NEWCASTLE INTERNATIONAL AIRPORT RADAR BLANKING STRATEGY. Newcastle International Airport Radar Blanking Strategy. April 2011

Transcription

1 NEWCASTLE INTERNATIONAL AIRPORT RADAR BLANKING STRATEGY 1

2 Contents 1. Introduction 2. Impact of wind turbines on radar 2.1 PSR 2.2 SSR Location, ownership and airspace 3.2 Safeguarding process 4. NIA response to wind farms 4.1 Mitigation of wind farms at NIA 4.2 PSR Blanking Implementation at NIA 4.3 Key Constraints 5. Financial implications of the strategy 6. Looking to the future 1

3 1. Introduction A large number of on-shore and off-shore wind farm developments are proposed in the North East of England with the aim of meeting government set targets for renewable energy in the region. Many of these have the potential to impact upon the operations of (NIA) and, in the absence of a strategy, the Airport Company (NIAL) would have no alternative but to object to those where an unacceptable impact was predicted. Instead, a has been prepared which will allow a number of wind farms to go ahead. This report sets out the, based upon the following:- A detailed radar modelling report from QinetiQ, which establishes those areas of the region where Radar Blanking could be necessary; Hazard analysis work from National Air Traffic Services (NATS ;) In-house Air Traffic Control (ATC) expertise. The report considers the effects of wind farms on both Primary Surveillance Radar (PSR) and Secondary Surveillance Radar (SSR). The report is also intended to link into the overall Safety Management System at NIAL. 2. Impact of wind turbines on radar In providing Air Traffic Services at NIA, Air Traffic Control Officers (ATCO s) use an S Band Marconi S511H PSR, which is based on site. In addition to this, NIA uses a Cosser Condor 9600M SSR based on site, with a back up feed from the SSR located at the Great Dunn Fell NATS site. 2.1 Primary Surveillance Radar (PSR) Wind turbines have the potential to affect radar in a number of different ways. In common with many other large man made structures, wind farms are a potential source of clutter, in two ways:- The wind turbine acts as a reflector and presents a static target to the radar system. This reflects energy which has the potential to produce radar returns which are significant enough to mask aircraft from the view of the radar; The wind turbine has the potential to paint a reflection on the radar. While the majority of this clutter is static and continually paints in the same location allowing it to be filtered out by the radar processor, the rotation of the wind turbine blades is a moving target and cannot therefore be filtered by the radar processor. This can result in the turbine blades painting on the radar in similar way to aircraft. When aircraft are moving they create a single aircraft return. Radar sweeps occur every 4 seconds so ATC view a track history of each aircraft, allowing them to see where the aircraft has been and which direction it is heading. Individual wind turbines would paint a single return on radar. Consequently, whilst a single turbine is a potential distraction to ATC, it could not be considered to be a potential aircraft. However, where a scheme involves more than one turbine, the sequence of rotations of the turbines has the 2

4 potential to present on the radar as a series of aircraft returns, in certain cases very similar to that of fast moving aircraft, with radar unable to distinguish between this false aircraft track and a real aircraft. Figure 1 below shows a radar screenshot of Prestwick Airport s radar screen, highlighting a number of wind farms presenting as clutter, alongside normal aircraft tracks. Figure 1: Excerpt from Glasgow Prestwick Airport Radar Display showing wind farm clutter. Courtesy of Glasgow Prestwick Airport In those circumstances where a false track is generated, the track may appear in conflict with other real aircraft. ATC cannot be certain that the false track is generated by a wind farm and as such must operate on the basis on an unknown aircraft. The controller, in order to prevent the two aircraft from colliding, must therefore implement avoidance procedures accordingly. The CAA Guidance (CAP 493 and CAP 764) requires NIA to reroute aircraft from the unknown aircraft by five nautical miles. In the event that one or more wind farm schemes, or one large scheme, went ahead in a particular area, and a large area of clutter was created on the radar, there would be the potential for genuine aircraft tracks to be masked or lost. This loss of situational awareness could compromise the overall safety of ATC operations at NIA. Again, in this situation, there would be a requirement for aircraft to be rerouted away from the clutter by five nautical miles. 3

