Aerospace Recommended Practice (ARP) 4754 Revision A (ARP4754A), Guidelines for Development of Civil Aircraft and Systems [1], and ARP4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment [2], together describe a complex set of intertwining processes which comprehensively prioritize development activities for a product's systems based on their safety criticality. These processes work at specific levels of detail (aircraft and system) and interact with a set of processes at lower levels of detail (item) defined by Radio Technical Commission for Aeronautics (RTCA) standards. The aircraft and system development process (ARP4754A) supplies functions, requirements, and architectural definitions to the System Safety process (ARP4761), which in turn supplies Development Assurance Levels back to the development process and on to the RTCA processes. The specific discussion of these levels of detail in this guidance inherently limits the processes from easily scaling to accommodate newer concepts such as Unmanned Aircraft Vehicles or Multi-vehicle Space Transport Systems. Though these system-of-system concepts are in areas with developing regulations, their imminent transition to civilian applications demonstrates impending challenges with the general approach of the ARPs. Further complicating this future civilian aerospace environment is the pace at which guidance gets updated. To resolve these issues, a more flexible approach to these processes can be developed which preserves the fundamental concepts described in the existing guidance but also provides greater scalability. The concepts described in this work would provide simpler, more stable sets of standards that regulators could use to produce more consistent guidance to accommodate a future environment of more diverse aircraft vehicle platforms.
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