TOWN AND COUNTRY PLANNING ACT 1990 TOWN AND COUNTRY PLANNING (INQUIRIES PROCEDURE)(ENGLAND) RULES 2000

Transcription

1 TOWN AND COUNTRY PLANNING ACT 1990 TOWN AND COUNTRY PLANNING (INQUIRIES PROCEDURE)(ENGLAND) RULES 2000 PUBLIC INQUIRY TO CONSIDER SECTION 36 ELECTRICITY ACT 1989 APPLICATION BY PEEL WIND FARMS (FRODSHAM) LIMITED FOR PLANNING PERMISSION TO CONSTRUCT AND OPERATE A WIND FARM OF UP TO 60MW (KNOWN AS FRODSHAM WIND FARM) ON FRODSHAM CANAL DEPOSITS GROUND, LORDSHIP LANE, FRODSHAM, CHESHIRE PROOF OF EVIDENCE OF KEL KIRKLAND ON AVIATION ON BEHALF OF PEEL WIND FARMS (FRODSHAM) LIMITED DECC REFERENCE: /466C CHESHIRE WEST AND CHESTER COUNCIL REF: 10/00597/DECC AVIATION Proof of Evidence of Mr Kel Kirkland 1 of 71

2 TABLE OF CONTENTS List of abbreviations used 3 1 Personal Experience 4 2 Introduction and scope of evidence 6 3 The effects of wind farms on aviation radar 8 4 Wind farm information 12 5 Radar analysis background information 14 6 Radar assessment 16 7 ATC Safety and operational impact 21 8 Mitigation general background 31 9 Mitigation for the Frodsham wind farm In-fill mitigation options Conclusions 68 AVIATION Proof of Evidence of Mr Kel Kirkland 2 of 71

3 List of abbreviations used in this proof of evidence Every effort has been made to make this evidence as non-technical as possible for maximum clarity. Inevitably, aviation and radar are topics which involve the use of many abbreviations and acronyms and these are listed below. ANSP ATC CAP CHA DECC ICAO IFR ILS LJLA MTI MW NATS NSL PSR RDP SID SRTM STAR SSR UHF UK CAA VFR VHF Air Navigation Service Provider Air Traffic Control Civil Aviation Publication Chester Hawarden Airport UK Government Department for Environment and Climate Change International Civil Aviation Organisation Instrument Flight Rules Instrument Landing System Liverpool John Lennon Airport Moving Target Indicator Megawatt UK National Air Traffic Services NATS Services Limited Primary Surveillance Radar Radar Data Processor Standard Instrument Departure Shuttle Radar Topography Mission Standard Arrival Route Secondary Surveillance Radar Ultra High Frequency United Kingdom Civil Aviation Authority Visual Flight Rules Very High Frequency AVIATION Proof of Evidence of Mr Kel Kirkland 3 of 71

4 1 Experience and Qualifications 1.1 I am Kel Kirkland. I am a consultant for NSL Global Consultancy providing advice in relation to air traffic control matters with particular expertise in relation to wind farm aviation issues. 1.2 I have 21 years operational air traffic control experience having worked as a controller at Edinburgh, Glasgow and Aberdeen airports. I have held watch manager, manager Air Traffic Control and General Manager posts at NATS airports. 1.3 I have been closely involved in wind farm issues at major airports for the last 11 years and have built up a positive and respected position within the renewable energy industry. Working with BAA at Edinburgh and Glasgow airports, I have taken a pro-active and positive position to engage with renewable developers to assist them in overcoming the serious issues that wind farms present to aviation radar. Most notably, I was closely involved in developing and implementing the radar data fusion solution at Glasgow which allowed the 140 turbine Whitelee wind farm (the largest on-shore wind farm in Europe) to be consented and built. This project represented the first time that a technical solution of this type and scale had been implemented. 1.4 My experience in operational air traffic control and wind farms allows me to provide an objective and comprehensive perspective on the aviation radar issues that face airports and renewable developers. 1.5 My current role within NATS is a global consultant specialising in wind farm aviation issues working with airports and renewable developers in developing and implementing mitigation solutions both in the UK and overseas. 1.6 NATS has considerable experience in conducting radar line of sight assessments and operational impact assessments in both the airport and enroute environments. The NATS strength is in relation to providing a detailed objective analysis from an operational ATC perspective. AVIATION Proof of Evidence of Mr Kel Kirkland 4 of 71

5 1.7 NATS adopts a proactive approach to the problems caused by wind turbines in the radar environment and has led work on technical mitigation solutions such as the radar data fusion solution successfully employed to mitigate the 140 turbine wind farm at Whitelee, near Glasgow airport. AVIATION Proof of Evidence of Mr Kel Kirkland 5 of 71

