Process and Tool for Development Assurance Level Allocation

SUMMARY & CONCLUSIONSThe objective of Design Assurance Level (DAL) assignment is to determine the DAL for functions, H/W, and S/W. The DAL assignment and allocation process begins with failure conditions and their classifications, proceeds to functions, then systems, and finally gets to H/W and S/W.Function Development Assurance Level (FDAL) defines the design and verification rigor required during development of a system and its constituent LRUs. This design rigor is based on the classification of failure conditions associated with the function being performed. This paper focus on the process followed by safety engineers to determine if the system will meet the safety requirements. FDALs are assigned to the top events defined in the SFHA and allocated to items according to the proposed system implementation. This process creates safety requirements (SRs) in the preliminary safety assessment which flows back to the systems, hardware and software domains. There may be several iterations of revising system descriptions and performing FDAL allocations.