A methodology and heuristics for re-architecting a legacy system

This paper documents the authors' process of re-architecting a legacy aircraft avionics system during a system upgrade and modification program. The modification program aimed to upgrade the system to implement functionality more efficiently, enhance overall system performance, and reduce system complexity. The lack of system-level architecture and design documentation and available subject matter expertise presented a challenge in applying the traditional Systems Engineering Process V-Model during the Operations and Maintenance phase of the system's life cycle. The lack of system-level information prevented the research team from following the traditional project definition process of Requirements Definition to Architecture Definition to Detailed Design. Taking a Model Based Systems Engineering approach that utilized Systems Modeling Language (SysML), the authors defined a new process of architecture re-definition for future project efforts that are faced with a lack of legacy system-level documentation. Guiding heuristics derived from program lessons-learned are presented alongside the re-definition methodology.