Model-Based STPA: Enabling Safety Analysis Coverage Assessment with Formalization

Abstract

Urban Air Mobility introduces safety-related challenges for future avionics systems. The associated need for increased autonomy demands novel functions based on highperformance algorithms. To provide such functionality in future air vehicles of all sizes, the trend is towards centralized and powerful computing platforms. That turns avionics into a complex, integrated, and software-intensive aircraft system. Simultaneously, this increases the need for adapted safety analyses. The System-Theoretic Process Analysis is a promising approach to analyze the safety of software-intensive systems. It enables consideration of interaction and specification issues additional to component failures. However, even when using state-of-the-art analyses such as STPA, claiming the sufficiency of the safety analysis efforts is a challenging tasks for systems with everincreasing complexity. To address this issue, this paper extends the coverage analysis concepts known from the software development to safety analyses. This is achieved with the utilization of failure graphs, i.e., formalized analysis summaries that can be automatically created during the safety analysis. Failure graphs have two advantages: they provide the possibility for visual analysis state indication and can be used to calculate various statistical metrics. Thereby, they allow to improve the knowledge about the depth, breadth, and state of the safety analysis. Both visual and statistical consideration complement each other to enhance the safety analysis coverage assessment for future avionic systems. To show all capabilities, the analysis of a flight assistance system serves as demonstrator.

Cybersecurity Engineering: Bridging the Security Gaps in Avionics Architectures and DO-326A/ED-202A

“…The RA2 shall establish resilience [4] by providing prevention, detection, response and recovery capabilities to ensure security and functional safety (fail-operational, fail-safe and fault-tolerant) [5], [11], [12] of UAM missions. This paper extends [9] and complements previously published research works [12], [13], [14], [15]. In this paper, the Resilient Avionics Architecture for Flight Assistance System (RA2FAS) has been chosen as an experimental use case.…”

“…The scope of this paper is on the cybersecurity engineering process for the RA2FAS. Complementary, the safety engineering process of the RA2FAS is covered in [14], [15].…”

A novel STPA approach to software safety and security in autonomous maritime systems

“…The purpose is to allow for safety trade-offs in the early design phase. Ahlbrecht and Durak [52] expand this work and combine STPA with failure graphs to visualize the safety analysis status and coverage. These works show the benefit of combining STPA with UML/SysML approaches.…”