Frequently Asked Questions

Aerodrome Safeguarding is the process by which an aerodrome protects itself from the effects of development or other activities which may have an impact on the safety of its operations or infrastructure. Safeguarding is a legal requirement for officially safeguarded aerodromes and is required under ICAO (International Aviation Organisation) and the UK CAA (Civil Aviation Authority) regulations.

A list of officially safeguarded aerodromes can be found in the following documents:

• England and Wales - The Town & Country Planning (Safeguarded Aerodromes, Technical Sites & Military Explosives Storage Areas) Direction 2002
• Scotland - Scottish Executive Circular 02/2003 ‘Safeguarding of Aerodromes, Technical Sites & Military Explosives Storage Areas

Provision for aerodrome safeguarding is made in the following circulars which are still current:

• England and Wales - The Town & Country Planning (Safeguarded Aerodromes, Technical Sites & Military Explosives Storage Areas) Direction 2002
• Scotland - Scottish Executive Circular 02/2003 ‘Safeguarding of Aerodromes, Technical Sites & Military Explosives Storage Areas

If an LPA wishes to approve a development contrary to the advice of an aerodrome operator they are required to notify the following:

• The Civil Aviation Authority (CAA) and the aerodrome or
• The Secretary of State for Defence

The development must not be granted permission within 28 days of notification. The notification enables the aerodrome stakeholder to take action to prevent development that would compromise the safety of their operation. See safeguarding circular 01/2003 (England & Wales) & Circular 02/2003 (Scotland) for further details at:

• England and Wales - The Town & Country Planning (Safeguarded Aerodromes, Technical Sites & Military Explosives Storage Areas) Direction 2002
• Scotland - Scottish Executive Circular 02/2003 ‘Safeguarding of Aerodromes, Technical Sites & Military Explosives Storage Areas

Many aerodromes will offer a pre-application advice service, (there may be a fee for this service).  For further details contact the aerodrome concerned.

An aerodrome operator is a statutory consultee for planning applications within the safeguarded zone. Aerodromes will normally issue each LPA within their safeguarded area with a safeguarding map; the map will clearly illustrate the criteria for the types of developments the aerodrome will need to assess. The safeguarding map generally covers a radius of 15km from the aerodrome, though this can vary, especially in the case of Technical Safeguarding (i.e. related to Communications, Navigation and Surveillance equipment).

The OLS completely surround the airport and generally extend out to 15km, however this can vary. They are designed to protect aircraft from obstacles when manoeuvring on the ground, taking off, landing or flying in the vicinity of the airport. It is important that these surfaces are not infringed by development.

The OLS represent the lower limit of the blocks of protected airspace around an aerodrome. They form a set of 3 dimensional surfaces which extend upwards and outwards from the runways encompassing the critical airspace utilised by air traffic.

Please refer to chapter 5 of CAP 738: Safeguarding of Aerodromes for further details of the OLS.

The equipment is collectively referred to as Communication, Navigation and Surveillance (CNS) and is essentially the ground infrastructure used by both Air Traffic Control (ATC) and aircraft. Aircraft can be those approaching/departing the aerodrome as well as those further away and in the cruise. This equipment is mostly a form of radio equipment.

Potential issues can include:

• Signal reflection
• Signal scattering causing performance issues or false plots on secondary surveillance radar (SSR)
• Interference/clutter and performance issues on Primary Surveillance Radar (PSR)

Any large areas of metallic/reflective materials are generally to be avoided as they can cause signal reflections and glint and glare distractions to aircrew and ATC.

Telecoms installations can affect CNS equipment, especially 5G whose spectrum can have an effect on S band radars. Therefore, it is essential that early consultation with the aerodrome takes place. For further reading please refer to the following:

Notice of aeronautical radar coordination

Ofcom list of military and civil radars to be protected 

5G has the potential to affect aircraft radio altimeters, this is currently being monitored by the Civil Aviation Authority (CAA) and they have issued a safety notice SN-2021/017: Potential Interference Risk to Radio Altimeters from 5G Mobile Technology

NATS offer a chargeable pre-planning assessment service for both buildings and wind turbines.

Wind turbines have the potential to adversely impact on primary radar returns because the rotating blades cause ‘clutter’ and false aircraft tracks on the radar operator’s screen. Secondary radar can also be disrupted as wind turbines can cause misplaced aircraft returns on the operator’s screen.

