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Background and requirements

ScottishPower Renewables (UK) Ltd (SPR) is developing three major offshore wind farms in the southern North Sea: East Anglia Three (EA3), East Anglia Two (EA2) and East Anglia One North (EA1N). Collectively known as the East Anglia Hub, the developments are located between approximately 30 and 70 kilometres off the East Anglian coast and represent one of the largest offshore wind programmes in the world, with a combined installed capacity of up to 3.1 GW.

Unlike single-asset offshore wind developments, the East Anglia Hub comprises three distinct yet geographically proximate wind farm sites, each with different construction, commissioning, and operational timelines. Taken together, the programme demanded a coordinated aviation mitigation strategy capable of addressing cumulative impacts across multiple assets while remaining adaptable to phased delivery.

When operational, the wind turbine generators associated with the East Anglia Hub were predicted to generate Primary Surveillance Radar (PSR) clutter on the NATS Cromer radar. Without suitable mitigation, this impact could have compromised aviation safety and prevented the wind farms from becoming operational.

To address these challenges, SPR was required to deliver a robust, future-proofed airspace solution in advance of wind farm commissioning. This solution needed to balance aviation safety, continued equitable access to airspace, civil and military operational requirements, international FIR constraints, and compliance with the CAP 1616 Airspace Change Process overseen by the Civil Aviation Authority (CAA).

 

Approach

SPR appointed Sagentia Aviation to provide specialist airspace change consultancy and programme leadership for ACP-2023-079 – East Anglia Hub Wind Farms Mitigation.

Sagentia Aviation supported SPR throughout all stages of the CAP 1616 process, providing end-to-end technical, regulatory, and stakeholder management support. This included:

  • Development of the Statement of Need and definition of high-level programme objectives
  • Design, evaluation, and comparison of a wide range of airspace mitigation options
  • Delivery of a comprehensive Design Principles Evaluation (DPE) across seventeen design options
  • Structured engagement with civil, military, and air navigation service providers
  • Preparation of the formal ACP submission, including supporting safety, environmental, and operational assessments

A broad suite of mitigation options was examined, including do-nothing scenarios, controlled airspace solutions, single- and multi-airspace configurations, and technical-only mitigations. Following detailed safety analysis and stakeholder engagement, the preferred solution combined:

  • Range Azimuth Gating (RAG) applied to the Cromer PSR to remove wind turbine-generated radar clutter
  • The establishment of three Transponder Mandatory Zones (TMZs) covering EA3, EA2 and EA1N, ensuring continued aircraft detectability through secondary surveillance systems

The final airspace design adopted a sympathetic, “rubber-banded” geometry, closely aligned to the wind farm boundaries while minimising unnecessary airspace restriction. Critical to this design was alignment with the London / Amsterdam Flight Information Region (FIR) boundary, ensuring harmonisation with mandatory transponder requirements in adjacent international airspace and avoiding the creation of unusable or misleading route structures for pilots operating close to the FIR.

Managing complex airspace interactions

The EA Hub airspace design required careful integration with several existing controlled and special use airspace structures, significantly increasing design complexity.

Part of the EA2 wind farm lies beneath the Clacton Control Area (CTA) Sector 5, a Class A airspace structure with a lower limit of FL85. To avoid encroachment into controlled airspace, the EA2 TMZ required vertical sectorisation, with the southern portion of the TMZ capped at FL85 and the northern sector extending to FL100. This sectorised design allowed full compliance with existing controlled airspace boundaries while maintaining a coherent and operationally manageable TMZ structure.

Additionally, the design of the EA3 TMZ was required to interface with the approved but not yet implemented Norfolk TMZ, providing future-proofing and avoiding airspace choke points should neighbouring offshore wind mitigations be introduced at a later date.

Governance, stakeholders, and adaptive delivery

The East Anglia Hub ACP operated at programme scale, requiring different governance models within a single regulatory framework. EA1N and EA2 were placed under a sole Controlling Authority model with No. 78 Squadron (Swanwick Military), while EA3 was delivered under a joint civil-military Controlling Authority arrangement involving 78 Squadron and Anglia Radar.

Sagentia Aviation led structured engagement with a wide range of stakeholders including NATS, the Ministry of Defence, Anglia Radar, and No. 78 Squadron, ensuring operational responsibilities, controller workload considerations, and procedural arrangements were fully agreed before regulatory decisions were made.

During programme delivery, additional complexity arose from planning-stage constraints applied after initial airspace approval, requiring reassessment of approved TMZ geometries for parts of the Hub. Sagentia Aviation supported SPR through this adaptive phase, facilitating targeted redesign and engagement with controlling authorities to reduce airspace footprint while maintaining safety and regulatory compliance, without triggering disproportionate re-engagement or delaying time-critical implementation.

In parallel with the technical and stakeholder challenges, the East Anglia Hub ACP progressed through a period of regulatory evolution within the CAP 1616 framework. The programme successfully accommodated updates to regulatory guidance without disrupting delivery timelines, ensuring that documentation, assurance activity, and stakeholder engagement remained aligned with the prevailing regulatory expectations. This additional factor was managed as part of the wider programme governance, reinforcing resilience and continuity across the multi-asset ACP.

Outcome

Following successful completion of the CAP 1616 process, the CAA approved ACP-2023-079, authorising the implementation of the East Anglia Hub airspace mitigation solution.

The approved outcome delivers:

  • Safe and effective mitigation of radar clutter generated by the East Anglia Hub wind farms
  • Continued provision of air traffic services across a complex civil-military operating environment
  • Minimal impact on civil, military, and general aviation users, supported by low traffic density and existing mandatory transponder environments
  • A scalable, phased, and future-proofed airspace design aligned with the CAA’s Airspace Modernisation Strategy

With the aviation mitigation in place, SPR was able to progress construction and operation of the East Anglia Hub, with EA3 and EA2 currently in construction, supporting the UK’s renewable energy ambitions while maintaining the highest standards of aviation safety.

The East Anglia Hub programme demonstrates Sagentia Aviation’s ability to support developers navigate complex and evolving airspace constraints, enabling nationally significant renewable energy infrastructure projects to progress safely, efficiently, and on schedule.

Images courtesy of ScottishPower Renewables.

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