Embedding aircraft system modeling to ATM safety assessment techniques: The runway excursion safety case for runway strips with reduced strength

Abstract

Several concepts were developed over the last years to fit safety assessment (SA) techniques to ATM operational needs. Quantitative SA models proved to achieve robust results if reliable data for hazard modeling and corresponding target levels of safety are available, inducing much effort in historic incident data gathering. Meanwhile, we consider hazard probability determination as a reliable mathematical process whereas consequence modeling as second risk component remains mainly a subjective technique. This paper presents an analytic approach to link a mechanical model of a representative critical aircraft part called TSIM (Tire-Soil Interaction Model) to an FEM (Finite Element Method) tire stress simulation to study critical aircraft part failures (here the landing gear) at high detail level during a hazardous condition. In doing so, we can show to significantly and robustly increase the transparency for allocating a severity category to a given hazard compared to current categories based on EASA and other international standards. The research also shows that risk-based aircraft part certification reveals weaknesses in data and setting of target levels of safety (TLS) as a risk considered to be acceptable in non-nominal situations. We apply the developed concept to a runway excursion scenario where the infrastructure is considered non-compliant to EASA/ICAO regulations.