I usually leave the regulatory topics to experts like John Frank and Mike Bush, but recent telephone conversations with several mechanic friends brought a couple of concerns to light. Owners’ not fully realizing their regulator responsibilities, and general misunderstanding of certain regulations. Fundamentally, both deal with reading.

Reading for Responsibility

My favorite “lack of training to be an aircraft owner” example is FAR 91 Appendix E, Maintenance, Preventive Maintenance, and Alterations 91.403(a) which states: “The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with part 39 of this chapter”.

Note that FAR 91 Subpart E for Maintenance, Preventive Maintenance, and Alterations is not located in FAR 43 for Maintenance, Preventive Maintenance, Rebuilding, and Alteration. FAR 91 is titled General Operating and Flight Rules, usually associated with pilots and flying the plane, not working on it. Its very location should signal a heads up as to whom the FAA wants reading it.

Very few pilot/owners pay much attention to FAR Part 39. Most couldn’t tell you its content without looking. In the AIM/FAR book for pilots, Part 39 requires only one page – one page can’t be very important!

The fact is, Part 39 Airworthiness Directives is the largest part in the chapter and is amended almost daily. Each new airworthiness directive (AD), or revision to an AD, is a new amendment to Part 39. The current amendment level is well past 15,700 and pushing 16,000. I’m guessing the FAA expends more continuous effort on Part 39 than any other regulation. If that is the case, and you the owner operator are directly charged with responsibility for compliance of the part, you might want to learn a bit more about it.

Reading the regulations in the earlier days of aviation regulations was much simpler.

The first AD for the Cessna 120 is AD 46-44-01 which required less than half of a sheet of paper with its text straight forward and to the point. By contrast, AD 2008-26-10 requires at least five pages to tell us some stickers may be improperly installed on new static ports and should be checked. Some ADs require several pages just to list which aircraft, engines, propellers, or accessories are covered. I’m not saying the extra text is just verbiage, only that more effort is required to comprehend the new regulations.

Most owners sub-contract the Part 39 search to their mechanic, which is perfectly fine. You may be as “hands off” as you want, but I strongly recommend at least getting a list of items searched by the mechanic. The list should include almost everything in the airplane with a data plate. This includes everything from seat belts to altimeters to transponders. Remember, it is still your responsibility to get it all.

Reading for Comprehension

I received one phone call from a mechanic friend having difficulty with his local Flight Standards District Office (FSDO) interpretation of FAR 91.403(c). This regulation states an aircraft with an airworthiness limitations section in its manufacturers’ maintenance manual or in its instructions for continued airworthiness, must follow the limitations set out in that section.

Unfortunately, the FSDO administrator misreads the regulation and tells my friend all limitations recommended in any manufacturers maintenance manual must be followed. This view would require all time limited items in legacy aircraft maintenance manuals be complied with. It would also negate FAR 43 Appendix D as the scope and detail of an annual inspection. Fortunately, that is not what the regulation states.

Since I almost didn’t make it out of high school due to my lackluster performance in Mrs. Hardin’s senior English class, I enlisted the assistance of #1 son Jay New. Jay is a very smart, highly educated, university graduated English Major, and current MFA student at USC. My close friends know Jay takes after his mother in the smarts department but DNA tests have confirmed he is mine as well.

The actual regulation in question: FAR 91.403(c) No person may operate an aircraft for which a manufacturer’s maintenance manual or instructions for continued airworthiness has been issued that contains an airworthiness limitations section unless the  mandatory replacement times, inspection intervals, and related procedures specified in that section or alternative inspection intervals and related procedures set forth in an operations specification approved by the Administrator under part 121 or 135 of this chapter or in accordance with an inspection program approved under §91.409(e) have been complied with.

Jay’s Evaluation of 91.403(c)

The preceding regulation, though grammatically correct and with proper punctuation, will easily confuse many readers. Its technical language mixed with its Melville-sized duration dodges the reader’s attention and short-term memory capacity, and memorization of the entire regulation seems the best way to digest it. The author(s) could restructure and segment the regulation a little and provide the reader with a more fluid and coherent read.

Breaking it down:

First of all, the reader should note that this is an exclusionary statement beginning with “no person may” rather than stating which persons can do the following act. (I know this feels a little like Mrs. Wormwood’s English class from hell rather than an assistance essay for pilot’s, but I promise it will pay off…I digress.)

Here’s the first twist: the sentence begins by passing guilt three consecutive times before ever stating what makes the offender guilty. First, the “person” cannot operate the aircraft. Then, “aircraft” is followed by its modifying prepositional phrase “for which.” Then, within the aircraft’s guilt lies the true culprit—“a manufacturer’s maintenance manual [MMM] or instructions for continued airworthiness [ICA].” Now we know what really matters: the MMM and ICA. So, if you’re not a person, don’t worry about it. If you’re not operating an aircraft, don’t worry about it. If you’re an aircraft without an MMM or ICA, don’t worry about it. The preceding sentence is important, in that many very old planes may not have an MMM or ICA.

Again, the MMM and ICA hold all the weight in this issue. “Or” is the big word to note between the manual and instructions. “Or,” both in Mathematics and English dictates union rather than intersection. (A union graph covers all the area of both equations rather than a set of intersecting equations using the word “and” that include only the area that is common to the set of equations.) Soooo, whatever the problem is, it does NOT have to be in both your MMM and ICA; it can be in either one and you’re grounded.

