Safety Analysis Methods in Aerospace: A Case-Based Comparison of FTA and MBSA

Safety-critical areas, such as aerospace, require in-depth and rigorous analysis of the systems under failures. In accordance with industry standards, complex assessments are created to describe how failures can lead to specific functional failures and to verify compliance with specific certification targets. This article reports on a comparison between two independent methods on which the assessments are based. The first is the well-known Fault Tree Analysis (FTA), the de facto industrial standard. While the second is the analysis of the system Failure Propagation Model (FPM) included within the newest paradigm of Model-Based Safety Assessment (MBSA). The objective of this work is to evaluate key parameters to highlight the characteristics of both techniques while integrating them into an industrial process for civil aviation development, in particular during the Preliminary System Safety Assessment (PSSA). A benchmark is provided by analysing a realistic rotorcraft flight control system on which both methods are developed.