Maintenance Matters

A&P mechanics and Experimental aircraft.


Experimental aircraft must have this passenger warning and an EXPERIMENTAL decal in places that are visible to any passenger. A condition inspection should not be signed off if these items are missing. A mechanic who has only worked on certificated airplanes may not be familiar with this requirement.

With more and more Experimental/Amateur-Built aircraft being owned by people who did not build them, there is more and more demand for A&P mechanics to perform maintenance and condition inspections on these aircraft. Unfortunately, there is little in the typical formal training or testing of A&Ps that prepares them specifically for these tasks. At first glance it may seem that the Experimental world is pretty much the “Wild West” where anything goes and aircraft are exempt from the normal rules, but that is an exaggeration at the very least. It is in fact a place where the rules are less clear, or at least less well defined, but good aviation practices still apply, or at least they should, if you, as an A&P mechanic, are going to sign your name to them. We should note that for the purposes of this article, Experimental refers primarily to Experimental/Amateur-Built (E/A-B).

A compression test should be part of every Experimental condition inspection, just as it is for a certificated annual inspection. Record the results in the engine logbook.

In the certificated world an A&P must have inspection authority (IA) to perform an annual condition inspection or sign off a major change, but for Experimentals this is not the case. An A&P (without IA) may perform a condition inspection, and anyone may perform maintenance or make a major change, subject to that aircraft’s operating limitations. This means that literally anyone who has the owner’s permission may modify and/or maintain an E/A-B aircraft with no prior certification or formal training. The intent of the E/A-B category is to allow for experimentation for the education and recreation of those involved. The only limits on that freedom are that once a year, either the holder of a repairman’s certificate for that aircraft or a licensed A&P mechanic must attest to the airworthiness of that aircraft, and after any major change, the aircraft must be returned to the Phase I flight testing period for at least 5 hours, until its airworthiness can be once again demonstrated. This major change language can be found in the operating limitations assigned to that aircraft. The good news is that this opens up a whole new world of potential customers to an A&P mechanic. The bad news is that this opens up a whole new level of responsibility to any A&P mechanic who chooses to put his or her name in someone’s logbook after these words: “I certify that this aircraft has been inspected on (date) in accordance with the scope and detail of 14CFR part 43, appendix D, and was found to be in a condition for safe operation.”

An oil change and inspection of the oil filter should be a part of an Experimental condition inspection, just as it is a part of a certificated annual inspection. Note the oil change in the engine logbook.


As was said before, there are no qualifications for working on an E/A-B aircraft. However, the condition inspection must be signed by the holder of a repairman’s certificate, which is only issued to the original builder, or by a licensed A&P mechanic. The builder obviously has experience working on the aircraft he or she built, but if the builder is no longer the owner, he or she is not likely to be available for the condition inspection, which leaves it to an A&P mechanic. Assuming that A&P has experience performing condition inspections on other aircraft, Experimental or not, there are no other qualifications required by the regulations.

Poor practices such as using zip ties to secure hoses and wires to engine mount tubes is not strictly prohibited, but it is not consistent with good aviation practices and should be corrected. As an A&P mechanic you do not have to accept poor practices just because they are not “illegal.”

That said, prudence and good judgment strongly recommend a reasonable familiarity with the type of aircraft involved. For example, a mechanic with lots of experience working on Lycoming and Continental engines would be ill-prepared to perform a condition inspection on a plane with a Rotax engine unless he or she had received additional training on Rotax engines. Similarly, a person with no composite experience would be well-advised to seek out the assistance of a more qualified person if a composite airplane is to be inspected. These are not regulations, just common sense.

The Inspection Process

The scope and detail of a condition inspection on an E/A-B aircraft is pretty much the same as for a certificated aircraft. 14 CFR 43, appendix D outlines the process. The problem for the A&P mechanic is that there is no type certificate data sheet (TCDS) or factory approved service instructions for an Experimental aircraft, because there is no type certificate. Experimental aircraft builders may build their planes any way they wish, as long as they are willing to attest to the plane’s airworthiness, convince the FAA that there is nothing obviously un-airworthy about it, and successfully test it as per the operating limitations. As an A&P it is your responsibility to certify that it is airworthy at the time you inspect it (or not), but you will not have any definitive criteria for making that judgment.

