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The proposed development of Manston Airport – consequences for Faversham

Chris Wright was asked to look into the implications of this for Faversham. This is his report.

What is being proposed

The project is being carried out by the RiverOak Strategic Partnership (RSP).  Quoting from its web site:

‘Our proposal is to reopen Manston as a global freight hub, enabling the airport to fulfil its role in helping the UK trade across the globe and to import vital and time-sensitive goods, including fresh fruit and medical supplies.’

In fact the airport will accommodate passenger traffic as well as freight traffic, but the passenger traffic will form only a small proportion of the total. 

Time scale

The airport terminal will be rebuilt over a period of 15 years, with 19 stands for cargo aircraft and 4 stands for passenger aircraft.  The company expects to gain approval for its air traffic management proposals in 2022; they are currently under negotiation with the UK Civil Aviation Authority.  Once agreed, the flight paths can’t be changed by the airport operator unless re-negotiated with CAA.

The consultation process

The planning process for a major change in air space takes place in 7 stages.  Stage 2 is approaching completion.  It has involved consultation with local authorities in the Thanet area, many of whom support the scheme because it will create employment for local people.  Consultation with the wider public will take place during stage 3, which is likely to start towards the end of this year.

Aircraft movements

As with most airports, there will be two categories of aircraft movement at Manston: (i) ‘general aviation’ (light aircraft including recreational traffic) (ii) commercial cargo and passenger airliners.  There will be no night traffic between 11 pm and 6 am.  

Management of air space

Flights over the UK are subject to restrictions laid down by the UK Civil Aviation Authority, which is currently developing a plan to modernise our national airspace (www.caa.co.uk), and European ATC organisations are now introducing what they call ‘Noise Preferential Routing’ which will presumably cut down the range of options.  An independent public-private partnership called NATS (National Air Traffic Services, https://nats.aero) handles most of the regulated airspace above the UK.  It is divided into 17 sectors.  The five major London airports are grouped within a single sector.  Manston appears to be located in the neighbouring Dover sector. 

Holding patterns

Holding areas are needed to accommodate aircraft during busy periods where they can queue before making their final approach.  Manston will have two distinct sets of holding areas: one for light aircraft (‘general aviation’), and one for commercial flights.  The first of these is relatively close to the runway and extends down to 2 000 feet; its impact will be small and localised. 

The commercial flight holding areas are further away and located at a higher altitude.  RSP have published two illustrations showing where the stacks might be located (Figures 1 and 2 below).  They appear to show the altitude of each stack as 3 000 feet, much lower than the 7 000 feet for Stansted. 

It seems that the four stacks shown on the RSP maps are not alternative proposals, but complementary.  The Manston runway is aligned roughly east-west.  When the prevailing wind is from the west, one would expect incoming flights to make their final approach from the east so they can land against the wind.  Figure 1 shows how they would converge at a point in mid-Channel at the beginning of their descent, together with their glide path over Ramsgate, then touchdown on the runway.  The two closed loops represent ‘stacks’ where aircraft will queue if the airport is busy.  When in use, the stack to the north would presumably accept arrivals from the north of the extended runway centreline, while the stack to the south would accept arrivals from the south.  In principle, both stacks are needed so that aircraft arriving from the north and those arriving from the south don’t have to cross the runway axis, and get in the way of other aircraft on their approach – an arrangement that reduces ‘conflicts’ and the risk of collision.

However, it appears that the arrangement shown in Figure 1 won’t be used very often.  The greater proportion of landings will actually be made from the west to reduce the noise impact on Ramsgate, as stated in this quotation from Tony Freudmann, Director of RSP that appeared on 7 August in Kent-on-line (https://www.kentonline.co.uk/thanet/news/row-over-secret-flight-paths-to-and-from-airport-231707/):

‘Lets say there are six movements an hour, three arrivals and three departures, what we hope to achieve is of those six arrivals, at least four or even five will be in the direction of Herne Bay.”  This statement isn’t clear, but possibly the majority of incoming flights will use the second holding pattern as shown in Figure 2.  It is more-or-less a mirror image of what appears in Figure 1.  Again, there are two ‘stacks’: the southerly one lies over Faversham, which would presumably be used for flights arriving from the south of the extended runway centreline. 

Take-off and climb

There is another potential issue.  Compared with landing, take-off creates more disturbance because the engines are operating at full throttle, and nearly full-throttle for much of the subsequent climb.  The greater proportion of departures from Manston will follow a westerly flight path because it is safer to take off against the prevailing wind rather than in the same direction, and as stated earlier, RSP prefer this direction because it reduces the noise impact on Ramsgate.  The Kent-on-line article shows a map with departure routes radiating in different directions from the airport (Figure 3).  I understand from a colleague who was once a practising aeronautical engineer that aircraft are likely to turn fairly soon after departure.  

