Maintenance Tip: Maintenance Records – Logbooks

Maintenance Tip: Maintenance Records – Logbooks

Maintenance Tip: Maintenance Records – Logbooks

In recent months I have been swamped with buyers considering King Airs for purchase. They have asked me to scrutinize the logbooks to figure out where the aircraft is maintenance-wise. In doing so, I encountered some really frustrating situations that could have been avoided if the log entries were clear, concise and complete. Over the course of my career I’ve slogged through a lot of logbooks, and early on formed some strong opinions on what makes a good log entry. Is this a topic of interest to the average King Air owner? Maybe not, but bear with me.

Crucial to Value

Accurate logbooks are crucial to the value of any aircraft. When an aircraft changes hands, the logbooks come under intense investigation. What about your log books? When it’s your time to sell, how will they hold up?

Too Vague

Here’s a real example of a very poor log entry: “Complied with all lube items currently due.”

This blew my mind! King Airs have lube item requirements due every 12 months plus a host of others due at 200-, 400-, 600-, 800-, and 1200-hour intervals. Each is a special inspection unto itself; they’re all different. Some contain service items (replace a gasket, service a filter) in addition to specified lubrication tasks. There is no overlap or duplication. Unless the shop can produce detailed write-ups and lube item checklists from their work order that prove exactly what was done, everything must be done at the seller’s expense.

Too Much Information

Another real example: “Pilot reported aircraft’s RH engine would not ignite. Troubleshooting carried out, igniter box Unison p/n 10-381550-1 s/n xxx found with very weak spark. New exciter Unison p/n 10-381550-4 s/n xxx (A.P.I. SO-xxx-xxx) installed. Aircraft ground run and operation of ignition system checked OK.”

This is the discrepancy and disposition write-up. It has no place in a logbook. It belongs on the work order. And what’s the sales order number doing in there? If a warranty issue cropped up down the road, you’d call the shop, they’d research the work order kept on file, and they’d take it from there. Keep clutter out of the logs.

My version of what the above entry should be: “Installed igniter box in new condition, R/H position, p/n 10-381550-4 s/n xxx; removed p/n 10-381550-1, s/n xxx.”

I put detailed squawk and disposition write-ups in my client invoices. I want the customer to see what it took to sort out and resolve their squawk. It’s important to the customer, but superfluous in the log entry.

Hobbs is not Enough

I see way too many airframe log entries with nothing but the Hobbs reading at the top. That doesn’t cut it. Hobbs meters fail and when replaced, they start over at 0.0 hours. The only acceptable proof of compliance with any hour-based requirement is by linking it to Aircraft Total Time (ACTT).

Recently, on a job, I struggled to find compliance for the lube items, the instrument air filter replacement (600 hours), and the power lever pin inspection (1,200 hours). I was faced with a long string of Hobbs-only entries in the airframe records. Was this the original Hobbs meter? I had no way of knowing. I rummaged through the records, looking for an entry that had Hobbs and ACTT. Finally, after going back quite a few years, I found an entry with both numbers. Eureka! I moved forward from there and calculated the ACTT for each entry based on elapsed Hobbs. In the end, I found proof of compliance for all those hour-based items. That seller lucked out. (And, by the way, it was not the original Hobbs.)

Engine Logs Need Airframe Time

All too often I find engine log entries with engine times and cycles, but no ACTT. This is my biggest pet peeve in log entries. Even the FARs, which give precious few specifics for log entry content, require that every log entry contain the ACTT (Ref. FAR 43.11). If you’ve only owned airplanes with original engines (which means the Engine Total Time and ACTT are the same number) consider yourself lucky. Engines come off one airplane and go onto another all the time. Great care is usually taken with the log entries at installation and removal. All the airframe information (registration, serial number in addition to ACTT) is put on the engine entries. The problem comes after installation. Somebody does an engine log and only puts in Engine TSO (Time Since Overhaul), and then everyone afterward does the same. I’ve seen this go on for 15 years. Then I come along, trying to calculate the time left on the starter generator, for example, and I’m stymied.

Starter generators are considered an airframe item even though they are attached to the engine. Their 1,000-hour overhaul belongs in the airframe book, but this is an area of great confusion. Many mechanics and shops don’t understand this. They think if it’s attached to the engine, then it belongs in the engine book. So, in my research, I bop back and forth between the engine and airframe books. In this example, I found an entry for the starter generator in the engine book with Engine TSO only. The engine wasn’t original to the airframe. Ultimately, I had to go back to the log entry when that engine was installed on that airframe to set the record straight on the starter generator. If the engine logs referenced the ACTT, I would have had a much easier time.

I heard a horror story about a Hot Section Inspection (HSI) performed 800 hours earlier than necessary because of a simple mistake in the logbooks. The engines were mismatched, and this was the “younger” of the two, but somewhere along the line a figure got transposed. Again, the engine logs only showed TSO with no reference to Airframe Total Time – an expensive omission. A cross reference to ACTT could have brought the problem to light before the engine was torn apart for no reason. When it hits you in your wallet it gets your attention! The log entry example on the next page shows the full array of airframe data included on an engine log.


In addition to keeping my log entries very concise, I’ve always composed them in a numbered list format. The most important maintenance items like ADs, major inspections, and required items come first; bulbs, o-rings and less consequential issues come last. It makes it so much easier to find what you’re looking for when doing research. Paragraph-style entries drive me nuts, and I’m clearly not alone. I see paragraph entries where someone before me used a highlighter to pick out the salient points, separating the wheat from the chaff.

Unfortunately, the FARs don’t dictate format, but in conversations with FAA and NTSB personnel, I found a strong preference for concise log entries formatted as a numbered list.

An example of what an entry in an engine log showing all the information that should be included in any entry, including airframe information (registration, serial number, in addition to ACTT).

Bring Logbooks to Maintenance

When your King Air goes in for maintenance, bring the logbooks! Some of those Hobbs-only airframe entries are because the shop never saw the books and could not compute the ACTT.

Each time a new shop sees your King Air, they need to research what’s been done and what needs doing.
If you’ve been going to the same shop for a decade, you should still bring your books. It never fails: If you leave your logbooks at home, the shop will run across something that needs logbook research. So, bring your logs to maintenance.

If you subscribe to a maintenance tracking service, they can send their report to the new shop. Just be aware of the pitfalls. These reports are long, complicated and contain errors. The data entry clerk who loads your logbook information into their system often has no clue what they’re looking at. Mistakes can run rampant. After 45 years in this business, I found nothing replaces having my own eyes on the logbooks. Bring your books!

Parting Shots

Check all log entries for Aircraft Total Time. If it’s missing, make the shop put it in. When a shop hands you a log entry in paragraph form, IN A FONT ABOUT THIS BIG, can you get them to reorganize it as a numbered list? Probably not. But ACTT is an FAR requirement. Stand firm.

You should also get a debrief after maintenance. Each time I returned a King Air to service after a Phase or major maintenance, I did a thorough debrief with the pilot or owner/operator. I went through the entire work order, squawk by squawk, discussing every item, with the log entries on the table for reference. I wanted my customer to review their log entries before they go in the book and out of sight.

When it finally comes time to sell your King Air, brokers and prospective buyers will be crawling all over your logbooks. Hopefully they will stand up to the scrutiny. In the meantime, however, enjoy the heck out of your King Air!

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