TSO finding closure
Closing coverage gaps against the certification basis in a TSO program
This is targeted support for equipment suppliers who find that their TSO article's certification basis has requirements with no compliance data planned against them. A certification specialist walks the full basis, marks each requirement that has no acceptable means of compliance or no owner, and builds a mapping from basis clause to evidence and owner. The work runs during the program, usually after a first reviewer pass exposes the holes, not after rejection. You get a closure brief that lists each uncovered requirement, an evidence request list naming what has to be produced or retrieved, and a disposition package a reviewer can read against the basis.
When this review is needed
- A reviewer comment lists basis paragraphs that the compliance data package never addresses.
- The certification plan was written before the basis was fully set, and the two never reconciled.
- A TSO minimum performance standard cites clauses the supplier assumed were covered by a supplier-furnished report that never arrived.
- The compliance matrix has rows for the applicable requirements but blank cells where the evidence reference belongs.
The problem
The basis is the contract the article is certified against, but the compliance data was assembled from what engineering happened to produce rather than from what the basis demands. Somewhere in the middle, requirements fall out: a paragraph nobody was assigned, a clause everyone thought a test report covered, a standard invoked by reference that pulls in obligations the plan never listed. Nobody notices until a reviewer reads the basis line by line and the supplier cannot point to the data.
What gets reviewed
- Every applicable basis requirement enumerated from the TSO, its invoked standards, and any special conditions or deviations
- Each requirement marked as covered, partially covered, or with no planned compliance data
- The acceptable means of compliance identified or selected for every uncovered requirement
- A named evidence owner and data source assigned to each open item
- Requirements pulled in by reference from cited standards, traced so they are not lost between documents
- A reconciled view of the compliance matrix showing the basis fully mapped end to end
What gets validated
- Every basis paragraph resolves to either a compliance data reference or an explicitly open item with an owner
- Requirements invoked by reference from a cited standard appear in the matrix rather than living only in the source document
- Each selected means of compliance is acceptable for that requirement and that article class, not borrowed from a different clause
- No matrix row cites a report that does not in fact address the paragraph it is mapped to
- Deviations and special conditions in the basis are carried into the mapping, not dropped as edge cases
Evidence normally required
- The certification basis, the applicable TSO, and any invoked minimum performance standard revisions
- The current certification plan and compliance matrix in whatever state they exist
- The compliance data package as submitted or drafted, including reports and analyses
- Any reviewer comments or minutes that flagged coverage concerns
- The list of special conditions, deviations, or equivalent-level-of-safety findings that apply
Common discrepancies
- A basis paragraph with no matrix row at all, missed when the matrix was built from the plan rather than the basis
- A requirement mapped to a report that covers an adjacent clause but not the one cited
- Obligations pulled in by a referenced standard that the plan treated as out of scope
- A special condition addressed in correspondence but never folded into the compliance data
What is at stake
Uncovered basis requirements do not stay quiet. Each one comes back as a formal comment, and a comment that the supplier cannot answer with existing data forces new analysis or new test on the critical path. A program that ships a submittal with basis holes trains its reviewer to distrust the whole matrix, so the next review is slower and more literal, and the schedule the supplier promised its installer no longer holds.
Move from findings to resolution
Identify the missing data behind the finding.
How the work runs
Enumerate the basis
Build the complete list of applicable requirements from the TSO, its invoked standards, and any special conditions or deviations.
Test coverage
Mark each requirement as covered, partial, or unplanned by checking whether real compliance data addresses that exact clause.
Assign closure
Select an acceptable means of compliance for every open item and name the owner and data source.
Reconcile the matrix
Rebuild the compliance matrix so it reads straight against the basis and hand over the disposition package.
What the buyer receives
- A closure brief listing each uncovered basis requirement with its selected means of compliance
- An evidence request list naming the report, analysis, or test that has to be produced or retrieved for each gap
- A reviewer-ready disposition package that reads the compliance matrix straight against the basis
Who uses the output
- Certification leadership deciding which gaps need new work versus a data reference
- Engineering leads who now know exactly which analysis or test to schedule
- Program management tracking the closure list against the submittal date
How the work fits into the transaction or program
This sits between the certification plan and the formal compliance submittal. It takes a matrix that was built bottom up from available data and reconciles it top down against the basis, so the package the supplier submits answers the basis rather than describing the work that happened to get done.
Start with a single asset
Confirm each requirement maps to substantiating evidence.
Jurisdiction-specific considerations
An FAA TSO authorization and an EASA ETSO for the same article draw their basis from different rule sets and can invoke different standard revisions, so a requirement covered under one authority may sit uncovered under the other. The mapping is built per authority rather than assumed to transfer.
Regulatory limits
The work maps requirements to evidence and identifies where evidence is missing. It does not make airworthiness determinations, does not grant or recommend a TSO authorization, and does not accept any means of compliance on behalf of an authority; those decisions stay with the certificating authority.
What this review does not cover
- Producing the missing test reports or analyses themselves
- Setting or renegotiating the certification basis with the authority
- Design changes to bring the article into compliance with an uncovered requirement
Specific to this review
- Coverage gaps cluster where a standard is invoked by reference, because the obligations it pulls in never get enumerated in the plan.
- A matrix built from the certification plan inherits the plan's blind spots; only a basis-first walk finds the paragraphs the plan never listed.
- The most expensive gaps are the ones that need new test, because they land on the critical path with no calendar left to absorb them.
- A single referenced special condition can carry several derived obligations, so counting basis paragraphs undercounts the real coverage work.
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.
European Union / EASA. EASA design and production certification, STCs, ETSO authorizations, and EASA Form 1 release.
Frequently asked questions
Our compliance matrix looks complete. How can there still be a coverage gap?
A matrix looks complete when every row it contains has a reference, but that only proves the rows present are filled. Coverage gaps are missing rows: basis paragraphs, and requirements invoked by reference from cited standards, that were never added because the matrix was built from the plan rather than walked out of the basis. The check has to start from the basis, not the matrix.
Relevant glossary terms
Related pages
Where this fits
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