Deferred maintenance
Boeing 747 family deferred-maintenance records review
This review reads the deferred-maintenance carried on a Boeing 747 asset and tests whether each open item still has a valid basis, a live time limit, and a clean path to closure. It is run by or for the party buying, returning, or holding the tail, ahead of the moment when someone counts the deferrals against a contract. Every entry on the deferred-maintenance log is checked against its MEL or CDL reference, its raise date, and any clearing entry that closed it. You receive an exception list keyed to the log, a source map behind each open item, and a closure plan for the deferrals that will not survive scrutiny as written.
When this review is needed
- A 747 is being returned and the lease terms cap how many deferrals can remain open at handover.
- A buyer wants the carried-forward defect list read before it prices the tail.
- A deferral has rolled forward through several checks and no one has confirmed its time limit is still live.
- The operator is moving the aircraft to a new program and needs the open deferrals reconciled first.
The problem
On a widebody that has flown for decades, the deferred-maintenance log tends to accumulate items that were raised correctly, then rolled forward until their origin blurred. A deferral cited to an MEL item that was later revised, or one whose repair interval quietly expired, sits on the tail looking routine while it is actually a live exposure. The person reading the log at return or sale inherits every one of those items, and the raise dates and clearing entries that would settle them are scattered across check packages that predate the current records team.
What gets reviewed
- Every open deferral on the log matched to the MEL or CDL item it was raised against
- Raise dates and category time limits checked against the current calendar and utilization
- Clearing entries reconciled to the deferrals they claim to close
- Rolled-forward items traced back through prior check packages to their origin
- Deferrals cited to an MEL revision that has since changed flagged for re-basing
- The count of genuinely open items reconciled against the log total
Scope this review
Tell us the asset, the event, and the evidence in scope, and we will outline a focused first engagement.
Send a representative, redacted record set and we will scope the review.
What gets validated
- Each open deferral cites an MEL or CDL reference that was valid on the raise date and remains applicable
- Category time limits are recalculated against current time and cycles, not trusted from the last check
- A deferral marked cleared has a corrective-action entry that names the same defect and tail
- A deferral rolled through multiple checks traces to a single original raise, not a chain that lost its start
- The open-item total on the log agrees with the count of individually supported deferrals
Evidence normally required
- The current deferred-maintenance log or deferral register for the tail
- The MEL and CDL revisions in force across the period the deferrals were raised
- Check packages and work orders that raised, rolled, or cleared the items
- Current time and cycle status to test category time limits
- Any redelivery condition or purchase term that limits open deferrals
Common discrepancies
- A deferral rolled forward past the category time limit its MEL item allowed
- An open item cited to an MEL revision that no longer contains that relief
- A clearing entry that closes the log line but names a different defect than the one raised
- A deferral whose original raise package cannot be located in the file
What is at stake
Deferrals that cannot be tied to a valid basis and a live limit turn into open findings at exactly the wrong moment, when a redelivery clock is running or a buyer is deciding whether to retrade. A deferral whose time limit has lapsed is not a paperwork nuisance; it is an item the receiving party can insist be cleared before acceptance, on their schedule and at the current holder's cost.
Move from findings to resolution
Move from findings to a documented resolution path.
How the work runs
Pull the open log
Assemble the current deferred-maintenance register and separate genuinely open items from those already cleared.
Re-base each item
Match every open deferral to the MEL or CDL reference valid on its raise date and confirm the relief still applies.
Test the limits
Recalculate category time limits against current time and cycles and trace rolled-forward items to their origin.
Plan the closures
List the deferrals that need clearing, re-basing, or a documented fallback before handover.
What the buyer receives
- An exception list keyed to the deferred-maintenance log, flagging the items that will not survive review
- A source map linking each open deferral to its raise, roll-forward, and clearing evidence
- A closure plan for the deferrals that need re-basing, clearing, or documented fallback
Who uses the output
- Asset managers deciding whether the carried deferrals affect the price or the return condition
- Records teams clearing open items before a redelivery or program transfer
- Continuing-airworthiness leads confirming that no lapsed-limit deferral is flying the tail
How the work fits into the transaction or program
The review sits between the day-to-day deferral tracking the operator runs and the acceptance test a buyer or lessor applies at handover. It converts a rolling log into a settled position, so the closure plan it produces is worked while the raising records are still reachable rather than after the tail has changed hands.
Aircraft-specific considerations
A 747 that has passed through several operators and a freighter or cabin reconfiguration carries deferrals raised under different MEL and CDL revisions, so an item's basis has to be read against the document in force on its raise date rather than the current one. Heavy-check packages on this widebody are large enough that a deferral can be cleared in one visit and silently re-raised in the next, which is why the log is traced item by item rather than trusted at its total.
Jurisdiction-specific considerations
An FAA-operated 747 moving toward an EASA register brings its deferral history under a continuing-airworthiness system that treats MEL relief and repair intervals on its own terms, so the review notes which open items will need re-basing or fresh evidence before the receiving system accepts them.
Regulatory limits
The review reads the deferred-maintenance record and tests each item against its stated basis and limit. It does not clear a deferral, perform the deferred work, or make an airworthiness determination on the tail.
What this review does not cover
- Performing or signing off the maintenance behind any open deferral
- Revising the MEL, CDL, or the operator's deferral procedures
- Any airworthiness determination on the aircraft
Specific to this review
- The most common false-clean on a long-lived 747 log is a deferral rolled forward until its category time limit lapsed without anyone recalculating it.
- A deferral's basis has to be read against the MEL or CDL revision in force on its raise date, because relief that existed then may have been withdrawn since.
- Clearing entries on a large widebody check package frequently name a different work item than the deferral they close, so each one is matched to the original defect rather than trusted by proximity.
Sources
U.S. Government (eCFR). Maintenance recordkeeping content and approval-for-return-to-service requirements, including 43.9, 43.11, and Appendix B.
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.
International Civil Aviation Organization. International standards for aircraft operation, including maintenance program and recordkeeping expectations.
Frequently asked questions
Why not just accept the deferral count the operator's log already shows?
Because the count on a long-lived 747 log hides items whose basis has changed or whose time limit has lapsed. The number looks manageable until each line is tested against the MEL revision it was raised under and the current utilization, which is exactly where the open exposure appears.
Relevant glossary terms
Related pages
Where this fits
Talk to an engineer who has done this work
We will walk through your current state, the records or evidence involved, and a scoped first engagement.
Talk through the aircraft, records, evidence, deadline, and next useful step.