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ANNEX A Calculation of Third Party Individual Risk: Determining Public Safety Zones for Airports CONTENTS A1 INTRODUCTION A1 A1.1 DESCRIPTION OF CALCULATION METHOD A1 A1.2 SUMMARY OF CALCULATION METHOD A1 A2 AIRCRAFT CRASH RATE A3 A2.1 AIRCRAFT CLASSIFICATION A3 A2.2 ALL CLASSES MOVEMENT WEIGHTED AVERAGE CRASH RATE A4 A2.2.1 Crash Rate (Crashes per Year) A5 A2.2.2 Average Crash Rate (Crashes per Movement) A5 A2.2.3 Weighted Average Destroyed Area A6 A2.2.4 Type of Crash A6 A2.3 ANNUAL CRASH RATE FOR EACH CRASH MODE A7 A2.4 LONGITUDINAL AND LATERAL DISTANCE CALCULATION A9 A3 IMPACT PROBABILITY CALCULATION - LARGE AIRCRAFT A12 A3.1 PROBABILITY DENSITY FUNCTIONS A12 A3.1.1 Take-off Overruns - Wreckage Location A13 A3.1.2 Landing Overruns - Wreckage Location A14 A3.1.3 Take-off crash (non overrun) A14 A3.1.4 Landing crash (non overrun) – Impact Location A15 A4 EVALUATION OF CRASH PROBABILITIES A17 A4.1 INDIVIDUAL RISK CALCULATION METHOD – ‘LARGE’ AIRCRAFT A17 A4.1.1 Take-off Overruns – Wreckage Location A21 A4.1.2 Landing Overruns – Wreckage Location A22 A4.1.3 Take-off Crashes (non overruns) – Impact Location A23 A4.1.4 Landing Crashes (non overruns) – Impact Location A23 A4.2 INDIVIDUAL RISK CALCULATION METHOD – ‘LIGHT’ AIRCRAFT A24 A4.3 METHOD FOR DETERMINING THE DIMENSIONS OF THE INDIVIDUAL RISK TRIANGLES A28 A1 INTRODUCTION This annex describes the calculation of the individual risk to persons in the vicinity of airports as a result of crashing aircraft. The individual risk values calculated are used to determine Public Safety Zones (PSZs). The purpose of PSZs is to protect the public on the ground from the small, but real possibility that an aircraft might crash in a populated area. Essentially, a PSZ is used to prevent inappropriate use of land where the risk to the public is greatest. A1.1 DESCRIPTION OF CALCULATION METHOD The calculation method is based on a model produced for the UK Department of the Environment, Transport and the Regions (DETR) (1) and subsequently reported by the National Air Traffic Services (NATS) (2). Environmental Resources Management’s (ERM’s) implementation of the model, as described in this annex, has been independently validated by a mathematician at the University of Manchester Institute of Science and Technology (UMIST), England (3). The NATS model considers aircraft with Maximum Take-off Weight Authorised (MTWA) of 4 tonnes and above (i.e. ‘large’ aircraft). Many airports have significant proportions of flights by ‘light’ aircraft (i.e. <4 tonnes MTWA). It could be assumed that the distribution of crashes involving light aircraft would be the same as for larger aircraft. However, this could result in inaccuracies, as light aircraft and their use differ significantly from large aircraft and hence their crash location distributions are different. Therefore, light aircraft crashes are modelled using a separate model specifically developed for light aircraft (see Section A4.2). A1.2 SUMMARY OF CALCULATION METHOD The calculation of risks upon which to determine Public Safety Zones (PSZs) in Ireland involved the following stages: 1. identifying the number of annual movements (i.e. landings and take-offs) with respects to aircraft types/classes (4); (1) Evans, A. W., Foot, P. B. et al. Third Party Risk Near Airports and Public Safety Zone Policy. June 1997. National Air Traffic Services Limited. R&D Report 9636. RDD File Reference 8CS/091/03/10. (2) Cowell, P. G., Foot, P. B. et al. A Methodology for Calculating Individual Risk Due to Aircraft Accidents Near Airports. January 2000. National Air Traffic Services Limited. R&D Report 0007. R&DG File Reference 8RD/07/002/11. (3) Muldoon, M. (28-Jan-02). Validation of ERM’s Public Safety Zone (PSZ). Department of Mathematics, UMIST, PO Box 88, Manchester M60 1QD. (4) The extent of PSZs is related to the number of aircraft movements and aircraft types. To minimise the need to periodically revise zone extents the number of aircraft movements for each runway has been set as either (a) the runway’s movement capacity, or (b) the expected maximum number of movements. Similarly, aircraft types have been categorised as either ‘large’ or ‘light’, and the proportion of both set to provide a good representation of the expected split. ENVIRONMENTAL RESOURCES MANAGEMENT DT & DOEHLG 7608 7-FEBRUARY- 2005 A1 2. calculating an ‘all classes’ movement-weighted average crash rate (crashes per million movements). This is done by using crash rates for each aircraft class (crashes per million movements) and multiplying it by the proportion of movements for that class, and summing the individual products; 3. calculating average crash areas (within which persons ‘on the ground’ are assumed to be fatally injured) for ‘large’ aircraft and ‘light’ aircraft. These are calculated by determining the average Maximum Aircraft