Popular DO-178B Myths

Michael Rielly

December 22, 2010

DO-178B has increasingly evolved into the de-facto standard for both commercial and military avionics; and more recently, general aerospace electronics. Yet, there are still a lot of questions and even a few myths surrounding the cost and benefits of DO-178B. Is DO-178B really expensive and does it add value? What are the true costs versus the benefits? Is Level A very difficult to achieve and does it really cost 50% more than Level B? HighRely has published an excellent whitepaper on the subject entitled: DO-178B Costs Versus Benefits. Here are a few excerpts...

[via] A popular myth is that DO-178B is expensive. As can be seen above, Level D certified software still has generally full planning, requirements, implementation, reviews, and basic testing processes applied. Additionally, configuration management, quality assurance, and DER liaison are applied to Level D. Yet the costs of Level D are hardly more than any non-certified commercial software process. Why? Because Level D is comprised almost entirely of normal industry-standard software engineering principals.

[via] Another myth is that the most significant cost escalation occurs when moving from DO-178B Level B criticality to Level A. Untrue. The cost impact of DO-178B is the most significant between Level D and Level C. Why? Level C requires the following which Level D does not and which results in Level C requiring 30% more budget and schedule than Level D:

  • Testing of low-level software requirements
  • Ensuring 100% coverage of all source code statements
  • Greater rigor placed upon reviews
  • In many cases more rigorous configuration management

Level B requires additional structural coverage (decision-condition, e.g. all branches in the source code), additional independence in reviews, and tighter configuration management. At first glance, it would seem that Level B should be significantly more expensive, e.g. 50% - 70%, than Level C. In theory, it seems to make sense, but as in many areas of life, common sense overcomes theory. In Level B (and C) there must be detailed, low-level software requirements and they must be thoroughly tested. During requirements-based testing, most (70-90%) of the branches in the source code are already executed and hence require no additional structural coverage testing if test capture and coverage tools are appropriately used! Therefore, the seemingly significant cost increase associated with Level B versus C structural coverage is already mitigated by requirements-based testing.

DO-178B is not free. However, DO-178B can be cost-effective when implemented properly. Why then are so many entities adopting DO-178B? Because of the actual DO-178B benefits! To learn more, feel free to download these whitepapers: