7.3. Aviation, Military and Communications

7.3.1. Introduction

  1. This section of the Array EIA Scoping Report identifies the elements of aviation, military and communications of relevance to the Array and considers the scope of assessment on aviation, military and aviation communications receptors from the construction, operation and maintenance, and decommissioning of the Array.
  2. There is also consideration of civil airports operations, the types and operational coverage of aviation radar over the Array, impact on civil aviation agencies, Search and Rescue (SAR) offshore helicopter operations and the Ministry of Defence (MOD) aviation operations including military aviation radar systems.

7.3.2. Study Area

  1. Whilst not definitive, CAA, Civil Aviation Publication (CAP) 764 Policy and Guidelines on Wind Turbines (CAA, 2016) provides criteria for assessing whether any wind turbine development might have an impact on aerodrome and radar related operations. Consideration of the Array's potential to impact on aviation stakeholders and receptors has been undertaken in accordance with the recommended consultation distance of within 30 km of an aerodrome with a surveillance radar facility, stated in CAP 764 (CAA, 2016).
  2. CAP 764 states that the operational range of a radar system is dependent on the type of radar used and its operational requirement. CAP 764 (CAA, 2016) provides a guide of 30 km for assessment of radar impact; however, impact is dependent on radar detectability of operational wind turbines, the radar’s operational range and the use of airspace in which the development sits. The operational impact assessment has considered the orientation of approach and departure flight paths, physical safeguarding of flight, airspace characteristics and procedures as published in the UK Integrated Aeronautical Information Package (IAIP) (NATS, 2022) and the Military Aeronautical Information Publication (Mil AIP) (MOD, 2022). The site boundary is provided in Figure 7.6   Open ▸ , the aviation, military and communications study area encapsulates the Array, the airspace between the Array, the UK mainland from the location of the NATS operated Allanshill Primary Surveillance Radar (PSR) to the north and the Brizlee Wood Remote Radar Head (RRH) Air Defence Radar (ADR) to the south.

Figure 7.6:
Array and Aviation, Military and Communications Study Area

Figure 7.6: Array and Aviation, Military and Communications Study Area


7.3.3. Baseline Environment

                        Desktop study

  1. A desktop study was undertaken to obtain information on civil and military stakeholders and radar systems. A variety of aviation publications contain information and guidance relating to the potential effects of an offshore wind development on aviation stakeholders. Data sources and guidance documents considered as part of the desktop review in the establishment of the baseline aviation situation include the following documents and charts, the list excludes those documents previously referenced in preceding text:
  • UK En Route Low Altitude British Isles (UK (L) 2) Chart (CAA, 2022a).
  • UK En Route Low Altitude North Sea West Off-Shore Installations (UK (L) 5 OIL (CAA, 2022b).
  • UK IAIP (NATS, 2022).
  • Radar Line of Sight (RLoS) Analysis (Osprey, 2022).
  • MGN 654 (M+F), (MCA, 2021).
  • International Civil Aviation Authority (ICAO), Document 8168 Ops/611 Procedures for Air Navigation Services Aircraft Operations (PANS-Ops) (ICAO, 2006).
  • ICAO Annex 14 Aerodromes Design and Operations contains Standards and Recommended Procedures (SARPs) (ICAO, 2022).
  • CAP 794 Policy and Guidance on Wind Turbines (CAA, 2016).
  • CAP 670 Air Traffic Services Safety Requirements (CAA, 2019).
  • CAP 437 Standards for offshore helicopter landing areas (CAA, 2021).
  • CAP 393 The Air Navigation Order (ANO) 2016 (CAA, 2016 amended 2022c).
  • CAP 168 Licensing of Aerodromes (CAA, 2022d).

                        Site-specific data

  1. The above documents and charts will be utilised to inform the EIA and will form the most up to date information publicly available which can be obtained. An additional RLoS analysis may be completed based on specific changes to PDE, project infrastructure (blade tip height) and response to scoping. Additionally, an analysis of any adjacent Instrument Flight Procedures (IFP) may be required dependent on stakeholder response to scoping.

