Answers to questions for NATS
On 16 May, NATS finally supplied answers (in blue) to our questions which we submitted in March:
- How are the reductions in populations overflown at below 4,000 feet, which featured in NATS press releases about the consultation, calculated? These calculations are not referred to in Appendix C where, it is claimed, the environmental methods are explained. The calculations in the Addendum are clearly described but are different from the originals and the NPRs applied to the calculation do not correspond to those published in the Luton Annual Monitoring Report (AMR).
- Why were area and population counts not included with the SEL footprints published on Friday 7 March? Can this data be provided, please?
- Could NATS retain the present non-PR-NAV westerly departure routing south of south Luton in order to avoid the appalling noise consequences for south Luton, Slip End, Caddington and Markyate? The decision on the easterly departure route to the north (Olney) is a precedent for this.
- The new easterly departure routes to the east and south east fly over west and north Stevenage, the Lister Hospital and almost the whole of the land designated for the building of 10,000 homes (the so-called SNAP area). Could this be moved further north with tighter turns, perhaps imposing a speed limit as for the south west route?
- How are the LAmax ranges calculated? Appendix C, “Technical details of the environmental analysis”, does little to explain this.
- Is there potential for mitigating the noise impact of Luton by employing 5.5 degree approaches in place of 3 degrees?
- As no major Airport in the south east has approval for significant expansion and changes of this kind can be implemented in a matter of months, is not this proposal premature? The only justification given is that NATS believes that it is necessary.
- How real is this consultation? How will the response influence NATS application to the CAA? Part A of the consultation implies that the only changes will come about if a consultee makes a point which NATS had not considered.
- NATS says that it does not consider the environmental effects of any increase in air traffic although the purpose of the proposed airspace changes is to accommodate more flights. The Government, in the consultation on expansion at Heathrow, only considered the impact close to the Airport, predominantly within the 57 Leq noise contour, suggesting by implication that these effects are the responsibility of NATS. What will be the medium whereby the full environmental impact of air traffic growth is assessed and presented to the public?
- NATS states that it is conducting more noise analysis to accompany the CAA submission. What form will this take?
- In Appendix C, “Technical details of the environmental analysis”, the NATS model for estimating emissions is cited but no technical details or references are given. Could these be supplied, please?
- There is a major gap between the climb performance of the poorest-performing aircraft likely to operate at Luton and that of the most common commercial aircraft. The departure route diagrams showing operational height bands are being interpreted by the general public to indicate that aircraft will stay within the swathes far further down the track than will necessarily be the case. We also note that the PR-NAV routings may well be adhered to more closely for longer than with the existing routings to minimise Controller workload. Is there no experience from elsewhere which might allow consultees to make a more realistic assessment of likely tracks and heights of aircraft overhead?
An addendum to the NPR calculation has been published on the web site. This provides the detail requested. Please see http://www.consultation.nats.co.uk/uploads/Addendum_NPR_count.pdf
[LADACAN comment: It appears, from this answer, that the figures originally published in table C2 of the consultation should have been those published in the later addendum. However, NATS has failed to address the final sentence of our question so, in our opinion, the figures for populations overflown which they rely upon are meaningless.]
The SEL metric provides a noise analysis for one aircraft movement following a route centreline. It takes no account of dispersal around a route. The route and fight path
maps clearly show that the proposal will affect dispersal in many areas. Given that a key element of the P-RNAV routes will be their affect on dispersal NATS considered the presentation of metrics which did not take this into account to be potentially misleading.
[LADACAN comment: This answer is nonsense as NATS’ own documents in which they present the SEL contours clearly follow the CAA’s guide in stating that SEL’s are used in the assessment of potential sleep disturbance. CAA (in CAP725) says that the population count is needed to calculate the approximate number of awakenings.]
Guidance from the CAA is that new routes should be designed to utilise P-RNAV technology. In designing such routes, NATS must comply with international safety standards for the design of P-RNAV routes, which do not apply to the existing routes. These safety standards dictate the position at which an aircraft may start its first turn following take-off on a P-RNAV route. For Luton Westerly departures this position is further from the runway than today and it is therefore not possible to
replicate the current departure route with an equivalent P-RNAV route.
