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Wind – Physical Safeguarding

What is physical safeguarding?

Physical safeguarding is the technical term for managing collision risks at licensed airports. Simplistically, this is achieved by constructing maps which define height restrictions within approximately 20 km of an airport (in some cases much less).

Collision risks at airports in most countries are managed in accordance with guidance from the appropriate Civil Aviation Authority or equivalent – or in some cases in line with European or International guidance. Individual airports can also have their own requirements. Military aerodromes are often protected by rules published by a military equivalent. For example, in the UK, most licensed airports follow the rules defined by the UK Civil Aviation Authority in their publication pertaining to licensing of aerodromes. In the case of London City Airport, bespoke rules apply that have been defined specifically based on the airport’s location and surroundings. Military aerodromes in the UK are protected based on similar rules published by the Military Aviation Authority.

Why carry out a Physical Safeguarding Assessment?

Physical safeguarding can be a significant constraint to development of wind turbines, buildings or any other physical structure. It is important to understand that:

  • The restrictions are based on the altitude of the airport runways (among other technical factors).
  • The restrictions are different depending on where a development is located relative to the runway.

This means that even if a proposed development is physically smaller than others in the general surroundings, it could still encounter significant restrictions due to collision risks.

What are the benefits of a Pager Power Physical Safeguarding Assessment?

It is beneficial to understand the level of constraint quickly and at the earliest stage possible.

Pager Power has designed custom software for the assessment of physical safeguarding constraints in accordance with rules defined by the relevant body. This includes rules published by the International Civil Aviation Organisation, the European Aviation Safety Agency, the Federal Aviation Administration (USA) and Civil/Military Aviation Authorities in the UK. We are well suited to research and understand bespoke requirements from specific stakeholders all over the world.

Despite relatively clear rules pertaining to the issue of collision avoidance / physical safeguarding, there are grey areas whereby developments can be considered on a case-by-case basis in coordination with the appropriate stakeholder. Breaching an obstacle limitation surface should be avoided, but there are many cases whereby these are infringed by developments in practice.

Pager Power has been conducting physical safeguarding assessments for more than fifteen years. All Pager Power reports are designed to be: 

  • Comprehensive – covering all the relevant aspects for each individual proposed development. 
  • Up-to-date with reference to current guidelines from the relevant bodies and recent industry developments.
  • Understandable to non-experts and experts alike. 

What does a Pager Power Physical Safeguarding Assessment Cover?

Obstacle Limitation Surfaces Chart

Obstacle Limitation Surfaces are imaginary barriers around and above airports that restrict the permissible height of new structures.

Pager Power will determine the applicable physical safeguarding rules at the associated airports. A chart is produced to display which Obstacle Limitation Surfaces extend over the development location.

Infringement Calculations

The level of infringement, or clearance, for the development is calculated based on the development height and location.


Recommended next steps are clearly defined based on the findings of the assessment.

“We have engaged Pager Power on air-safeguarding and telecoms assessments for wind farm proposals, including resolving specific technical issues with particular airports or protected zones.

We have always found Pager Power’s professional services to be of good quality, efficient and friendly. Services have been delivered to scope and to budget, and your technical specialist knowledge on air-safeguarding has always been reliable.”

Michael Philips
Principal Consultant, Dulas








Good news for the #renewables industry!
Boris Johnson has announced his pledge to invest £160 million in offshore wind farms, to generate enough electricity to power every home in the UK by 2030. Learn more: https://bit.ly/33TCvkz #renewableenergy #windenergy #offshore

Pager Power has undertaken a number of assessments for WPD who are developing an offshore wind farm to the West of the Taiwanese capital Taipei. This topic was recently covered in a news piece on Taiwanese television. https://bit.ly/370vGzp

NATS has announced that it is replacing the existing Primary Surveillance Radar at Lowther Hill with a new radar that is less likely to be affected by wind farms. Learn more: https://bit.ly/2GsoH6Y #windpower #windenergy #windfarms #windfarm #radars

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