PIR procedure. Eventually, after an extended period of time, the CAA published their findings of that review. The results are no comfort to those residents living under the NPR 's .

There will be no return to "dispersal" and the "concentration " of flight paths remains in place.

I felt that this significant decision needed to be made public, as there are many people within the community who were hoping that their voices would be heard and the CAA would take notice of their concerns. The CAA sadly, has not done so".

Prior to circulating this email, I made contact with a senior member of the Gatwick team. It was suggested that if residents were concerned about the decisions made by the CAA in their recent PIR, or wanted to know the rationale behind those decisions, they should complain to the CAA.

It was also suggested that the CAA were going to look at the possibility of "concentration v respite (not dispersal)", albeit there was no time scale.

Based upon their past performance, i.e the PIR , I hold out little or no hope on that suggestion. We simply donít appear on the CAA's radar!


Ken Harwood