Reading Between the Logbook Lines

Reading Between the Logbook Lines

Reading Between the Logbook Lines

The real meaning behind the words “Maintenance,” “Inspection” and “Repair.”

Three Airworthiness Responsibilities

Maintenance is something actively done to maintain airworthiness before something breaks. Maintenance cannot usually be put off until the next annual inspection (although some maintenance functions are routinely re-done as part of an annual).

Inspection is done to confirm that the maintenance effort has been successful, and to detect items that need repair, but which are not immediately obvious (if it’s obvious, fix it). Inspections may be informal (preflight) or follow specific guidelines (100-hour, annual).

Repair is what you do when something breaks, often from failure to perform routine maintenance, or if something is found to be abnormal (wearing, rubbing, etc.) during an inspection. Whereas sometimes maintenance can be delayed, repairs cannot be deferred.

How much does it cost to get an annual inspection?” That is a common question among airplane owners, as well as frequent topic of discussion on internet chat lines and bulletin boards. Many times, the question is really a prologue to a discussion of what it costs an owner to return an airplane to service at the end of the most recent annual inspection.

A variation on this theme is, “How much did your first annual inspection cost?” for a specific model of airplane. Another common thread describes, “the annual from hell,” one that cost the owner far more than he or she expected because of the number of items that had to be addressed before the Authorized Inspector could certify it was in compliance with its Type Certificate.

Questions and comments like these show a misunderstanding of what an annual inspection is really about. An annual inspection (also a 100-hour inspection, if required for the way the airplane is operated) is a thorough inspection of the airplane for the specific purpose of determining to the maximum extent possible that it fully conforms to the requirements of its Type Certificate and any Supplemental Type Certificates (STCs). The Type Certificate is the federal document that defines what makes a specific model “airworthy.” STCs refers to supplements or changes to the Type Certificate for approved modifications.

Conducting an annual inspection requires certain actions by the inspector, which in turn drives certain costs. For example, the time it takes to remove and reinstall the interior to gain access to items requiring inspection is usually part of the quoted cost. The shop rate for the time to remove and reinstall the interior, in this example, is included in your bill for the annual inspection. Changing the oil — including the cost of the oil and filter itself — is another example of an item that is usually included in the annual inspection cost. If you choose to send a sample off for oil analysis, however, the cost of the sampling kit, postage and the professional analysis itself will usually be added to your bill as an additional charge.

Many shops set a flat rate for an annual inspection on a particular model of airplane. If you do an owner-assisted annual, meaning you do some of the labor and leave the inspection itself to the authorized inspector, the inspector may give you a discount on the annual inspection rate (or, as the joke says, charge you more for being in the way). Bear in mind that this is just the cost of the inspection itself, which is the inspector’s fee, including time to do the required items. It does not cover anything extra (oil analysis, for example). Most notably, it does not cover the expense of discrepancies that may be found in the process of the inspection. Those extra charges would be for maintenance or repair.

Making the Distinction

There’s a tendency for many airplane owners and even some mechanics to use the terms maintenance, inspection and repair interchangeably. The three words have three distinct meanings. If we make the proper distinction it may answer a lot of questions many owners have about keeping their airplane safe, airworthy and reliable at the lowest possible cost.


Maintenance includes all those things that need to be done to keep it in conformity, by inhibiting wear and staving off the effects of use and fatigue. The root word of maintenance is “maintain.” That is what maintenance is all about: a continual process to maintain compliance with the certification standard, to keep it airworthy before anything wears or breaks. It is a common aircraft owner fallacy that maintenance items are something that are done during the annual inspection. Sure, there are some maintenance functions that are routinely re-done during an annual inspection, for example, engine oil and filter change. In most cases, however, if you wait a year to grease the landing gear, replace chafing wires, address a minor valve issue or some other maintenance task, it will become much costlier to fix by the time the next annual comes around. If you defer maintenance to the annual, you’re far more likely to find the airplane broken when you want to make a flight, or to find yourself (and your family or customers) stranded far from home when a failure prevented a return trip. Think of it like this: maintenance is what you do so you don’t have to make a repair.

Many Airplane Flight Manuals (AFMs) and Pilot’s Operating Handbooks (POHs) add the adjective preventive to the word maintenance.  In reality that’s redundant—by definition all maintenance is preventive.  If this semantic redundancy makes it easier to visualize the concept of continually keeping the airplane airworthy, however, all the better. 


An inspection determines that the airplane is in conformity with its Type Certificate and any STCs. On a routine basis pilots inspect the airplane for airworthiness before every flight. Many pilots conduct a short post-flight inspection also, to detect any changes in airworthiness standards that occurred during the flight.

An annual or 100-hour inspection follows an extensive checklist of items to visually and operationally check. The inspection, however, is just that: a very close look at the airplane to ensure it meets certification standards. That’s all…a close look.


A repair is required when an item no longer meets its certification standard, or is worn or fatigued to the point that it is near the limits of airworthiness. Except as allowed by regulations concerning flight with inoperative equipment, a repair is something that cannot wait for the next inspection. In most cases it will need to be done before the next flight.

If an aircraft owner has an “annual nightmare,” it was really almost always a lack of ongoing maintenance that made it a repair nightmare. The need for repair was only discovered (or acted upon) during the inspection, when signing the airplane off as in compliance with its Type Certificate and STCs forced the owner stop putting it off.

The Airworthiness Concept

The full airworthiness concept is: Maintain the airplane continually.

Inspect the airplane before and after flight, and more invasively during annual (or as required) to see if your ongoing maintenance efforts are effective.

Repair anything that’s broken or worn right away, not waiting for the next annual inspection.

Put succinctly, we maintain airplanes continually to prevent the need for repair, we inspect them before flight and at routine intervals to confirm the success of our maintenance efforts and to detect any wear or failure that is not obvious, and we repair any worn or broken items immediately upon discovery.

Most horror stories we hear about the cost of an annual inspection are really tales of the wild expense required to repair discrepancies that were deferred, often resulting from lack of ongoing maintenance. The total cost may not be very different if you maintain your airplane year-round and repair any broken or out of-tolerance items right away, but at least you won’t have the sticker-shock of seeing it all on the same bill that comes due all at once. You may even save money by fixing little squawks before they become major problems. More importantly, you’ll have a safer and more dependable airplane that’s ready to fly when you are…because you keep it in top shape.

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