[LADACAN comment: This “only obeying orders” response contrasts with NATS’ recent indications to MPs and Councillors that “hybrid” routes would be possible.]
[LADACAN comment: This question was combined with similar ones posed by others but has not been answered.]
NATS employed the CAA’s Environmental Research Consultancy Department (ERCD) to undertake all noise analysis utilising the ANCON noise model. A range of scenarios were considered, which has lead to the range of results presented for each height band on pages F75 and F76. The high end of the range represents the worst case, assuming an aircraft is:
• at the lowest height of the defined height band, i.e. for 4000-5000ft this would be 4000ft
• in the noisiest phase of flight , i.e. for departures a high climb rate and arrivals level flight
• above the highest ground in the region.
[LADACAN comment: It would have been helpful to explain the low end of the range too.]
It is not possible to increase the angle of the glide path for arriving aircraft
because this would require special certification, training, and would not be flyable
by all aircraft types. It is only appropriate to meet specific operating constraints.
NATS does not have any control over airport development. This proposal is not associated with, and does not assume, future development of Heathrow, Stansted or any of the other airports in the region. The future traffic figures used in the proposal have been primarily based on historical trend data. Apart for Heathrow terminal 5 (which was not operational at the time of the forecasts), no additional development to airport infrastructure (runway or terminal) has been assumed within the period covered by the forecasts, namely 2007-2014. Any subsequent airport development that requires changes to the airspace structure would be subject to its own separate consultation and approval processes.
All responses will be considered. However NATS has already considered many of the competing factors, such as seeking to avoid populated areas at lower heights whilst at the same time trying to reduce the impact on AONBs. The wide range of differing stakeholder interests inevitably raises conflicting expectations and our continuing challenge is to find the most accommodating overall solution. We will use the feedback from the consultation exercise to inform further analysis and development of the proposal.
This consultation follows guidelines laid down by the Civil Aviation Authority (CAA) in their airspace change process (see caa.co.uk). The CAA guidance adheres to government policy relating to the development of airspace. Full details of the scope of the consultation process may be found in the consultation document.
[LADACAN comment: It appears that no organisation will take responsibility for assessing the wider impacts of growth in air traffic.]
[LADACAN comment: This question has not been answered.]
The emissions analysis undertaken in the preparation of the TCN proposal airspace change design that is currently being consulted upon is detailed and highly technical. Interpretation of the results is complex and requires relevant background knowledge in the design and the technicalities of fuel and emissions modelling. The material produced as part of that exercise has not been designed for external consumption (i.e. it does not explain the background knowledge relating to the technicalities of fuel and emissions modelling and, as such, could be unhelpful and misleading).
Furthermore, it should be noted that the design process is still ongoing and therefore the emissions analysis may need to be revisited in the light of the proposed changes.
NATS will produce records of the TCN emissions analysis for submissions as part of any future ACP, which are in the context of our ongoing discussions with the CAA about the methods of analysis employed by NATS. These records will be presented to the relevant technical experts at the CAA to assess whether the process followed has been sufficiently robust and accurate. NATS does not intend to release extracts from the analysis material for external review as this could be misleading for the reasons stated above.
[LADACAN comment: It is unacceptable that such important material is not subject to peer review. This invalidates any claims on emissions and fuel use which NATS may make.]
NATS has presented the worst case in terms of aircraft heights as these are the aircraft that would generally have the most impact in terms of noise. Doing otherwise would open NATS to criticism of not being clear about the heights of aircraft that have the most impact.
[LADACAN comment: While the worst case is important, noise disturbance is known to depend on the number of noise events and their magnitude. It would, therefore, be most helpful for the public to assess the likely impact on their lives if more typical aircraft performance could be provided.]
We have been very concerned that some noise contours (SEL) published by NATS, which are used to represent the noise footprints of individual flights as an indicator of likely sleep disturbance, are inaccurate. We wrote to NATS on 1 May and received a reply on 4 June. We are not yet satisfied that the contours are correct and have exchanged further letters with NATS:
Page archived 20 June 2008- no further updates
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Luton & District Association for the Control of Aircraft Noise - site updated 06 July, 2008
