Specific words have specific meanings. That’s why we have so many of them. Sometimes, though, a word or term bullies its way to the fore. “Google” has become synonymous with “search” (though I’ve never Googled my toolbox for a missing Cleco pliers). “Kleenex” displaced “tissue” decades ago. In aviation, “annual” is what people say when they mean “condition inspection.” And then there’s “Advisory Directive” (AD). Strictly speaking, ADs don’t exist in the world of Experimental/Amateur-Built (EA-B) aircraft. Per the FAA, “Airworthiness Directives (ADs) are legally enforceable regulations issued by the FAA in accordance with 14 CFR part 39 to correct an unsafe condition in … an aircraft, engine, propeller, or appliance.” The FAA doesn’t issue ADs for EA-B aircraft and can’t enforce safety notifications issued for EA-B aircraft. That would get in the way of the whole “experimental-amateur built” thing. But—and this is a big but—the FAA can enforce safety notifications issued for aircraft licensed in the ELSA or SLSA categories.
In the absence of the FAA getting handsy with EA-B owners on safety-related repairs and maintenance, kit manufacturers—the ones that wish to keep both their business and their customers alive—step up, like good corporate citizens, and issue their own safety directives. They are issued under a variety of names such as “Service Bulletin,” “Safety Bulletin,” and “Safety Directive,” though RANS keeps it traditional with “Advisory Directive.” Neither the FAA nor the issuing kit manufacturer can enforce compliance of such bulletins. William Wynne of Fly Corvair sums it up like this: “I cannot require any builder to take any action, I can only appeal to his better judgment by making a serious recommendation.”
Ignore Service Directives at Your Own Peril
There are two entities that have the power to make you wish you had complied with all applicable service bulletins: your insurance company and the legal system. Setting aside a tragedy that claims a life, even a small accident that involves other people’s property can put you in a bind. The first thing an insurance company does is look for a reason to not pay a claim. That taxi light you took out when your gear collapsed, as well as the damage to your aircraft, might come out of your pocket when an inspection of your airframe’s logbook reveals you didn’t address a four-year-old service bulletin for potential axle failure. (For an example of how to record compliance with a service bulletin in your airframe or engine logbook, see “Arion Aircraft” below.) The cost and legal jeopardy of not complying with all applicable service directives can be sky-high.
If you own or fly an EA-B, or have been tasked with performing a condition inspection on one, it is in your very best interest to contact the kit manufacturer, the engine manufacturer, and the propeller manufacturer and ask about applicable mandatory service items and then make sure they have been performed on your aircraft. Keep in mind a pilot in command deems an aircraft airworthy each time they take to the sky.
A Sampling of Service Bulletins
I visited kit aircraft (and engine) websites to see how accessible critical safety information is to an end user. I was pleased to find most companies published the information on their website, though a time or two I had to really poke around for it. One company, which still offers a kit for a 50-year-old design, had a finance tab but nothing for support beyond a contact page that promised they’d “do our best” to respond “as soon as possible.” (Sometimes the red flags plant themselves.) By no means is the following list all-inclusive, but it illustrates how individual companies handle critical safety information and the terminologies in play.
Van’s Aircraft
vansaircraft.com/service-information-and-revisions/
Van’s Aircraft compiles bulletins by aircraft model and, conveniently, presents the information in PDF format, making it easy for an owner to print and archive a paper copy to keep with their aircraft’s records. Van’s has clearly defined the terms they use and the expected level of compliance for each. From the Van’s website:
Safety Directive and Alerts For all ELSA or SLSA aircraft, these documents represent critical safety of flight notifications that require immediate action before further flight. Safety Directives and Safety Alerts are mandatory and may be enforced by the FAA. Note that for EA-B aircraft, similar-level published information may be included under the “Service Bulletins” category of documents.
Service Bulletins Service Bulletins typically do not mandate immediate action from a regulatory perspective but do strongly recommend future action. Timeframes and methods to comply may vary and are described in each document. These are items that represent an important or critical need and should be reviewed and complied with per the contents of each document in the specified timeframe. Van’s Aircraft strongly encourages all owners and operators to comply with the information in these documents.
RANS
RANS breaks its critical safety data into three categories: Airworthiness Directive, Operational Alert, and Assembly Alert. Each safety bulletin includes the urgency of compliance (Mandatory, Optional/Voluntary).
Zenith Aircraft
The “Builder Resources” portion of Zenith’s website is password protected but, while typing an email to their support department inquiring about service bulletins, I saw a link that says, “Continued Airworthiness … Service Letters and more. Visit www.newplane.com.” So I did. That page is headed “Zenair” with a link to “Continued Airworthiness of Zenair / Zenith Aircraft ‘CH’ Designs.”
