DO-331 Introduction – Model Based Development

Modern avionics increasingly use Model Based Development (MBD) and this DO-331 Whitepaper discusses MDB for avionics software development. Avionics MBD provides many advantages but also has pitfalls; this DO-331 MDB whitepaper provides a brief tutorial and best practices for DO-331 MBD, particularly DO-178C MBD.

DO-331, Model-Based Development and Verification Supplement to DO-178C and DO-278A, is a 125-page guideline governing MBD usage in airborne and ground-based aviation software. However, since MBD is relatively new to aviation software, the authors of DO-331 faced a large hurdle: how to provide meaningful guidelines to persons generally unfamiliar with model-based development? The answer was artfully handled within DO-331 by combining workable “guidelines” with a high-level MBD tutorial which laid a common foundation for MBD terminology and application.

Ask any software developer (and their manager!) “What is the Holy Grail of software development?” and there will be one predominant answer: “perfect software with perfect reusability”. Admittedly, that answer will be provided with a smile (or a smirk, if interpreted by the manager). But software is never perfect nor is it perfectly reusable. In fact, aviation’s factual assessment of software is succinct, and few would deny aviation software is among the best, if not the best, in the entire world. Aviation authorities operate on the underlying factual premise that no software is perfect and all software eventually fails. That fact is unquestioned because the “answer” within aviation software is in detecting and mitigating such failures. Now, broaching modern software development practices causes one to embrace MBD as the “next great hope” in getting us a little closer to that Holy Grail: perfect and perfectly reusable software …

Many readers have been to a safety-critical engineering training class provided by the author of this whitepaper. Such attendees know that one of the secrets to keeping students engaged in a seemingly boring technical topic is combining the Socratic method of teaching with frequent quizzes. Keep the student engaged and assess knowledge along the way, not at the end when it is too late to modify the teaching.

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