Aircraft numbers matter

One of the most significant, and most welcome, sentences in the Government’s Aviation Green Paper (1) is this:

“the government recognises that statistics showing past and future improvements in noise do not necessarily match the experience of some people living under flightpaths, for whom the benefits of quieter aircraft can be cancelled out by greater frequency of movements or the effects of concentrated traffic associated with more accurate navigation technology” 

It is official recognition that, for many people, it is the number of planes overhead that can be the all-important factor in how disturbed they are by the noise.

And the Government expects a big increase in aircraft numbers by 2050:

The table, taken from a major study the Government commissioned from the CAA (2) shows increases at individual airports of up to 83% (with an average just under 40%).

The CAA study found that, despite the projected increase in flight numbers, the numbers people impacted by noise would fall.

The study, the most comprehensive ever undertaken to assess future noise levels, found that the fall would be greater if it weren’t for the fact that a lot of new homes will have been built in the impacted areas by 2050.

The CAA study also found that the number of people highly annoyed by noise would fall at most airports.

The main reason why the CAA expects numbers to fall is the progressive introduction of less noisy aircraft.

It is not the purpose of this blog to criticise the CAA's study. It would be arrogant and ignorant to do so. It is an impressive piece of work. All this blog wants to do is make the case that the total number of aircraft passing over a community may be the all-important factor.

The prime – and very often only concern – for most people is how many planes go over their own community.  They are much less interested in the total number of aircraft using the airport or even how many runways it has.  And many of them have little interest in other communities.

The challenge, therefore, for the industry and government is to find a way to cap number of flights over any one community.  

This is likely to require the introduction of multiple flight paths.  This can be made possible by new technology.  Across the world airports are moving from ground-based technology to a satellite system to guide planes in and out of airports.  It is known as Performance Based Navigation (PBN).  PBN will mean the introduction of narrow, precision flight paths.  If a number of them can be introduced at any airport, they can then be rotated, to give each community some respite from the noise and thereby cap the number of aircraft going over any one area.  It would allow for some growth at the airport while protecting local communities.

The Green Paper not only proposes multiple flight paths as an option for airports to consider but also proposes a noise cap or noise reduction plans for airports.

These all could be useful tools for capping flight numbers over communities.

A noise cap can be more than a movement cap.  The Green Paper says: “A noise cap (also known as a noise envelope) is any measure which restricts noise. In its crudest form this could be a simple movement cap, but the government proposes advocating caps which are based on setting maximum noise exposure levels (such as contour area or noise quota).”  It could also include heights of aircraft, compensation packages and night flights.

But, while there is a clear upside to capping, there are two downside which would need to be addressed.   The first is the introduction of multiple flight paths might necessitate the creation of flight paths over new areas.   In my view, the latter should be avoided wherever possible – it is a brutal act to create a new flight path and would result in a lot of people becoming very angry and annoyed.  It should only be done if it is the only way to benefit communities currently under a flight path.  

The second is that at single runway airports – the vast majority in most countries – people under the final approach path cannot by definition benefit from multiple flight paths.  They should be first in line for a generous compensation and mitigation package.  But, if the time comes when any of these communities, even with good mitigation, cannot tolerate any more noise, perhaps that it is the signal that their particular airport has reached the point where further growth is no longer an option, certainly until much quieter aircraft can be introduced.  

Bobby Seagull, who shot to fame in University Challenge a couple of series ago, said that his book The Life-Changing Power of Numbers is part biography, part a love letter to numbers.  I’m not sure I love numbers like that but I suspect aircraft numbers will be critical to the future noise climate experienced by communities.

John Stewart 


(1) Green Paper: Aviation 2050, The future of UK aviation, A consultation

(2) CAA Study: Aviation Strategy: Noise Forecast and Analyses, CAP 1731

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