By Lisa Turner, EAA Lifetime 509911
This piece originally ran in Lisa’s Airworthy column in the October 2024 issue of EAA Sport Aviation magazine.
The history of flight is rooted in creative ideas. The drive to test “what ifs” is fundamental to our nature. We get to breakthrough discoveries by combining inventions and experiments with the willingness to accept risk. Children do this best. Ask any 8-year-old how to do something, and they will be happy to describe innovative ideas and methods.
The problem with experimentation in the airplane world is that risk gets the best of us. For the brave inventors out there, risk is part of the job. For the rest of us, I’m going to recommend that the testing be left to them and not us.
Why can’t we have both worlds? In some ways, we can. Not in fitting up some PA-18 wings to the Miata and seeing how fast we can get going before it lifts off (don’t try this at home), but in the small and practical things we can add to our projects, both homebuilts and certified aircraft.
The other purpose of additions and refinements in our aircraft is to reduce distraction. You’re probably already well aware of the tendency to run off the road when you’re driving or not see another car because you were fiddling with something or looking at your phone. We have a tendency in the airplane of fiddling with electronics or looking for something and discover we’ve lost 200 feet of altitude and 10 degrees of heading.
In 1985, Tony Bingelis was thinking these additions through in articles he called “Aircraft Interiors.” He includes plans for map cases, a stack vent, rudder pedal extensions, a glareshield, visors, and more.
The homebuilt kits of today have added more amenities since then, but they have also made the process so closed that it may be hard to make a change. I wouldn’t let this stop you, but I would check with the manufacturer on the changes or additions you want to make. You’ll likely find that the manufacturer has already thought of many of the things on your list.
If you are in the plansbuilder group, this is less of a problem in terms of freedom to experiment. However, if the designer is still around for consultation, I would run the changes you want to make by them.
A few years ago, I wrote about gotchas in making changes in both experimental and certificated aircraft (see EAA Sport Aviation, Airworthy, “Changing Things: Top Traps,” July 2022). A major change, whether it be an experimental or a certificated airplane, can affect weight and balance, structural strength, reliability, performance and flight characteristics, and airworthiness in general. These changes are tightly regulated for certified aircraft and subject to review and a possible retesting phase in experimentals, depending upon what the change is and what the operating limitations tell you to do.
What I’m going to suggest are what we’d call “minor changes,” or changes that won’t affect operating characteristics, structural integrity, or weight and balance. Minor changes are simpler and have less regulation around them, but there are still some caveats we should know when making modifications to our airplanes.
According to FAR 21.93, a minor change is “one that has no appreciable effect on the weight, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness of the product. All other changes are ‘major changes’ (except as provided in paragraph (b) of this section).”
As we look at the things we can do in our homebuilt or our type-certificated airplane, review the additions or changes carefully to make sure you’re not crossing the line into what could be classified as a major change. Here are some things to consider.
Homebuilts
The best time to brainstorm ideas is before you begin your build, though you can still do a lot if you are halfway through the build or even later than that on things like visors, locks, and handholds. Just as you can add accessories to a car you buy, you can add plenty of extras to an airplane whether you built it or not.
Controls. As soon as you’re able to climb into the cockpit and make engine noises, see how the fit will be for controls. Check the rudder pedals, the brakes, freedom from interference in the footwell, your seating position, your line of sight, your throttle and switches, and areas where you might mount a GPS or tablet. Do you like the setup? What would you change? For example, a machine shop can change heel brakes to toe brakes or add extensions.
Seating. Unless you are planning on keeping your airplane forever, plan for the next owner. Many homebuilt seat arrangements are not adjustable. In this case, make the reach farther away, and use cushions to take up space.
Compartments. There is plenty of opportunity to build in spaces for lockable, hidden, or visible containers for things such as pens and pencils, charts, paperwork, flashlights, gloves, cellphones, coins, etc. These are best added at the beginning.
Carpeting and soundproofing. The manufacturer may have already thought of this, but if not, you can decide. The obvious problem with soundproofing and or carpet is weight. I added both to my Pulsar, but I’m a lightweight, and I wasn’t thinking about resale. It ended up not adding a lot of weight, and the next owner was pleased with how quiet the airplane was.
Mounts or holders for fire extinguishers, headsets, extra electronics, oxygen kits, and sun shields.
Baggage compartment security. Add cleats or D-rings to keep stuff where it belongs, add a separator to keep things organized, and add covers and locks.
Extra panels. Depending on the configuration of your aircraft, consider adding another switch panel where it’s easy to see and reach, or break up the gauge locations.
Certified Aircraft
If you’re restoring an aircraft, you have quite a bit of leeway to make alterations and additions, but you need to follow the rules for approvals. These can include finding an STC for what you want (like a better set of brakes), filing a 337 (change form) if you already have FAA-approved data, or locating a designated engineering representative to review and approve a modification. Your supervising A&P mechanic will help you with these.
Items to think about on your restoration can include a map case, armrests, handholds, headset holders, compartments, and mounts for electronics.
Things to Think About
If you’re building or restoring an airplane, you probably love the tinkering and the detail. This doesn’t mean that you can’t plan the additions and give them to a craftsperson to execute, just as you would with upholstery, panels, and paint.
Don’t reinvent the wheel. Before jumping into a scratch design, look around for aftermarket accessories for airplanes, cars, trucks, and motorcycles. Map pockets, compartments, mounts, and other amazing things are found during online shopping.
Consider labeling items once installed. Not everyone will know what everything is.
Some of the items you add will have plans (location, dimensioning, material). Make sure these go with the pilot’s handbook and the maintenance manual for specifications and troubleshooting for the next owner.
For side or console compartments, make sure you’ve installed secure but removable bulkheads or separator panels near or over any control linkages. You don’t need things falling into the cables to jam in flight.
Check the weight of the airplane as you go. We almost always end up with heavier airplanes than the manufacturer’s specification listing. Check the final weight and balance carefully. While the added items may be small, they add up.
Ask your technical counselor for advice. They can add perspective and additional ideas.
Make sure you don’t compromise any structure with your creations. For example, building in a chart case (“glove box”) hanging from the avionics panel may require reinforcements or present interference problems that you won’t find out about until you fly the airplane.
Finally, run your ideas past the builders/owners group for your airplane. The feedback will be helpful, and they may have suggestions you didn’t think about.
Don’t forget the cup holders.
Lisa Turner, EAA Lifetime 509911, is a manufacturing engineer, A&P mechanic, EAA technical counselor and flight advisor, and former designated airworthiness representative. She built a Pulsar XP, a Kolb Mark III, and half of a RotorWay Exec helicopter. Her book, Dream Take Flight, details her Pulsar flying adventures. Lisa loves hearing from readers. Write her at Lisa@DreamTakeFlight.com.