5 2.2 Secondary Surveillance Radar (SSR) SSR differs from PSR in its tracking of aircraft. Where PSR tracks aircraft movements, the main functions of SSR are to allow ATC to ascertain the barometric level and establish the identity of an aircraft. It is immune from the clutter described earlier which affects PSR, except where an area of clutter is particularly large. SSR works by sending out interrogation signals which an aircraft carrying a transponder would then transmit a response to, providing ATC with details of the altitude and identity of the aircraft. SSR may, however, be affected by wind turbines when they are located within a 10 nautical mile radius of the SSR site. Within this radius, turbines can cause false returns to show on the radar display. These would duplicate actual aircraft, creating doubt in the minds of ATCO s as to the position of an aircraft, and would therefore be unacceptable. In order to combat this problem, an additional SSR would be required in a separate location, which was more than 10 nautical miles away from a wind turbine. This would allow ATC to switch between both the on site and off site SSR s to create a picture which is free from clutter, preventing any loss of situational awareness. NIA currently takes a secondary SSR radar feed from Great Dun Fell in Cumbria as part of its existing ATC arrangements. This is capable of being used to track aircraft within 10 nautical miles of the main SSR.. NIA had been expecting to use this radar as its sole SSR feed from 2011 onwards. The implementation of this RBS requires an onsite radar as well as a back up SSR from Great Dunn Fell Location, ownership and airspace NIA is located on the boundary of Newcastle upon Tyne and Northumberland, approximately 10 KM north-west of the city centre. In 2010 it was the 11 th busiest airport in the UK, handling over 4.5 million passengers. The Airport is owned by Copenhagen Airports and seven local authorities:- Durham County Council; Gateshead Metropolitan Borough Council; City of Newcastle Upon Tyne; North Tyneside Metropolitan Borough Council; Northumberland County Council; South Tyneside Metropolitan Borough Council; City of Sunderland. As with all of the main UK airports, an area of controlled airspace exists around NIA. This controlled airspace covers an area 5 nautical miles either side of the runway centreline and 11 nautical miles at either end, with an extension south along airway P18 to Manchester to link up with UK controlled airspace. Within this area, all aircraft have to be in constant contact with NIA ATC, to determine their positions and headings. Outside 4

6 of this area, aircraft have to request permission to enter the airspace. Figure 2 shows the Controlled Airspace around Newcastle. 3.2 Safeguarding process In accordance with The Town and Country Planning (Safeguarded Aerodromes, Technical Sites and Military Explosives Storage Areas) Direction of 2002, and The Air Navigation Order, made under Section 60 of the Civil Aviation Act, 1982, NIAL has been designated as a Statutory Safeguarding Consultee in respect of wind farms for the Local Planning Authorities (LPA) within a 30km radius. Civil Aerodromes are officially safeguarded on the basis of their importance to the national air transport system in order to ensure that their operations and developments are not inhibited by buildings, structures or works which infringe protected surfaces, obscure runway approach lights or have the potential to impair the performance of aerodrome navigational aids amongst other things. Since 2005 NIAL has received over 250 wind farm consultations. While this covers the entire safeguarding region, the majority of these consultations are in Northumberland. Figure 3 shows those schemes where sufficient information is available. As can be seen, should all schemes go ahead without mitigation then the impact on the airspace, particularly to the north of the airport, would be severe. NIA currently operates approximately 230 flight movements per day with many of these traversing across the areas affected by proposed wind farms. At the present time, other than the operational mitigation set out in 2.1, there is yet to be a fully accepted technical mitigation for use in the ATC environment that eliminates the effects that wind farms can cause to PSR. NIAL has therefore responded to this challenge by creating its own strategy of mitigation of wind turbines unique to its airspace. 4. NIAL response to wind farms 4.1 Mitigation of wind farms around NIA Having identified the impact of wind turbines on Primary and Secondary Radar, NIAL has set out to identify an appropriate mitigation response. CAP 764 identifies several mitigation techniques. The most viable option is the use of Primary Surveillance Radar (PSR) Blanking. PSR Blanking, formerly given a working title of Non Acquisitions Areas by the Wind Farm Statutory Safeguarding Team at NIA, is the process of blanking an area of the radar display that has the potential to be affected by clutter, such as that created by wind turbines. While preventing ATCOs from seeing the clutter from wind turbine interference, PSR Blanking also blanks out any plots from aircraft. This results in a loss of detection of aircraft while they are travelling through the PSR Blanking site. Consequently, the size, location and relative proximities of PSR Blanking Areas must be carefully considered. The introduction of PSR Blanking will allow ATC to manage the effects of wind farm developments within NIAL s area of responsibility. In identifying PSR Blanking, those issues associated with the potential for unidentified aircraft as outlined in section 2 of this document can be avoided. This will allow for the existing safe levels of operations 5