There I found well-organized tables of Safety Alerts, Service Bulletins, and Notifications/Service Letters, each with its own compliance interval (Before next flight, Every 50 hours, etc.). However, I’m not sure if there is additional information locked away in the “Builder Resources” section. I recommend contacting them for your specific model to be sure you have a full list of all applicable service items.
Sport Performance Aviation
flywithspa.com/panther-service-bulletins/
Sport Performance Aviation, home of the Panther, has two tables: one for mandatory service bulletins and one for optional service bulletins. Easy.
Sonex
sonexaircraft.com/service-bulletins/
Sonex publishes both required and optional service bulletins. They divide the bulletins into categories: general and model-specific. General service bulletins are issued when a safety item spans multiple designs in their stable. Model-specific service bulletins are issued when a safety item pertains to a specific design (e.g., Onex, Waiex, SubSonex, etc.). The information provided includes the reason the service bulletin came to being, the required corrective action, and ongoing inspections, if any.
Kitfox
kitfoxaircraft.com/maintenance/
Kitfox neatly organizes and publishes three categories of service-related documents. Per Kitfox:
Service Bulletins A Service Bulletin is the equivalent of an AD on a certified aircraft. They are considered mandatory items and should be completed.
Service Letters A Service Letter is either a suggested change or designed as an assistance to the owner for an area where multiple difficulties arise.
Service Alerts Service alerts are precautionary and may turn into service letters. Take proactive action on these items as they are evaluated.
Timber Tiger
timbertigeraircraft.com/service-bulletins
In contrast to the company I found with a 50-year-old design that, apparently, has never had a service bulletin issued, the adolescent Timber Tiger has issued two for its ST-L model—both are mandatory. While some may see that as negative, I see it as a positive. That indicates the company cares about its customers. I worry far more about a company that has issued no service bulletins as fleet hours grow and builders provide feedback.
Arion Aircraft
flylightning.net/ls-1-service-bulletins.html
I’m including this language from an Arion Aircraft Lightning LS1 service bulletin as it details how the completion of the service bulletin must be documented for both the SLSA and ELSA versions of the LS1. For EA-B aircraft, it would be wise for the qualified individual (A&P, or the person who holds the Repairman Certificate for the EA-B on which the work is being performed) to note a bulletin’s compliance in a similar manner:
“Level of certification required for SLSA Lightning LS-1. Any work called for by this letter must be carried out by personnel holding a Light Sport Repairman / Maintenance rating or a licensed A&P mechanic. On completion of the work, the authorized repairman must note the completion of the actions required by this letter in the aircraft’s maintenance logbook. This note should specify what work was carried out, reference this Notification, indicate the date of the work and the identity (including license number where appropriate) of the person carrying out the work.”
Engines and the AD/Service Bulletin
While many think of ADs/Service Bulletins as applying to airframes, engines (and propellers and “appliances”) are affected as well. It goes without saying an AD issued by a certified aircraft engine manufacturer should be complied with even if the engine is bolted to an EA-B. Then there are the engines that fall under the experimental category. These are often land-based vehicle engine conversions, or engines, like the Jabirus, which are certified in other countries but not the U.S. As with my airframe survey above, this is by no means a complete list of engines.
Jabiru Engines
jabiru.aero/service-bulletins-letters/
Arion Aircraft, the U.S. Jabiru engine distributor, defers to Jabiru Aircraft Pty Ltd (Australia) for service bulletins related to the engines. Jabiru groups all service bulletins by airframe or engine. In my brief look at some engine service bulletins, I did not find clear language defining the urgency of individual bulletins, but the preface to the listing includes this common-sense statement: “Jabiru strongly recommends the implementation of all service notices, in the interests of safety, regardless of the product’s certification basis or the aviation authority under which the product is operated.”
Viking Aircraft Engines
Viking publishes service bulletins segregated by those that apply to all engines in their line and those specific to each model. Some are marked mandatory, others not.
AeroConversions AeroVee
aeroconversions.com/support/aerovee_sb.html
AeroConversions (the name under which Sonex markets its VW-based engine conversion) published a chart of both required and optional service bulletins. They fall into the categories of required, suggested, and optional.
Fly Corvair
flycorvair.net/category/safety-alerts/
William Wynne uses the term “Safety Alert” and calls for “Suggested Action” because, in his words, “Corvairs are experimental engines, and as such, do not have Airworthiness Directives and Service Bulletins in the same form as certified engines do.” His safety alerts read more like a conversation. That’s not an indictment; in fact, it’s somewhat refreshing. It feels like he’s invited you to take a seat while he explains the origin of the problem and details how the corrective action came to be.
Very informative article, but I believe you are incorrect regarding the FAA being able to enforce compliance with safety notifications for experimental light sport aircraft. ELSA is experimental just like EAB, so once airworthiness has been issued, there is no means for enforcing compliance. Compliance of all previously issued directives is required at certification.
