Final Report on the Risk Analysis in Support of Aerodrome Design Rules
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RESTRICTED - COMMERCIAL AEAT/RAIR/RD02325/R/002 Issue 1 Final Report on the Risk Analysis in Support of Aerodrome Design Rules A report produced for the Norwegian Civil Aviation Authority Mark Eddowes Jon Hancox Anne MacInnes December 2001 RESTRICTED - COMMERCIAL RESTRICTED - COMMERCIAL AEAT/RAIR/RD02325/R/002 Issue 1 Final Report on the Risk Analysis in Support of Aerodrome Design Rules A report produced for the Norwegian Civil Aviation Authority Mark Eddowes Jon Hancox Anne MacInnes December 2001 RESTRICTED - COMMERCIAL RESTRICTED - COMMERCIAL AEAT/RAIR/RD02325/R/002 Issue 1 Title Final Report on the Risk Analysis in Support of Aerodrome Design Rules Customer Norwegian Civil Aviation Authority Customer reference 200001893 Confidentiality, Restricted - Commercial copyright and reproduction This document has been prepared by AEA Technology plc in connection with a contract to supply goods and/or services and is submitted only on the basis of strict confidentiality. The contents must not be disclosed to third parties other than in accordance with the terms of the contract. File reference RD02325 Report number AEAT/RAIR/RD02325/R/002 Report status Issue 1 Stokes House Risley Warrington Cheshire WA3 6AT United Kingdom Telephone +44 1925 254482 Facsimile +44 1925 254641 AEA Technology is the trading name of AEA Technology plc AEA Technology is certificated to BS EN ISO9001:(1994) Name Signature Date Author Mark Eddowes Jon Hancox Reviewed by Chris Kingscott Approved by Anne MacInnes RESTRICTED - COMMERCIAL AEA Technology ii RESTRICTED - COMMERCIAL AEAT/RAIR/RD02325/R/002 Issue 1 Executive Summary The Luftfartstilsynet, the Norwegian Civil Aviation Authority, commissioned AEA Technology to carry out a risk analysis study in support of the development of aerodrome design rules, intended to define the Norwegian requirements for the physical design of aerodromes that can provide for adequately safe traffic handling. Current requirements in Norway are based primarily on those set out in Annex 14 of the International Civil Aviation Organization (ICAO). Taking account in particular of the special topographic conditions surrounding Norwegian aerodromes, it is anticipated that there may be some scope for improving the effectiveness of that basic framework as applied specifically in Norway. In addition, there may be a more widespread interest in the general refinement and optimisation of aerodrome design requirements. The risk analysis has been undertaken with particular reference to the following aspects of aerodrome design: · length and reference codes of runways and taxiways; · runway and taxiway strips; · runway end safety areas; · separation distances between runways and taxiways; · definition of obstacle limitation surfaces. Against this background, the intention has been to develop a more “objective-based” or “risk-based” system of design requirements that will enable a certain “target level of safety” (TLS) to be met. Essentially, the project objective has been to relate the residual risk associated with relevant operational hazards to the design features that provide protection against those hazards. This should allow definition of the dimensional requirements to achieve a desired TLS, according to the nature of operations at an aerodrome. (It should be noted that the dimensional requirements defined within the project are based on physical safeguarding only and do not account for technical safeguarding1; allowance for technical safeguarding may lead to increased restrictions in certain physical design rules, particularly in relation to obstacle limitation surfaces.) The rationale behind the adoption of this “risk-based” approach is simply that provision of safety involves sacrifices in terms of the cost and effort required to provide it and the foregoing of the use of land for other purposes. It is important to ensure that this effort and these sacrifices are properly directed so as to maximise the safety benefit derived from them. The approach adopted has relied, to a large extent, on the development of empirical risk models based on operating experience and the insights gained from it. In adopting this approach, it is recognised that such models have their limitations, arising in part from the fact that the resources that can be made available in conducting such a study are not unlimited and from the wide range of issues addressed. Notwithstanding these limitations, we believe that the “risk-based” approach offers real benefits and these could be enhanced by further and more detailed analysis to address the limitations of the work undertaken to date. 1 Technical safeguarding relates to the protection of communication, navigational and surveillance (CNS) system