AFuzion’s new DO-178C SOI and DO-254 SOI Services: SOI’s Explained

27 Jan



Aviation system development typically requires Stage Of Involvement (SOI) activities which comprise formal audits of:

  1. Plans (SOI #1)
  2. Implementation (SOI #2)
  3. V&V (SOI #3)
  4. Conformity (SOI #4)


Originally, DO-178 (the predecessor to DO-178C, DO-254, DO-278, ARP-4754) based development did not require or even have SOI’s.  A problem arose because of divergence between different development organizations and even projects versus what certification authorities expected.  In keeping with the continual evolution of aviation certification and oversight, SOI’s were informally added and became a defacto “standard” applied to most projects.

Required SOI attendance can actually be quite limited:  only the project’s Quality Assurance (QA) representative and Certification Authority representative must attend.  In reality, multiple additional personnel attend including key members from the project’s Safety, Systems, Software/Hardware and Management teams.  Similar to military aviation’s SSR/PDR/CDR/TRR meetings, the SOI’s commonly have multiple attendees to ensure depth of knowledge (and shared responsibility).

Today, there is a movement afoot which lessens the usage of SOI’s for many reasons:   availability of cert authority personnel and potential subjectivity of applied SOI criteria are two oft-cited reasons.  However, many projects believe in and rely upon effective SOI’s to ensure regulatory compliance and prevent mistakes instead of relying upon fixing mistakes after-the-fact.


Like building a commercial building or even a house, governments require advance Plans then reviews of those Plans, followed by in-process building inspections and then a final audit of the building for compliance and habitability.  Aviation systems are more complex than buildings so the aviation SOI protocol is even more important.  Remember:  SOI #1 assesses the Plans and Standards versus regulatory standards and guidelines.  SOI #2 assesses project-specific implementation against those approved Plans, Standards, and Guidelines.  SOI #3 assesses verification and validation of that implementation.  SOI #4 assesses the key final process completion including conformance of:  traceability, configuration management and problem report disposition, build/manufacturing processes and artifact integrity.




If an aviation product developer has great experience, perfect execution, and perfect luck, the SOI’s are a mere and easy formality.  However, in real-life, all projects have varying risks which are mitigated by thorough SOI planning and execution.  The following are common SOI mistakes which AFuzion’s engineering auditors have observed on 200+ aviation projects the past twenty years.   For a complete list and free DO-178C and DO-254 SOI whitepaper, see here:   (DO-178C SOI and DO-254 SOI Best Practices Free Whitepaper Here::



AFuzion SOI Services

For 15+ years, AFuzion’s engineers have provided SOI services to 150+ clients in 20+ countries worldwide.  Remember:  if you have perfect engineers, perfect projects, easy certification authorities, and perfect luck, you won’t need AFuzion.  Otherwise, 100% of AFuzion’s clients agree that AFuzion’s SOI services saved them 10X more money than the cost of those services.   When AFuzion performs DO-178C Gap Analysis or DO-254 Gap Analysis, common gaps include SOI optimization.  For DO-178C optimization and DO-254 optimization, including SOI’s, see AFuzion DO-178C Gap Analysis and DO-254 Gap Analysis data here:  DO-178C Gap Analysis & DO-254 Gap Analysis Info Here


For a fun 1-minute video “What is AFuzion“, click here: Fun 1-Minute AFuzion Video – What Is AFuzion?





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