6 2 Introduction and scope of evidence 2.1 This inquiry relates to the Frodsham wind farm, a development of 19 turbines which Peel wind farms (Frodsham) Limited propose to construct and operate near Frodsham, Cheshire. This proof of evidence deals with the issues related to aviation the effects of wind turbines on aviation radar and how these predicted effects will impact upon the air traffic control operations at Liverpool John Lennon Airport and Chester Hawarden airport. 2.2 An overview of the effects of wind turbines on aviation radar is first presented to assist in understanding my evidence and provides background to the subject matter. 2.3 An analysis of the radar line of sight from the existing radar systems at both airports was carried out and the results are explained in my evidence. 2.4 Given the position and nature of the new radar system being installed at Chester Hawarden Airport, an assumption has been made that the coverage of the new system would be very similar to the present radar system. This assumption is based upon the similar location of the new radar, similar known characteristics and experience of such radar replacements. 2.5 Taking the results of the line of sight analysis, an operational assessment has been carried out in relation to each of the ATC operations at LJLA and CHA. 2.6 The operational assessment examined how the predicted area of clutter from Frodsham wind farm would appear on the respective radar screens of each operation, and, using site visits and dialogue with controllers and managers at each airport, an opinion has been formed as to the likely impact upon each operation. 2.7 The predicted effects on the safety and operational impact upon air traffic operations at each airport are summarised and the opinions of AVIATION Proof of Evidence of Mr Kel Kirkland 6 of 71

7 each ATC operation noted, as are the reasons for the potential objections to the development. 2.8 A summary of the mitigation options generally available to ATC operators is provided. 2.9 An assessment of those mitigation options which may be appropriate to mitigate the Frodsham development is presented A summary of mitigation options which could be utilised is presented A more detailed assessment of the practical in-fill options available is presented Conclusions as to the most appropriate forms of mitigation is given. AVIATION Proof of Evidence of Mr Kel Kirkland 7 of 71

8 3 - The effects of wind farms on aviation radar 3.1 The effects of wind turbines on aviation and other radars are well documented. These effects are almost universally accepted by both civil and military radar operators, airport authorities, wind farm developers and aviation regulators. 3.2 Radar systems - background information Radar systems used by civil and military air traffic control units are of two distinct types. 3.3 Primary surveillance radar (PSR) Primary radar systems rely on powerful transmitters which send out pulses of electromagnetic energy from the spinning radar head. These pulses of energy will be reflected back from any objects that are encountered. The returns are detected by the radar system and the direction and range of the objects are computed by the radar data processing system and displayed on a radar map Many different types of object will reflect radar signals clearly the most desirable ones are the aircraft themselves but any solid object including buildings, trees, vehicles and flocks of birds will lead to a return on the radar screen. Less solid objects will also produce returns including weather clutter, heavy rain, hail and similar meteorological events Filtering techniques are used to prevent most returns from showing on the radar screen and modern radars are very effective at removing unwanted returns from the screen thereby leaving a clean picture which only shows aircraft within the range of the radar system. One of the most useful filtering AVIATION Proof of Evidence of Mr Kel Kirkland 8 of 71

9 techniques used in primary radar is that of the moving target indicator (MTI) which recognises all returns that are stationary and removes them from the display. This will effectively filter out ground clutter, buildings and other stationary targets. As most aircraft are moving at a recognisable speed, the MTI filter will not remove aircraft from the display Primary surveillance radar systems will accurately display the position of returns on a radar map display but cannot discern height of the target. Typical displays will show a primary return as a cross or + symbol. Often, the primary return will have a trail of about 8 dots behind it to show the last 8 positions this gives the controllers a good indication of the speed and direction of the aircraft if the dots are close together, it indicates a slower speed than if they are spaced far apart In order to ensure safety, primary radar systems are very sensitive and will show returns even from small moving objects at some distance gliders and small microlight aircraft can be detected on the radar system and this provides controllers with the ability to keep traffic under their control well clear of unknown contacts such as light aircraft which are lost or which are infringing airspace. This is a key factor in ensuring safety in the air traffic system Typical wind turbines consist of three large blades with tip heights of 100 to 150 metres. Due to the aerodynamic requirements of wind turbines, the blades are large both in length and chord and offer a huge radar crosssection to primary radar systems. This means that the reflected radar signal is very large typically, each blade produces a return of the order of a Boeing 747 aircraft. Wind turbines will weathercock they will turn to face the wind in order to maximise efficiency and this means that the aspect of each blade in relation to the radar signal is ever-changing and complex. Typically, it means that the return from a wind turbine can actually produce more than one return on the screen as different blade positions are recorded by each sweep of the radar. AVIATION Proof of Evidence of Mr Kel Kirkland 9 of 71

10 3.3.7 Due to the speed of the turning blades, the moving target indicator can not filter out moving turbine blades the radar processor sees the turbine blades as if they were large aircraft Typical range for an airport primary radar system is 50 to 60 nautical miles and longer range en-route radars typically operate out to 90 miles. 3.4 Secondary surveillance radar (SSR) SSR is a more advanced radar system than primary surveillance radar. The radar head sends out a signal which interrogates the airspace around it. Each aircraft equipped with SSR will carry an on-board transponder unit which will detect the interrogation signal and send a response. The response is a coded signal which is interpreted by the ground-based system and allows key information to be displayed on the radar screen. Typically, this information is aircraft callsign, speed and height additionally, SSR systems will also show whether the aircraft is climbing, descending or in level flight The additional information displayed by SSR allows a considerably increased capacity in the airspace system and more advanced controlling techniques which reduce the need for many radio calls between ATC and pilots Typically, the radar display will show a combination of PSR and SSR for each aircraft. Normally, an SSR radar return will consist of a small square with the aircraft callsign, speed and height displayed in proximity to the box. 3.5 Effects of wind turbines on radar systems The following effects on the two types of radar system are well known and documented. AVIATION Proof of Evidence of Mr Kel Kirkland 10 of 71