I do agree that not complying with a safety directive, just because you don’t have to, is not a smart choice.
I know there is no way the list can be exhaustive, but I’d like to add two more to the mix (and yes, I have a direct connection to them – nothing to hide there!)
Sling Aircraft – all information available as PDFs on the website, from least to most urgent:
Information Letters – https://slingaircraft.com/technical-documents/information-letters/
Notifications – https://slingaircraft.com/technical-documents/notifications/
Service Bulletins – https://slingaircraft.com/technical-documents/service-bulletins/
Safety Alerts – https://slingaircraft.com/technical-documents/safety-alerts/
Rotax Engines – you can get information based on terms as general as the type of engine to as specific as by serial number, and they do have service bulletins based on S/N:
https://www.flyrotax.com/p/service/technical-documentation
Just to throw wood on the fire…I realize that AC’s are advisory and not regulatory, but I question the totality of the applicability of your statement Kerry “The FAA doesn’t issue ADs for E/A-B aircraft and can’t enforce safety notifications issued for E/A-B aircraft.”
AC 39-7D says in paragraph 9b on page 4:
b. Non-TC’d Aircraft and Products Installed Thereon. Non-TC’d aircraft (e.g., amateur-built aircraft, experimental exhibition) are aircraft for which the FAA has not issued a TC under part 21. The AD applicability statement will identify if the AD applies to non-TC’d aircraft or engines, propellers, and appliances installed thereon. The following are examples of applicability statements for ADs related to non-TC’d aircraft:
(1) “This AD applies to Honeywell International Inc. Auxiliary Power Unit (APU) models GTCP36-150(R) and GTCP36-150(RR). These APUs are installed on, but not limited to, Fokker Services B.V. Model F.28 Mark 0100 and F.28 Mark 0070 airplanes, and Mustang Aeronautics, Inc. Model Mustang II experimental airplanes. This AD applies to any aircraft with the listed APU models installed.” This statement makes the AD applicable to the listed auxiliary power unit (APU) models installed on TC’d aircraft, as well as non-TC’d aircraft.
(2) “This AD applies to Lycoming Engines Models AEIO-360-A1A and IO-360-A1A. This AD applies to any aircraft with the listed engine models installed.” This statement makes the AD applicable to the listed engine models installed on TC’d and non-TC’d aircraft.
Good reply! I think folks should just wrap their head around this: don’t expect an AD issued for your airframe. But the engines, propellers, appliances are fair game.
Blanket statements that ADs are not applicable to Experimental Amateur Built airplanes is misleading.
Well researched article! Thank you for making the time and effort to create this informative article.
WAIT A MINUTE! YOU’re NOT UP TO DATE on the S-LSA requirements, Kerry.
Once an E-LSA meets it’s ASTM compliance and is issued an E-LSA airworthiness certificate, it can be modified, as desired by the owner/operator, and — in effect — is in the same category as an E-AB airplane which you correctly define. It WAS compliant but any changes made by the owner / operator are authorized at that point. SOME builders even went so far as to change the category of license from E-LSA to E-AB but this wasn’t really required. Scott, above, has this correct.
Your first paragraph statement, ” … the FAA can enforce safety notifications issued for aircraft licensed in the ELSA or SLSA categories” is now INCORRECT. For E-LSA, it was never correct after it was deemed “compliant.” For S-LSA, it WAS correct. This just changed due to MOSAIC with changes to FAR 92.327 as explained by SAIB 2026-06 dated March 12, 2026..
For instance, if someone built a Vans RV-12iS, it would have to be built “compliant” with Vans designs/drawings UNTIL it received it’s airworthines / compliaince E-LSA certificate. At that point, it — effectively — is a pseudo E-AB and could be modified by the owner/operator and was not subject to Vans safety bulletins.
For all E-AB designs as well as E-LSA and S-LSA, the manufacturer is still required to provide safety directives — or whatever they’re called — but they are NO LONGER MANDATORY for S-LSA.
This does NOT alleviate the requirement for an aircraft to be “airworthy” per FAR 91.7, but airworthiness no longer requires compliance with the safety directives. THIS IS THE BIGGIE, here.
I see this as a positive because your article subtly points out a shortcoming of the system as it WAS. Persons performing a condition inspection had a heckuva time finding out what the safety directives WERE. Now, the FAA will issue AD’s against the S-LSA aircraft and it’ll be easy to find them in a standard way.
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On March 12, 2026, the FAA issued SAIB 2026-06, Light Sport Category Aircraft Continued Airworthiness, which says, in part:
“Prior to MOSAIC, continued operational safety of light-sport category aircraft was managed through manufacturer’s safety directives, which were issued as part of their continued airworthiness system to correct safety of flight issues per § 21.190(c)(5) (amendment 21-85). Owners or operators of affected aircraft were required by § 91.327(b)(4) (amendment 91-378) to comply with applicable safety directives.
