AML STC
AML STC expansion support: adding models to an approved list
AML STC expansion support helps an equipment supplier or modifier add aircraft models to an approved model list STC. It is used by holders extending an existing AML STC to new makes, models, or configurations. It reviews the eligibility substantiation for each candidate model, the delta against the originally approved installation, and the data that has to change when the airframe, systems, or environment differ. You receive a per-model eligibility assessment and a structured set of the delta substantiation an expansion submission needs.
When this review is needed
- An approved model list is being extended to new makes or models and each addition needs eligibility substantiated.
- A candidate model differs from the originally approved airframe in ways that touch the installation envelope.
- The systems or electrical environment on a new model differs enough that the original substantiation no longer covers it.
- A holder wants the delta data checked before committing each model to a submittal.
The problem
An approved model list grows one addition at a time, and each candidate gets compared against an installation that was substantiated for a different airframe. The interface, the electrical environment, and the structural attachment shift from model to model, and the original substantiation quietly stops covering the delta. When a model is added on the assumption that it behaves like the first one, the gaps do not show up until someone asks what data backs the eligibility.
What gets reviewed
- Per-model eligibility against the originally approved installation and its limitations
- The delta in airframe interface, structural attachment, and installation envelope for each candidate
- The electrical and environmental differences that affect the original qualification basis
- Systems integration differences where the new model carries different equipment
- Instructions for continued airworthiness coverage for the added configurations
- Traceability from the original approval to the substantiation each addition rests on
Scope this review
Tell us the asset, the event, and the evidence in scope, and we will outline a focused first engagement.
Identify what is missing against the means of compliance.
What gets validated
- Each candidate model has substantiation that addresses where it differs from the approved installation
- Structural attachment and interface deltas are covered rather than assumed equivalent
- Environmental qualification still bounds the conditions the new model imposes
- Systems integration data reflects the equipment configuration on each added model
- Instructions for continued airworthiness cover every configuration the expansion adds
- The eligibility claim for each model traces to substantiating data, not to the original model alone
Evidence normally required
- The current approved model list and the original STC substantiation
- The candidate models and their airframe and systems configurations
- Delta analyses and any model-specific test data assembled so far
- The original instructions for continued airworthiness and any drafted additions
- Field reports or open questions tied to models already on the list
Common discrepancies
- Models added on assumed equivalence with no delta substantiation behind the eligibility
- Structural or interface differences the expansion package never addressed
- Environmental conditions on a new model that exceed the original qualification envelope
- Instructions for continued airworthiness that do not cover the added configurations
- An eligibility list broader than the substantiation actually supports
What is at stake
An expansion submission that asserts eligibility without the delta substantiation behind it draws questions on every model the data does not cover. The additions stall, the field demand that drove the expansion goes unmet, and the holder carries an approved list that promises coverage the package cannot defend.
How the work runs
Anchor on the original
Establish what the original STC actually substantiated and the limitations its approval carries.
Size the delta
For each candidate model, identify the airframe, systems, and environmental differences against that baseline.
Test the eligibility
Check whether the existing substantiation covers each delta or whether model-specific data is required.
Order the additions
Deliver a per-model eligibility assessment and a closure plan ranked by demand and data risk.
What the buyer receives
- A per-model eligibility assessment tied to the substantiation behind each addition
- A delta substantiation index showing where each model departs from the approved installation
- A list of models whose data is missing, thin, or out of envelope
- A prioritized closure plan ordered by expansion demand and data risk
Who uses the output
- Certification leads preparing the model-list expansion
- Engineering teams closing the delta substantiation per model
- Program management sequencing additions against field demand
How the work fits into the transaction or program
The work supports the holder's own AML STC expansion. It separates the models the existing substantiation already covers from the ones that need delta data, so each addition rests on evidence rather than on resemblance to the first model.
Start with a single asset
Reduce finding cycles by checking the package first.
Regulatory limits
Endeavor Elements supports the applicant's expansion data. It does not approve a model for the list, issue or amend the STC, or determine that a model is eligible. The applicant and the certifying authority keep their roles.
What this review does not cover
- Approving, issuing, or amending the AML STC
- Determining model eligibility on the authority's behalf
- Performing the model-specific qualification testing
Specific to this review
- An approved model list STC carries a single STC across many aircraft models, so adding a model is a delta exercise against the originally approved installation rather than a fresh program.
- Eligibility on an AML rests on substantiating that each model stays within the approved installation's assumptions, which is why assumed equivalence is the most frequent gap.
- Environmental qualification is model-sensitive, because vibration, temperature, and installation location can move enough between airframes to push a new model outside the original DO-160 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. STC application process, certification basis, and continued airworthiness obligations of an STC holder.
European Union / EASA. EASA design and production certification, STCs, ETSO authorizations, and EASA Form 1 release.
RTCA. Environmental qualification test categories and procedures referenced by TSO and equipment qualification.
Frequently asked questions
What makes an AML STC expansion different from a new STC?
An approved model list STC already exists; the expansion adds aircraft models to it. The work is a delta exercise that substantiates each new model against the originally approved installation, rather than building a program from a clean basis.
Can a model be added if it sits outside the original qualification envelope?
Not on the original substantiation alone. Where a model's environment or interface exceeds the approved installation's assumptions, the expansion needs model-specific data. The review flags exactly which models that applies to.
Relevant glossary terms
Related pages
Where this fits
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We will walk through your current state, the records or evidence involved, and a scoped first engagement.
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