APU status & history
Auxiliary power unit records review
An APU records review reconciles the auxiliary power unit's serial-number trace, its accumulated hours and cycles, its shop-visit and life-limited-part evidence, and the directives and bulletins that apply to it, against the APU status the records claim. It is used by lessors, airlines, and acquisition teams when the APU carries a defined return condition or affects dispatch and value. It reviews the APU logbook, shop-visit reports, the installed-serial trace, and the APU AD and bulletin status. You receive a reconciled APU status with a serial and life trace and a list of trace, shop, or compliance discrepancies.
When this review is needed
- A return condition sets an APU standard in hours, cycles, or time to next shop visit that has to be confirmed against the records.
- The installed APU has changed during the lease and the serial trace and release evidence need verifying.
- An APU is a removable, serial-tracked asset whose history travels separately from the airframe and has to be reconciled.
- APU directives or bulletins affect dispatch or value and their status has not been checked against accomplishment evidence.
The problem
The APU is a serial-tracked unit that is removed, swapped, and shop-visited on its own cycle, so its records often travel separately from the airframe and reconcile poorly. A status list can show APU hours, cycles, and a shop-visit position while the installed serial does not match the logbook, an APU LLP change at a shop visit never posted, or an APU-specific AD sits open behind a status that reads compliant. The APU is small relative to the engines, so its records are the ones most often left thin.
What gets reviewed
- The installed APU serial number traced to the logbook and installation records
- Accumulated hours and cycles reconciled across removals and reinstallations
- Shop-visit reports, workscope, and release evidence for the APU
- APU life-limited-part changes reconciled into the APU status
- APU-specific Airworthiness Directives and their accomplishment evidence
- APU service bulletins and modification status by effectivity
- The APU status list reconciled against the logbook and shop records
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
- The installed APU serial number matches the logbook and installation records
- Accumulated hours and cycles reconcile across every removal and reinstallation
- Each APU shop visit carries workscope and a release covering the work performed
- APU LLP changes at a shop visit are carried into the APU life status
- APU-specific ADs show the required method of compliance with accomplishment evidence
- APU bulletin and modification status reflects the actual installed configuration
- The APU status list reconciles with the logbook and shop records behind it
Evidence normally required
- APU logbook and installation and removal records
- APU shop-visit reports and workscope packages
- APU status list showing hours, cycles, and shop-visit position
- Release certificates for the APU and its life-limited parts
- APU AD and service-bulletin status with accomplishment evidence
Common discrepancies
- An installed APU serial number that does not match the logbook in the records
- Accumulated hours or cycles that do not reconcile across a removal and reinstallation
- An APU LLP change at a shop visit that never posted into the APU status
- An APU-specific AD left open behind a status that reads compliant
- A shop-visit release that does not cover the workscope performed
- An APU status list that disagrees with the logbook and shop records
What is at stake
An APU that fails its return standard, runs on an unsupported serial trace, or carries an open directive can hold up a redelivery, force an unplanned shop visit, or reduce what the asset trades at. Because the APU drives dispatch capability, a compliance gap on it is not only a value question but an operational one.
Move from findings to resolution
Move from findings to a documented resolution path.
How the work runs
Confirm the serial trace
Match the installed APU serial to the logbook and installation records and reconcile hours and cycles across removals.
Reconcile shop and LLP
Tie each APU shop visit and LLP change to its workscope and release and carry the changes into the APU status.
Rebuild compliance
Establish the APU-specific AD and bulletin status against accomplishment evidence and the installed configuration.
Report and route
Deliver the reconciled APU status and trace, list the discrepancies, and identify the APU record needed to close each.
What the buyer receives
- A reconciled APU status with serial trace, hours, cycles, and shop-visit position
- A serial and life trace across removals and reinstallations
- A list of trace, shop-visit, LLP, and compliance discrepancies
- A closure path for each gap with the supporting APU record identified
Who uses the output
- Continuing-airworthiness teams confirming APU compliance and dispatch capability
- Asset and acquisition teams pricing APU condition and exposure into a deal or return
- Records teams assembling the APU package for a transaction or redelivery
How the work fits into the transaction or program
The review treats the APU as the removable, serial-tracked asset it is, reconciling its separate history into the aircraft status. It pairs with the engine shop-visit and AD compliance reviews so the whole powerplant and auxiliary-power picture is supported.
Aircraft-specific considerations
APU models differ in LLP populations, shop-visit drivers, and how hours and cycles are counted against airframe utilization, so the APU is reviewed against its own model standard rather than a generic powerplant assumption. Whether the APU is on a separate maintenance or warranty arrangement also changes which records exist.
Jurisdiction-specific considerations
The APU carries its own directives and bulletins as a separate type-certificated article, so its AD status is rebuilt against the receiving authority on a registry change, and an APU released on one authority's form is checked for whether the receiving authority recognizes it.
Regulatory limits
The review confirms that the APU records, serial trace, life figures, and compliance status are complete, consistent, and supported. It does not test or inspect the APU, certify its condition, make an airworthiness determination, or guarantee an authority's acceptance.
What this review does not cover
- Physical inspection, run, or test of the APU
- Overhaul, repair, or certification of the APU or its parts
- Any airworthiness determination on APU status
Specific to this review
- The APU is a separately type-certificated, serial-tracked article whose records are removed, swapped, and shop-visited on their own cycle, so its history frequently travels apart from the airframe and reconciles poorly.
- Because the APU is small relative to the engines, its records are the ones most often left thin, while the directives that apply to it can still be dispatch-limiting.
- An installed-serial mismatch between the unit and the logbook is a common APU finding because units are interchanged more readily than engines.
- The APU carries its own AD and bulletin set distinct from the airframe and engines, so its compliance status is reconstructed as a separate trace rather than assumed from the aircraft status.
Sources
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.
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). The legal basis for issuing and enforcing Airworthiness Directives on U.S.-registered products.
Federal Aviation Administration. Completion and use of FAA Form 8130-3, Authorized Release Certificate, for new and used parts.
European Union / EASA. Continuing airworthiness, maintenance records, CAMO responsibilities, and the airworthiness review process in the EASA system.
Frequently asked questions
Why review the APU separately from the rest of the aircraft?
The APU is a separately type-certificated, serial-tracked unit that is removed and shop-visited on its own cycle, with its own directives and life-limited parts. Its records often travel apart from the airframe, so reconciling them as a distinct trace catches gaps the aircraft-level status hides.
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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