7 currently experienced at NIA to be aided by reducing controller workload through the elimination of the uncertainty created by the appearance of unidentified aircraft. 4.2 PSR Blanking implementation at NIA Radar Blanking Areas will be identified according to a sequential methodology. The steps are as follows:- Identify areas where the radar is likely or unlikely to detect turbines. This has been done on a region wide level, on behalf of NIAL, by QinetiQ. This propagation modelling will assist NIAL in determining for each scheme whether a Radar Blanking Area is necessary, or whether mitigation is not required because the turbines are unlikely to show on radar. In those cases where we believe that turbines may show, the developer would be asked to do a radar impact assessment in order to ascertain the nature and scale of the predicted impact on radar; Once it has been established that the proposed turbines will be visible to NIA PSR, the location of the airspace then requires consideration. If the turbines proposed are deemed to be in an operationally significant area of airspace, PSR Blanking would be unsuitable. In areas of lower operational significance, PSR Blanking could be utilised to reduce the likelihood of loss of situational awareness to ATCO s or mitigate against the issues highlighted in 2.1; The magnitude of the effects of turbines is dependent on the aircraft transit time over the wind farm and the same can be said for the effects of PSR Blanking on the detection of aircraft. The speed of aircraft will impact upon the transit time, with this study based on the assumption that the slowest aircraft will be those which are not equipped with SSR transponders as identified in the PSR Blanking safety case as produced by National Air Traffic Services (NATS). A maximum size limit for any PSR Blanking Area implemented is 4km². This represents a maximum allowable, based on areas of low operational significance, with more complex airspace having the potential to reduce the maximum size considerably. The size achievable will also be determined by factors such as location and proximity to other areas of PSR Blanking; In considering the separation between PSR Blanking Areas, based on the resolution of the radar and the standard afterglow of the NIA radar display being 8 updates, the minimum separation in order to allow aircraft to be fully detected, identified and tracked without any loss of situational awareness to ATCO s is 960 metres in range and/or 6 degrees in bearing. This equates to four sweeps of the radar, to identify a potential track history and when looking at bearing allows separation equivalent to four beam widths of the radar, allowing four potential paints to be visible, again showing the track history of the aircraft. This is a minimum identified for areas of low operational significance and this would increase in areas of operationally significant airspace. It must be stressed that these separation distances and angles are minima and are subject to analysis by NIA s safeguarding team in order to establish the acceptability of PSR Radar Blanking Areas. This document was created to provide the rationale behind radar blanking and is not a tool to allow developers to determine the acceptability of their proposed scheme. 6

8 To establish their suitability as PSR Blanking Areas, individual wind farm schemes will be assessed on a case by case basis in order to establish that they conform to the outlined criteria. The impact of each PSR Blanking Area will build up cumulatively and so each potential new PSR Blanking Area must be assessed against those which have been previously identified or adopted as PSR Blanking Areas. For each scheme, a safety case would be produced, based on cumulative information and taking account of traffic during the peak summer period. Consideration would be given to the number of PSR Blanking Areas within a locality, their size and the carrying capacity of the airspace. Following this, a live trial would commence, which would involve implementing a PSR Blanking Area over the proposed wind farm site on a specially designated radar VDU screen, and making an assessment of the traffic passing over it for a fixed period. The result of the trial would then be fed into a final safety case for approval by the Safety Regulation Group of the CAA. Upon approval of the safety case and following the signing of a Legal Agreement, NIAL would be in a position to implement a PSR Blanking Area on the site and formally discharge any planning conditions, thus allowing the wind farm to be delivered. The number of PSR Blanking Areas that are possible is unknown but is expected to be limited, based upon the carry capacity of airspace. It is anticipated that in looking at each proposal on a cumulative basis, this tipping point will be identified, and no further Blanking Areas will be permitted. Similarly, some areas of the airspace may reach tipping point before others. 4.3 Key Constraints In identifying areas suitable for PSR Blanking NIA has identified a number of factors as constraints associated with PSR Blanking implementation. These are illustrated on Figure Departure and arrival routes Due to the nature of the complicated airspace environment close to Newcastle, the amount of airspace which can accommodate PSR Blanking Area s is limited. Immediately surrounding the aerodrome, the use of PSR Blanking Area s would be considered unsuitable. This area accommodates both the departure and arrival tracks for aircraft. This complex area of aerial activity forms part of controlled airspace and ATC must therefore be informed of the location of all aircraft at any given time. Blanking out sections of radar in this area would therefore be unacceptable. Similarly, immediately outside the controlled zone, unidentified military aircraft at low level, gliders, helicopters and general aviation aircraft are all in operation, often without established radio contact with ATC Danger Areas To the West and North West of NIA lie RAF Spadeadam (D510) and the Otterburn Range (D512). RAF Spadeadam is used extensively by military aircraft and is unique in the training it provides to military pilots, with aircrew from all over Europe using the facility. Otterburn Range is primarily for use by land based military forces, with occasional use by military fast jets in support of ground based exercises. Aircraft may 7

