Boeing 737NG deferred maintenance records review

When this review is needed

• A 737NG deferral log has to be shown clean before a redelivery or sale.
• An open MEL item is approaching its category time limit and its status must be confirmed.
• A deferral was cleared and the corrective action behind it needs to be in the file.
• The aircraft is inducting and the shop needs the carried deferrals proven before it starts.

The problem

Deferrals are meant to be temporary, and on a 737NG in active service the log turns over constantly as items open and close under the MEL and CDL. A deferral can sit open past the category time it was allowed, an item can be cleared on paper while the corrective action never made it into the record, and a category classification can be wrong so the item was carried longer than its MEL basis permitted. A log that looks short can still hide an expired item, and reconstructing the clearing history under a deadline is where a bad deferral gets accepted.

What gets reviewed

• Each open deferral checked for its MEL or CDL category and time limit
• Cleared deferrals traced to the corrective action that closed them
• Category classifications confirmed so each item was carried on the right basis
• Repeat deferrals of the same item identified across the log
• Deferrals approaching or past their allowable interval flagged
• Clearing entries reconciled against the task or component that resolved each item

What gets validated

• Every open deferral states an MEL or CDL category and a time limit it is within
• Each cleared deferral traces to a recorded corrective action, not a bare closed status
• The category assigned to each item matches the MEL basis it was carried under
• No deferral in the log was carried past the interval its category allowed
• Repeat deferrals of the same item are identified rather than treated as unrelated

Evidence normally required

• The deferred maintenance log, both open and cleared items
• The applicable MEL and CDL for the aircraft
• Corrective-action records for cleared deferrals
• The technical log entries that raised and carried each deferral
• Task or component records that resolved cleared items

Common discrepancies

• An open deferral carried past the category time limit its MEL basis allowed
• A cleared deferral with no corrective-action record behind the closure
• An item categorized wrongly so it was carried longer than the MEL permitted
• The same item deferred repeatedly with no record of an underlying fix

What is at stake

An expired deferral is an open condition the operator was not entitled to carry, and a buyer treats it as a finding that reopens the aircraft's dispatch history. A deferral cleared without a corrective-action record is an unproven fix, and a mis-categorized item means the MEL basis it relied on never applied. Carried into a transaction, a dirty deferral log undermines confidence in the whole dispatch record and forces the receiving operator to re-examine items it should have been able to trust.

How the work runs

What the buyer receives

• An exception list of expired, mis-categorized, and unsupported deferrals
• A source map from each deferral to its MEL or CDL basis and clearing record
• A clearing plan naming what each open or unproven item needs to close

Who uses the output

• Records teams proving the deferral log clean before a redelivery or sale
• Inducting shops confirming carried deferrals before they open the aircraft
• CAMO leads reviewing the dispatch history for repeat and expired items

How the work fits into the transaction or program

The deferral log is the near-term face of the maintenance record, and it connects to the non-routine and task-card reviews because a cleared deferral should trace to the work that closed it. A clean deferral state confirmed here lets the redelivery or induction proceed on a dispatch record the receiving side can trust.

Aircraft-specific considerations

A 737NG in high-frequency short-haul service turns its deferral log over quickly, so the volume of opened and cleared items is large and an expired item is easy to miss in the churn. Repeat deferrals of the same cabin or avionics item are common on this type and can signal an unresolved underlying fault rather than a string of unrelated events. Items deferred against the CDL for configuration reasons need their basis checked as carefully as MEL items, since a wrong classification there is just as consequential.

Jurisdiction-specific considerations

A 737NG operated under an FAA MEL and later under an EASA one will show deferrals carried under each authority's minimum equipment basis, and the review checks each item against the MEL in force when it was carried. It records which authority's MEL governed each deferral so the receiving side can read the dispatch history in context.

Regulatory limits

The review reports whether deferrals were valid and properly cleared as records. It does not clear a deferral, approve an MEL relief, make an airworthiness determination, or substitute for the operator's own dispatch and MEL administration.

What this review does not cover

• Performing the corrective action to clear an open deferral
• Physical inspection of the deferred condition
• MEL or CDL development, which sits with the operator and its authority

Specific to this review

• On a 737NG, a short-looking deferral log can still hide an expired item, so every open deferral is checked against its category time limit rather than the log's overall length.
• A repeat deferral of the same item is read as a possible unresolved fault, because the same fault cycling through the log is a pattern a single entry conceals.
• A cleared deferral without a corrective-action record is treated as unproven, since the closed status alone does not show what actually resolved the item.

Sources

Frequently asked questions

Relevant glossary terms

Related pages

Where this fits