14.7. Baseline Environment

14.7.1. Overview of Baseline Environment

  1. The following sections provide a summary of the aviation, military and communications baseline environment. Volume 3, appendix 14.1 and volume 3, appendix 14.1, annex A include full details of the analysis undertaken to develop the aviation, military and communications baseline and information on civil and military radar in the aviation, military and communications study area.

14.7.2. Existing Baseline Scenario

  1. In aviation and airspace terms, the world is divided into Flight Information Regions (FIR2) for the allocation of responsibility for the provision of an ATS to aircraft. The airspace above and around the Array is used by both civil and military aircraft, which are tracked by radar systems operated by both NATS and the MOD. The Array will be located within the Scottish FIR2 in an area of Class G[1] uncontrolled airspace, which is established from surface up to FL 195 (approximately 19,500 ft). Above this Class G Airspace is Class C[2] Controlled Airspace (CAS).
  2. Aircraft operating within CAS must be in receipt of an ATS from NATS, military air traffic controllers located at a NATS ACC or under the control of military air defence controllers.

                        Civil aviation

  1. The UK civil airport nearest to the Array is Aberdeen International Airport, which is located approximately 50 nm north-west of the site on a bearing of 292°.
  2. Airports with published IFPs have associated Minimum Sector Altitudes (MSA). A MSA defines the minimum safe altitude an aircraft can descend to within a sector of radius 25 nm (approximately 46 km). These sectors provide obstacle clearance protection of at least 1,000 ft to aircraft within that area. This allows pilots of aircraft flying under Instrument Flight Rules (IFR)[3] the reassurance of properly designated obstacle and terrain clearance protection whilst making an approach and landing at an airport in poor weather.
  3. Volume 3, appendix 14.1, annex A, includes full details of the IFP analysis undertaken to develop the aviation baseline. This concluded that the Array will not have an effect on the Obstacle Limitation Surfaces (OLS) and IFP that serve Aberdeen International Airport.
  4. Volume 3, appendix 14.1, includes full details of the radar LoS analysis undertaken to develop the aviation baseline.
  5. The radar LoS analysis indicates that the Perwinnes PSR will theoretically detect operational wind turbines at a maximum height of 399 m, which is likely to create a detrimental effect to the operation of the PSR. The Allanshill PSR will theoretically detect, intermittently, operational wind turbines located within the northern quarter of the Array (the closest to the radar location) (see volume 3, appendix 14.1, Figure 3.2). However, NATS have confirmed that the Allanshill PSR will not be effected. The potential impacts wind turbines may have on radar systems through radar detection of operational wind turbines may include the following:
  • Twinkling appearance/blade flash effect can distract the air traffic controller from their primary task.
  • Masking of real aircraft targets caused by increased clutter being displayed on the radar data display screen.
  • Increase in unwanted targets or false aircraft tracks.
  • Receiver saturation.
  • Target desensitisation causing loss of valid aircraft targets that are of a small Radar Cross Section (RCS).
  • Shadowing behind the wind turbines caused by physical obstruction (blocking of radar transmitted signal).
  • Degradation of target processing capability and processing overload.
  • Degradation of tracking capabilities including track seduction.
  1. The CAA advises that effects on Secondary Surveillance Radar (SSR) are only relevant for consideration when wind turbines are located less than 10 km from the SSR CAP 764 (CAA, 2016a). The Array lies outside the area of interaction with any aviation related SSR systems therefore, as agreed in via consultation on the Array EIA Scoping Report, aviation SSR systems are scoped-out and not considered further in the Array EIA Report.

