APU records
APU logbook records review
An APU logbook review is for lessors, airlines, and acquisition teams confirming the auxiliary power unit history that sits beside the airframe and engine records. It runs ahead of a purchase, a lease return, or an APU exchange. It verifies the APU history across shop visits and overhauls, the hours and cycles or APU-hour basis, the serial-number continuity through any exchanges, and the release evidence. You receive a reconstructed APU history, a register of gaps, and the records needed to close them.
When this review is needed
- An aircraft is changing hands and the fitted APU's history has to be confirmed alongside the airframe and engines.
- An APU was exchanged on a serviceable swap and the serial-number continuity through that exchange is unconfirmed.
- Recorded APU hours and cycles, or the APU-hour basis, have not been checked against the entries that build them.
- An overhaul or hot-section visit is referenced but the supporting shop record is not in the APU file.
The problem
The APU is the component most often exchanged on a serviceable basis and the one whose records get the least attention, so its logbook tends to be the thinnest on the aircraft. Exchanges break serial-number continuity, the hour basis the APU is tracked against can be ambiguous, and overhaul records go missing between operators. The APU is small in value terms next to the engines, but a broken APU record still stops a clean redelivery.
What gets reviewed
- APU logbook history across recorded shop visits, overhauls, and exchanges
- Shop-visit, hot-section, and overhaul records reconciled with the logbook
- Recorded hours and cycles, or the APU-hour basis the unit is tracked against
- Serial-number continuity of the fitted APU through every recorded exchange
- Release evidence for the APU and for parts fitted during shop visits
- Installation and removal history tying the APU to the airframe
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 shop visit or overhaul in the logbook reconciles with a corresponding shop record
- The fitted APU serial number traces continuously through every recorded exchange
- Recorded hours and cycles, or the tracked hour basis, are consistent across logbook and status list
- Release evidence supports the APU at each change of custody and for parts fitted
- Installation and removal entries reconcile with the airframe records
- Life-limited or hard-time items on the APU carry consistent status across entries
Evidence normally required
- APU logbooks and any digital record extracts
- Shop-visit, hot-section, and overhaul records for the unit
- Current APU hours and cycle status
- Exchange and serial-number records for the fitted unit
- Authorized release certificates for the APU and parts fitted at shop visits
- Installation and removal history tying the APU to the airframe
Common discrepancies
- A serial-number break where an APU exchange is not fully documented in the logbook
- A recorded overhaul or hot-section visit with no matching shop record in the file
- Hours or the tracked hour basis disagreeing between the logbook and the status list
- Release evidence missing for the APU at a change of custody
- An installation or removal that is absent from the airframe records
- A hard-time or life-limited APU item with inconsistent status across entries
What is at stake
An APU with a broken history or unconfirmed serial continuity can hold up an otherwise complete return or transaction. The unit may need re-tracing, a replacement APU with a clean record may be demanded, and a small component then drives a disproportionate delay at handover.
Move from findings to resolution
Move from findings to a documented resolution path.
How the work runs
Build the file
Assemble the APU logbook, shop and overhaul records, and exchange history into one ordered file.
Trace the serial
Follow the fitted APU serial number through every recorded exchange and confirm release evidence at each.
Confirm the basis
Establish the tracked hour or cycle basis and reconcile the status against it.
Register and close
Record each gap and recommend the records needed to confirm the fitted unit's standing.
What the buyer receives
- A reconstructed APU history across shop visits, overhauls, and exchanges
- A register of continuity and time gaps with the record each touches
- A recommended path to close each gap or confirm the fitted unit's standing
Who uses the output
- Asset and acquisition teams confirming the fitted APU's standing
- Records teams completing the APU file for a redelivery or data room
- Continuing-airworthiness staff checking APU status supports the current configuration
How the work fits into the transaction or program
The review closes out the APU as the third major recorded asset beside the airframe and engines, so a thin APU file does not stall a return or a deal. It reconciles its installation history against the airframe records and feeds the same discrepancy register.
Aircraft-specific considerations
APU tracking bases vary by aircraft and APU type, with some units tracked on APU hours and others on a cycle or calendar basis. The review confirms which basis applies and checks the status against that basis rather than assuming a single convention across the fleet.
Jurisdiction-specific considerations
An exchanged APU may have been overhauled and released under a different authority than the airframe operates in. The review checks that the release evidence behind the fitted unit supports the configuration the receiving authority and the next operator will accept.
Regulatory limits
The review confirms that the APU history, serial continuity, and time status are consistent and traceable. It does not certify the APU, determine its remaining life, or make an airworthiness determination on the unit.
What this review does not cover
- Physical inspection, borescope, or test run of the APU
- Re-life or re-certification of the APU or its parts
- Any airworthiness determination on the unit
Specific to this review
- The APU is the component most commonly swapped on a serviceable exchange, so serial-number continuity through exchanges is the defining check on its records.
- APUs are tracked on differing bases, including APU hours, so the review first confirms the applicable basis before reconciling the status against it.
- An APU is minor in value next to the engines, yet a broken APU record is a frequent and disproportionate cause of redelivery delay.
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.
Federal Aviation Administration. Completion and use of FAA Form 8130-3, Authorized Release Certificate, for new and used parts.
European Union Aviation Safety Agency. EASA authorised release certificate for components, equivalent in function to FAA Form 8130-3.
European Union / EASA. Continuing airworthiness, maintenance records, CAMO responsibilities, and the airworthiness review process in the EASA system.
Frequently asked questions
Why does the APU need a separate review when it is low value?
Because an APU is frequently exchanged on a serviceable basis, its serial continuity and release evidence break more often than its low value suggests, and an unresolved APU record is a common cause of delay at redelivery.
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.
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