Changing Things: Top Traps

By Lisa Turner, EAA Lifetime 509911

This piece originally ran in Lisa’s Airworthy column in the July 2022 issue of EAA Sport Aviation magazine.

“You just haven’t flown until you fly a Stearman,” Ed said as he waved his arms in the air. “Being out there in the rushing wind is such a kick.”

“True, but my ultralight does the same thing for a lot less machinery — and you can see out of it,” Wendy laughed. “Have you decided to buy Tom’s Stearman?”

“I think so. It was converted years ago from a duster, but he flies it all the time, so it should be just fine.”


“No. They’re expensive, and Tom takes good care of the airplane. I can’t imagine what could be wrong with it.”

“Ah, I don’t want to be a wet blanket, but…” Wendy said. She lost Ed’s attention as he looked at the ad sheet Tom had given him. I better not say anything, she thought.

The next week, as Wendy was doing a preflight on her Quicksilver, she looked up to see Ed landing the Stearman. It was a beautiful blue color with silver stripes. Ed taxied up to the hangars, idled the big radial for a minute, and then shut down.

“Beautiful,” Wendy said. “That engine looks bigger than my entire airplane.”

“Come fly.”

“Not now. I’m going up in the aircraft with visibility.”

“Don’t say that. Once you’re up there in this aircraft, the view is wonderful.”

“To each their own. So, you’re happy?”

“Very. Next week I’m getting the annual done.”

“Why didn’t you ask Tom to include the annual as a condition of the sale?”

“Because he gave me a special deal without it.”

Wendy continued to have misgivings about Ed’s purchase as she taxied to the grass. Little did she know.

* * *

Ed greeted the A&P/IA mechanic.

“Ed? Hi, I’m Scott.”

“I have all the covers off for you, and the logbooks are right here,” Ed said.

“Very helpful. Thank you.”

Scott began the inspection in the cockpit, making notes and taking pictures. “Uh-oh,” Scott said. “The data tag is not original. Looks like someone ordered this from Amazon.”

Scott moved methodically around the plane with a stern expression.

“The wings and the metal ailerons on the airplane are not approved for this category and will have to be replaced. These dynamic and static balancers have to go. Show me your logbooks, please.”

Ed’s stomach began turning into painful knots as he handed the logbooks to Scott.

Scott continued around the airplane.

“I don’t see a logbook entry for the balance tabs on the ailerons. The hopper has been removed and a seat installed — another logbook entry that is missing. I brought a list of the ADs, and I don’t see that any of them were complied with. And no 337s.”

Scott stopped for a minute and turned to Ed. “Okay, look. I’m going to stop here and give you a chance to have someone qualified get these corrected. Once they are completed, call me and I’ll come back. In the meantime, don’t fly this airplane because it’s illegal.”

“But I just bought this, and the owner said it’s been annualed every year,” Ed stammered.

Scott smiled wryly. “I hear that all the time.”

* * *

Changes: Top Traps

In my 20s, I was obsessed with cars. I purchased a used Honda Civic. For those of you who remember that far back, these were the definition of basic. No electric anything. A few simple instruments. An underpowered engine. Crank windows. No air conditioning. I would go to sleep with the JC Whitney catalog under my pillow.

I added electric windows, cruise control, a bank of VDO electrical gauges, a high-performance clutch, a wood steering wheel, and a gearshift knob. It was so much fun. I remember thinking the only thing more fun would be if it could fly.

This explains why, 20 years later, I took a similar approach to the aircraft kit I was putting together. I had to get a thinner pillow because the Aircraft Spruce & Specialty catalog was so thick. While experimenters have a lot of latitude to make “changes,” the certificated airplanes don’t have quite the same luxury. It’s easier to coast to the side of the road safely in an over-modified car than in an over-modified airplane, which is why we have FAA regulations.

If you are willing to find the regulations that apply to upgrades, modifications, and additions for aircraft, you might be surprised at how easy it is to accomplish them legally. Patience, perseverance, and proceeding step by step will get you there. With that said, when you read through the FAA paragraphs on “acceptable data,” “approved data,” “major change,” and “minor change,” it can make your head spin. It’s not always clear-cut, and mechanics can disagree about interpretation.

Rather than get into a bog of semantics, let’s just talk about some of the traps and how to stay out of them. At whatever point you get confused and need help, consult your local A&P/IA mechanic. The FAA offices also have folks who are experts and can help you navigate the details.