                        Baseline characterisation

  1. In aviation and airspace terms, the world is divided into Flight Information Regions (FIR)s for the allocation of responsibility for the provision of an air traffic service 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 FIR in an area of Class G[10] uncontrolled airspace, which is established from surface up to FL 195 (approximately 19,500 feet (ft)). Above this Class G Airspace is Class C[11] Controlled Airspace (CAS).
  2. All aircraft operating within CAS must be in receipt of an Air Traffic Service (ATS) from NATS, military air traffic controllers located at a NATS Area Control Centre (ACC) or under the control of military air defence controllers.
Civil aviation
  1. The UK civil airport nearest to the Array is Aberdeen Airport, which is located on a bearing of approximately 292°/50 nm north-west of the site.
  2. Airports with published IFP 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)[12] the reassurance of properly designated obstacle and terrain clearance protection whilst making an approach and landing at an airport in poor weather.
  3. Preliminary RLoS analysis indicates that the Perwinnes PSR will theoretically detect operational wind turbines at a maximum height of 399 metres (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 which are placed within the northern quarter of the Array area (the closest to the radar location). The generalised effects wind turbines have on radar systems through radar detection of operational wind turbines are as follows:
  • 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 to consider when wind turbines are located less than 10 km from the SSR CAP 764 (CAA, 2016). The Array lies outside the area of interaction with any aviation related SSR systems.
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 557. Due to their role in the defence of UK airspace; any identified effect of wind turbines on the ASACS Radar Systems that serve the airspace above the Array may potentially reduce the capability of the ASACS Force. The nearest ADR to the Array is the TPS-77 (Type 92) ADR located at RRH Buchan, Aberdeenshire which is located on a bearing of approximately 316°/48 nm from the closest boundary of the Array. RRH Brizlee Wood in Northumberland operates a TPS 77 type ADR and is located on a bearing of approximately 215°/80 nm from the closest boundary point on the south-west of the Array. RLoS analysis predicts that the operation of the Buchan ADR may be impacted by the detection of operational wind turbines placed within the Array. The Brizlee Wood ADR will theoretically not detect 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). Leuchars Station PSR is located on a bearing of approximately 245°/73 nm from the closest boundary of the Array, 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 service in the area of the Array which will be located outside of Leuchars area of responsibility, which is expected to extend around a 40 nm radius from the Leuchars Station PSR position. As such, Leuchars is proposed to be scoped out of the Array assessment. Within Class G airspace an air traffic service may be provided by NATS or military controllers located at an Area Control Centre (ACC) or air defence controllers subject to suitable radar and radio coverage being available to them.
  2. Military low flying activities take place in uncontrolled airspace below 2,000 ft, offshore, above mean sea level (amsl)) within defined Low Flying Areas (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 location, and any potential cumulative effect of the site with regards to military low flying operations will be established, the MOD Defence Infrastructure Organisation (DIO) (who safeguard MOD infrastructure) will be consulted in this. It is common practice for DIO to request aviation obstruction lighting to be fitted to wind turbines in accordance with CAP 393 (CAA, 2016 amended 2022c). The fitment of aviation lighting will be detailed within a Lighting and Marking Plan (LMP) which will be produced and consulted on post-consent.
  3. The UK En Route Low Altitude British Isles Charts (CAA, 2022a) provides the location of military Practice and Exercise Areas (PEXA). The Array does not lie within, or underneath, any military Practice and Exercise Areas (PEXA) and therefore no assessment of military PEXA is required within the EIA and this impact is scoped out.
Helicopter operations
  1. Commercial offshore helicopter operations in this region 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. The closest SAR helicopter base to the Array is Inverness Airport. SAR operations often involve flying at low level. Assessment of potential impacts on SAR operations will be included within the Array EIA Report, mitigation (if required) will adhere to guidance set out in (MCA, 2021).
  2. Helicopters supporting offshore oil and gas, in the northern North Sea, use Helicopter Main Route Indicators (HMRI), radiating from Aberdeen Airport (the main support base) on a hub/spoke radial pattern. These HMRIs lie to the north of the Array; the closest being 4 nm to the north of the Array north-eastern boundary. The CAA recommend within CAP 764 (CAA, 2016) that there should be no obstacles within 2 nm either side of the centreline of a HMRI. 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. Engagement with NATS (Aberdeen Radar) will be completed to establish any perceived impact.
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 (Met Office, 2015). The Array is located outside of the consultation zone for the nearest Met Office radar at Hill of Dudwick, Aberdeenshire. Due to the distance of the Array there is no potential for a significant effect on any Met Office radar therefore, this impact will be scoped out of further assessment within the EIA.

