Airworthiness Directives and Experimental Aircraft

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John McClanahan

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May 29, 2025, 9:25:40 AM5/29/25
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Group - This question came up after I e-mailed the group regarding compliance with AD 2024-21-02 which mandates inspection of oil filters and etc. for bronze particulates after oil changes in many Lycoming engines.

Several of our members have stated their belief that AD’s don’t apply to experimental aircraft.

Let’s take a look and see if that’s true - 

First, my original position was that AD’s do apply because 14 CFR 91.403 requires compliance with Part 39 (Airworthiness Directives) with no carve out for Experimentals.

I was feeling pretty smug about determining that when I found this bit from the FAA - scroll down to “Ask the Inspector”, you’ll see the author says exactly what I said - no carve out for Experimentals.


Having said that, we find the EAA with their position that AD’s don’t apply to the Experimental world (mostly) - 

“Airworthiness directives continue to be a point of contention for experimental aircraft owners. The FAA document AC 39-7D, Airworthiness Directives, reads, “ADs only apply to type-certificated aircraft, including ADs issued for an engine, propeller, and appliance.” But because ADs are issued to correct an unsafe condition in an aircraft, aircraft engine, propeller, or appliance, my recommendation is to comply with all ADs. My reasoning, and the reasoning you can use with the owner, is that the aircraft, whether experimental or not, should be “in a condition for safe operation.”


So we have the FAA on one side (sometimes) and the EAA on the other side (sort of) with us in the middle.

Here’s a good article in KitPlanes.  It even quotes our own Vic Syracuse -


So to summarize, here’s what I come up with -

First and foremost, the FAA requires us to maintain our aircraft in an airworthy condition -

14 CFR 91.403 - “The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition”

And it can not be flown unless it’s in an airworthy condition -

14 CFR 91.7 - “No person may operate a civil aircraft unless it is in an airworthy condition.”

With that in mind, I think it would be very easy for an FAA inspector/judge/NTSB to make the case that ignoring an AD would make the aircraft un-airworthy regardless of whether there was an explicit mandate to comply.  And that would put you in violation of 91.403 and 91.7.

And then, for good measure, they could throw in 91.13 since ignoring airworthiness is “careless or reckless” - 

“No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another.”

So yes, the EAA makes a good case that AD’s don’t apply explicitly to Experimental aircraft.

However, the basic requirement of 91.403 to maintain airworthiness clearly seems to override much of the EAA legal mumbo-jumbo.

So here’s what I think is the bottom line -

Since compliance with this AD is trivial and examination of oil filters at oil change should be standard practice for all of us, it seems logical to simply comply with the AD by inspection and a log entry.

And that brings me back to my original e-mail with three possible scenarios -

1.  You know the AD doesn’t apply (applicability, AD 2024-21-02, Table 1) - make a log entry stating that and you’re done.

2.  You know the AD applies - make a log entry at every oil change. (You’re making a log entry anyway so add a statement of compliance for the AD).

3.  You’re not sure whether the AD applies because you don’t know what parts are in your engine - same as #2, add the compliance statement to your log entry.

So I think this should put the whole thing to rest.  A word of caution though -

Be careful what you take from the Van’s Air Force forum, .  I find some folks on there believe what they want to believe and state their beliefs as though they’re facts.  And if they don’t back up those statements with references, they seem quite likely to be unfounded opinions.

Please feel free to comment.

Thanks -

John McClanahan

vic syracuse

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May 29, 2025, 9:33:12 AM5/29/25
to John McClanahan, FalconRV-List
John, thanks for expounding on this. I have always disagreed with the FAA on their stance as it is just an anti-authority stance, and I was vocal about it when I was on the BOD and Safety Council. This attitude is prevalent on the VAF forums as well, which is why I no longer participate there. I do believe the accident rate for AB aircraft will increase as our fleet ages and this attitude prevails.

We owe it to our passengers and for our reputations, that we keep our airplanes in a condition for safe operation. As I said earlier, it would not be defensible in a court of law. I am not a lawyer, but I would never want to find myself having to defend why I think I know more than Lycoming, Hartzell, Van's etc. Even some of the SB's that are issued by Van's would be AD's in the certified world. Especially the ones that start with "prior to further flight."

