Over the years, we've heard almost everything there is to say about Airworthiness Directives (ADs). Even today, plenty of misconceptions (i.e., “hangar lore”) still exist, and in some cases, continues to steer mechanics down a dark path of non-compliance. As Mark Twain said, "It ain't what you don't know that gets you into trouble—it's what you know for sure that just ain't so."
"It ain't what you don't know that gets you into trouble—it's what you know for sure that just ain't so." -Mark Twain
This piece approaches Airworthiness Directives the way regulators and courts do: as the product of law, not lore. ADs do not emerge in a vacuum, nor are they simply reactions to accidents or mechanical failures. They are the result of a structured legal process grounded in the Federal Aviation Regulations (FARs), informed by NTSB accident findings, and refined through FAA legal interpretations and enforcement precedent.
In our conversations with mechanics, FSDOs, inspectors, and interpreting FAA legal interpretations alongside NTSB case law, here are the top 10 myths we've heard.
In our piece, “E Stands for Experimental, Not ‘Exempt’”, we wrote about the rumors flying around the experimental (and homebuilt) community that ADs simply don’t apply to them. Strangely enough, the EAA actively promotes this UNSAFE position. After the release of AC 39-7D which gave examples of how Experimental aircraft were subject to ADs, Sean Elliott, the Vice President of Safety & Advocacy, publicly stated the OPPOSITE, saying, “This is an outcome that is the result of many hours of hard work on EAA's insistence that ADs do not apply to experimental aircraft.”
Mr. Elliott’s statement is false. Part 39 applies to all aircraft. Like any other aircraft, the applicability statement is where one would look to see if an AD applied to their airframe, engine, propeller, or appliance, and the category of aircraft (if stated).
While it is a fact that AC 39-7D gives guidance on how the applicability statement now REQUIRES explicit language to incorporate Experimental aircraft, i.e., “applies to all aircraft in any category, etc.,” to give a blanket statement stating that experimental aircraft are EXEMPT is reckless, even careless, given that ADs are issued when a KNOWN SAFETY CONDITION EXISTS on a product as per 39.5(!)
91.7 is explicit in its language that “no person may operate a civil aircraft unless it is in an airworthy condition”, although airworthy in this context is a little different to the literal meaning in 3.1 (conforms to its type certificate and is in a condition for safe operation). For Experimental, the term "airworthy" might be substituted to mean something more akin to “complies with its operating limitations AND is in condition for safe operation”. 91.7 also states “the pilot in command for civil aircraft is responsible for determining whether that aircraft is in a condition for safe flight…”
Experimental were never meant to be a gateway to skirting regulations or safety directives. You can see for yourself simply by looking at the operating limitations of an Experimental aircraft where you'll find a statement such as, “no person may operate this aircraft unless it is in a condition for safe operation" is there to remind us to BE SAFE.
The FAA guidance is actually a good thing, helping improve accountability. By incorporating Experimentals into the applicability statement, they remove the "grey area" regarding applicability of ADs and the ambiguity surrounding "condition for safe operation". From a legal standpoint, compliance with ADs is black and white, making the "proof" of non-compliance very easy to establish in a court of law. On the other had, proving an unsafe condition exists is VERY difficult, requiring the FAA/NTSB to establish, without a doubt that a) the owner knew or should have known; b) the condition posed an ACTUAL safety risk to that specific aircraft (not hypothetically); and c) the aircraft was unsafe AT THE TIME OF OPERATION. Not easy to do.
For those with an Experimental or homebuilt, we encourage you to take a proactive approach to safety over a nonchalant one. As we wrote in our piece,
“As the homebuilder, you are the OEM, and your homebuilt is only as good as the maintenance done on it. That means taking known safety concerns—whether via the AD process or the kit-maker’s safety bulletins—seriously. We strongly believe that proper safety practices, i.e. a method, serve not to confine but to liberate. There is a freedom in discipline that ignorance will never reach.”
False. When the FAA supersedes an AD, the superseded AD “is considered no longer in effect.” Oftentimes, compliance with the superseded AD can grant you credit for the superseding AD, but not necessarily—the superseding AD can add new or repetitive actions, force you to repeat (or even re-do) prior actions, change intervals, add terminating actions, or change what “counts” as compliance.
Because credit is not automatic, if the superseding AD doesn’t say your prior compliance satisfies the new requirements, then prior compliance with the old AD alone is not a legal defense—you still must meet the superseding AD’s requirements. Not complying with the superseding ADs requirements (if applicable) is an automatic failure to comply with an AD under Part 39 (and other potential issues across Part 43 and 91).
"Not complying with the superseding ADs requirements (if applicable) is an automatic failure to comply with an AD under Part 39 (and other potential issues across Part 43 and 91)."
