ABSTRACT
As of today, two of major topics in Reliability, Availability, Maintainability and Safety (RAMS) field are how to deal with the growing complexity of new systems and how to reduce the time required to perform RAMS analysis. Complexity is perceived as the most challenging factor when developing “safe proved” critical systems. During the last decade Model Based System Engineering has been broadly deployed in the industry in order to manage complexity. Complexity is also managed by adopting incremental and/or iterative development lifecycles. It is therefore imperative to integrate RAMS analyses with such means and processes. This implies dealing with a live, changing design baseline. To deal with the two major topics detailed above, a new practical RAMS modelling methodology is presented in this paper, based on a generic Model Based System Engineering (MBSE) tool with an Engineering Model (EM) shared between Design and RAMS teams. Requirements, Functional Trees, System Architecture and Detailed Design are included in this model. Furthermore the model includes Functional Failure Mode and Effect Analyses (FMEAs), Components FMEAs, Feared Events and related Fault Tree Analysis. In this way, safety and engineering models are intrinsically linked and RAMS teams can fully exploit traceability (established and maintained by the design team) between Functions and Components & Interfaces. An automated export of RAMS related data, (Reliability Data & Fault Tree topologies) allows numerical calculations in a reliability tool. This methodology can deal with both software and hardware technologies. It is valid for highly critical systems (safety related) but also for less critical systems with complex availability modelling (production means). A real use case for this methodology is presented; the Ariane 6 Control Bench Family (A6 CBF). A6-CBF is a family of 9 control benches, covering all the ground control needs of future Ariane 6 launcher in terms of production, validation, training and launch operations.
