How to read aircraft logbooks before you buy

The logbooks are the aircraft’s medical record, and a buyer who reads them properly before the pre-buy inspection will know more about the airplane than most sellers do. Most buyers skim them. Here is how to read them like someone who has been burned.

What you should be handed

At minimum: the airframe log, the engine log, and the propeller log, from new. Plus the AD compliance record, all FAA Form 337s (major repair and alteration), the weight and balance with equipment list, and the current airworthiness certificate and registration. Supplemental type certificates (STCs) for anything added to the aircraft should have paperwork too.

If any of those is missing, that is your first finding. Ask why, in writing, and get the answer before you spend money on an inspection. “The last owner lost it” happens; it also lowers the value of the airplane, and you should be pricing for it.

Increasingly, sellers provide scanned logbooks up front. Take them. A serious seller or broker digitizes the logs precisely so you can do this homework before you travel.

Read in this order

1. The last annual and the last few years. Who signed it, where, and what they found. An annual that reads “inspected IAW manufacturer’s checklist, aircraft airworthy” with nothing else, year after year, tells you the inspection was a signature. Real annuals list what was found and what was fixed.
2. Engine history. Find the major overhaul entry: date, hours, who did it, and to what standard (new limits or service limits, and which parts were replaced). Then follow the cylinders: top overhauls, individual cylinder replacements, and the pattern behind them. Four cylinders replaced one at a time over three years is a story. On a turboprop the equivalent questions are hot-section inspection dates, cycles, and whether the engine is on a program; the maintenance tracking report should match the log.
3. Damage history. Search for words like “repair,” “replaced,” “straightened,” “IRAN” (inspect and repair as necessary), “gear-up,” and “prop strike.” A prop strike should be followed by an engine teardown inspection entry; if it isn’t, ask. Every major repair should have a matching 337.
4. AD compliance. The AD list should show every airworthiness directive applicable to the airframe, engine, propeller and appliances, with the method of compliance and, for recurring ADs, when the next one is due. A list that stops updating a few years ago, or that cites ADs by number with no compliance detail, deserves a hard look.
5. Alterations. Every STC and every 337 for an alteration should be traceable to an entry, a weight and balance change, and a current equipment list. Avionics that appear in the panel but not in the paperwork are a red flag for how the rest of the work was done.
6. The gaps. Lay the entries out by date. Months or years with no entries mean the aircraft sat, or the logs are incomplete. Either one matters: an airplane that sat for three years has its own corrosion and seal questions.

Red flags that end the conversation

• Missing logbooks with no credible explanation.
• A damage repair with no 337 and no shop name.
• Prop strike with no teardown inspection.
• An engine overhaul entry from a shop you can’t find or verify.
• Annual sign-offs by the same IA for twenty years with no findings ever recorded.
• Entries that have been altered, pages that don’t match, or a logbook that is suspiciously new.

None of these means the aircraft is bad. All of them mean the seller is asking you to carry risk the paperwork should have retired, and the price has to reflect that.

What the logs can’t tell you

Logbooks document what was done. They don’t document what was skipped, and they can’t show corrosion, a cracked cylinder or a worn gear bushing. That is what the pre-buy inspection is for, and the logbook review is what tells the inspecting shop where to look first.

Why this is the first thing I do

The airplane I bought had a tidy logbook that read clean. The annuals were paper. The lesson was that a clean logbook and a sound airplane are two different things, and you need the logs read by someone who knows what a bad one looks like. For sellers, listing representation includes digitizing and organizing every log so buyers can do this review before they get on a plane. For buyers, it is the first hour of any engagement. Either way, reach out and tell me what you fly, or what you’re looking for.