Accident scenarios for an integrated aviation safety model

1. Accident scenarios for an integrated aviation safety model Alfred Roelen (roelen@nlr.nl) Rombout Wever National Aerospace Laboratory Flight Safety and Aircraft Operations Department

2. Outline • Objective • Accident types and scenarios • Modelling approach • Scenario development process • Example loss of control accident scenario development • Results accident scenarios for an integrated aviation safety model

3. Objective • Development of the top layer of an Integrated Safety Model. • Provide an initial framework for staged development and integrating work by the different organisations accident scenarios for an integrated aviation safety model

4. Integrated Safety Model (Framework) accident scenarios for an integrated aviation safety model

5. Scenario clustering Collision with ground Collision with object General disintegration accident scenarios for an integrated aviation safety model

6. Accident types accident scenarios for an integrated aviation safety model

7. Flight phases En-route Descent Climb Take-off Approach Landing accident scenarios for an integrated aviation safety model

8. Fatal accidents and flight phases accident scenarios for an integrated aviation safety model

9. Proposed scenario matrix accident scenarios for an integrated aviation safety model

10. Accident scenario representation From ... To ... accident scenarios for an integrated aviation safety model

11. Event Sequence Diagram Pivotal Event Initiating Event Pivotal Event Comment End State accident scenarios for an integrated aviation safety model

12. Event Sequence Diagram Initiating Event Pivotal Event Pivotal Event End State Comment End State Pivotal Event End State End State accident scenarios for an integrated aviation safety model

13. Modelling Approach: selection of Initiating event and pivotal event • Initiating Event • Deviation from normal operation • Active failures (triggering events) • No latent failures (softer/deeper) • Pivotal Event • Event with possible intervention • Different causal pathway • Active failures • No latent failures (softer/deeper) accident scenarios for an integrated aviation safety model

14. Modelling Approach: Level of detail • Transparency. • Limited complexity at the top layer of the model. • ESD need further detail by means of Fault Trees and Bayesian Belief Nets. • Minimise inter-dependencies of Fault Trees. • ESDs can be quantified with available accident- incident- and flight data. accident scenarios for an integrated aviation safety model

15. ESD development steps • 1) Individual accidents are analyzed and represented as a sequence of events. • 2) Accident scenarios are generalized per type of accident, initiating event 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, accident investigation report available accident scenarios for an integrated aviation safety model

16. 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 accident scenarios for an integrated aviation safety model

17. Loss of control accident scenario initiators • System • e.g. flight control system failure, propulsion system failure • Environment • e.g. wind shear, turbulence, ice • Flight Crew • e.g. spatial disorientation accident scenarios for an integrated aviation safety model

18. Example • Accident type: Loss of control • Flight phase: En-route/approach • Initiating event: Propulsion system failure accident scenarios for an integrated aviation safety model

19. Step 1From accident report to accident scenario accident scenarios for an integrated aviation safety model

20. British Midlands, 737-4Y0, G-OBME, East Midlands, January 8, 1989 accident scenarios for an integrated aviation safety model

21. ESD British Midland 737 G-OBME accident scenarios for an integrated aviation safety model

22. Atlantic Southeast Airlines, EMB 120RT,N256AS, Carrollton, Georgia, August21, 1995 accident scenarios for an integrated aviation safety model

23. ESD ASA EMB 120RT N256AS accident scenarios for an integrated aviation safety model

24. Step 2Generalising the accident scenarios accident scenarios for an integrated aviation safety model

25. ESD British Midland 737 G-OBME generalising added branch through systematic analysis and generalising, combining accident scenarios for an integrated aviation safety model

26. Step 3 From generalised specific accident scenarios to one generic scenario accident scenarios for an integrated aviation safety model

27. Generic ESD ‘loss of control’Flight phases: climb-cruise, landingInitiating event: propulsion system failure accident scenarios for an integrated aviation safety model

28. accident scenarios for an integrated aviation safety model

29. Results • 35 different generic accident scenarios covering all accident types and all flight phases. • Fully quantified • All integrated into a single ‘Master Logic Diagram’ accident scenarios for an integrated aviation safety model