Tall wind turbines also have the potential to infringe the Obstacle Limitation Surfaces (OLS) and impact on Instrument Flight Procedures (IFPs). For further reading please refer to CAP 764: CAA Policy and Guidelines on Wind Turbines.

Radar, or other CNS “mitigation” can refer to any form of solution which may be identified and agreed between an aerodrome (or CNS operator) and a developer. This can range from complex solutions such as the purchase of a new radar or modification of an existing one, to more simple ones such as altering the layout or  reducing the height of proposed turbines or development. This may reduce or remove a potential impact. “Mitigation” may also refer to the provision of further evidence or data which may alleviate an aerodrome’s concern; this could be more accurate terrain or materials/construction data enabling more detailed assessment and addressing of earlier concerns.

Confirmation of mitigation being viable, coupled with a formal agreement between developer and aerodrome to ensure costs and implementation measures are secured, generally leads to planning conditions. These allow an LPA to grant planning permission and the developer to proceed with their development once the mitigation requirements have been undertaken.

Instrument Flight Procedures are a series of predetermined manoeuvres, by reference to aircraft flight instruments coupled with ground based navigational aids or satellite navigation-based waypoints, with specified protection from obstacles.

An IFPs primary purpose is to provide clearance from obstacles and to allow safe aircraft operations to/from the runway to/from the airways network or the local airspace.    

Please Note: IFPs extend further from the airport than the Obstacle Limitation Surfaces (OLS) and the IFP protected surfaces or minima may be lower than the OLS in certain areas. This is dependent on the type of IFP.

If a development is likely to impact on an IFP(s) we will request that a full IFP assessment is carried out by the Approved Procedure Design Organisation (APDO). The cost of the assessment and analysis of the findings, will be borne by the developer.

Further information can be found in CAA publications:

• CAP 785A: Oversight of UK Approved Procedure Design Organisations 
• CAP 785B: Implementation and Safeguarding of Instrument Flight Procedures (IFPs) in the UK

At night and in periods of poor visibility during the day, pilots rely on a particular pattern of aeronautical ground lights, principally the approach and runway lights, to aid in aligning themselves with the runway to land at the correct point. Depending on their location several types of lighting have the potential to cause issues for example:

• Temporary lighting e.g., construction lighting, light shows, temporary installations
• Advertisements
• Lighting of buildings and other structures
• Street and car park lighting
• Flood lighting at sporting venues or similar

No lighting should be displayed which could distract pilots or confuse them by being mistaken for aeronautical ground lights. Further details about the design of road lighting in the vicinity of aerodromes can be found in British Standard BS 5489 1:2020 ‘Code of Practice for the Design of Road Lighting’.

When designing any lighting in the vicinity of an aerodrome, including temporary e.g., construction lighting, the following must be taken into consideration:

• Any aeronautical ground lighting is not obscured from the pilot’s view
• Any proposed lighting cannot be confused with aeronautical ground lighting, for example replicating the same patterns or colours
• Any proposed development must not include a high level of background lighting which could diminish the effectiveness of aeronautical lighting
• Any proposed lighting must not have the potential for glare or dazzle to pilots or Air Traffic Control (ATC)
• Any proposed lighting must not infringe the Obstacle Limitation Surfaces (OLS) for the aerodrome

The Air Navigation Order (ANO) under Part 8 ‘Aerodromes & Lighting’, Chapter 2 directs that:

Owners of lights must always follow any notice that may be issued under the ANO to dim or extinguish lights, pending resolution of any problems that arise when the lights are in use.

For further information please refer to CAP 736: Operation of Directed Light, Fireworks, Toy Balloons and Sky Lanterns within UK Airspace

It is possible for solar installations and aerodromes to co-exist; in fact, some airports have their own installations. However, solar installations need to be carefully assessed as depending on their location and overall size, they have the potential to deflect radar and can cause glint and glare. In some circumstances we may request that a developer submits an aviation perspective solar hazard glint and glare assessment with their proposals.

Solar installations can also be attractive to birds for nesting roosting and loafing, therefore the supporting structures may need to be bird proofed and regularly monitored.

If a solar installation is roof mounted, there is the potential for it to infringe the Obstacle Limitation Surfaces (OLS) and to impact on Instrument Flight Procedures (IFPs) and Communication, Navigation and Surveillance (CNS) equipment.

