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Although the probability of an accident per flight is very small, local risk levels around airports are higher than one might expect. This is caused by the fact that, while the probability of an accident per take-off or landing is very small, the number of landings and take-offs is often very large (typically several hundred thousand at a major international hub airport). The resulting annual probability of an accident at a large airport therefore, is usually much greater than the small probability of being involved in an aircraft accident as a passenger.
Third party risk around airports is still a relatively new issue for airports, but it is now becoming a major consideration for airport expansion plans that are intended to keep pace with increased demands for capacity. Therefore, understanding third party risk and decreasing the likelihood of accidents and of third parties being involved is becoming a high priority issue for airports and their communities.
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How does aviation affect third party risk? |
The closer air routes are to an airport, the greater the concentration of over-flight and hence of risk. Similarly the continuous growth in demand for air transport is also increasing over-flight of residential areas. These facts coupled with difficulties in enforcing land-use planning restrictions, means that for some airports the number of people in risk areas is increasing as is the number of over-flights.
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How does third party risk affect aviation? |
Third party risk is sometimes covered in the formal “Environmental Impact Assessment” undertaken to evaluate an airport’s ‘major’ proposals for growth. The EC EIA Directive 85/337/EEC does not specifically require a “third party risk” assessment, however as it requires the assessment of the direct and indirect effects of a project on human beings, it can be taken as implicit if 85/337/EEC is applied.
In Europe, third party risk based obligations now exist in the UK and the Netherlands. This include the purchase and demolition of “at risk” housing and offers to help to relocate families affected.
Although at present of less significance than noise and air-quality, it is widely believed that third party risk is moving rapidly up the policy agenda. The results of this could be increased constraints and obligations.
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How can third party risk be quantified? |
There are relatively few example of the assessment of third party risk and all broadly follow a similar approach. Quantification entails a details analysis of airport, airspace and demographics and is best left to experts in the subject.
The assessment of direct third party risk is indicated in the diagram below:
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It is recommended that secondary third party risk should be taken into account if critical installations such a refineries or power plant could result in major secondary harm if struck by an aircraft.
At present, no Pan-European legislation exists to give guidance on what level of individual risk is acceptable. The two main examples of national guidelines that exist in this area are those in the UK and The Netherlands.
In the UK, the Health and Safety Executive has recommended that individual risks higher than 10-4 per annum be regarded as intolerable for the public and those below 10-6 per annum be regarded as broadly acceptable. In addition, it has been recommended that the UK base Public Safety Zones (PSZ) around airports on the 10-5 per annum contour. New housing development should not be permitted within the PSZ and dwellings within the 10-4 per annum contour should be purchased by the airport operator and the occupants moved away.
In the Netherlands, in addition to criteria based on individual risk, criteria also exist for use of F-N curves (a way of presenting Group Risk) although these have not been applied in practice to Dutch airports.
It is advisable to seek guidance on the tolerability of risk arising from aircraft impacts from State bodies.
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How can third party risk be managed? |
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Third party risk depends on primary risk factors such as runway incursion management, bird hazard management and land-use planning support, which could reduce third party risk. These in turn are affected by a range of other influences such as airfield equipment provision, safety management skills and community relations. Good guidance on these issues is given by ICAO and by EUROCONTROL.
Thus the following measures may be adopted. Some are a part of good safety practice others are specific to third party risk and should only be undertaken if the risk demands it:
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- Adequately assess the range of factors that may contribute to third party risk and the third party risk itself using best practice methods. This is especially required when major airport or Terminal Control Area changes or development are planned.
- Employ an adequate safety management system, especially covering runway incursions or any operational safety issue (e.g. Foreign Object Damage) that may cause an accident involving third parties (e.g. impacting on terminal buildings or residential areas).
- Control bird hazard through a mixture of passive (ecological) and active (bird scaring) means, and by land-use planning support such as restricting the development of rubbish tips close to an airport.
- Seek adequately enforced land-use planning protection that prevents inappropriate development in risk zones.
- Where such development already exists, seek to relocated third parties, preventing the re-habitation of the buildings cleared.
- Operate a well tested major incident recovery plan.
- Operate a vortex strike repair scheme to respond to minor third party risk incident caused by vortices impacting on roofs.
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Last validation: 14/07/2005
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