11 Primary surveillance radar (PSR) Receiver Saturation Constant false alarm rate Defeating moving target processing (obscuration) False radar returns (clutter) Plot extractor/filter memory overload Shadow effect Secondary surveillance radar (SSR) SSR reflections Shadow effect AVIATION Proof of Evidence of Mr Kel Kirkland 11 of 71

12 4 Wind farm information 4.1 The wind farm proposal being considered by this evidence is for up to 19 turbines with turbine tip height of 125 metres and rotor diameter of 90 metres. The turbine positions are indicated on this diagram. Figure 1 turbine positions AVIATION Proof of Evidence of Mr Kel Kirkland 12 of 71

13 4.2 Objections from LJLA and CHA Both LJLA and CHA have expressed concerns and have objected to this development. This evidence will deal with the issues faced by LJLA and CHA. AVIATION Proof of Evidence of Mr Kel Kirkland 13 of 71

14 5 Radar analysis - background information 5.1 Overview Analysis of the radar system is done using line of sight techniques and specialist software packages. Terrain data down to 50 metre resolution is used to accurately model the path of the radar signal and the likely signal strength that will be returned to the radar sensor. 5.2 Factors affecting radar line of sight A number of factors can affect the detection of turbines by a specific sensor including: The curvature of the Earth Atmospheric refraction of the radar signal Height and angle of the sensor antenna Height of the turbine blades The height profile of the terrain between the radar and turbine Forestry, buildings and other structures may also influence the radar signal Radar line of sight is slightly different to visual line of sight in that the radar LOS assessment calculates refractive influences. This gives a more accurate prediction of signal strength that will be returned Standard radar reflective cross-sections based on turbine blade length are used for the analysis. The results are representative for any turbine that might be chosen by Peel. AVIATION Proof of Evidence of Mr Kel Kirkland 14 of 71

15 5.2.4 Probability of detection is also factored in on top of the geometrical and refractive factors and this is based on the particular radar s set up and minimum discernible signal settings Radar line of sight modelling has been refined in recent years using actual turbine developments to fine tune and optimise predictive results. AVIATION Proof of Evidence of Mr Kel Kirkland 15 of 71

16 6 Radar assessment 6.1 Analysis There are up to 19 turbines proposed for the development. Tip height is 125 metres for each turbine. Terrain data is to 50 metre resolution. Data is provided from Shuttle Radar Topography Mission sources. Data of this resolution has proven to be very accurate in predicted versus actual coverage comparisons Radar data used was as follows: 6.2 Liverpool John Lennon Airport primary radar 1 Tower location (WGS84) E N 2 Antenna Electrical centre AGL 13.16m 3 Antenna Tilt 0.8 deg 0dB 4 Radome losses at 3GHz (if applicable) - not applicable 5 Radar type is ASR Liverpool John Lennon Airport primary radar is a modern, Raytheon ASR 10 system with plot extracted display of primary targets. Plot extraction systems display a computer-generated symbol, a small square, wherever the system detects a radar return above a set strength hence, all returns are the same sized symbol on the radar screen. Secondary Surveillance Radar is sourced as a feed from St. Annes and also from Cleehill NATS en-route radars. Standard separation approval is 3 nautical miles Approval to operate SSR-only has been granted using 5 nautical mile separation but this is only in situations where PSR is not available such as radar failure or maintenance. Radar Data Processor (RDP) in use is from Flight Refuelling. AVIATION Proof of Evidence of Mr Kel Kirkland 16 of 71

17 6.3 Hawarden airport primary radar 1 Tower location (WGS84) E N 2 Antenna Electrical centre (AGL) m 3 Antenna Tilt 0.3 deg 0dB 4 Radome losses at 3GHz (if applicable) - not applicable 5 Minimum Discernable Signal (MDS) 104 dbm 6 Radar type AR Chester Hawarden airport primary radar system is an analogue AR15 system which does not use plot-extracted technology and therefore displays primary returns on the radar screens as a blip which will be sized proportionately to the radar cross section signal received ie the bigger the target, the bigger the blip on the screen. Secondary Surveillance Radar is provided by a feed from Clee Hill en-route radar and this is used for labelling purposes but not for separation. Separation applied is 5 nautical miles Chester are installing a new radar PSR system and the new radar is predicted to be in direct line of sight of the turbines and clutter will be produced on the radar screen New Chester PSR details 1 Tower location (WGS84) E N 2 Antenna Electrical centre (AGL) m 3 Antenna Tilt not known 4 Radome losses at 3GHz (if applicable) - not applicable 5 Minimum Discernable Signal (MDS) not known 6 Radar type EASAT with EA 5025 antenna The radar is planned to be operational in late AVIATION Proof of Evidence of Mr Kel Kirkland 17 of 71