9 overfly Otterburn Range, but aircraft arriving and departing Newcastle are generally flying at levels below the maximum height restriction of the range and must therefore route around it. This limits an ATCOs options should there be radar returns which are, or appear to be, aircraft. Similarly, aircraft may fly over RAF Spadeadam, depending on the extent of the activity within this range. The type of activity within and around the site raises the likely probability of small, fast non-transponding aircraft flying within this area and popping up on NIA s radar. PSR Blanking would not therefore be suitable within this area. The restriction in use of PSR Blanking would also extend to 5 nautical miles surrounding this area in order to ensure that any aircraft rerouted from this area as a result of aircraft on potentially conflicting flight paths can be tracked through this rerouting by NIA ATC. Factoring in these physical constraints, NIA has identified 2 Broad Areas of Less Constraint for PSR Blanking provision. These are identified in Figure 5 as the Northern Zone of Less Constraint and the Southern Zone of Less Constraint, albeit that the two areas co-join in the east and far west. Each proposal within these specified zones will be considered on its merits with PSR Blanking Areas assessed according to the criteria outlined in section 4.2 of this document. It is anticipated that due to the finite number of PSR Blanking Areas available, the strategy will exist as a short term enabler to wind farm development, particularly within the Northumberland area. In the longer term a more overarching method of mitigation of wind farms will be required. 5. Financial Implications for NIAL The implementation of a PSR Blanking Strategy at NIA requires that the status quo of radar provision is maintained for the lifetime of the Radar Blanking process or until such time as the Radar Blanking process is superseded by an all encompassing solution to the problems of wind turbines on airport radar. The current Primary Surveillance Radar (PSR) at NIA will provide service until 2018 and the Secondary Surveillance Radar (SSR) will provide service until December NIAL has made a policy decision that in order to support PSR Blanking it will retain both PSR and SSR under its control, and will recover the cost of replacement of both the PSR and SSR as part of this Strategy. In addition, other costs including software and equipment upgrades, legal fees, research and development, training and administration will also be recovered. It is anticipated that the total cost recovery will be in the region of 5M. In benefiting from the, developers will be required to enter into a Legal Agreement with NIAL. The Legal Agreement will document obligations on the part of the developer and NIAL, and will refer to two contributions:- Firstly, an initial non-refundable payment of 20,000 which facilitates all administration, including the preparation of a safety case document and the operation of a trial PSR Blanking Area at the site. This is required in order to ensure that NIA is able to retain an appropriate level of radar coverage to operate safely as an aerodrome. The outcome of this will be a document which will be fed into the Safety Management System of NIAL and is audited by SRG of the CAA, allowing NIA to continue to operate safely with a in place. Secondly, a proportionate contribution to the PSR Blanking Strategy cost recovery. The amount would be calculated based upon the number of turbines in 8

10 the scheme, with the rate per turbine reducing according to a sliding scale such that larger schemes benefit from some economies of scale, as shown below. This contribution would be placed in a stakeholder bank account and released to NIAL on the developer s issue of a notice to proceed 6 months prior to commencement of development, or on an important milestone which is mutually beneficial to NIAL and the developer. In the event that all potential PSR Blanking Areas are allocated, and not all of the required costs are recovered, NIAL would fund the remaining investments itself. If the costs are recovered and it looks likely that further Blanking Areas are possible, then the levels of contribution would be reduced. Number of turbines Cost per turbine ( ) Total cost ( ) 1 125, , , , , , , , , , , , , , , , , , , , , , , , , , Looking to the future The PSR Radar Blanking strategy currently identified, given its finite nature, is seen as a short term strategy in the mitigation of wind farms of radar by NIAL. While the CAA and others have made a concerted effort to explore a long term and more overarching solution to this issue, none of the emerging technologies are yet proven. NIAL is committed to exploring, alongside other stakeholders, whatever alternatives might emerge, but can only commit itself at the point at which a technology is proven. 9

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