Model-Based Safety Assessment for Flight Control Systems: Methodology and Case Study

Technological advances have increased complexity of avionics systems, requiring methods to efficiently and accurately derive both quantitative and qualitative safety assessments for certification. To address this challenge, Model-Based Safety Assessment techniques have emerged as promising solutions over the years. In December 2023, the new version of ARP4761A integrates MBSA formalism into the recommended practices for safety processes, as an alternative to classical safety assessment techniques (e.g. Fault Tree Analysis). The main contribution of the paper is to provide a case study demonstrating a successful application of an MBSA technique, to support the aforementioned safety process required by the certification authority. Accordingly, the generated outputs include probability of occurrence, DAL allocation, the elicitation of independence principles and requirements traceability. The example reported is a comprehensive MBSA process of an industrial rotorcraft Flight Control System: the article follows the architecture description, explains the safety model creation and comments on the derived results. In the final part of the article, lessons learned from the implementation of MBSA technology in an industrial environment are reported.