Aircraft are highly vulnerable to wildlife strike risk and species such as deer, badger and foxes can cause safety concerns, however birds are the most problematic species in the UK. It is estimated that damage to aircraft and flight delays resulting from wildlife strikes around the world cost hundreds of millions of pounds per year.

Bird strikes are one of the aerodromes top risks and they are required under ICAO & CAA regulations to ‘reduce the attractiveness of the area to birds/wildlife on and in the vicinity of the airport’. Aerodromes will have a robust wildlife hazard management regime with regular patrols by dedicated personnel on the airfield and some will also undertake regular monitoring out to a radius of 13km from the airport

Developments that have the potential to increase the bird strike risk are:

• Areas of water such as reservoirs, lakes, ponds and wetlands including Sustainable Urban Drainage Systems (SUDS)
• Sites being used for the handling, compaction, treatment and/or disposal of household and/or commercial wastes
• Nature reserves or bird sanctuaries
• Sewage disposal, treatment and outfalls
• Mineral extraction, quarrying and their restoration schemes
• Large landscaping schemes with a high percentage of berry/fruit bearing species that could attract flocking birds in large numbers
• Buildings with large areas of flat, shallow pitched and/or green roofs. There are now significant numbers of Gulls moving inland and nesting and roosting on these types of roofs. The potential is there for Gulls to transit the aerodrome and approach/take off paths when travelling between roosting and feeding/bathing sites. We may ask that a Bird Hazard Management Plan be entered into to ensure that Gulls do not become established on roofs.
• Large areas of ground re-profiling works as they can uncover worms and insects which could attract birds in large numbers
• Golf courses which may offer opportunities for waterfowl due to the creation of new water bodies and the short grass provide potential feeding opportunities for grazing Feral Geese.

The aerodrome operator will consider all developments on a case-by-case basis.  Whether a proposal has the potential to present an issue depends upon the scale, design, proximity to the airport and known bird sites/behaviour. The development must not increase the net risk of a Birdstrike to aircraft. It is often possible to mitigate against risk with amendments to design and robust management.

Biodiversity enhancements and the need to not increase the bird strike risk to the aerodrome can co-exist if designed correctly.

For further reading please refer to CAP 772: Wildlife Hazard Management at Aerodromes

Cranes and other construction equipment such as piling rigs, mobile lifting platforms etc. can impact on the safe operation of the airport by way of them infringing the Obstacle Limitation Surfaces (OLS) and becoming an obstacle. They can also impact upon Communications, Navigation & Surveillance (CNS) equipment and/or Instrument Flight Procedures (IFPs).

Anyone operating a crane or tall construction equipment within 6km of an aerodrome, though this can vary, is required to apply for a permit from the aerodrome concerned, unless the crane/construction equipment is under 10m high or is shielded on all sides by trees or structures that are taller.

For further information with regard to the crane permit process please refer to CAP 1096: Guidance to crane users on the crane notification process and obstacle lighting and marking

It must be stressed that crane permits need to be processed by an aerodrome amongst other duties, and in the case of a potential impact on CNS also have to be submitted to the technical authorities for equipment. Where an impact is confirmed, this may in turn also require engaging with stakeholders such as Air  Traffic Control or require NOTAMs and other processes to be put in place. As such, 30-days’ notice is generally required to ensure permits can be approved.

Public safety zones are areas at either end of the runway and development is restricted within these zones to minimise the risk of death or injury to humans should an aircraft overshoot the runway on Take-Off or fall short on landing.

Further details please refer to the DfT Policy Paper ‘Control of development in airport public safety zones’.

Wind shear and turbulence caused by buildings in the vicinity of airports have been recognised as a cause of aircraft instability during landing or take-off for some time. Buildings can cause variations in wind speed due to the structures disturbing the flow of wind. If a development is on airport or very close to the airport boundary, depending upon the scale of the proposals, it may need to be assessed to ensure that it will not create any building induced turbulence or wind shear that has the potential to affect aircraft taking off or landing.

If a site is close to or under the approach and take off paths, there could be potential thermal uplift for example from vapour plumes from cooling towers. Under those circumstances an aeronautical technical study may be required.

Metallic or reflective materials, for instance cladding and large areas of glass can cause radar reflections and/or glint and glare which can impact on aircrew and Air Traffic Control (ATC).

Depending on the extent of the surface and the proximity of the development to the airport an aviation perspective glint and glare study may be required