18 6.3.4 Throughout this proof of evidence, the assumption is made that the new Chester radar system will be of similar coverage and specification as the present analogue system and therefore that the turbines from Frodsham wind farm will produce returns on the radar display at Chester. The validity of this assumption is based upon the following The new radar is to be positioned in a similar location to the present system Electromagnetic characteristics of the new system will be comparable to the present system The lack of terrain between radar antenna and turbine blades means that the blades will continue to be visible to the new system and therefore produce the same clutter effects 6.4 Analysis results The results from the radar line of sight analysis for each radar shows that all turbines will be visible to both radars. Each turbine will produce a strong return on the radar displays at Liverpool and at Hawarden `The clutter produced on the Liverpool radar screen will manifest itself as multiple, plot extracted primary returns these are small square/diamond shapes The clutter produced on the Hawarden radar screen will manifest itself as multiple analogue primary blips of varying size. The size of the returns will be dependent on the relative aspect of the turbine blades to the primary radar signal. When the new radar is installed, the effects will be similar to those expected on the Liverpool radar screen as the new system will also be a modern plot-extracted system. AVIATION Proof of Evidence of Mr Kel Kirkland 18 of 71

19 6.4.4 Results for both Hawarden and LJLA are shown overleaf and it is clear that there is no terrain shielding between the radars and the proposed wind farm. AVIATION Proof of Evidence of Mr Kel Kirkland 19 of 71

20 Fig 2 - Representative radar line of sight analysis from Liverpool radar AVIATION Proof of Evidence of Mr Kel Kirkland 20 of 71

21 Fig 3 - Representative radar line of sight analysis from Hawarden radar AVIATION Proof of Evidence of Mr Kel Kirkland 21 of 71

22 7 ATC safety and operational impact Figure 4 - Diagram of Hawarden airspace showing relative positions of both Liverpool and Chester Hawarden airports AVIATION Proof of Evidence of Mr Kel Kirkland 22 of 71

23 7.1.1 The ATC operational impact of this proposed wind farm is clearly one that is vital to understand in some detail. It is important, therefore, to understand the facts, the risks and the safety issues that are related to this wind farm proposal with respect to the operation of the airports both now and into the foreseeable future. Safeguarding of airport operations and the airspace surrounding them are vital and mandatory functions that cannot be undertaken lightly There are two specific areas which need to be considered: Safety Operation of the airport It is essential that these areas are considered in terms of the present day operation but also that the future likely expansion of the airports and changes to surrounding airspace and traffic levels are also considered. 7.2 Safety general perspective a requirement is placed on the licensee to take all reasonable steps to ensure that the aerodrome and its surrounding airspace are safe at all times for use by aircraft CAA CAP 764 (KK/Appendix 1) CAA guidance does state that the onus is on the developer to prove no detrimental effect on safety. Understandably, this is a very difficult task for the developer as it cannot foresee the future expansion of the airport and associated airspace changes, traffic increases and legislative changes for the lifetime of the wind farm. In reality, nobody can foresee such changes over a 25 year period so it rests to all parties to rely on industry trends, airport aspirations and the professional knowledge of all stakeholders. AVIATION Proof of Evidence of Mr Kel Kirkland 23 of 71

24 7.2.2 From an airport perspective, they are clearly very keen to preserve their present-day businesses as well as safeguarding for future expansion. In terms of safety, airport operators and ATC providers have an over-riding duty to comply with CAA legislation and to live up to their safety accountabilities. Accountability for safety of the public is not an easy task it requires those holding accountabilities to think and act pro-actively and to do everything reasonable to ensure a safe operation Safety is one of the two key elements of the impact of this development (the other being the operational aspect) - safety in the current operation and also safety in the near future of an airport that is committed to sustainable and predictable growth. 7.3 How could this wind farm impact on safety at Hawarden? The wind turbines will produce clutter on the radar screen An additional effect is that it will also reduce the effectiveness of the radar in detecting aircraft in the shadow of the wind farm and also directly above the wind farm. This is a known and documented phenomenon. 7.3,3 The primary returns of any aircraft which over-fly the wind farm clutter may be lost within the clutter. Whilst it may still be possible to observe SSR labels, the identification of the aircraft will be lost and therefore separation from other aircraft may not be achieved Any unknown aircraft or aircraft which are lost and not transponding not using or carrying SSR transponder equipment - would not necessarily be known or visible to ATC at Hawarden and therefore the risk in taking aircraft under ATC control through the clutter area would be significant under these circumstances. AVIATION Proof of Evidence of Mr Kel Kirkland 24 of 71

25 7.4 How could this wind farm impact on safety at Liverpool? The wind turbines will produce significant clutter on the radar screen An additional effect is that it will also reduce the effectiveness of the radar in detecting aircraft in the shadow of the wind farm and also directly above the wind farm. This is a known and documented phenomenon The primary returns of aircraft which over-fly the wind farm clutter may be lost within the clutter. SSR returns may still be visible, however, identification based on the primary returns would be jeopardised Any unknown aircraft or aircraft which are lost and not transponding not using or carrying SSR transponder equipment - would not be known or visible to ATC at Liverpool and therefore the risk in taking aircraft under ATC control through the clutter area would be significant under these circumstances The number of aircraft that infringe the Liverpool airspace in the region of the proposed wind farm is small. The incidence of transponder failure is also very small and therefore it could be argued that within the controlled airspace around Liverpool, there is a very small risk that an unknown, non-transponding aircraft could be encountered over the wind farm. Whilst this risk of occurrence is relatively small, it does remain significant in terms of the potential outcome of such an occurrence. Liverpool ATC, if faced with such clutter, would take actions to prevent an impact upon safety. This could take the form of avoiding the clutter area in AVIATION Proof of Evidence of Mr Kel Kirkland 25 of 71

