On July 14th, the pilot of an experimental amateur-built Cassutt aircraft took off from runway 26 at Rosamon Skypark (L00). Just after his wheels left the runway, the engine rpm dropped suddenly. The pilot, in attempt to regain lost power, began playing with the fuel/air mixture and began a left turn. He never made it back around, stalling, and immediately crashed, destroying the aircraft (miraculously, the pilot survived).
In the post-accident analysis that followed, it was learned that the builder had ignored airworthiness directives and service bulletins related to the carburetor and venturi. While there are many out there that still believe ADs don’t apply to homebuilts, if you have an unsafe product on your experimental aircraft, in the interest of your life, your family, the experimental community, and general public…you should probably fix that.
It has been said that any serious homebuilder worthy of an experimental certificate would go beyond ADs and ensure compliance of any known safety directives, which carry no legal obligation beyond S-LSA. As Marc Cook writes in his piece, “Do ADs Apply to homebuilts?”, “you are the holder of the repairman certificate for your airplane, so it’s incumbent on you to think like an IA”.
With this backdrop in mind, we find it quite baffling that homebuilders are still arguing that they don’t have to legally comply with ANY type of directives whatsoever, safety be damned. To make matters worse, the EAA supports this view.
Because ADs follow a well-researched, documented process of identifying unsafe issues, going against such well documented evidence is foolish, even reckless. With over 30,000 amateur-built (E-AB) aircraft under N-Registry and over 4,000 accidents by homebuilders since the year 2000, this becomes less of a laughing matter. “We all know ADs are written in blood,” an inspector told me.
Back in the 1960’s, Part 39 originally imposed two restrictions on AD issuance. The unsafe condition giving rise to an AD must (1) have been found as a result of service experience and (2) be with respect to a design feature, part, or characteristic. Both restrictions were originally imposed prior to the Federal Aviation Act (which combined the safety rulemaking authority of the CAB and CAA and vested it in the FAA). In 1964, a change was made (30 FR 8826) to broaden the FAA’s authority related to airworthiness directives, removing the two restrictions and allowing AD ’s to be issued for unsafe conditions however and wherever they were found.
The next major shift came in 2002 when the FAA clarified some of the ambiguity between Part 21 and Part 39 concerning the definition of “product”. In Part 21, product is defined as "aircraft, engine, or propellers", whereas in Part 39 it is specifically defined to include appliances as well. The FAA went on to say,
“We will continue to issue ADs applicable to ‘appliances.’ To clarify that we will use this term in this part, we have revised the wording in this section [39.3] to state that ADs cover the following products: aircraft, aircraft engines, propellers, and appliances.”
In 2011, the AD Aviation Rulemaking Committee (ARC) within the FAA clarified some new questions (read: loopholes) related to AD compliance, namely, if owner operators had to continually comply with ADs forever (vs. once) and arguments against having to comply with overly prescriptive AD actions.
The argument from those against continuous compliance were that ongoing inspections went beyond the scope of the FAA’s mandate to address an initial unsafe condition under 39.11. In response, the FAA made it crystal clear that just because you complied with an AD at that initial time, that doesn’t mean you’re off the hook down the road. Knowingly forgoing to deal with an AD safety issue that happened to return after compliance would still be in violation of 43.13(b) on the maintenance side and 91.403(a) on the operator side.
With respect to those ADs that are overly prescriptive—and believe me, there are a handful we know are a royal PITA—the FAA responded back that the Administrative Procedure Act (which created the Federal Register and the procedures that government may propose and establish regulations, like ADs) is prohibited from making rules that are “arbitrary and capricious”. Provided that the actions of the AD are reasonable related to the purpose of resolving the unsafe condition, the FAA has full discretion to do so. For those wishing to obtain relief from what they might consider an overly burdensome AD, the FAA noted the the NPRM and AMOC (alternative methods of compliance) approval process.
In 2012 the FAA issued a new Advisory Circular updating guidance related to the applicability of ADs from a broad interpretation of the language to an explicit interpretation, saying that unless otherwise stated, ADs of any category applied ONLY to type-certificated aircraft. This was the key line the experimental community was looking for, since they believed ADs didn’t apply to them.