False. We continue to receive angry calls that begin like this, “my aircraft was manufactured in 1974 so ADs that came out prior to ‘74 aren’t applicable! You need to filter those out!” Same with engine overhaul/reset dates: "my engine was overhauled in '21, why am I still seeing ADs prior to that?!"
"My engine was overhauled in '21, why am I still seeing ADs prior to that?!"
ADs are legally enforceable rules under 14 CFR Part 39, applying to any or all products identified in the applicability statement. The key concept here is APPLICABILITY, i.e., aircraft models, serial number ranges, part numbers, or configurations—NOT the year the aircraft was built (unless explicitly mentioned in the applicability statement).
We believe this rumor originated from ADs where the serial number cutoffs often (read OFTEN, not ALWAYS) correlated with years, making future ADs not applicable. Over time, people just assumed the ADs cutoff at the serial numbers when the AD came out. While this shorthand rule may work for some ADs, it is simply not true for all ADs.
"Over time, people just assumed the ADs cutoff at the serial numbers when the AD came out. While this shorthand rule may work for some ADs, it is simply not true for all ADs."
False. The FAA’s Gagnon Interpretation states:
“A person “performing and completing an inspection required under Part 91 must determine the status of all applicable ADs in order to determine the aircraft is in an airworthy condition”.
We see this as a natural extension of 43.15(a)(1), which requires that the person performing the inspection shall “perform the inspection so as to determine whether the aircraft, or portion(s) thereof under inspection, meets all applicable airworthiness requirements.
The rule of checking all ADs at inspection is emphasized in AC 39-7D, Section 13.b, which states:
“When a 100-hour, annual, progressive, or any other inspection required under 14 CFR part 91, 121, 125, or 135 is accomplished, § 43.15(a) requires the person performing the inspection to determine that all applicable airworthiness requirements are met, including compliance with ADs.”
While there are some caveats/carve-outs for progressive and continuous inspections, you can't skirt checking all ADs without EXPLICITLY calling that out with language such as, “compliance with ADs applicable only to portions of the aircraft being inspected”, in the mx logs.
We were not surprised to find the language from AC 39-7D lifting the language from the case Administrator v. Kilrain (1996), where a mechanic did not comply with a few ADs in the annual inspection of a Grumman American and therefore, when he returned the aircraft to service, “the aircraft did not meet all of its airworthiness requirements" violating Section 43.15(a).”
False. As explained in the Easter Interpretation, blanket statements such as “All ADs complied with” or “All ADs complied with through revision X/X” does NOT comply with the requirements of 91.417(a)(2)(v), which requires the registered owner or operator to keep records containing “the current status of applicable airworthiness directives and safety directives including, for each, the method of compliance, the AD or safety directive number and revision date.” Additionally, 91.405 requires the owner (or operator) to ensure that maintenance personnel who accomplish the work (required by an AD) make the required entries as per 43.9.
In an often-cited case related to AD compliance, Administrator v. Scott (1993), the Board held that a "blanket" AD entry certifying an aircraft as airworthy after a 100-hour inspection violated FAR Section 43.11(a)(1), in that it did not adequately describe the extent of the inspection when it said ‘All ADs c/w’. The law judge noted that such a notation is MEANINGLESS without some reference to which ADs were applicable to the aircraft and the method of compliance…” The Board said, “Failure to ensure that a particular AD had been complied with was a clear violation of 43.13(a)”.
"'All ADs C/W' is meaningless without some reference to which ADs were applicable to the aircraft and the method of compliance." - The Judge
Best practice is to have the sheet, but ensure you make the appropriate entries in the logbook. For more on this, see our Logbook Do’s & Dont’s Webinar (this was the #1 pet peeve!)
False. The belief that AD compliance is ONLY required at the time of a required inspection (i.e., Annual or 100-hour) is NOT correct. The required compliance time for each AD is specified within each AD, which MAY or MAY NOT coincide with an inspection cycle. Finally, no person may operate the affected product after expiration of that stated compliance time without an AMOC approval for a change in compliance time. See AC 39-7D (Section 11 – Compliance time or date)
The required compliance time for each AD is specified within each AD, which MAY or MAY NOT coincide with an inspection cycle.
False. 21.41 Specifically states:
“Each type certificate is considered to include the type design, the operating limitations, the certificate data sheet, the applicable regulations of this subchapter with which the FAA records compliance, and any other conditions or limitations prescribed for the product in this subchapter.”
The Witkowski Interpretation explicitly ties airworthiness to both type design and airworthiness, stating, “While most mechanical, electrical, or structural unairworthy conditions would probably implicate issues with the type design, our answer applies to the broader concept of airworthiness that includes compliance with the type certificate, including supplemental type certificates, and airworthiness directives.”