Be sure to do a thorough check of enclosed areas that may be accessible to unwanted pests. You just never know what you may find.

“No definitive criteria” does not mean no criteria at all. There is AC 43.13-1B, which covers a great deal of what is and what is not airworthy. An Experimental builder can certainly say that this does not legally apply to Experimental aircraft, but you as an A&P can also say that you are not going to sign the condition inspection. In addition to industry standard practice, the manufacturer of each kit has plans and/or assembly instructions that can shed light on how the plane was supposed to be built. These are not legally binding, but they are a good starting point for evaluating the construction of a plane if there is some doubt about its airworthiness. Hopefully these have been forwarded to the current owner, but sometimes not, so you may have to do some digging to find what you need.

Every successful condition inspection will end with this sentence in the aircraft logbook. Your signature, name, and certificate number need to be included, along with the date and tach time.

Perhaps the biggest difference between certificated and Experimental aircraft when it comes time for a condition inspection is that you cannot assume that the aircraft in question was built according to plans. Cessnas are built according to a type certificate, Experimentals are not, and may or may not be built according to the kit maker’s plans. There is some satisfaction in knowing that an Experimental airplane has been flying for at least a year before you got there, but there is an added layer of responsibility placed upon the A&P performing a condition inspection if he or she is not familiar with the type of aircraft being inspected. Luckily, a large number of Experimentals are one model or another of the RV series, and there is a lot of similarity between the various models, so an investment of time in the first condition inspection will likely pay off in the future.

ADs and Service Bulletins

As a general rule, airworthiness directives (ADs) do not apply to Experimental aircraft. In fact, the FAA has said clearly that ADs do not apply unless Experimentals are specifically called out in the AD as being covered. No such ADs have been issued with this requirement as of this writing. However, the general admonition that an aircraft must be in a condition for safe operation does apply. This presents a conundrum for the A&P mechanic, in that he or she must decide what needs to be applied to any particular aircraft. Certainly, if a propeller hub has an AD in effect that says the hub needs to be inspected every 100 hours, it is not unreasonable for an A&P mechanic to demand that the inspection be performed before signing the condition inspection. The owner is also not legally required to comply, just as you, the A&P mechanic are not legally required to sign the condition inspection if you aren’t comfortable with the aircraft.

Experimental airplanes are very seldom subject to airworthiness directives, which can at most apply to certificated components such as engines and props. But many kit makers issue service bulletins that should be complied with and noted in the airplane’s logbook. This is not legally required, but is highly recommended.

Service bulletins are similar in that they specify changes and/or inspections that the kit manufacturer believes are prudent for continued safe operation, but they have no legal status and are thus not required. There is also a great deal of variation from one kit maker to the next as to how diligent they are about issuing service bulletins. It is my opinion that service bulletins should be addressed as part of the condition inspection. How they are addressed may be subject to some interpretation, depending on the aircraft involved and how it was constructed, but skipping a service bulletin should only be done for a very good reason, few of which come to mind.

Where Do You Draw the Line?

As an A&P mechanic you are faced with requiring your customer to do things that are not absolutely required under the law but make good sense. The time to talk about these things is before you have done a lot of work that you have not yet been paid for. If you don’t do this at the beginning, it can put you in a poor position to refuse to sign a condition inspection when the owner does not want to spend the money or take the time to comply with a service bulletin or AD. Establish boundaries up front and stick to them. If you know of applicable ADs or service bulletins (you should make it your business to know), then point them out to the owner and make your expectations clear.

Not every A&P is troubled by this situation. I recently began a condition inspection on a 19-year-old RV-4 that had no service bulletins signed off or performed. There were 18 signed condition inspections in the logbook when I got there and nothing else (which is admittedly perfectly legal), but there is now a list of service bulletins that have been completed and signed by the owner, since he is the one who did the work. These things weren’t difficult or expensive to do, and the airplane is now safer because of it.

A budding entrepreneur came up with a fix on his own for something that may or may not be a problem on some RV models. The owner of this plane decided that he would feel better with these reinforcements installed. As an A&P mechanic signing off on a condition inspection, you will need to decide if such an addition to the airframe is a detriment to safety. In this case, it seems likely that it will do no harm.