7.3.4. Potential Array Impacts

  1. A list of all potential impacts on aviation, military and communications which may occur during the construction, operation and maintenance, and decommissioning phases of the Array in the absence of designed in measures is included in Table 7.9   Open ▸ .


Table 7.9:
Potential Impacts Identified for Aviation, Military and Communications in the Absence of Designed in Measures

Table 7.9: Potential Impacts Identified for Aviation, Military and Communications in the Absence of Designed in Measures


7.3.5. Designed in Measures

  1. A range of possible designed in measures exist to minimise physical obstruction effects which will be created by the placement of the wind turbines. These mitigation measures would comply with guidelines in place at the time of the application and be consulted upon with the appropriate stakeholders as follows.
  2. CAP 764 (CAA, 2016) sets out the mandatory requirements for lighting of wind turbine generators in UK territorial waters as follows:
  • Legislation requires the fitting of obstacle lighting on offshore wind turbines with a height of 60 m or more above the sea at the Highest Astronomical Tide (HAT).
  • If four or more wind turbine generators are located together in the same group, with the permission from CAA only those on the periphery of the group need to be fitted with at least one medium intensity steady red light positioned as close as reasonably practicable to the top of the fixed structure.
  • The obstruction light or lights must be fitted as to show when displayed in all directions without interruption. The requirement of the peak of the beam and peak intensity are defined within CAP 764 (CAA, 2016).
  1. CAP 437 (CAA, 2021) sets out a procedure to indicate to a helicopter operator that the wind turbine blade and nacelle are safely secured in position prior to helicopter hoist operations commencing as follows:
  • CAP 437 (CAA, 2021) states that this is best achieved through the provision of a helicopter hoist status light located on the nacelle of the wind turbine within the pilot’s field of view, which is capable of being operated remotely and from the platform itself or within the nacelle.
  • A steady green light is displayed to indicate to the pilot that the wind turbine blades, and nacelle are secure and it is safe to operate. A flashing green light is displayed to indicate that the wind turbine is in a state of preparation to accept hoist operations or, when displayed during hoist operations, that parameters are moving out of limits. When the light is extinguished, this indicates to the operator that it is not safe to conduct helicopter hoist operations.
  • Obstruction lighting in the vicinity of the winching area that has a potential to cause glare or dazzle to the pilot or to a helicopter hoist operations crew member should be switched off prior to, and during, helicopter hoist operations.

7.3.6. Potential Impacts After the Implementation of Designed in Measures

  1. The impacts that are proposed to be scoped into the Array assessment are outlined in Table 7.10   Open ▸ together with a description of any additional data collection (e.g., site-specific surveys) and/or supporting analyses (e.g. modelling) that will be required to enable a full assessment of the impacts.
  2. The potential impacts to aviation, military and communications that have been scoped out of the assessment are described in Table 7.11   Open ▸ .


Table 7.10:
Impacts Proposed to be Scoped Into the Array Assessment for Aviation, Military and Communications. Project Phase Refers to Construction (C), Operation and Maintenance (O) and Decommissioning (D) Phase of the Array

Table 7.10: Impacts Proposed to be Scoped Into the Array Assessment for Aviation, Military and Communications. Project Phase Refers to Construction (C), Operation and Maintenance (O) and Decommissioning (D) Phase of the Array


Table 7.11:
Impacts Proposed to be Scoped Out of the Array Assessment for Aviation, Military and Communications

Table 7.11: Impacts Proposed to be Scoped Out of the Array Assessment for Aviation, Military and Communications