Mid-lease audits
AD compliance status review for MRO teams in a mid-lease audit
MRO teams get pulled into mid-lease audits because they hold the accomplishment evidence behind the operator's AD status list. This review compares each AD line against applicability notes, method-of-compliance records, and the signed work that closed it, catching entries that assert compliance without support. It is scheduled around the lessor's mid-lease visit, well before those entries harden into redelivery findings. The MRO's quality team receives a line-by-line register showing which statuses stand on evidence and which need documents pulled from the work-order archive.
When this review is needed
- A lessor's mid-lease audit is scheduled and the operator has asked its MRO to substantiate the AD work it performed.
- The AD status list asserts compliance for tasks accomplished across several check events and the underlying work orders live in the MRO's archive.
- An AMOC was used for one or more directives and the approval letters need to be produced alongside the accomplishment records.
- Recurring AD inspections are tracked in two systems and the audit will compare them.
The problem
The AD status list travels with the aircraft, but the proof lives in the MRO's work-order archive: task cards with the method of compliance, sign-offs by authorized staff, and the references tying the work to the directive's paragraphs. Mid-lease auditors pick AD lines and ask for that chain on the spot. Pulling it together during the audit, from an archive indexed by work order rather than by AD number, is slow enough to turn routine questions into written findings.
What gets reviewed
- Sampled AD status lines traced from the status list to the accomplishment record in the MRO's archive
- Applicability determinations reviewed for directives marked not applicable
- Method-of-compliance references checked against the directive's own terms, including revision and paragraph
- AMOC-based compliance matched to the approval letter and its conditions
- Recurring inspections verified for interval tracking and the next-due calculation
- Superseded directives checked for correct disposition of the predecessor's requirements
Scope this review
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What gets validated
- Each sampled compliance entry cites a work order the archive can actually produce, with the AD number on the signed record
- Not-applicable determinations state the reason in terms of the directive's applicability clause, by serial, configuration, or modification status
- The method of compliance recorded matches a method the directive or an AMOC permits
- Recurring AD intervals in the status list agree with the accomplishment dates and the directive's repeat requirement
- Terminating action claimed for any directive is supported by the modification record that achieves it
Evidence normally required
- The AD status list as issued to the auditor
- Work orders, task cards, and sign-off records for the sampled directives
- AMOC approvals and any authority correspondence on compliance methods
- Modification and SB accomplishment records supporting terminating action or applicability calls
Common discrepancies
- Compliance entries citing a check event where the AD task was raised and then deferred to a later input
- Not-applicable calls justified by configuration without the record showing the configuration
- AMOC compliance recorded without the letter, or with a letter whose conditions were not carried into the recurring tracking
- Recurring inspections tracked from the wrong anchor date after a status-list migration
What is at stake
An AD entry that cannot be evidenced during the audit gets written up as unsupported, and unsupported AD status is the finding lessors escalate fastest, since it touches the airworthiness baseline of the asset. Findings left open compound at redelivery, where the same lines get retested with less time and higher stakes, and where the MRO's relationship with the operator absorbs the friction.
How the work runs
Profile the status list
Classify AD lines by risk: recurring items, AMOCs, not-applicable calls, and terminating actions.
Assemble the chains
Pull the accomplishment evidence for the high-risk lines and index it for immediate retrieval.
Repair before the visit
Correct fixable entries and document explanations for the rest, with the operator's records team.
Support the audit
Answer sampling requests from the prepared register and log anything new the auditor raises.
What the buyer receives
- A substantiation register showing each sampled AD line with its evidence chain, complete or broken
- Retrieval-ready archive references so audit-day requests can be answered in minutes
- A pre-audit fix list for entries the MRO and operator can correct before the visit
Who uses the output
- MRO quality leadership fielding the auditor's sampling requests
- Operator continuing-airworthiness staff who own the status list itself
- MRO program managers protecting the customer relationship through the audit
How the work fits into the transaction or program
For an MRO, the mid-lease audit is a test of archive discipline as much as compliance. This review front-loads the retrieval work: the sampled chains are assembled before the auditor arrives, and the broken ones get fixed or explained on the MRO's schedule instead of the audit's. The same register shortens the next event, since redelivery teams sample many of the same lines.
Start with a single asset
Confirm release certificates and component traceability are complete.
Jurisdiction-specific considerations
FAA directives under 14 CFR Part 39 and EASA ADs are separate obligations, and an aircraft with mixed-regime history can carry parallel status lists. Compliance shown to one authority's directive does not close the other's, even where the technical content overlaps, so the review keeps the two populations distinct in the register.
Regulatory limits
The review verifies that recorded AD status is supported by retrievable evidence. It does not determine applicability where the record is silent, does not approve methods of compliance or AMOCs, and does not issue any airworthiness finding; those remain with the operator, certifying staff, and the authorities.
What this review does not cover
Specific to this review
- Auditors sample AD status against the directive text, so an entry can match the operator's system perfectly and still fail against paragraph-level requirements.
- Archive indexing is the usual bottleneck: work orders filed by check event answer AD questions slowly, and audit findings often reflect retrieval speed rather than actual non-compliance.
- Deferred AD tasks are a classic trap; the status list shows the raising event as the compliance event, and the actual accomplishment sits in a later work order.
- A mid-lease audit typically samples between a handful and a few dozen AD lines; preparing the historically weak categories, recurring inspections and not-applicable calls, covers most of the exposure.
Sources
U.S. Government (eCFR). The legal basis for issuing and enforcing Airworthiness Directives on U.S.-registered products.
U.S. Government (eCFR). Records an owner or operator must keep, including total time in service, current status of life-limited parts, and AD compliance.
European Union / EASA. Continuing airworthiness, maintenance records, CAMO responsibilities, and the airworthiness review process in the EASA system.
Frequently asked questions
The operator owns the AD status list. Why is the MRO doing this work?
The list is the operator's, and the evidence behind most entries is the MRO's. Auditors follow the chain to whoever holds the signed record, so the MRO's archive determines whether the operator's status survives sampling.
Relevant glossary terms
Related pages
Where this fits
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