The Logbooks Tell All — Or Do They?

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Before buying any used aircraft, a thorough review of its maintenance records is essential. Some logbooks provide only the sketchiest details of an aircraft's service history, while others read more like War & Peace. A professional aircraft appraiser explains what you can tell from this...and what to do if any of the logbooks are missing.

Part of my job as an aircraft appraiser is to research the logbooks of each aircraft I inspect. It's amazing how much, or how little, you can tell about a particular airplane by what's in the maintenance logs. Some airplane records detail every nut and bolt that has ever been tightened, while others tell little or nothing about the maintenance that has been done over the years.

Should the lack of information in an aircraft's logbooks make a potential buyer suspicious that perhaps it has not received the care that is required to keep it in a safe and airworthy condition? Before I answer that question lets discuss what should or should not be in a set of logbooks when you look at them.

What must be logged? Not much!

InspectionEach light aircraft used for non-commercial civil purposes must be inspected annually unless it is on an alternative approved inspection program. Some manufacturers offer FAA-approved "progressive" inspection programs, usually tied to the number of hours an airplane flies. Such programs generally make sense only for aircraft that fly at least several hundred hours a year, and consist of a series of phased inspections to be performed usually in increments of 25, 50, or 100 hours.

When you look through a set of logbooks, you should see an annual inspection signoff for each year (or an entry for each phase inspection if the airplane is on a progressive inspection program). The problem with such entries is that many mechanics don't take the time to include a summary of the work that was completed. They will stamp the next page in the airframe or engine log with an entry saying that they have completed the annual or phase inspection, sign it, but offer little detail about what preventative or corrective maintenance was done.

There's nothing illegal about such de-minimus logbook entries, by the way. The FARs don't say anything about how long-winded an A&P must be when logging his work.

Sometimes there will be an accompanying entry that refers the reader to a work order number that is on file at the shop that did the work. But those records are not always easily located, especially if the shop has gone out of business or enough time has passed that the records have been relegated to the company's "archives." FAA-approved repair stations are required to retain such records for only two years, and other shops don't even have that requirement.

Telling the full story

Other mechanics write down every little detail of the work they did on the aircraft. Though it takes time to read through these entries, you can often get a good feel for how the aircraft has been maintained. The entries themselves can tell an interesting story, though most pilots looking to buy an airplane don't understand the implications of everything that is written down, and often skip over much of the detail. They figure that because there is a lot of detail in the logbooks, the airplane must have been well cared for. That's sometimes true, but not always.

The devil is often in the details. Recently I was looking through the books of a Dakota that had come back to the U.S. from Canada. In a 1983 entry there was a one liner. It simply said, "repairs made to aircraft." After a lengthy research period it turned out that the airplane had been severely damaged in a landing accident. The Canadian equivalent of the FAA Form 337 (Major Repair or Alteration) had been removed from the aircraft maintenance records, and anyone who did not take the time to study the books carefully would have missed the reference to the damage altogether.

Logbooks that have more detail in them can give a buyer a clue as to how thorough the maintenance on the aircraft has been. But the lack of detail does not necessarily mean the aircraft was neglected. Some FAA-certified repair stations that are known for their thoroughness put little detail in the books. They prefer to keep the original inspection forms in their files and don't take the time (for which they would have to charge the customer) to transcribe the detail in the logbooks.

Unfortunately, some mechanics who want to cover up a cursory annual inspection make the same kind of minimal logbook entry. That makes it tough on a prospective buyer of an airplane with skimpy logbook entries, who has no recourse but to do a very thorough pre-purchase inspection to make up for the lack of detailed maintenance records.

The case of the missing logbook

Every so often someone will hand me only the "current" logbooks for the airplane I am to look at when I have specifically requested that all logs and records be present. Of course, it is impossible to get a good feel for the airplane without having all the logbooks, and sometimes it turns out that part or all of the records have been lost.

Do lost logbooks impact the value of an airplane? Yes, but not necessarily to the extent you might expect.

Several years ago I received a call from a gentleman who said that his local FBO had lost one of his airframe logbooks during the recently completed annual inspection of his Piper Cherokee. The FBO agreed to pay for an objective appraisal so that the amount of diminished value could be determined. I looked at the airplane and examined the remaining logbooks. The owner and the mechanic both knew that the aircraft had never been damaged, and the engine log verified the airframe time for the few years that had been lost. I determined that the diminished value for the loss of one airframe log came to $1,700.