                        Military aviation

  1. The MOD through the Air Surveillance and Control System (ASACS) is responsible for compiling a Recognised Air Picture (RAP) to monitor the airspace in and around the UK to launch a response to any potential airborne threat. This is achieved through the utilisation of a network of long-range ADR systems, some of which are located along the east coast of the UK. ADR systems are similarly impacted by the detection of operational wind turbines as listed in paragraph 25. Due to their role in the defence of UK airspace; any identified impact of wind turbines on the ASACS Radar Systems that serve the airspace above the Array may potentially reduce the capability of the ASACS Force.
  2. The nearest ADR to the Array is the TPS-77 (Type 92) ADR located at RRH Buchan, Aberdeenshire, which is located approximately 48 nm north-west of the site on a bearing of 316° from the closest Array boundary. RRH Brizlee Wood in Northumberland operates a TPS 77 type ADR and is located approximately 80 nm south-west of the site on a bearing of 215° from the closest Array boundary.
  3. Radar LoS analysis predicts that the operation of the Buchan ADR may be affected by the detection of operational wind turbines placed within the Array (see volume 3, appendix 14.1, Figure 3.3). The Brizlee Wood ADR will theoretically not detect operational wind turbines placed within the Array at a blade tip height of 399 m; however, occasional detection cannot be ruled out in the southernmost part of the Array (the closest to the radar location) (see volume 3, appendix 14.1, Figure 3.5).
  4. Leuchars Station PSR is located approximately 73 nm south-west of the site on a bearing of 245° from the closest Array boundary. Although there is potential for this PSR to detect the operational wind turbines of the Array, it is not envisaged that Leuchars air traffic controllers will be providing a radar ATS in the close (less than 10 nm) vicinity of the Array as this will be located outside of Leuchars Area of Responsibility (AoR), which is expected to extend around a 40 nm radius from the Leuchars Station PSR position. Within Class G airspace an ATS may be provided by NATS, or military controllers located at an ACC or air defence controllers subject to suitable radar and radio coverage being available to them.
  5. Military low flying activities take place in uncontrolled airspace below 2,000 ft Above Mean Sea Level (AMSL) within defined LFA. The Array is adjacent to LFA 14; however, low flying activity also extends offshore therefore, military low flying is likely to take place above and around the Array. The MOD DIO (who safeguard MOD infrastructure) commonly request aviation obstruction lighting to be fitted to wind turbines in accordance with CAP 393 (CAA 2016, as amended 2022a). The fitment of aviation obstruction lighting will be detailed within a Lighting and Marking Plan (LMP), in line with CAP 764 (CAA, 2016a), which will be produced and consulted on post-consent. The outline LMP for the Array can be found in volume 4, appendix 26.
  6. UK En Route Low Altitude North Sea West Offshore Installations (UK (L) 5 OIL) (MOD, 2023b) chart provides the location of military PEXA. The Array does not lie within any military aeronautical PEXA, however, it does lie beneath D613, a managed high intensity manoeuvring area ( Figure 14.2   Open ▸ ). The MOD have confirmed through engagement (21 November 2023) that no effect will be created to D613; therefore, D613 has been scoped out from further assessment.

                        Helicopter operations

  1. Commercial offshore helicopter operations in the North Sea encompass support to offshore oil and gas exploitation and SAR operations. Bristow Helicopters Ltd hold the UK Government national contract to deliver SAR operations on behalf of the MCA.
  2. SAR are not constrained by Commercial Air Transport (CAT) Regulations as these flights are generally flown by His Majesty’s Coastguard (HMCG) SAR aircraft operating under CAP 999 (CAA, 2023b). The Coastguard helicopters are operated as State Aircraft under National Regulations and are not constrained by the higher weather limits in CAT Regulations (CAA, 2023b)[4]. The closest MCA SAR helicopter base[5] to the Array is Inverness Airport, approximately 114 nm north-west of the Array. SAR operations often involve flying at low level.
  3. Helicopters supporting offshore oil and gas, in the northern North Sea, use Helicopter Main Route Indicators (HMRI), radiating from Aberdeen International Airport (the main support base) on a hub/spoke radial pattern (see Figure 14.2   Open ▸ ). These HMRIs lie to the north of the Array; the closest being 4 nm to the north of the north-eastern boundary of the Array on a bearing of 21. The CAA recommend within CAP 764 (CAA, 2016a) that there should be no obstacles within 2 nm either side of the centreline of a HMRI; the Array is located outside of the CAA recommended obstacle free distance. Moreover, the CAA also recommend that dependent on radar low level coverage required and the type of radar service required, it may be necessary to maintain a greater buffer than 2 nm.

