Part 25 display systems
Part 25 certification-basis support for a transport display system
This support maps a transport-category display system to the Part 25 paragraphs that form its certification basis, then checks whether the evidence package actually carries each finding. A certification or engineering lead requests it while building a submittal or answering an authority finding. It works across the software life-cycle data under DO-178C, the human-factors and crew-interface assumptions the display relies on, and the DO-160G environmental qualification behind the hardware. You get a paragraph-by-paragraph standards map, a gap list keyed to the missing evidence, and a closure sequence that puts the highest-risk findings first.
When this review is needed
- A display unit is heading into a submittal and the team needs the certification basis pinned to specific paragraphs before it goes in.
- An authority finding asks how a display behavior is substantiated and the answer is scattered across separate reports.
- The DO-178C life-cycle data was produced by a software group that never mapped it to the airframe-level Part 25 findings.
- A crew-interface assumption in the design has to be shown as covered rather than asserted.
The problem
A display system arrives at certification as three parallel bodies of work: software life-cycle artifacts, human-factors rationale, and environmental test reports. Each was produced correctly on its own, but none of them names the Part 25 paragraph it is meant to close. When the authority asks how a specific finding is met, the team scrambles to assemble an answer from documents that were never indexed to the basis, and the gaps only become visible under that pressure.
What gets reviewed
- Applicable Part 25 subpart and paragraph set identified for the display function and its failure conditions
- DO-178C software life-cycle data checked against the assurance level the display function requires
- Human-factors and crew-interface assumptions traced to the evidence that supports them
- DO-160G environmental qualification mapped to the installation and operating envelope
- Display behavior in failure and degraded modes matched to the substantiation on file
- Each mapped finding marked as supported, partially supported, or open
What gets validated
- Every Part 25 paragraph in the basis links to a named document rather than a general assertion of compliance
- The software assurance level claimed for the display matches the failure-condition classification behind it
- Human-factors substantiation addresses the actual crew tasks the display drives, not a generic interface argument
- DO-160G test categories cover the environment the display sees at its installed location
- Degraded and failure-mode display behavior is backed by evidence, not left to the reader to infer
Evidence normally required
- The proposed or agreed certification basis and any issue papers on the display
- DO-178C life-cycle data including the plans and the accomplishment summary
- Human-factors analysis and crew-interface design rationale
- DO-160G qualification test reports for the display hardware
- The system safety assessment that classifies the display's failure conditions
Common discrepancies
- A software artifact that meets its own objectives but was never tied to the Part 25 finding it supports
- A human-factors assumption stated in the design that has no evidence behind it in the package
- Environmental qualification run to a category that does not match the installed environment
- A failure-mode display behavior with no substantiation for how the crew is expected to respond
What is at stake
A package that cannot show a clean line from each Part 25 paragraph to its supporting evidence draws findings that stall the submittal. Late discovery that a crew-interface assumption was never substantiated, or that a software artifact does not reach the assurance level the display function demands, forces rework at the point where the schedule has the least room to absorb it.
Move from findings to resolution
Identify gaps against the means of compliance.
How the work runs
Fix the basis
Identify the Part 25 paragraphs that apply to the display function and its failure conditions.
Index the evidence
Link each software, human-factors, and DO-160G artifact to the finding it is meant to close.
Mark the gaps
Flag findings that are unsupported, under-supported, or backed by the wrong category of evidence.
Sequence closure
Order the open items so the highest-risk findings are cleared before submittal.
What the buyer receives
- A Part 25 standards map linking each paragraph to its supporting evidence and its status
- An evidence gap list keyed to the specific document or analysis that is missing
- A closure sequence ordered so the findings with the most schedule risk are addressed first
Who uses the output
- Certification leads assembling the submittal and answering authority findings on the display
- Engineering leads deciding what evidence has to be produced or reworked before submittal
- Compliance managers tracking which Part 25 findings are closed and which still carry exposure
How the work fits into the transaction or program
The mapping runs between the point where the display's engineering evidence is produced and the point where the submittal is compiled. It converts a stack of correct-but-unlinked reports into a basis-indexed package, so the team enters the finding response with a known position instead of discovering gaps while the authority watches.
Start with a single asset
Confirm requirements trace through verification.
Jurisdiction-specific considerations
An FAA basis under Part 25 and an EASA basis under CS-25 track closely but diverge on some human-factors and software expectations, so the map notes where a display accepted on one side needs additional or restated evidence for the other rather than assuming the package transfers unchanged.
Regulatory limits
The mapping shows how the display's evidence lines up against the Part 25 basis and where it falls short. It does not issue a compliance finding, grant an approval, or make an airworthiness determination on the display or its installation, all of which rest with the authority.
What this review does not cover
- Producing the missing software, human-factors, or environmental evidence
- Issuing a compliance finding or any approval on the display
- Redesigning the display or its crew interface to close a gap
Specific to this review
- A display's software assurance level is driven by its worst-credible failure condition, so a mismatch there invalidates the life-cycle argument no matter how complete the artifacts are.
- Human-factors findings are the ones most often asserted without evidence, because the design rationale reads as substantiation until an authority asks for the underlying analysis.
- Environmental qualification is easy to reuse from a prior program at the wrong DO-160G category, which surfaces only when the installed location is checked against the test envelope.
Sources
U.S. Government (eCFR). Type certificates, STCs (Subpart E), TSO authorizations (Subpart O), PMA (Subpart K), and export airworthiness approvals (Subpart L).
Federal Aviation Administration. FAA type certification process, certification basis establishment, and compliance findings.
SAE International. Development assurance process at aircraft and system level, including requirements capture and validation.
Frequently asked questions
Do you produce the missing evidence, or only identify it?
This work identifies which Part 25 findings lack support and what document or analysis would close each one. Producing the software, human-factors, or environmental evidence itself sits with your engineering groups, and the map tells them exactly what to target.
Relevant glossary terms
Related pages
Where this fits
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