The aircraft owner was perplexed because someone had told him that a missing logbook could reduce the value of his aircraft by 50%, and he'd asked for my appraisal in the expectation that he'd get a check for half the value of his airplane. But in this case, there were other ways of arriving at most of the information contained in the lost logbook, so the impact on value was minor. As it turned out, the whole problem became moot a year later when the mechanic found the missing logbook in the folder of another airplane he had worked on at the same time.

Lost or missing logbooks result in a much higher diminished value claim when what is left does not provide sufficient information to verify the airframe time, engine time since major overhaul, or the status of AD compliance and other important components that are subject to time or life limitations. If those times can be verified independently by going back to the shop that overhauled the engine, or by recreating events from the records kept by a shop that did the majority of the maintenance on the aircraft, the loss is not as great.

Old Cessna 172If there are no logbooks, as there might be in the case of an aircraft that is repossessed or seized by a government agency, there is a considerable loss of value. I remember an old Cessna 172 that was seized by the IRS due to the owner's failure to pay his income taxes. The agency auctioned off the airplane amidst rumors that the former owner was offering to sell the logbooks to the new owner. In another case an East Coast bank repossessed a Cessna 402 many years ago only to find that most of the remote mounted avionics were missing. The former owner's pilot told the bank that he would sell them back the equipment for the amount of money he was owed for his services. Eventually some kind of agreement was reached and the gear was returned to the bank. So, if you are interested in a repossessed or seized airplane be sure you know the status of all the equipment and records of the airplane before you bid on it.

Damage history and FAA 337 forms

One problem with our system of record keeping is that some mechanics feel they do not need to make a logbook entry when an FAA Form 337 has been filled out and added to the aircraft's paperwork. What they don't realize (or perhaps some do) is that it is very easy to remove that piece of paper from the aircraft records. If that is done, as was in the case of the Canadian Dakota, the aircraft can be represented by the seller as undamaged while in fact it may have a considerable damage history. Some repairs are done so well that it is difficult to tell the airplane has been damaged during a pre-purchase inspection, while other repairs are done so poorly they are obvious from half way across the hangar.

If the repairs were so well done as to be difficult to detect, why should it matter? Well, perhaps it shouldn't, but it does! The problem with damaged airplanes is not the quality of the repair work (unless it is poor), it's the psychology of the market. Some buyers simply won't buy a damaged airplane at all, while others will insist on a substantial price adjustment. It's just a fact of life.

Sellers know this, and all too often they remove the FAA 337 forms from the aircraft records in an effort to cover up damage history. However, copies of each 337 are kept on file at the FAA Aircraft Registry in Oklahoma City and are not difficult to obtain. You may order them from the firm that does your title search, or you can call the Aircraft Registry (405-954-3116) and order them yourself.

Logging engine overhauls

Lycoming engineEngine overhaul shops often issue a new logbook for an overhauled engine, and the lack of old logs confuses some purchasers. Several years ago I had a Cherokee 160 for sale, and its engine had been overhauled by a very well-known shop. That shop retained the old logbooks and issued a new one that carried forward the engine's total time with the first entry showing the current engine time as 0 hours since major overhaul.

Two foreign pilots who were living in the United States came to look at the airplane. They had with them a book on how to buy airplanes that insisted that all aircraft and engine logs had to be present. I tried to explain to them that all that was required of the engine shop was that they carry forward the engine's total time in the new book, but they kept referring to the paragraph in the book they had with them. They thought I was trying to cover something up by not showing them the rest of the logbooks, and finally they went away thinking I was some kind of shyster salesman.

The logbook entry for a major engine overhaul should include a list of the parts that were replaced, and there should be yellow tags for various engine components that indicate that they have been inspected and certified. A handwritten entry that does not detail the complete overhaul, but merely states that it was done in accordance with the manufacturer's overhaul manual, might well mean that the engine received an el-cheapo service-limits overhaul that has little chance of making it through another TBO period.

Logbooks and other maintenance records are much more important than most people who are looking to buy airplanes realize. The entries in those logbooks constitute a history of where the aircraft has been and how it has been maintained. Sometimes they are not clear and easy to read, but as a prospective buyer you must try your best to decipher them (possibly with the help of a trusted mechanic or appraiser) in order to assure yourself that you're paying a fair price for the aircraft and that there won't be any nasty surprises down the road.