If the Aircraft Has Been Annualed, Then It Is Airworthy

Humans love shortcuts and rationalization. I’m not sure where this trait came from, but it is ubiquitous in everything we do. “Well, this was working fine on last week’s flight. I’m sure it’s fine now” is one I hear a lot.

Of course, we’re not supposed to skip things because we know the omission could bite us. So, we need to “safety” our propensity for assuming all is well with good checklists and good procedures. The thing we may not want to do is dig into paperwork. I understand. But paperwork can be critical. We may not be doing the work or the annual, but as owners and operators, we are responsible for the airworthiness of the aircraft. The only way to do that is to make sure others are doing what they are supposed to be doing.

A 1946 Aeronca Champ went to a restoration shop for its third restoration since rolling out of the factory. After a year of work, it was ready for its first flight. On final checks of paperwork, the A&P/IA mechanic asked if the 1948 airworthiness directive (AD) to install leading edge reinforcements (additional PK screws) had ever been done.* The answer was no. This was an AD to correct potential structural failure in flight. After the discovery, the wings were removed and the fabric was torn off (with much angst) to begin again with the correct mechanical reinforcements installed per the AD.

On any annual, make sure the checklist has been completed, along with the documentation. It’s not difficult to do this, but it takes some discipline. It’s worth it.

*ADs are issued by the FAA per 14 CFR Part 39 to correct an unsafe condition in a product. Part 39 defines a product as an aircraft, engine, propeller, or appliance.

If the Aircraft Is Experimental, It Doesn’t Matter What You Do to It

Designing an aircraft? It’s experimental — the very definition of trying things to see if they work. Yes, of course you can do this. Be as creative as you want and play as much as you like. But once you feel you are ready to test it, get qualified help — think engineering advice — to evaluate it. Then be disciplined as you go down the “condition for safe operation” path. If you are an engineer yourself, it’s still a good plan to have someone else review the design and the test plan.

Once you have an airworthiness certificate, you may need advice from your inspector or designated airworthiness representative (DAR) for further changes to the design. Restrictions can be found in your operating limitations that the FAA inspector or DAR gave you. FAA Part 43, Maintenance, Preventive Maintenance, Rebuilding, and Alteration, does not apply to experimental certificates.

Far more common, builders assemble a kit where everything has already been tested by the manufacturer. Good craftsmanship will turn out a safe and reliable airplane. Once again, your restrictions will be listed in the operating limitations for the aircraft. If you want to change wing designs later knowing that it will affect weight and balance and flight characteristics, give your DAR or the FAA office a call and find out what you need to do. A big design change may mean reentering a Phase I test plan.

While the term experimental may sound like the Wild West, it is well controlled. There is a lot of leeway, however, and if you follow procedures, you’ll discover it isn’t that hard to make changes.

If the Aircraft Is Certificated, You Can’t Add Anything New Because It’s Too Complicated

This is where I’m going to encourage you to be creative. As long as you follow the rules, you’ll be amazed at what you can do. This is where patience and perseverance come in.

One owner who fell in love with a 1937 Waco cabin wanted dual brake pedals and a better designed parking brake. Many mechanics might say, “Don’t change a thing,” but this owner’s mechanic said, “Sure.” They designed a more effective parking brake and found an FAA designated engineering representative to review and approve it. On the dual pedals, the upgrade only required an FAA Form 337 detailing the change since it used existing approved data. While not completely painless, it was relatively easy.

STCs can also be used to modify aircraft. STCs are additions to the aircraft’s original type certificate that allow for changes to the original design. See the links at to find out more.

Avoiding the trap means opening up your mind to possibilities. The worst thing that could happen would be for the FAA to say no. If you follow the process and get a yes, then you’ve got the changes you want in an airplane you love.

* * *

Whether you are buying a used aircraft, restoring an aircraft, or building an aircraft, make sure you are flying a machine that is in a condition for safe operation — and that your paperwork reflects it.

When we wonder why there are so many regulations around aircraft maintenance and repair, we need only look at the outstanding safety record of general aviation. In my mind, it’s a worthy trade-off for the delights of flight.

Lisa Turner, EAA Lifetime 509911, is a manufacturing engineer, A&P, EAA technical counselor and flight advisor, and former DAR. She built and flew a Pulsar XP and Kolb Mark III and is researching her next homebuilt project. Lisa’s third book, Dream Take Flight, details her Pulsar flying adventures and life lessons. Write Lisa at and learn more at

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