Interconnections in Model-Based Safety Analysis and Systems Design on the Example of a Fuel Cell Thermal Management System for Commercial Aircraft

The impact of the introduction of new technologies for aircraft systems or adaption of such is difficult to estimate in early design stages. The integration of new technologies immediately confronts aircraft manufacturers and suppliers with unseen and novel challenges, especially in regards to safety and inevitable inter-system dependencies. Aviation technology currently used in commercial aircraft has undergone rigorous and extensive testing and development resulting in vast experience of aircraft manufacturers. New technologies will have to be implemented with rigorous design and safety processes, to meet current safety levels. For aviation to accomplish it's self-set goal of carbon neutrality in the future, the incorporation of yet unused energy transformation principles, for example fuel cell systems, with little to no in-service experience to rely on, is imperative. In our ongoing research, we incorporate the established design and safety processes of the Society of Automotive Engineers' (SAE) Aerospace Recommended Practices (ARP) 4761 and 4754A into an operative model-based systems engineering (MBSE) framework. The resulting safety analyses on aircraft level and systems level provide important insight into systems' emerging requirements and their traceability. Additional potential benefits may include an increase of the system architectures’ comparability and reusability. The paper examines whether and how integrating safety analysis into model-based systems engineering during conceptual system design can improve early system architecture comparability and reusability through increased traceability. This could offer benefits for design studies in early stages with uncertainty of safety requirements from neighbouring and internal systems. To demonstrate the proposed approach, conceptual fuel cell systems (FuCS) and their respective thermal management systems (TMS) will be used as an illustrative case. Three applications for the FuCS will be defined, each with different safety criticality. For each application Aircraft Functional Hazard Analyses (Aircraft FHA), Preliminary Aircraft Safety Assessments (PASA) and System Functional Hazard Analyses (System FHA) have been carried out. The results of the safety show improved reusability and comparability between the models despite high design uncertainty.