signals from either physical or electromagnetic interference/obstruction. RESTRICTED - COMMERCIAL AEA Technology iii RESTRICTED - COMMERCIAL AEAT/RAIR/RD02325/R/002 Issue 1 The process for risk assessment undertaken during the study has comprised the following elements: · Development of quantitative risk standards or “target levels of safety” (TLS) against which to evaluate the level of safety provided by the design features of interest; · Functional Hazard Analysis (FHA) to identify hazards to operations and the relationship between aerodrome features and the mitigation they provide against those identified hazards; · Development of quantitative risk models, typically allowing the characterisation of risk in terms of the likelihood of occurrence of certain hazard scenarios, the location of an aircraft during such an event in relation to the intended path and the safety margin provided by the relevant aerodrome design feature, and the severity of the incident consequences. This risk assessment process was underpinned by an initial review of standards and practices of aerodromes in Norway. The basic TLS against which to evaluate residual risk levels associated with the various aerodrome design features has been established primarily by reference to historical incident rates. On this basis we identify a fatal (total hull loss) accident rate for airport related accidents of approximately 0.2 per million movements (2 x 10-7 per movement) as the primary residual risk benchmark for “first world” operations. A number of distinct hazard scenarios contribute to this total rate and therefore, if this total risk “budget” is apportioned between different hazards, the TLS for any single hazard will be correspondingly lower than this overall rate. On this basis, we propose the use of a basic “benchmark” TLS of 10-7 per movement, recognising that we would wish to improve upon this where possible, such that a TLS of 10-8 per movement might be preferred where practicable. Risks below 10-9 per movement may generally be regarded as small and of minimal regulatory concern. Having proposed these basic quantitative standards we identify the need for caution when employing them and the need to give particular consideration to the circumstances in which they are to be applied. In the current context we note that overrun and controlled flight into terrain (CFIT) accidents on approach and landing are major contributors to the overall total hull loss rate of 2 x 10-7 per movement. We note further that historical accident rates vary significantly according to the nature of operations, with some types of operation exhibiting a risk that is somewhat higher than the recent historic average and others exhibiting a risk that is correspondingly lower. It may therefore not be realistic to expect that the TLS of 10-7 per movement based on the average accident can be generally achievable, even when apportioned between a number of hazard scenarios. We conclude that some flexibility is required when considering the use of a TLS as a safety management tool. In addition, we note that operational practices and procedural measures as well as aerodrome design features contribute to airport safety. In some situations, safety improvements might be more effectively achieved through directing attention to such measures rather than increasing the safety margins provided by aerodrome design. The severity of incident consequences is a further consideration in the setting of safety targets. Certain aspects of aerodrome design may protect against incidents that are unlikely to result directly in catastrophic consequences, such as low speed aircraft wingtip collisions during RESTRICTED - COMMERCIAL AEA Technology iv RESTRICTED - COMMERCIAL AEAT/RAIR/RD02325/R/002 Issue 1 taxiing operations. The acceptable level of frequency with which such incidents occur will obviously be higher than for catastrophic events, and hence a higher TLS will be appropriate. The risk analysis undertaken during the study was based primarily on review of operational experience, in particular accident and incident data, taking account of the findings of a Functional Hazard Analysis undertaken in the initial stages of the study. (A Functional Hazard Analysis is a formal and systematic process for the identification of hazards associated with an activity. The purpose of the FHA in the context of this Aerodrome Design Rules study was to determine relevant hazards to aircraft associated with aerodrome operations (e.g. approach, landing, taxiing, take-off roll, and associated fault sequences) and the physical design of aerodromes.) A series of quantitative risk models was developed that describe a number of distinct hazard scenarios and these models enable the safety margins provided by the various aerodrome design features of interest to be evaluated.