Aerodrome safeguarding – A balanced approach is required

Aircraft take-off near Hatton Cross, London Heathrow Airport

With development proposed at or near to many of the UK’s airports and airfields, it is important to establish the possible impacts on aviation safety.

Many airports and airfields are formally safeguarded either as part of their licensing conditions and/or through formal and informal safeguarding maps lodged with relevant local authorities. This process requires local authorities to take account of the safeguarding issues in planning applications for development at or near these airports and airfields. Some 28 of the larger airports in the UK and one in Wales are formally safeguarded under the Town and Country Planning Direction 20021.

A number of other airports and airfields have informally lodged safeguarding maps with local authorities, although this is rather patchy. Where no safeguarding map has been lodged, it is possible that the Local Plan, including any allocation of sites for new housing will not necessarily protect the aerodrome’s interests and safeguarding is ignored in the planning process.

1The Town and Country Planning (Safeguarded aerodromes, technical sites and military explosives storage areas) Direction 2002.

The UK has 123 CAA licenced or certificated aerodromes which are required to meet the relevant obstacle clearance surfaces (OCS) for take-off and approach at the airfield.
As such, all buildings or other obstacles, including temporary obstructions such as cranes must be beneath the relevant approach and take-off OCS for all licensed runways. Whilst there are no legal requirements, the safety implications of building and other obstacles on or close to the approach and take-off paths at non-licensed aerodromes need to be taken into account in planning consents, based on aircraft performance, pilot experience and other safety criteria.

In addition to the OCS, new buildings and other obstacles at or close to an airport or airfield can impact on the performance of navigational aids and radar installations. As such. the possible impact on aviation needs to be assessed. This particularly applies in the case of new wind turbines which can create clutter on both primary and secondary radar screens. Solar installations can also deflect radar signals and create glare for pilots.

Further safeguarding criteria that need to be assessed include the risk of bird strikes, particularly if the proposed development includes or increases the size of areas of water or waste disposal. Many safeguarding maps require local authorities to consider any possible increased risk of bird strikes up to 10-15 miles from the airport or airfield.

The UK’s busier airports with over 18,000 air transport movements (ATMs) per annum are all required to have Public Safety Zones (PSZ) at the ends of each runway where development is restricted within these zones to minimise the risk of death or injury in the event of an aircraft accident on take-off or landing. The PSZs are elongated isosceles triangles and are based on the calculated risk of an aircraft accident causing death or injury to those on the ground. Whilst there is a general presumption of no development within PSZs, there are certain exceptions, including the use of risk appraisal and cost-benefit analysis to justify some development in particular circumstances.

Farnborough Airport – Public Safety Zones

It should be noted that, whilst the safeguarding criteria described above should be applied, there are no other statutory safeguarding requirements for other planned development close to the airport or airfield. It is possible however that some development may occur underneath or close to flight paths but not necessarily infringe the airport or airfield’s obstacle clearance surface. An issue here is that this development might potentially impact on aviation safety if it restricts the availability of a suitable forced landing area for aircraft in the event of an engine failure or other emergency. In this context, it should be noted that, whilst there is no statutory requirement for safeguarding in these cases, it is generally regarded as good practice for such issues to be taken into account in planning decisions. In practice, the pilot has full responsibility for flight safety outside the airport or airfield boundary, although it is possible that an airfield may object to a nearby development if it believes that pilots would be unwilling to use the airfield in these circumstances.

Following a Public Inquiry for a new Motorway Services Area (MSA) near Denham Aerodrome in Buckinghamshire held earlier this year2, the Inspector ruled that, whilst the loss of land at the MSA would technically increase the safety aviation risk in the event of a forced landing, this would not be of such magnitude to prevent pilots from flying from Denham Aerodrome.

Similar considerations apply in the case of the planned development of 3,000 new homes at Chalgrove Airfield in Oxfordshire which would co-exist with aviation operations by the existing leaseholder, the ejector seat manufacturer, Martin-Baker. Whilst the developer, Homes England, believed that the development would not compromise aviation safety, this was challenged by Martin-Baker and the CAA’s Aviation Advisory Team who argued that combined housing and aviation use at the site would not be possible. Homes England has now withdrawn its planning application but intends to submit alternative proposals in the future.

2Appeal Ref: APP/X0415/W/21/3272171. Land between Junctions 16 and 17 of the M25, near Chalfont St Peter.

Ultimately a balanced approach is needed where planning consent for development near airport and airfields may potentially infringe on aviation safety. In most instances, such planning consent will not be granted where a development breaches statutory safeguarding requirements such as the OCS. In other cases, detailed risk assessments need to be carried out based on the likelihood and potential severity of any aircraft accident or other incident. It should be noted that the acceptability of the aviation safety risk may depend on the types of aircraft flown. It might be reasonable to expect that pilots of single engine piston aircraft would accept a higher safety risk than say, pilots of commercial aircraft responsible for their passengers carried.

As specialist aviation consultants, Alan Stratford and Associates has undertaken a wide variety of airport and airfield safeguarding studies for developers, local authorities and community groups. In our experience, many safeguarding issues can be overcome with appropriate modifications to plans or through some adaptation of airport or airfield operations eg changes to flight paths or circuits.

Given the scarcity of suitable sites in the UK, it is inevitable that plans for development near airports and airfield will continue to be put forward. Whilst each case is different, it is often possible for this to co-exist with aviation operations with no significant increase in the safety risks, provided there is mutual understanding and compromise on either side.

BGL CommunicationsAerodrome safeguarding – A balanced approach is required