                        Other radar and communications

  1. The Met Office safeguards its weather radar and provides site-specific (radar) pre-planning advice for proposals sited in Met Office consultation zones; these zones extend to a 20 km (11 nm) radius of Met Office radar sites (OPERA, 2009). The Array is located outside of the consultation zone, at approximately 96 km from the nearest Met Office radar at Hill of Dudwick, Aberdeenshire. The Met Office have confirmed in response to engagement that the Array will not impact Met Office radar operations; therefore, Met Office radar is not considered further in the Array EIA Report.

                        Summary of baseline environment

  1. A description of the aviation baseline environment is provided within the Aviation, Military and Communications Technical Report volume 3, appendix 14.1. The key sensitivities identified as part of the baseline assessment are as follows:
  • aviation and radar systems; civil and military; and
  • civil and military low flying including HMRIs and SAR.

Figure 14.2:
Aviation, Military and Communications Study Area Airspace Construct

Figure 14.2: Aviation, Military and Communications Study Area Airspace Construct


14.7.3. Future Baseline Scenario

  1. The EIA Regulations require that “a description of the relevant aspects of the current state of the environment (baseline scenario) and an outline of the likely evolution thereof without implementation of the project as far as natural changes from the baseline scenario can be assessed with reasonable effort, on the basis of the availability of environmental information and scientific knowledge” is included within the Array EIA Report.
  2. If the Array does not come forward, an assessment of the ‘without development’ future baseline conditions has also been carried out and is described within this section.
  3. The North Sea Transition Authority (NSTA) Oil and Gas Authority (OGA) Annual Report and Accounts 2022-2023 (NSTA, 2023) reported a predicted decline in gas production and usage in following years. Oil and gas operators continue to find it difficult to predict production accurately as older fields mature and their reliability reduces. The Prime Minister’s Office (PMO) and the Department for Energy Security and Net Zero (DESNZ) reported during July 2023 that the Prime Minister has committed to future oil and gas licensing rounds with two areas in the North Sea chosen as locations for carbon capture usage and storage clusters. The independent Climate Change Committee predicted around a quarter of the UK’s energy demand will still be met by oil and gas when the UK reaches net zero in 2050, the UK Government states that it is taking steps to slow the rapid decline in domestic production of oil and gas, which will secure UK domestic energy supply and reduce reliance on hostile states.
  4. North Sea Natural Resources Ltd undertook previous works to drill an appraisal well in hydrocarbon licence Block 27/5 which is located 19 km north-east of the Array. This work was completed in November 2023 and the permit for drilling works expired at the end of January 2024. However, as old oil and gas fields are decommissioned it is considered that helicopter use to oil and gas platforms associated with these fields will eventually decline; however, as helicopter support to offshore wind increases it is expected that there may be increased aviation activity as new offshore areas are developed to support net zero targets.
  5. Based on the timings of the development of the Array, the baseline environment for the aviation, military and communications assessment is not expected to change. The present airspace construct or usage, civil and military aviation, above and around the Array is not expected to change significantly.

14.7.4. Data Limitations and Assumptions

  1. The data used in this chapter is the most up to date publicly available information which can be obtained from the data sources as cited. Data have also been provided through engagement with the stakeholders detailed in Table 14.4   Open ▸ . For the purposes of the aviation, military and communications assessment, it should be noted that the results of the radar LoS analysis (volume 3, appendix 14.1) are theoretical, and considered to be conservative. These results are provided in order to establish the reasonable worst-case possibility of impact to aviation, military and communications stakeholders.