In the updated Advisory Circular, the FAA updated its language to show examples of how this new interpretation might be used. "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 used in the Advisory Circular to determine if the ADs apply:
In reality, the FAA didn’t do much to settle the argument for either side other than to repeat what everybody was already doing: read the letter of the AD. Nevertheless, folks from both sides took it to mean whatever they wanted it to mean, and took their plea to the forums, shouting “Experimental Aircraft Exempted from ADs!” to anyone who would listen.
In simple terms, Part 39—which is law—says that if you have the product on your aircraft, the AD applies, while AC 39-7D—which is guidance—says it only applies if the AD mentions a broad statement related to all aircraft.
In the interest of safety, let’s look at how this interpretation might affect an E-AB aircraft with a Lycoming IO-360-A1A engine in it. Based on the below, of the 16 engine ADs affecting it, only 3 have the specific language, “but not limited to…”! Of the 5 appliances in this example, only 2 have the specific language, “certificated in any category” or the “but not limited to” phrasing, meaning they would apply to non-TC'd aircraft (as per AC 39-7D):
If experimental owners are foregoing 80% of ADs (13/16) over their interpretation of the TC vs. non-TC’d aircraft, this is pretty disconcerting. We’d like to think most experimental owners with a type certificated engine (or appliance) in their experimental aircraft are staying up to date, but it’s probably safe to assume many are not.
Analyzing NTSB Accident data for homebuilder accidents with reciprocating engines, we see over 4300 accidents since 2000, with over 800 related to known some type of “maintenance issue” or “inadequate inspection”. While we can't tell what may have caused an engine failure or mechanical problem, you can bet a few of these are going to be related to missing AD compliance. Staring at the list of crankcase issues, connecting rod failures, fuel leaks, and gearbox malfunctions across the homebuilts with certificated engines is truly shocking, if not jarring.
The experimental community is a large one, with passionate builders, pilots, and mechanics focused on building a flyable airplane. The certification process itself, while having no specific Type Design, essentially makes you the OEM of record. It’s a wonderful process that comes with natural limitations on what you can and can’t do with that aircraft (i.e., can’t carry people for hire, instruction, etc.)
While specifically exempt from Part 43, experimental category aircraft are NOT exempt from the other federal aviation regulations. Often, the FAA will have to deal with someone trying to convert a type-certificated aircraft into an Experimental so that they can avoid whatever expensive repairs that aircraft might need.
The EAA condones this behavior outright on their website: “it is FAA policy that experimental certification should be used for certain specific purposes, and is not to be used as a way around type certification, Airworthiness Directives (AD’s), Supplemental Type Certificates (STC's) and field approvals.”
Experimental aircraft and builders are tied to safety initiatives and safeguards just like everybody else. Here is a table outlining a potential homebuilders safety risk matrix:
By definition, if an AD exists that affects your experimental aircraft’s engine, propeller, or appliance, then you may be in a situation where an unsafe condition exists or is likely to develop. While Part 39.5 explicitly says ADs are issued in the event that a) an unsafe condition exists in the product and b) the condition is likely to exist or develop in other products of the same type design, there are multiple safeguards in place (see table above) designed to catch unsafe conditions, reckless behavior, or owners looking to skirt safety.
The NTSB accident databased is filled with homebuilder accidents, many with inspection or maintenance issues clearly determined in the post-accident report and many more where we will never truly know what happened. The list is sobering, no matter what type of aircraft or certification your flight operation falls under.
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.
Our attempt in this writeup was to address safety concerns within the general aviation community around ADs as they pertain to experimental aircraft. We are not the FAA, but we care deeply about safety, and are proponents of whatever can help improve the safety record of the entire community. We believe in this stuff – which is why we’re constantly investing in our products to help operators, maintainers, and even the FAA, access pertinent safety data for their aircraft or their operation.
If you care about safety and putting in place proper maintenance and safety processes, come and see why over 30% of the GA fleet is using our tools to stay safe, legal, and compliant. We offer a 10-day free trial here.
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