Still looking for the problem though. Good grief.

Now that we know the MMM or ICA can be at fault, the guilt is passed along yet again (that’s four times so far). Either your MMM or ICA must contain “an airworthiness limitations section.” If your MMM or ICA does not have an airworthiness limitations section, then you’re free according to FAR 91.403c…and don’t worry about it (almost).

If you are a person, and you’re a person operating an aircraft, and if that aircraft has an MMM or ICA, and if either the MMM or ICA has an airworthiness limitations sections…well, then, you should keep reading. Sorry.

The truly guilty party has been identified, and the reason of guilt is at hand. But here’s where things get really sticky. When the regulations states, “…specified in that section,” the word “section” refers to the airworthiness limitations section. With the word “section,” we should have come to the very end of all guilty parties; instead, the author tacks on one more when he/she continues, “…or alternative inspection intervals and related procedures…” meaning that an MMM or ICA might have an airworthiness section or an alternative inspection intervals and related procedures section that contains the mandatory replacement times, inspection intervals, etcetera. Our “or” problem again.

It seems there are really two “sections” that cause guilt; herein lies the greatest reading discomfort. With this additional section dropped into the middle without commas surrounding it, it is very difficult to determine which of the following modifying phrases belongs to what. The bit beginning with, “set forth…” and ending, “…approved under 91.403c,” could justify another page of deciphering that we won’t delve into. To keep it short, the amount of prepositional phrases and two more “or” (that’s 4 “or” and 2 “and” in one sentence, if you’re keeping count) requires more understanding than I have degrees, certifications, and licenses to accommodate.

Here’s the big question: Is this part—“or alternative inspection intervals and related procedures set forth in an operations specification approved by the Administrator under part 121 or 135 of this chapter or in accordance with an inspection program approved under §91.409(e)”—necessary?

Let’s read without it: “(c) No person may operate an aircraft for which  a manufacturer’s maintenance manual  or instructions for continued airworthiness  has been issued that contains an airworthiness  limitations section unless the mandatory replacement times, inspection intervals, and related procedures specified  in that section have been complied with.”


Much better, right? But the lack of  commas (meaning it’s an essential phrase or clause) and the word “or” signifies that the author intends for both phrases to be complied with, and the one we hid entails pre-existing FAA approvals, just to make it even more pleasurable.


To top it off, the author holds the verb “complied” until the end. So, someone  used to reading Japanese will have no problem wondering what’s happening,  but most people quickly tire of reading nouns, objects, and modifiers without any direction for where they’re headed. Finally, the author ends with a preposition. Ending a sentence with “with” leads to endless debates on Latin prescriptive grammar versus our language’s Germanic origins, and so on. We’ll skip it to say that the “with” does not cause a misunderstanding, but in a legal, federal document, this kind of grammar should  be steered away from. (Oops, just did it, but then I’m not the FAA).

Ultimately, the regulation states that nobody can legally operate an aircraft unless certain manuals contain (and they might not contain—in which case, you’re fine) certain sections that are FAA approved and mechanic/pilot followed. My suggestion for readers is this: start at the ending. Something must be complied  with…what?…move back a step and find out…what is this a part of?…move back a step and find out…and continue until you get to “person” because that’s whom everything gets dumped on even though what causes the guilt is hidden away somewhere in the deep, dark center of ole 91.403c.


While we’re on the subject of how to decipher our own language, don’t listen to Dad’s ramblings about how he did so poorly in school. He just wanted to take honor classes to see my mom; hence, he probably didn’t pay attention like he should have. Now, he’s a master  of airplanes but insists on using too many prepositions and too many passive linking verbs rather than strong transitive ones.

Paul’s Summation

If you have any questions about Jay’s take on the regulation, please don’t embarrass Mrs. Hardin by asking me. Consider this: if Jay can spend this much effort on one sentence, we mere mortals shouldn’t be discouraged to expend some effort making sense of it either.

To put 91.403(c) in terms I understand; if not an FAA approved requirement it’s not required. The required FAA document here is an “airworthiness limitations section” in either the aircraft maintenance manual or instructions for continued airworthiness. None of our piston powered legacy airplanes have an approved maintenance manual and therefore no airworthiness limitations section. The restart 172/182/206 airplanes have an FAA approved maintenance manual but no chapter 4 for airworthiness limitations. The “new to us” 300/350/400 airplanes have a chapter 4 which includes required time change and inspection items like ELT batteries, main batteries, and a 6000 hour airframe inspection.

Instructions for continued airworthiness might come in the form of  maintenance items as part of an Supplemental Type Certificate (STC) and very well could include an airworthiness limitations section. As a supplement to the original type certificate, an STC is an FAA approved document and its stated requirements are mandatory.

The real message is our responsibility to read and understand the regulations, including Part 39. We (most of us) are just as capable to read and understand the written English language as the FAA. If you or your mechanic disagrees with the local FAA  administrator I suggest you challenge him/her in writing. Be certain you are correct and careful in your approach as you don’t want to burn any bridges with the FAA.