“When the paperwork weighs as much as the airplane, you’re ready to fly.” I wish this was further from the truth than it is. Maintenance logbooks, in the eyes of many pilots, can read like a bound collection of mechanics poorly written notes to an imaginary friend. Just when you thought you’d managed to figure out all the acronyms in aviation as a pilot, mechanics add their own special shorthand and acronyms. But just like TAFs and METARs, they can usually be decoded to reveal incredibly useful information. Like whether or not the airplane you’re about to take on a checkride is airworthy. Whether you are an owner or a renter, understanding the implications of these “notes” cannot be understated.
Part 43.9 and 43.11 of the FARs lay out the basic requirements for maintenance logbook entry content. The basic requirements laid out in 43.9 for repairs are: A description of the work performed, the date of completion, the signature of the person approving the work, the certificate number and type certificate held by the person approving the work. Part 43.11 spells out the basic content of a log entry for an inspection as such: The type of inspection being performed, a brief description of the extent of the inspection, date of the inspection, total time in service, signature, certificate number and certificate type of the person approving the return to service. It goes on to lay out the verbiage of the approval statement to be this, or similar to: “I certify that this aircraft has been inspected in accordance with (insert type) inspection and was determined to be in airworthy condition.” These are the minimum requirements, and most go beyond in some way or another.
Definitions of commonly used maintenance acronyms:
- A&P: Airframe and Powerplant mechanic
- IA: Inspection Authorization
- AD: Airworthiness Directive
- IAW: In Accordance With
- TT: Total Time
- AFTT: Air Frame Total Time
- TSMOH: Time Since Major Overhaul
- TTSN: Total Time Since New
- PN: Part Number
- SN: Serial Number
- WO: Work Order
- CRS: Certified Repair Station
Typically, each aircraft will have multiple logbooks; one for the airframe, one for each engine, and one for each propeller. For older, higher time aircraft, you can expect multiples for each component as well. Occasionally you will see separate logbooks for avionics, but this is rare, and in my opinion, stupid. In most instances, the airframe logbook is the only one that is of any concern. Not that the engines and propellers aren’t important, but as far as conformity and legality, the airframe logs are where it’s at, so to speak.
Let’s review the various inspection requirements for an aircraft operated under part 91. We can start with the most obvious, the annual inspection. Due every 12 calendar months, without an annual inspection, the aircraft in question is definitively not airworthy. When an annual is performed, there are log entries made in all of the logbooks mentioned above, except for the stupid avionics log. But the one that a pilot actually cares about is in the airframe logbook. When an A&P with an IA performs an annual inspection, and finds it to be in airworthy condition, by default they are including the engine and propeller in the closing statement spelled out in 43.11. You can’t very well say that an aircraft was found to be in airworthy condition if the engine isn’t, right? The airframe entry is the all-encompassing blessing to go fly. By signing that entry, the approving individual is stating that the aircraft as a whole conforms to the Type Certificate under which it was approved, or its properly altered condition, at that time. The ELT inspections as prescribed by 91.207 are, more often than not, included in the annual inspection entry as well due to the frequency of the inspection requirements. Because annual inspections have to be performed by an A&P mechanic with an IA, look for the IA next to the signature or certificate number at the bottom to help quickly identify the entry as the annual inspection.
The 100 hour inspection, as required by 91.409, is identical to the annual inspection, with two exceptions; it’s due every 100 hours (crazy, right?), as opposed to every 12 calendar months, and the A&P performing the inspection is not required to have an IA. Other than that, the scope and detail of the inspection is identical.
For IFR pilots, there are a couple more inspections that they need to be concerned with, on top of the annual/100 hour. 91.411 dictates the inspection requirements for the altimeter, altitude reporting equipment and static system. It is commonly referred to as the pitot-static system test, but has nothing to do with the pitot system, or the airspeed indicator, directly. The transponder inspection, found in 91.413, when done in conjunction with the “pitot-static” are commonly known as the “IFR cert. Both inspections are due at the same interval, every 24 calendar months. Due to the nature of the inspections, and the cost of the equipment required to perform them, they are more often than not done by certified repair stations, as opposed to your local A&P mechanic. The logbook entries for these are found in the airframe logbooks, unless you are unlucky enough to find a stupid avionics logbook, in which case, they may deem it appropriate to put them in that.
Airworthiness Directives are an aspect of maintenance records that owners and pilots need to understand. ADs are regulatory in nature, and can effectively ground an aircraft. Unfortunately, with older, higher time planes, they can also be numerous and complicated. When an aircraft is signed off at annual, one can be sure that all of the applicable ADs have been complied with, at that time. There are recurring ADs that need to be addressed at specific hour or calendar intervals. The inspection intervals are dictated by the AD itself. There are ADs that require attention before further flight. To expect a pilot to fully understand whether an aircraft is airworthy between major inspections is a tall one. An AD compliance inspection on an aging GA airplane can take days to do. That being said, most logbooks will include a separate section for AD compliance. The recurring ADs will often be listed on a single sheet, showing the last compliance, as well as when it is next due, either by date or tach time. Short of trusting the maintenance provider implicitly, a pilot can check this to verify that any applicable recurring ADs have been addressed.
Looking over the maintenance logs for any airplane you fly should be something that every pilot does at least once. We hope you will find your paperwork in order and can continue to fly with confidence that your airplane is airworthy, fit to fly, and properly documented.