Weight (MAW) for each class, multiplying the average crash area by the proportion of annual crashes for that class, and summing the individual products; 4. calculating the probability that crashing aircraft impact a specified location. For ‘large’ aircraft, this is performed by integrating probability density functions over the calculated average crash area. A similar calculation is performed for ‘light’ aircraft; 5. calculating the annual frequency that crashing aircraft impact a specified location (i.e. the individual risk). This is performed by multiplying the annual probability of a crash for the specified location by the appropriate average crash rate and associated number of movements (landings and take-offs) for each runway end; 6. using the individual risk results to determine ‘best fit’ zones representing specified annual individual risks (e.g. 1 in 100,000 per year and 1 in one million per year for the proposed inner and outer PSZs). The shape of each contour (extending away from the runway end) is very similar to that of a triangle. Therefore, to provide a simple geometric area that can be readily defined and easily reproduced on maps and plans, the risk contours are represented by zones alongside and parallel to the runway and triangular zones extending away from the runway ends. ENVIRONMENTAL RESOURCES MANAGEMENT DT & DOEHLG 7608 7-FEBRUARY- 2005 A2 A2 AIRCRAFT CRASH RATE The numbers of annual movements for the airport must be provided, according to aircraft type. This information can be collated from airport movement records for a recent year or derived from the estimated future, or maximum capacity. A2.1 AIRCRAFT CLASSIFICATION Examples of the Boeing aircraft classes are summarised in the DETR report (see footnote 1, page A1) and are detailed in Table A2.1. Table A2.1 Examples of Aircraft Grouped According to Boeing Class Boeing Class Aircraft Type I Aerospatiale Caravelle BAe Comet Boeing 707/720 General Dynamics CV880 General Dynamics CV990 McDonnell Douglas DC-8 II BAe (BAC) ‘One-Eleven’ BAe (HS) Trident BAe (Vickers) VC-10 Boeing 727 Boeing 737 100/200 Dassault Mercure Fokker F28 McDonnell Douglas DC-9 VFW 614 III Airbus Industrie A300 BAe/Aerospatiale Concorde Boeing 747 Lockheed Tristar McDonnell Douglas DC-10 IV Airbus Industrie A310 Airbus Industrie A320/321 Airbus Industrie A330 Airbus Industrie A340 BAe 146 Boeing 737 300/400/500 Boeing 757 Boeing 767 Boeing 777 Canadair Regional Jet Fokker 70 Fokker 100 McDonnell Douglas MD11 McDonnell Douglas MD80 Turboprop T1 Aerospatiale ATR 42 Aerospatiale ATR 72 BAe ATP BAe Jetstream 31 BAe Jetstream 41 ENVIRONMENTAL RESOURCES MANAGEMENT DT & DOEHLG 7608 7-FEBRUARY- 2005 A3 Boeing Class Aircraft Type DeHavilland Dash 7 DeHavilland Dash 8 Dornier 228 Dornier 328 Embraer Brasilia - EMB110 Embraer Bandeirante - EMB120 Fokker 50 SAAB 340 SAAB 2000 Shorts 330 Shorts 360 Turboprop T2 BAe (HS) 748 BAe (Vickers) Vanguard BAe (Vickers) Viscount Convair 540/580/600/640 Handley Page Dart Herald DeHavilland Twin Otter Fairchild F27 Fairchild FH227 Fairchild Metro Fokker F27 Gulfstream 1 Lockheed Hercules Lockheed Electra Shorts Skyvan Executive Jets Learjet 35/60 Eastern Jets Tupolev 134/154 Light Cessna 172/177 Notes 1. Aircraft grouped in classes I-IV are Western airliner jets. 2. Aircraft grouped in class ‘Turboprop T1’ are turboprop aircraft designed and first delivered after 1970. 3. Aircraft grouped in class ‘Turboprop T2’ are turboprop aircraft designed and first delivered prior to 1970. 4. Aircraft grouped in class ‘light’ are those with a maximum take-off weight of less than 4 tonnes. The method requires a distinction to be made between, aircraft of less than 4 tonnes Maximum Take-off Weight Authorised (MTWA) and aircraft greater than 4 tonnes MTWA. Therefore, Classes I-IV, Turboprops T1 and T2, Executive and Eastern Jets are referred to as ‘large’ aircraft and others (less than 4 tonnes MTWA) referred to as ‘light’. A2.2 ALL CLASSES MOVEMENT WEIGHTED AVERAGE CRASH RATE Crash frequency data are summarised in Table A2.2 and explained below. ENVIRONMENTAL RESOURCES MANAGEMENT DT & DOEHLG 7608 7-FEBRUARY- 2005 A4 Table A2.2 Crash Frequency Summary Boeing Class Number of Crash rate Crash rate Average Destroyed movements (crashes per (crashes per MTWA area per year movement) year) (kg) (hectare) NATS MODEL Class I jets NBC,1 RBC,1 RBC,1NBC,1 WBC,1 ABC,1 Class II-IV jets (PAX) NBC,2 RBC,2 RBC,2NBC,2 WBC,2 ABC,2 Class II-IV jets (NP) NBC,3 RBC,3 RBC,3NBC,3 WBC,3 ABC,3 Eastern jets NBC,4 RBC,4 RBC,4NBC,4 WBC,4 ABC,4 Executive jets NBC,5 RBC,5 RBC,5NBC,5 WBC,5 ABC,5 Turboprops T1 (PAX) NBC,6 RBC,6 RBC,6NBC,6 WBC,6 ABC,6 Turboprops T1 (NP) NBC,7 RBC,7 RBC,7NBC,7 WBC,7 ABC,7 Turboprops T2 NBC,8 RBC,8 RBC,8NBC,8 WBC,8 ABC,8 Miscellaneous NBC,9 RBC,9 RBC,9NBC,9 WBC,9 ABC,9 TOTAL N AVERAGE R A AEA LIGHT AIRCRAFT MODEL Piston engine NBC,10 RBC,10 RBC,10NBC,10 WBC,10 ABC,10 Notes 1.