Accident categories represented as Event Sequence Diagrams (ESDs) Alfred Roelen ([email protected]) Accident ICAO definition: An occurrence where : •a person is fatally or seriously injured, or •the aircraft sustains damage which adversely affects the aircraft 2 Scenario clustering Collision with ground Collision with object General disintegration 3 Accident types Abrupt manoeuvre Personal injury Uninhabitable cabin environment (Fire/O ) Personal injury Collision with ground Accident Loss of control (unrecovered) Controlled flight into terrain Aircraft destroyed Forced landing Aircraft damaged Mid-air collision Collision with object Collision on ground Structural accident General disintegration Fire/ Explosion 4 Flight phases Cruise Climb Take-off Taxi Landing Approach 5 Proposed scenario matrix Taxi Abrupt maneuver Uninhabitable cabin environment (fire, O2) X Loss of control (unrecovered) Take-off Climb X X X X X X X X X X X X X X X X X Controlled flight into terrain En-route Approach Landing X Forced landing X Mid-air collision Collision on ground X Structural accident Fire/Explosion X X X X X X X X X X X X X X X 6 Scenario represented as event sequence diagram (ESD) Undesired Aircraft States Event causing deviation from normal operation (initiating event) Normal Operation C F (failure/accident) B Recovery A ESD Model Generic Scenario 7 Event Sequence Diagram 8 Modelling Approach: selection of IE and PE • Initiating Events (IE) – deviation from normal operation – active failures (triggering events) • Pivotal Event (PE) – event with possible intervention – other causal pathway entered – active failures 9 Accident scenario representation From ... To ... 10 Modelling Approach: Level of detail • Transparency • Limited complexity • Minimise inter-dependencies • ESDs can be quantified with NLR air safety database (accident/incident/flight data) 11 ESD development steps 1) Individual accidents are analyzed and represented as a sequence of events. 2) Accident scenarios are generalized per type of accident, IE and flight phase. 3) Generalised scenarios are combined into one generic ESD so that this ESD covers a class of accidents. • Selection of accidents/incidents: ~ past 15 years, commercial air transport, ‘Western built’ aircraft, official accident report available 12 Example : Loss of control accident • Accident type: loss of control • Flight phase: en-route/approach • Multiple ways to loose control over the aircraft: – different loss of control accident scenarios 13 Loss of control accident scenario initiators • System induced – Degraded aircraft performance, e.g. weight & balance related, aerodynamic degradation, propulsion system failure, ... – Degraded flight control system, e.g. structural failure of tail, stuck flight controls, ... • Environment induced – e.g. wind shear, turbulence, ... • Crew induced – e.g. spatial disorientation, ... 14 Example • Accident type: Loss of control • Flight phase: En-route/approach • Initiating event: Propulsion system failure 15 Step 1 From accident report to accident scenario 16 British Midlands, 737-4Y0, G-OBME, East Midlands, January 8, 1989 17 ESD British Midland 737 G-OBME 18 Atlantic Southeast Airlines, EMB 120RT, N256AS, Carrollton, Georgia, August 21, 1995 19 ESD ASA EMB 120RT N256AS 20 Step 2 Generalising the accident scenarios 21 ESD British Midland 737 G-OBME generalising added branch through systematic analysis and generalising, combining 22 Step 3 From generalised specific accident scenarios to one generic scenario 23 Generic ESD loss of control initial climb-landing, IE propulsion system failure 24 Results • 33 different generic accident scenarios covering all accident types*) and all flight phases. *) Unlawful acts are excluded 25 Overview of all scenarios ESD 1: Aircraft system failure ESD 18: Single engine failure in flight ESD 2: ATC event ESD 19: Unstable approach ESD 3: Aircraft handling by flight crew inappropriate ESD 21: Aircraft weight and balance outside limits during approach ESD 4: Aircraft directional control related system failure ESD 5: Incorrect configuration ESD 6: Aircraft takes off with contaminated wing ESD 7: Aircraft weight and balance outside limits during take-off ESD 8: Aircraft encounters a performance decreasing wind shear after rotation ESD 9: Single engine failure during take-off ESD 10: Pitch control problems ESD 11: Fire onboard aircraft ESD 12: Flight crew spatially disoriented ESD 13: Flight control system failure ESD 14: Flight crew incapacitation ESD 15: Anti-ice/de-ice system not operating ESD 16: Flight instrument failure ESD 17: Aircraft encounters adverse weather ESD 23: Aircraft encounters wind shear during approach ESD 25: Aircraft handling by flight crew during flare inappropriate ESD 26: Aircraft handling by flight crew during landing roll inappropriate ESD 27: Aircraft directional control related system failure during landing ESD 28: Single engine failure during landing ESD 29: Thrust reverser failure ESD 30: Aircraft encounters unexpected wind ESD 31: Aircraft are positioned on collision course ESD 32: Incorrect presence on runway in use ESD 33: Cracks in aircraft pressure cabin ESD 35: CFIT ESD 36: Collision on taxiway/apron ESD 37: Wake vortex encounter 26 ESD 1: Aircraft system failure 27 ESD 2: Air traffic related event 28 ESD 3: Aircraft handling by flight crew inappropriate 29 ESD 4: Aircraft directional control system failure 30 ESD 5: Incorrect configuration 31 ESD 6: Aircraft takes off with contaminated wing 32 ESD 7: Aircraft weight and balance out of limits during take-off 33 ESD 8: Aircraft encounters a performance decreasing windshear after rotation 34 ESD 9: Single engine failure during take-off 35 ESD 10: Pitch control problems 36 ESD 11: Fire on-board aircraft 37 ESD 12: Flight crew disoriented 38 ESD 13: Flight control system failure 39 ESD 14: Flight crew incapacitation 40 ESD 15: Anti-ice/de-ice system not operating 41 ESD 16: Flight instrument failure 42 ESD 17: Aircraft encounters adverse weather 43 ESD 18: Single engine failure in flight 44 ESD 19: Unstable approach 45 ESD 21: Aircraft weight and balance outside limits during approach 46 ESD 23: Aircraft encounters wind-shear during approach 47 ESD 25: Aircraft handling during flare inappropriate 48 ESD 26: Aircraft handling during landing roll inappropriate 49 ESD 27: Aircraft directional control related system failure 50 ESD 28: Single engine failure during landing 51 ESD 29: Thrust reverser failure 52 ESD 30: Aircraft encounters unexpected wind 53 ESD 31: Aircraft are positioned on collision course 54 ESD 32: Incorrect presence on runway in use 55 ESD 33: Cracks in aircraft pressure cabin 56 ESD 35: CFIT 57 ESD 36: Collision on taxiway/apron Ground collision imminent ATC fails to resolve the conflict Flight crew fails to resolve the conflict Ground crew fails to resolve the conflict Aircraft damaged yes no Aircraft continues taxi Aircraft continues taxi Aircraft continues taxi 58 ESD 37: Wake vortex encounter Wake vortex encounter yes no Flight crew fails to maintain control Personal injury Collision with ground Personal injury Aircraft continues flight 59
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