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. September 2006 accident scenarios for an integrated aviation safety model 2 Outline Objective Accident types and scenarios Modelling approach Scenario development process Example loss of control accident scenario development Results

3. September 2006 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

4. September 2006 accident scenarios for an integrated aviation safety model 4 Integrated Safety Model (Framework)

5. September 2006 accident scenarios for an integrated aviation safety model 5 Scenario clustering Collision with ground Collision with object General disintegration

6. September 2006 accident scenarios for an integrated aviation safety model 6 Accident types

7. September 2006 accident scenarios for an integrated aviation safety model 7 Flight phases Take-off Climb En-route Descent Approach Landing

8. September 2006 accident scenarios for an integrated aviation safety model 8 Fatal accidents and flight phases

9. September 2006 accident scenarios for an integrated aviation safety model 9 Proposed scenario matrix TaxiTake-offClimbEn-routeApproachLanding Abrupt maneuverXXXX Uninhabitable cabin environmentXXXXXX Loss of control (unrecovered)XXXXX Controlled flight into terrainXXX Forced landingX Mid-air collisionXXX Collision on groundXXX Structural accidentXXXXX Fire/ExplosionXXXXXX

10. September 2006 accident scenarios for an integrated aviation safety model 10 Accident scenario representation To... From...

11. September 2006 accident scenarios for an integrated aviation safety model 11 Event Sequence Diagram Pivotal Event Initiating Event Comment End State Pivotal Event

12. September 2006 accident scenarios for an integrated aviation safety model 12 Event Sequence Diagram Initiating Event Pivotal Event Pivotal Event Pivotal Event Comment End State

13. September 2006 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)

14. September 2006 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.

15. September 2006 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

16. September 2006 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

17. September 2006 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

18. September 2006 accident scenarios for an integrated aviation safety model 18 Accident type: Loss of control Flight phase: En-route/approach Initiating event: Propulsion system failure Example

19. September 2006 accident scenarios for an integrated aviation safety model 19 Step 1 From accident report to accident scenario

20. September 2006 accident scenarios for an integrated aviation safety model 20 British Midlands, 737-4Y0, G-OBME, East Midlands, January 8, 1989

21. September 2006 accident scenarios for an integrated aviation safety model 21 ESD British Midland 737 G-OBME

22. September 2006 accident scenarios for an integrated aviation safety model 22 Atlantic Southeast Airlines, EMB 120RT, N256AS, Carrollton, Georgia, August 21, 1995

23. September 2006 accident scenarios for an integrated aviation safety model 23 ESD ASA EMB 120RT N256AS

24. September 2006 accident scenarios for an integrated aviation safety model 24 Step 2 Generalising the accident scenarios

25. September 2006 accident scenarios for an integrated aviation safety model 25 ESD British Midland 737 G-OBME generalising added branch through systematic analysis and generalising, combining

26. September 2006 accident scenarios for an integrated aviation safety model 26 Step 3 From generalised specific accident scenarios to one generic scenario

27. September 2006 accident scenarios for an integrated aviation safety model 27 Generic ESD ‘loss of control’ Flight phases: climb-cruise, landing Initiating event: propulsion system failure

28. September 2006 accident scenarios for an integrated aviation safety model 28

29. September 2006 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’