26 order to ensure safety but this would lead to an unacceptable impact upon the operation of the airport in terms of efficiency and capacity. AVIATION Proof of Evidence of Mr Kel Kirkland 26 of 71

27 7.5 Wind farm effect on airport operations Hawarden airport A considerable amount of traffic inbound to runway 22 at Hawarden airport routes via a downwind left hand pattern, taking it close to the planned wind farm at Frodsham Some permanent echoes are present on the Hawarden radar screen, notably on 7 nautical mile final approach to runway 22, from Stanlow oil refinery. In addition, a large area of clutter is sometimes apparent from Delamere forest, on a left base position for runway Aircraft being vectored to ILS approaches from the South can be vectored to avoid the clutter from Delamere forest. In addition, the permanent echo from the power station on final approach is relatively small It is therefore understandable why Hawarden airport would object to this wind farm proposal, however there is one factor which could give rise to this objection being challenged It is clear that the wind farm site is well within the Liverpool airport airspace and therefore that any control of aircraft within this airspace by Hawarden must be co-ordinated with Liverpool this means that Liverpool must grant permission to Hawarden ATC each time they control aircraft within the Liverpool airspace. The basis upon which this permission is granted includes the proviso that Liverpool have no traffic to affect the anticipated movement of Hawarden traffic. In ATC terms, this is often referred to as being clean of any Liverpool traffic Whilst it may be convenient to allow Hawarden to control traffic within Liverpool airspace, and whilst such practices are common and perfectly AVIATION Proof of Evidence of Mr Kel Kirkland 27 of 71

28 acceptable in ATC terms, it does essentially mean that Liverpool retain responsibility for ensuring that such traffic remains clean of any traffic that may appear in their airspace If Hawarden were to be operating in isolation, outside controlled airspace, the proposed wind farm would represent a serious threat to the operation of the airport. As the wind farm is within Liverpool airspace, it can be argued that there is additional protection of a known ATC environment (ie that ATC should be made aware of all traffic in that airspace and have issued it with a clearance). AVIATION Proof of Evidence of Mr Kel Kirkland 28 of 71

29 Liverpool airport The clutter area that would be produced by the Frodsham wind farm on the Liverpool radar screens would be in a downwind left hand circuit position for the westerly runway. Due to airspace and other restrictions, the majority of inbound traffic to Liverpool during prevailing westerly operations would be radar vectored close to, or over the clutter. In addition, a large percentage of inbound aircraft is cleared by ATC for visual approaches for the purposes of traffic expedition and fuel economy. Although Liverpool airspace is somewhat restrictive, Liverpool ATC do have a responsibility to provide Continuous Descent Approaches insofar as is possible. There is increasing pressure for all airports to operate their traffic in as fuel-efficient a method as possible and this invariably requires a flexible use of available airspace. Any restriction on the airspace available would negatively impact on the capability of Liverpool ATC to provide fuel-efficient CDA approaches and visual approaches By far the largest impact on the ATC operation would be the effect of having to avoid the clutter area. If ATC assess that taking large numbers of aircraft through an area of clutter on a regular basis presents too much risk, they will be forced to avoid that clutter area in order to assure safety. Avoiding the clutter area for safety reasons would normally also require a margin around the clutter area to be avoided in order that controllers had sufficient opportunity to observe and avoid any unknown aircraft emerging from the clutter area. It would be reasonable to expect a 2 or 3 nautical mile margin around the clutter area for this reason `The impact of having such a sterile area would be highly significant. A strategy of avoidance in such a critical, dense traffic area would be limiting to the efficiency and capacity of the Liverpool operation, particularly during busier inbound traffic periods. AVIATION Proof of Evidence of Mr Kel Kirkland 29 of 71

30 It is not unreasonable for Liverpool ATC and the airport authority to have serious concerns about the impact upon their present, and future operation, unless properly mitigated. Cumulative effect There is no doubt that while small wind turbine developments can have an effect that has an adverse impact on aviation; proliferation of developments and the subsequent cumulative effect is of far more significant concern the combined effect of numerous individual turbines or multiple wind farm developments can be hard, if not impossible, to mitigate. CAA CAP 764 (KK/Appendix 1) For Hawarden, the existing clutter represents an issue which would be compounded by additional clutter from the wind farm being proposed It is anticipated that Hawarden s new plot-extracted radar system will be more effective in filtering out static terrain clutter such as that currently detected in relation to the Stanlow oil refinery For Liverpool, the constraints of the airspace within which they work, both vertically and horizontally, leave only a limited amount of flexibility in terms of available airspace in which to vector their traffic. Any significant clutter from a single wind farm such as Frodsham will therefore represent a cumulative effect which is much more significant than if the airspace was less constrained. In short, clutter from Frodsham would severely limit the options available to ATC for avoiding that clutter and still providing an efficient service to the airport unless properly mitigated. AVIATION Proof of Evidence of Mr Kel Kirkland 30 of 71