The MOSAIC final rule amended § 21.190 requirements for issuance of special airworthiness certificates for light-sport category aircraft, effective July 24, 2026. Per the amended § 21.190(d)(9), the manufacturer continues to be required to monitor and correct safety-of-flight issues through the issuance of safety directives.
The MOSAIC final rule also removed the § 91.327(b)(4) requirement for an owner or operator of a light-sport category aircraft to comply with safety directives issued by the aircraft manufacturer. This removal in effect rescinds the operator’s mandatory compliance with manufacturer-issued safety directives beginning October 22, 2025, including safety directives issued prior to the final rule. The FAA notes, however, that § 91.7 prohibits any person from operating a civil aircraft unless it is in an airworthy condition. Where a safety-of-flight condition exists on an aircraft, that condition would need to be corrected for the aircraft to be considered in an airworthy condition to satisfy the § 91.7 requirement.
The FAA acknowledges that it does not typically issue ADs for products lacking type certificates, nor has it historically done so for light-sport category aircraft. As of October 22, 2025, the requirement under § 91.327(b)(4) that an owner or operator of a light-sport category aircraft comply with applicable safety directives has been rescinded. Consequentially, the responsibility for mandating continued airworthiness requirements of light-sport aircraft now resides with the FAA in conjunction with the operators’ requirement to limit flight to airworthy aircraft in accordance with § 91.7.
Many safety directives identify critical safety-of-flight or other airworthiness issues and serve as an important means of maintaining the safety of light-sport category aircraft. The FAA will evaluate these safety directives and monitor safety data related to light-sport category aircraft to determine if mandatory FAA action is necessary through the issuance of an AD.
Monitoring safety data largely depends on voluntary reporting from general aviation operators and maintainers. As such, operators and maintainers of light-sport category aircraft are encouraged to report safety events through the FAA’s Service Difficulty Reporting System at sdrs.faa.gov. The FAA places particular emphasis on light-sport category operators voluntarily reporting in-service safety of flight issues.
Updates to FAA policy to address the continued operational safety changes for light-sport category aircraft have been made to FAA Order 8110.107 Revision B Change 1, “Monitor Safety/Analyze Data,” dated September 25, 2025, available through the FAA’s Dynamic Regulatory System at drs.faa.gov. Additional changes to policy and guidance may be forthcoming.
Recommendations
FAA recommends light-sport category aircraft owners, operators, and maintainers:
1. Continue to comply with existing and future manufacturers’ safety directives to address safety concerns on their aircraft.
2. Voluntarily report any instances of failures, malfunctions, or defects through the FAA’s Service Difficulty Reporting System at sdrs.faa.gov. Such voluntary reporting is especially important to alert the FAA of in-service safety of flight issues.”
(N.B.: Highlighting and underlining are my own to accentuate important points of the new SAIB which was written to explain changes to FAR Part 91.327)
_______________
The crux of this change is that the FAA says an owner / operator is no longer mandated to perform every safety bulletin or whatever issued by manufacturers. In essence, the FAA is taking over this function and WILL issue an AD against the S-LSA (read, ASTM compliant LSA per MOSAIC, Light Sport 2.0 Part 2 coming this summer), IF FAA feels it necessary. They say that it’s a good idea to do the required ‘whatever’ but it’s no longer mandatory and failure to incorporate is no longer cause for challenge by the FAA.
Sorry for the long diatribe but — as a very long time A&P — I feel this is a subtle albeit MAJOR change to the way these airplanes will meet continued airworthiness and is NOT receiving proper accentuation. EAA put out a brief statement on it but that was all.
I want to underscore one additional point spelled out specifically in SAIB 2026-06:
“This removal in effect rescinds the operator’s mandatory compliance with manufacturer-issued safety directives beginning October 22, 2025, including safety directives issued prior to the final rule.”
So, this means that this rule is RETROACTIVE. Any manufacturer safety directive issued prior to October 22, 2025 is NOT MANDATORY, compliance is RECOMMENDED but failure to comply does not automatically render the S-LSA aircraft not airworthy.
The FAA … making simple stuff hard since 1958
To all: I just detected a copy / paste error in what I printed above quoting SAIB 2026-06.
I missed a third paragraph which should be inserted above which underscores that the manufacturers of S-LSA are still responsible for producing safety directives per FAR 21.190(d)(9) prior to pointing out that owners / operators are no longer REQUIRED to comply with them (including retroactively) in the fourth paragraph of the SAIB:
“The MOSAIC final rule amended § 21.190 requirements for issuance of special airworthiness certificates for light-sport category aircraft, effective July 24, 2025. Per the amended § 21.190(d)(9), the manufacturer continues to be required to monitor and correct safety-of-flight issues through the issuance of safety directives.”
I tried to get it right but missed that important paragraph three.