However many of the aircraft pass over Herne Bay and it is possible that some will continue in a straight line as far as Faversham.  If so, we need to know how high they will be flying when they get here.  Jet aircraft climb as quickly as possible because the engines work more efficiently and there is less drag at cruising altitude, which is usually over 30 000 feet.  The maximum climb angle for a typical passenger jet seems to be in the region of 15 degrees, and since Manston is 20 miles away, it could theoretically reach 20 × 5280 × tan(15°) = 28 000 feet when it arrives overhead, which is not far short of cruising altitude.  But in practice, an aircraft will only sustain such a steep climb for a short while after take-off, and after that, it might climb typically at 2 000 feet per minute.  Regulations limit the maximum speed when flying below 10 000 feet to 250 knots, or 6076 × 250 / 60  =  25 317 feet per minute, so it will take most flights around 20 × 5280 / 25317  =  4.17 minutes to reach Faversham.  So climbing steadily at a rate of 2000 feet per minute, the aircraft would arrive here at an altitude of around 8000 feet.  

Consequences for Faversham

Arrivals

At many airports, a single runway can accommodate arrivals at two-minute intervals or even less.  Given the maximum frequency of movements at Manston will be limited to 5 per hour, most will start their final approach without needing to enter a holding pattern at all.  It appears therefore that few will ‘stack’ over Faversham, and they will do so only when several happen to arrive at the same time.

So what will be their environmental impact when they do form a stack, and will people notice?  Apart from a small amount of exhaust gas pollution, an aircraft has both a visual impact and a noise impact.  The 200 foot wingspan of a Boeing 747 at 3000 feet makes it appear many times larger the sun or the moon, so it will be highly visible.  But personally, I doubt whether people will complain if it occurs only at rare intervals. 

The noise may be less welcome.   In a holding pattern, aircraft fly slowly on reduced power, so they make less noise than they do on take-off, when the engines are producing maximum thrust.  Nevertheless, one source (https://www.nats.aero/environment/aircraft-noise/) quotes the noise generated by a descending Boeing 737 at 3 000 feet as about 70 dBA at ground level.  This is roughly equivalent to the noise of a vacuum cleaner (https://www.iacacoustics.com/blog-full/comparative-examples-of-noise-levels.html), which would be annoying if it occurred frequently.

Departures

The position with departures is less clear.  Most will start off in westerly direction: any that continue as far as Faversham will still be climbing at an altitude perhaps of 7 000 – 8 000 feet when they arrive, and the engines will be working harder than they would in a holding pattern.  I estimate the noise level for a passenger jet at climbing at this altitude to be around 60 – 65 dBA, which is noticeable but not severe.  The overall impact will depend on the frequency of such flights.

Other stakeholders

The noise impact will be much greater for residents living closer to the airport and especially those living along the extended centreline of the runway.  The communities most affected will be: Ramsgate, Manston, Wade, West Stourmouth, and Pegwell Bay (see the PEIR [Preliminary Environmental Information] non-technical summary document of 2018, chapter 12, para 1.1.82 at https://rsp.co.uk/documents/rsp-documents/03-non-technical-summary-peir-2018/)

Any holding area imposes a ceiling on general aviation: small aircraft can fly underneath but not through the controlled air space.  Members of the Kent Gliding Club, which is based near Challock, are concerned that a holding area over Faversham will interfere with their activities.

Road traffic generation

Road traffic generation by the airport is covered in the PEIR summary document, chapter 12, para 1.1.95, where RSP claims that ‘only 7 of the 31 (potential) receptors trigger the need for a detailed assessment’.  These receptors are local roads around the airport periphery, and the detailed assessment concluded that the traffic effects ‘are not significant’. 

I am skeptical – the airport will generate goods traffic, some of which will add to the demand on the M2 at junction 7, which is now approaching saturation.  Highways England has no immediate plans for an upgrade.

Conclusion

Aircraft flying in or out of Manston Airport will inevitably generate noise.  In my opinion, the noise associated with any particular flight over Faversham will be noticeable, but not severe.  At the moment don’t know enough about their frequency to determine whether in total, they will result in significant disturbance.

Questions to be answered

  1. Manston lies almost on the boundary between three air traffic control centres: London, Dover, and Clacton – under which control centre does it fall?
  • Commercial aircraft mostly follow defined ‘airways’ over Europe that are five miles wide.  We need to know the existing airways over East Kent, and how the pattern will change when Manston re-opens.  This is a matter for the CAA to decide, but it would be useful to know what RSP have asked for.
  • It would be useful to confirm the minimum altitude for aircraft in the holding pattern.
  • How much road traffic will the airport generate, and what will be the effect on M2 junction 7?

CW          31 August 2020

Further information is available here

Airport Watch

Campaign against the reopening of Manston Airport

https://www.thanet.gov.uk/info-pages/manston-airport-information/

September 7, 2020

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