31 8 Mitigation general background 8.1 Mitigation at planning stage Often, a number of turbines can be estimated as being marginal in terms of the predicted return levels on a particular radar system. Clearly, any estimation regime involves a level of potential error. Many factors affect predicted and actual coverage and are well documented elsewhere By way of example, radar signals in real life are affected by climatic conditions, vegetation and trees in the line of sight and by precipitation and road and rail traffic. Suffice to say that, despite accurate and proven prediction technology and methodology, there will be situations where the prediction of whether a turbine will show up on a radar screen cannot be absolute. In situations such as this, NATS will often attempt to work with the developer to assist in re-siting individual turbines in order to reduce the likelihood of detection. Given the strong predicted returns in the case of Frodsham, re-siting is not an action that would produce any mitigation. 8.2 Mitigation technology Mitigation technologies fall into three main categories: Radar-contained mitigations Typically, these mitigations are based upon filtering or algorithms within the radar processing equipment. A number of companies have developed such technologies but no mainstream use of such technology has been utilised to date to mitigate against strong, multiple turbine returns in the civil ATC environment. Huge advances have been made in this technology recently, and a number of radar-contained mitigations are being promoted and tested by various companies, including Raytheon and Thales. AVIATION Proof of Evidence of Mr Kel Kirkland 31 of 71

32 Full-scale testing by these companies has already taken place with some promising results Non Auto-initiation zone techniques are based on radar processing which prevents new tracks from being initiated from within the clutter area. These techniques are discouraged by CAA for a number of safety reasons. Chapter 4 Section 4.13 of CAA publication CAP 764 refers (KK/Appendix 1). This technique is rarely, if ever, used as mitigation for wind turbine clutter in the UK. Materials and turbine-based technology Mitigation based upon the materials and shape of turbine blades and nacelles stealth technology has been mooted for some years. A number of companies have promoted the concept as a mitigation against turbines showing up on primary radar systems. As yet, no full-scale demonstration within the civil ATC environment has taken place so, whilst the technology shows promise, it is not available as a mitigation at this time except on an experimental basis. In-fill radar technology In-fill radar technology (sometimes referred to as radar data fusion or gap-filling) is the process of removing an area of primary radar coverage and then filling in the gap with a separate source. If that separate source is correctly positioned such that the coverage is not as low as the main primary radar, then it is possible for the radar to detect aircraft above the wind farm at suitable low levels whilst not detecting the turbines This type of solution has been deployed at Glasgow airport in order to mitigate the Whitelee wind farm. Such a system is very successful. There are complexities in such an approach in terms of the technology, safety assurance in order to get CAA Safety Regulation Group approval and issues AVIATION Proof of Evidence of Mr Kel Kirkland 32 of 71

33 around ownership of the solution technology. This technology does however represent a realistic mitigation for many proposals The Glasgow solution employs an in-fill technique using a full-scale ATC radar system which is positioned in such a way as to be terrain-shielded from the turbines, but still provide low coverage of aircraft above the turbines. Other new technologies which do not rely on terrain-shielding are available. These include short-range and low-power in-fill systems which do not rely on terrain-shielding to filter out the turbine returns whilst retaining aircraft returns. 8.3 Operational mitigations Blanking Blanking involves removing those areas of the radar coverage which contain the clutter. In some radar systems where the technology permits, small areas can be successfully blanked to remove small number of turbines. Larger developments are rarely blanked in areas where aircraft operate as blanking removes all coverage from that area and this clearly is not consistent with safety. Avoidance One of the simplest mitigations is for the controller to ensure that aircraft under his/her control avoid the returns on the radar screen. Whilst this is a simple mitigation, it is one that most airports cannot consider for a number of reasons: Traffic levels and patterns are such that avoidance is not an option there simply is not enough airspace to accommodate an avoidance strategy. AVIATION Proof of Evidence of Mr Kel Kirkland 33 of 71

34 Adjacent airspace restrictions such as danger areas or areas of high intensity traffic and adjacent ATC units can all hinder avoidance options The problem of cumulative effect is prevalent other wind farms in the region will affect profoundly the overall situation and airports would normally take into account other proposals in their response to individual proposals Avoidance of wind farms will often lead to additional track miles being flown by aircraft. This can affect CO2 emissions over a long period of time and will often affect the ability of aircrew to fly consistent fuel-efficient approaches. Airspace restrictions and rules Many airports are afforded the protection of airspace such as control zones or mandatory transponder areas. Any airspace which requires all pilots to obtain a clearance from ATC before entering that airspace will automatically ensure that this airspace is a known environment. In theory, this means that ATC will have knowledge of all aircraft operating in that airspace and therefore the risk of an unknown aircraft being hidden within the wind farm clutter is very low. In reality, however, light aircraft and microlights do get lost and often stray into controlled airspace unknown to the controller. This is an extremely dangerous situation which could prove to be catastrophic if the controller vectors his known traffic over the wind farm which is masking another aircraft at the same level The risk can be higher in situations where the airport does not have airspace around it that requires all pilots to receive a clearance. In such circumstances, in Class G airspace, for example, any aircraft can operate without contacting ATC. This creates a risk that is fundamentally higher than for airspace such as Class D control zones which require an ATC clearance to AVIATION Proof of Evidence of Mr Kel Kirkland 34 of 71