Vic



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Dean M.

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May 29, 2025, 9:55:55 AM5/29/25
to John McClanahan, FalconRV-List
Referencing only the logbook writeup: The CI entry has catch-all phraseology already. It has to, because it's not practical to list each and every regulatory item.

"Condition Inspection performed in accordance with FAR 43 Appendix D and..."

Dean



John McClanahan

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May 29, 2025, 10:11:55 AM5/29/25
to Dean M., FalconRV-List
Hey Dean - I think you can certainly do that.  But to me, a log book is a working and practical document, i.e. more than just a legal minimum thing.

It imparts confidence and saves time when I see a concise statement of recurring AD compliance in the log.

When I see only the minimum, it makes me think only the minimum (or less) was done.

Thanks for the comment -

John McClanahan



Joseph Subits

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May 29, 2025, 10:13:17 AM5/29/25
to Dean M., John McClanahan, FalconRV-List
More and more, it seems like whatever exceptions, gaps or loopholes the FAA may leave on the table, insurance companies close with more restrictions in policies along with higher premiums. It always pays to read every last clause of your liability and hull damage coverage each and every year.  

To view this discussion visit https://groups.google.com/d/msgid/falconrv-list/CA%2Bze03XDCyAWEQPZf%3DPZezZFT_Om7YR1OtXrGhyagfadwDxzTQ%40mail.gmail.com.

Jim Faber

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May 29, 2025, 4:44:45 PM5/29/25
to John McClanahan, FalconRV-List
Hi John,
I decided to ask AI if ADs apply to experimental aircraft. It's response is listed below and and makes a lot of sense. Without further comment here is what it said

Generally speaking, Airworthiness Directives (ADs) do not directly apply to the airframe of experimental aircraft. This is because experimental aircraft, by definition, are not "type certificated" by the FAA, meaning they don't have a specific design that the FAA has approved for mass production. ADs are typically issued against type-certificated aircraft, engines, propellers, and appliances.
However, there are important nuances:
 * Components with Type Certificates: If an experimental aircraft incorporates components that do have a type certificate (e.g., a certified engine, propeller, or certain appliances), then any ADs issued for those specific certified components do apply to them, regardless of what aircraft they are installed in. While the FAA doesn't issue ADs on experimental aircraft, they do issue them on products. If that product is installed in an experimental aircraft, the AD still applies to the product.
 * "Condition for Safe Operation": Even though not legally required to comply with all ADs, experimental aircraft owners and builders are still responsible for ensuring their aircraft is in a "condition for safe operation." If an AD addresses a known safety issue in a component installed on an experimental aircraft, it is highly recommended to comply with it for safety reasons. Insurance companies may also consider compliance with relevant ADs when evaluating claims.
 * Advisory Circulars and Industry Best Practices: The FAA and aviation organizations like the EAA (Experimental Aircraft Association) provide guidance on this topic. While ADs aren't legally binding for experimental airframes, they often highlight critical safety issues that builders and owners should be aware of and address. Service bulletins from manufacturers of engines or other components, while not legally mandatory, also serve as valuable safety information.
 * Specific AD Applicability: In rare cases, an AD might explicitly state that it applies to non-type-certificated aircraft, usually in situations involving immediate safety-of-flight issues or products commonly installed in both certified and experimental aircraft.
In essence, while the legal framework for AD compliance is different for experimental aircraft, responsible operation dictates that owners and builders should be aware of and consider complying with ADs and service bulletins that address safety concerns related to their aircraft's components.


James

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May 29, 2025, 6:39:40 PM5/29/25
to Jim Faber, John McClanahan, FalconRV-List
I’ve been following this email chain closely and decided to follow John’s and Vic’s recommendations to document in the logbook what I was already doing with my oil changes with regard to this AD. I noted though that the AD lists applicable engines (but not serial numbers), with specific parts installed within a certain production date range. 

My engine is an IO-375 which is not listed in the AD, but falls within the specified range. Because it is a Lycoming “clone,” assembled by Aerosport Power, many of the part numbers do not match what would be included in a stock engine and consequently, what is listed in the AD. Technically I believe I could argue that the AD doesn’t apply to my engine, but the alternative is to ignore any bronze particulates I might find during an oil change.

I think not.
Cheers!
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