Major Changes

The definition of a major change or modification is similar for Experimental and certified aircraft, but how they are handled is quite different. The operative section of the FARs is 21.93. This defines a major change as any change that is not a minor change. A minor change is one that “has no appreciable effect on the weight, balance, strength, reliability, operational characteristics or other characteristics affecting the airworthiness” of the aircraft. Added clarification will be available from the local FAA FSDO, which must be contacted and provide a written response for any requested major change and will also assign a test area as required by the operating limitations.

The biggest differences an A&P will see with a major change are these: Anyone can do the work, including a non-builder owner, and a major change requires re-entering Phase I Flight Testing for a least five hours, along with the required logbook entries. No engineering data is required. Form 337 is not applicable. There are no STCs or field approvals. The owner just does the work and flies it. However, within the next several months, a condition inspection must be signed off by someone who is willing to look at the major change and declare it (and the rest of the plane) safe for flight. That someone is either the original builder and holder of the repairman’s certificate or an A&P mechanic such as yourself.

Some major changes require additional paperwork—Form 8130-6. These changes include going from a fixed to a constant-speed prop or vice versa and going from one type of engine to another—reciprocating to turbine for example.

The logbook should note the major change before the first test flight and be properly endorsed at the end of the flight test period as per the operating limitations. If a major change has been performed without the appropriate logbook entries and flight testing, it is in violation. You should not sign a condition inspection on such an aircraft. Don’t forget that a major change will require new weight and balance paperwork. You will need to verify that it has been done or take care of it yourself.

If possible, it would be time well spent to talk to the person who performed the major change work to get a better feel for the scope of what was changed. For example, a relatively common major change is to switch from an auto-conversion powerplant to a Lycoming engine. That change can involve alterations to not only the engine and the motor mount, but also the prop, the cowl, the fuel system, and the electrical system, plus other things. You may be the first person to give this work a thorough examination since it was done. You will have much to consider.

Why Get Involved?

By this time, it sounds like an A&P mechanic would have to be a little crazy to take on an Experimental condition inspection for a few hundred dollars and who knows how much liability. There is something to that argument, but it isn’t really as bad as it may first appear. Most owners want to have safe planes and will do what it takes to get them that way and keep them safe. And most Experimentals are fairly simple and fairly well built. Finding what is wrong with most planes and fixing it is not brain surgery. This is a large potential market and this is work that you as an A&P can do. That said, you will need to learn how to spot problem planes and problem owners quickly if you are to avoid trouble.

Just as with certified airplanes, Experimentals that haven’t flown for quite a while are likely to have more problems than planes that fly regularly, and that means a bigger bill to get it through a condition inspection. Owners that talk about not wanting to spend any money or about not being legally obligated to do needed repairs or maintenance are likely to cause you grief. You don’t have to work for them and, in at least some cases, simply shouldn’t. But you can also help them save money by letting them do the work, except for the actual inspections. The best thing to do is take the time to get familiar with the aircraft and then talk to the owner about what you see and what you will require to be done to get the plane signed off. If there is not a meeting of the minds little has been lost. Create reasonable expectations on both sides and then meet them. If this can’t be done, then move on.

Dave Prizio is a Southern California native who has been plying the skies of the L.A. basin and beyond since 1973. Born into a family of builders, it was only natural that he would make his living as a contractor and spend his leisure time building airplanes. He has so far completed three—a GlaStar, a Glasair Sportsman, and a Texas Sport Cub—and he is helping a friend build a fourth, an RV-8. When he isn’t building something, he likes to share his love of aviation with others by flying Young Eagles or volunteering as an EAA Technical Counselor. He is also a licensed A&P mechanic and a member of the EAA Homebuilt Aircraft Council.

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Dave Prizio
Dave Prizio has been plying the skies of the L.A. basin and beyond since 1973. Born into a family of builders, it was only natural that he would make his living as a contractor and spend his leisure time building airplanes. He has so far completed four—two GlaStars, a Glasair Sportsman, and a Texas Sport Cub—and is helping a friend build an RV-8. When he isn’t building something, he shares his love of aviation with others by flying Young Eagles or volunteering as an EAA Technical Counselor. He is also an A&P mechanic, Designated Airworthiness Representative (DAR), and was a member of the EAA Homebuilt Aircraft Council for six years.


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