35 enter. Liverpool airport operations are largely carried out in Class D airspace and Chester Hawarden operations in Class G airspace If you also have a situation in which ATC are controlling aircraft without Secondary Surveillance Radar (SSR) but using primary-only then the risk increases by another significant factor. In such airspace, the controller is working in an unknown environment where he/she has incomplete knowledge of traffic in the area and also a radar display system that is the only means of detecting and avoiding other aircraft. Any area of clutter that is introduced into such a display in such an environment creates a significant risk to that operation Feasibility of operational mitigations are very much dependent on the prevalent situation at the airport concerned as there are so many variables which can affect the situation. Secondary surveillance radar Mitigation of effects on SSR is normally achieved by ensuring that the wind farm is no closer to the SSR radar head than 10 kilometres, although CAA guidance suggests that effects can exist out to 24km. CAA CAP 764 (KK/Appendix 1) AVIATION Proof of Evidence of Mr Kel Kirkland 35 of 71

36 9 Mitigation for the Frodsham wind farm Liverpool John Lennon Airport 9.1 Mitigation at planning and pre-planning stage The turbines are predicted to be very clearly line of sight to the primary radar at Liverpool and therefore there is no scope for optimising turbine positions or indeed heights, in order to render some or all of them invisible to the radar. 9.2 Radar-contained mitigations There are some mitigation that could theoretically be employed in the Liverpool radar system. A number of companies are working on radarbased filtering and algorithm systems that show some promise but these have yet to be proven or demonstrated on the specific radar system in use at Liverpool Analysis of tilting the radar head in order to cut out low-level coverage was done but this showed that a tilt of something in the region of 5 degrees would be required to cut out the turbines and this would lead to unacceptable loss of coverage for ATC purposes. 9.3 Materials and turbine-based technology Stealthy blades are being proposed as a feasible method of cutting down turbine reflections but as yet, this technology has not been proven and has not been tested on full-scale turbines. This technology is therefore considered to be in its infancy and not feasible as a short-term mitigation for this development. AVIATION Proof of Evidence of Mr Kel Kirkland 36 of 71

37 9.3.2 The latest testing to be done has been with a single blade on a turbine about half the size of those proposed for Frodsham. Publicly released reports have suggested that the results were in line with predictions that is a very positive sign. Any mitigation strategy using stealthy materials and technology would be considered to be an experimental or proving project which would not necessarily have a certain outcome at this particular time. 9.4 Infill radar technology Infill techniques have been successfully deployed at Glasgow airport to mitigate against the Whitelee wind farm. This technique involves an additional primary radar feed from a source which is shielded from the turbines by terrain, or by advanced algorithm filtering techniques or holographic 3D technology In principle, this technology is clearly feasible terrain shielding has been approved and is in operation at Glasgow and will shortly go into service at other UK locations. Major advances in advanced filtering technologies indicate that such technologies would also be feasible within the required timescales for Frodsham wind farm In-fill radar is feasible for Liverpool airport and there is sufficient confidence from previous and ongoing regulatory approval work to suggest that approval from CAA Safety Regulation Group would be achievable It is not envisaged that it would be necessary to provide an in-fill feed to Hawarden as the existing agreement and operation of the airspace between Liverpool and Hawarden is such that it is not strictly necessary for Hawarden to provide a service to aircraft over the Frodsham wind farm Any solution based upon an in-fill system that worked for LJLA could also work for CHA. From many perspectives, it would be desirable for AVIATION Proof of Evidence of Mr Kel Kirkland 37 of 71

38 LJLA and CHA to both receive an in-fill feed independently from a common in-fill sensor. This would provide redundancy in the event of failure or removal from service for maintenance of the Liverpool PSR. From a workshop held in 2010, it was clear that Peel Energy favoured an equitable solution that mitigated the effects of the wind farm on both LJLA and CHA radars. 9.5 Operational mitigations Blanking Blanking of the radar display in the region of the wind farm is not normally an acceptable mitigation option as it would remove a significant area of the display and safety approval issues would prevent use of this technique. Blanking is normally utilised in association with in-fill radar or with SSR-only approvals In-fill radar is discussed above SSR mandatory zones have been used in various locations as mitigation but they are generally only acceptable in areas of low traffic density and where the likelihood of non-transponding aircraft is very low. They have also been employed as temporary mitigations where the short-term risk is deemed acceptable Given the traffic levels and volume of light aircraft operations in the Frodsham area, it is not likely that SSR-only operations on a permanent basis would be acceptable on safety grounds to LJLA. AVIATION Proof of Evidence of Mr Kel Kirkland 38 of 71

39 Avoidance Avoidance of wind farms is a recourse to ensuring safety Implications of avoiding the Frodsham wind farm would be considerable given the location of the proposed development an area that currently carries a large percentage of LJLA commercial traffic The options for avoiding the clutter area are extremely limited due to the airspace constraints and there would be a significant impact upon the efficiency of the Liverpool operation should an avoidance strategy be employed. Airspace restrictions and rules Currently, the affected airspace is a known environment and therefore, in theory, all traffic should be known to ATC. In reality, there are occasions when aircraft transponders fail and when non-transponding traffic accidentally stray into controlled airspace. Whilst for Liverpool, the rate of such incidents is low, it is still a real and justifiable concern. SSR mitigations Requirement for SSR mitigation is not being considered for this proof of evidence as it is not necessary. AVIATION Proof of Evidence of Mr Kel Kirkland 39 of 71

