STC evidence gap
Incomplete supplemental type certificate package in the records
An incomplete STC package means a supplemental type certificate is shown as installed but the records hold only part of what the modification needs, such as the certificate without the approved drawings, the installation evidence, or the continued-airworthiness instructions. It is a problem for lessors, airlines, and MROs at redelivery, induction, or transaction diligence. The check reads the STC list against the documents each entry should carry. You receive a list of STCs with missing components and the path to recover each.
When this review is needed
- A redelivery requires that each STC on the aircraft is delivered with its full approval and installation package.
- An aircraft is inducted and the incoming operator needs to confirm every listed STC is supported before accepting the configuration.
- A transaction data room is being built and a partial STC entry has to be completed or flagged before close.
The problem
An STC certificate on its own does not prove the modification was installed to the approved data. The full package pairs the certificate with the drawings, the conformity and release evidence, and the continued-airworthiness instructions, and it is the supporting pieces that tend to go missing across operators and shop visits. A certificate filed alone reads as complete to a status list while leaving the installation unsupported.
What gets reviewed
- Each STC on the modification list by certificate number and applicability
- The approved drawings and installation data the STC references
- Installation conformity and release evidence for the embodiment
- The continued-airworthiness instructions tied to the STC
- Applicability of the STC to the specific airframe serial and configuration
Scope this review
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What gets validated
- Each STC certificate is present with the approved data it depends on
- The installation evidence shows the modification was embodied to that data
- The STC applies to the airframe serial and configuration it is recorded against
- Continued-airworthiness instructions for the STC are present and incorporated
- One-time and recurring obligations from the STC are reflected in the program
Evidence normally required
- STC and modification status list
- Supplemental type certificates and approved data sheets
- Installation work packages and release evidence
- Continued-airworthiness instructions filed for each STC
Common discrepancies
- An STC certificate on file with no approved drawings or installation data behind it
- Installation evidence that does not show the modification was embodied to the STC data
- An STC recorded against a serial or configuration it does not actually cover
- Continued-airworthiness instructions absent for an STC the status list shows as installed
What is at stake
An STC with a partial package may be treated as unsupported until the missing data is recovered, which can mean obtaining a copy from the STC holder or, where the holder is gone, reconstructing the approval basis. At a transition the gap can stall acceptance of the configuration and reduce what the asset can be re-leased against.
Move from findings to resolution
Sequence the fixes and the documentation that closes each finding.
How the work runs
Enumerate the STCs
Build the STC list for the airframe by certificate number, with the applicability each entry claims.
Inventory each package
Check whether the certificate, approved data, installation evidence, and continued-airworthiness instructions are all present.
Test applicability and embodiment
Confirm the STC covers the airframe serial and that the installation evidence shows it was embodied to the approved data.
Map recovery
For each incomplete entry, set the path to obtain data from the holder or escalate an unsupported certificate.
What the buyer receives
Who uses the output
- Asset managers pricing the configuration risk in a transaction or re-lease
- Engineering judging whether an embodiment is supported by the data on file
- Records teams assembling the data room or redelivery binder
How the work fits into the transaction or program
The review isolates STC package completeness within a wider configuration review, so a modification that is approved but thinly documented is separated from one whose approval basis is genuinely in doubt. It feeds the configuration baseline and the redelivery binder.
Aircraft-specific considerations
Some types accumulate STCs through aftermarket cabin, connectivity, and avionics work, where a single tail can carry dozens of certificates layered over a decade. The completeness check is run against the embodied list for that airframe, since two aircraft of the same type can hold entirely different STC sets.
Jurisdiction-specific considerations
An STC issued by one authority is not automatically valid under another. Where the aircraft is moving registries, the package is read for whether the modification has a validated or accepted basis in the receiving system rather than only the issuing one.
Regulatory limits
The review confirms whether the STC package is complete and consistent. It does not issue or validate an STC, approve installation data, or make an airworthiness determination on the modification.
What this review does not cover
- Issuing, validating, or amending an STC
- Approving installation or modification data
- Physical conformity inspection of the embodied modification
Specific to this review
- A standalone STC certificate is treated as unsupported until its approved data and installation evidence are in the file, because the certificate alone does not show the embodiment matched the data.
- When an STC holder no longer exists, recovering the package can require reconstructing the approval basis rather than requesting a copy.
- Applicability is checked against the specific airframe serial, since an STC can be valid for a model yet not cover the exact configuration recorded.
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. Completion and use of FAA Form 8130-3, Authorized Release Certificate, for new and used parts.
European Union / EASA. EASA design and production certification, STCs, ETSO authorizations, and EASA Form 1 release.
Frequently asked questions
Is a filed STC certificate enough on its own?
No. The certificate shows the modification was approved in principle. Without the approved data and the installation evidence, the file does not show the embodiment matched the data, so the entry is treated as unsupported until the package is complete.
What happens when the STC holder no longer exists?
Recovery shifts from requesting a copy to reconstructing the approval basis. We document what is held, flag the entry as unsupported, and map the path to substantiate or escalate it rather than assuming the modification is covered.
Relevant glossary terms
Related pages
Where this fits
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