What Stages of Involvement are
Stages of Involvement (SOIs) are the four points in a DO-178C program where the certification authority, or a Software DER acting within delegated authority, reviews the software life-cycle processes and data. The framework is defined in FAA Order 8110.49A, Software Approval Guidelines, and DO-178C itself is recognized as an acceptable means of compliance by AC 20-115D.
The depth of review at each stage scales with the software level (DAL A through D), the applicant's experience, and the novelty of the technology. Level A software typically gets the deepest look at every stage.
SOI #1: Planning review
Held once the plans and standards are complete and under configuration control. The reviewer assesses whether the plans, if followed, would satisfy the DO-178C objectives for the assigned software level.
- Plan for Software Aspects of Certification (PSAC)
- Software Development Plan, Software Verification Plan, Software Configuration Management Plan and Software Quality Assurance Plan
- Requirements, design and code standards
- Tool qualification plans under DO-330, and any DO-331, DO-332 or DO-333 supplement usage
SOI #2: Development review
Held when a meaningful portion of development data exists, so the reviewer can sample real requirements, design and code rather than placeholders. The question is whether development is following the approved plans and standards.
- High-level and low-level requirements, software architecture and source code samples
- Traceability between system requirements, high-level requirements, low-level requirements and code
- Evidence that standards are applied and that SQA and configuration management are active
SOI #3: Verification review
Held when a meaningful portion of verification has been performed. The reviewer checks that reviews, analyses and tests are being done as planned and that they actually demonstrate the objectives.
- Requirements-based test cases, procedures and results, with traceability to requirements
- Structural coverage analysis appropriate to the level (MC/DC for Level A)
- Review records, problem reports and their dispositions
- Qualified tool usage and data
SOI #4: Final certification software review
Held at the end of the program on the final software build. The reviewer confirms the software is complete, all objectives are met, open problem reports are acceptable, and the configuration being certified is the one that was verified.
- Software Accomplishment Summary (SAS) and Software Configuration Index (SCI)
- Closure of findings from SOI #1 through #3
- Open problem report assessment and conformity of the final build
How to prepare for any SOI
- 01Run an internal pre-audit against the DO-178C objective tables (Annex A) for your level.
- 02Have traceability and configuration data retrievable on demand, not assembled during the audit.
- 03Close prior-stage findings first; open findings carried forward signal process problems.
- 04Track every finding in a comment/response matrix with owner, response and disposition.
- 05Engage the Software DER before SOI #1 so plan gaps are fixed while they are still edits.