40 Chester Hawarden airport 9.7 Mitigation at planning and pre-planning stage The turbines are predicted to be very clearly line of sight to the primary radar at Hawarden and therefore there is no scope for optimising turbine positions or indeed heights, in order to render some or all of them invisible to the radar A new plot-extracted radar system is being installed at Chester Hawarden Airport and this may present an opportunity to implement a possible mitigation during the radar setup. Assuming a standard high beam/low beam configuration, it would be worth investigating whether the cutoff point at which these beams are implemented could provide sufficient mitigation this will depend on the operational requirements of Chester ATC but it is worth exploring this option at an early stage. 9.8 Radar-contained mitigations There are some mitigations that could theoretically be employed in the new Chester radar system. A number of companies are working on radar-based filtering and algorithm systems that show some promise but these have yet to be proven or demonstrated on the specific radar system in use at Chester A suitable mitigation put in place at LJLA should be capable of providing an opportunity for the same mitigation to mitigate the radar clutter at CHA. This could be done by either utilising the clean Liverpool picture that the mitigation produces and integrating this into the Chester system or for the mitigation sensor (assuming an in-fill solution) being fed to both Liverpool and Chester independently. AVIATION Proof of Evidence of Mr Kel Kirkland 40 of 71

41 9.8.3 No analysis was done specifically on the tilting of the radar head in order to reduce the impact of turbine returns but it is not considered that this would be appropriate given the requirement for low-level coverage and the inherently strong nature of the returns predicted from the line of sight analysis. 9.9 Materials and turbine-based technology Stealthy blades are being proposed as a feasible method of cutting down turbine reflections but as yet, this technology has not been proven and has not been tested on full-scale turbines. This technology is therefore considered to be in its infancy and not feasible as a short-term mitigation for this development, except in an experimental capacity with no guarantee of success at this time Infill radar technology Infill techniques have been successfully deployed at Glasgow airport to mitigate against the Whitelee wind farm. This technique involves an additional primary radar feed from a source which is shielded from the turbines by terrain. The radar signal does therefore not see the turbines but does see the aircraft just above the wind farm Alternatively, short-range gap filling radars that do not rely on terrain shielding are becoming available The radar feed from the main radar (in this case, the LJLA and CHA radars) would be blanked in the area of the turbines and the infill source is transplanted into the display to give an un-cluttered picture. AVIATION Proof of Evidence of Mr Kel Kirkland 41 of 71

42 In principle, this technology is clearly feasible, albeit with associated regulatory and technical issues and assuming both acceptable integration capability and successful implementation of the new plotextracted radar system at Chester. There are no reasons to suspect that either of these factors would prevent such a solution from being implemented As has been discussed elsewhere, it is not considered necessary for Hawarden to control aircraft over the wind farm area and therefore it is not considered that in-fill or other mitigation is essential for Hawarden, but can be considered desirable from the perspective of independent operations. Peel has stated a preference for providing a mitigation which provides equal levels of mitigation to each airport s radar issues so as to preserve the status quo in terms of procedures and operational practices. This would be achieved by providing independent feeds to each airport from a common infill radar system Operational mitigations Blanking Blanking of the radar display in the region of the wind farm is not a mitigation option as it would remove a large area of the display and safety approval issues would prevent use of this technique. Avoidance Avoidance of the wind farm may be possible, given the location of the wind farm, the airspace in which it is contained, and the local agreement on traffic co-ordination with Liverpool. AVIATION Proof of Evidence of Mr Kel Kirkland 42 of 71

43 Airspace restrictions and rules Currently, the affected airspace is a known environment and therefore, in theory, all traffic should be known to ATC. In particular, it is possible for Liverpool ATC to be the prime controlling authority above the wind farm area proposed which therefore does not require Hawarden ATC to control aircraft in this region. SSR mitigations Requirement for SSR mitigation is not being considered for this proof of evidence as it is not necessary. AVIATION Proof of Evidence of Mr Kel Kirkland 43 of 71

44 9.12 Mitigation summary It is not considered that mitigation is automatically required for Hawarden ATC. The reason for this is that in certain circumstances, authority for radar operations in the Hawarden area of responsibility is ultimately with Liverpool ATC such that it could be possible for Liverpool to remain as the sole controlling authority for the airspace above the wind farm area within Liverpool s existing airspace This approach, would, in effect, mean that the radar issue is solely a Liverpool one. Whilst this issue remains significant for Liverpool, it does mean that mitigation only needs to be sought for one airport. Having stated that, it is desirable to have a mitigation solution for both LJLA and CHA radars. The ideal solution would be to have a mitigation source that would provide equal levels of mitigation for both Liverpool and Chester Airspace-based mitigations such as auto non-initiation areas, simple blanking and SSR-only scenarios are not practical for safety and/or regulatory reasons Avoidance of clutter areas will be resisted by both airports due to the operational impact and, for Liverpool, such a strategy would be very damaging to their capacity and efficiency. Liverpool could make a strong argument for the requirement to avoid the clutter area due to safety concerns from unknown aircraft A successful mitigation strategy would be based upon removal of the turbine clutter from the Liverpool radar screens and this points clearly to either in-fill radar or stealth technology. AVIATION Proof of Evidence of Mr Kel Kirkland 44 of 71