This "two prong test" for airworthiness is referenced often in a couple of notable case, Bailey v Avila (1994) and Administrator v. Doppes (1985), both summarizing that “No person may operate a civil aircraft unless it is in an airworthy condition…To be airworthy an aircraft must: (1) conform to its type certificate and applicable Airworthiness Directives; and (2) be in a safe condition for operation.”
To be airworthy an aircraft must: (1) conform to its type certificate and applicable Airworthiness Directives; and (2) be in a safe condition for operation.”
Note: this logic fails for experimental aircraft, where the LEGAL bar to prove an unsafe condition exists is much more difficult if they do not comply with an AD that is NOT applicable to their engine or appliance but is applicable to certificated aircraft...
False. Because complying with applicable ADs is maintenance, they require an entry/signature under 43.9, as per AC 39-7D and AC 43-9C ("The person accomplishing the AD is required by § 43.9 to record AD compliance. The entry must include those items specified in § 43.9(a)(1) through (a)(4)").
"Complying with applicable ADs is maintenance and requires proper entries and sign-off as per 43.9"
In Administrator v. Scott (1993), the mechanic forgot to date an AD compliance entry and was faulted for missing 43.9(a)(2), requiring maintenance entries to include the date the work was completed. Furthermore, 91.417(a)(2)(v) requires records to be kept for the CURRENT status of all applicable airworthiness directives (ADs). Note: this is where our AD compliance software makes it easy to track, update, and comply with ADs!
False. A recent AD legal interpretation states that, “a change in product configuration does NOT necessarily mean that the unsafe condition has been eliminated, and in some cases, the unsafe condition may be aggravated. So it is necessary to emphasize that the “Applicability” paragraph of the AD determines APPLICABILITY, not the configuration of the individual airplane.” (emphasis ours)
"The 'Applicability' paragraph of the AD determines Applicability, not the configuration of the individual airplane.”
91.417(a)(2)(v) requires a registered owner or operator to keep records containing "the current status of applicable airworthiness directives and safety directives including, for each, the method of compliance, the AD or safety directive number and revision date.” If the AD is applicable (i.e., by make) you NEED TO DOCUMENT why you think it is NOT applicable (or does not apply). While there are legal grey areas related to serial number applicability or parts not installed, the best practice (from an IA/A&P standpoint) is to always document. See our piece on "Operational Integrity: The Three Pillars of Maintenance Records & Safety Compliance" on the principles of good maintenance documentation.
To the extent ADs are NOT documented appropriately, the result is an INVALID Airworthiness Certificate. As AC 43-9C lays out clearly:
“Adequate aircraft records provide TANGIBLE EVIDENCE that the aircraft complies with the appropriate airworthiness requirements. In accordance with the terms and conditions listed in block 6 of FAA Form 8100-2, insufficient or nonexistent aircraft records may render that Standard Airworthiness Certificate INVALID.” (emphasis ours)
False. Similar (but different) to the myth related to only checking ADs at inspections, the required compliance time for each AD is specified within each AD, which MAY or MAY NOT coincide with an inspection cycle or maintenance.
"Compliance time for each AD is specified within each AD, which MAY or MAY NOT coincide with an inspection cycle or maintenance."
There are certain ADs that are tied to maintenance activities, requiring them to be checked/complied with at that time. One example is 24-21-02, the "Lycoming Connecting Rod Bushings" AD. This AD requires a visual inspection of the oil filter, oil pressure screen, and oil suction screen for bronze metal particulates AT EVERY OIL CHANGE until the connecting rod bushings are replaced. While this can be accomplished by the pilot/owner, compliance and the relevant documentation of that compliance, is required at every oil change until replacement! Failure to comply, or document, is an AUTOMATIC failure of airworthiness and 43.9 /91.417(a)(2)(v).
False. Removing a component only eliminates AD compliance if the AD is no longer APPLICABLE to the aircraft’s APPROVED configuration. However convenient or appealing it may be, as mentioned explicitly in 39.15, “…an airworthiness directive applies to each product identified in the airworthiness directive, even if an individual product has been changed by modifying, altering, or repairing it in the area addressed by the AD.”
“…an airworthiness directive applies to each product identified in the airworthiness directive, even if an individual product has been changed by modifying, altering, or repairing it in the area addressed by the AD.”
Removing or altering a component to eliminate the AD requirement is NOT an accepted compliance method unless the AD specifically allows it or the AD no longer applies due to a configuration change approved as part of the type design (STC). If you want to comply with an AD by another means not specified in the AD itself, an AMOC must be requested and approved.
If you made it this far, we commend you for your commitment to aviation safety! Good mechanics aren't quitters, and if you liked this piece, be sure to check out more of our insights, published bi-weekly.
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Links & Sources:
AC 39-7D, Airworthiness Directives
FAA Legal Interpretations Search
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