Thanks to CAD, Building an Aircraft Kit Has Never Been Easier

Michael Molitch-Hou | Comments | December 12, 2017

Where I live, there is a small airport that can fly me to a handful of major cities on the West Coast, but it’s not an easy trip. There are usually stopovers and other obstacles that make any flight out of town a weighty decision. This has led me to ask my wife if, someday, we could just buy a tiny plane that we can fly on our own.

Not that I’d trust my piloting skills, but there is one company that might make it possible to make the flight from my tiny town to somewhere globally more relevant.

The CH750 Cruzer from Zenith Aircraft Company. (Image courtesy of Zenith Aircraft Company.)

Zenith Aircraft Company sells airplane kits. These aren’t the sorts of kits you pick up from a hobby shop for a meticulously fun Sunday afternoon. These are full-scale aircraft. We spoke to Zenith founder Sebastien Heintz to learn what it takes to create an airplane kit, including the CAD tools used to make one.

The Birth of the Kit Aircraft Industry

Heintz’s father, Chris Heintz, inspired the creation of Zenith. The elder Heintz earned an engineering degree in the 1960s, which he applied to design work on the Concorde. At the time, he wanted to own his own aircraft, but such a dream seemed out of reach— unless he built his own.

Chris Heintz went about designing his own two-seat, all-metal aircraft, which led to fellow flying aficionados commissioning designs and parts from him before he ultimately helped spawn an entire aircraft kit industry.

Sebastien Heintz grew up in the family business, developing a love for airplanes and all things flying. After attending business school, he founded Zenith Aircraft Company in Missouri in 1992. Through Zenith, the younger Heintz not only extended the work of his father, but modernized it, moving the business over from pen-and-paper drafting and manual manufacturing, to a completely digital workflow, including the use of SOLIDWORKS.

What It Takes to Make Kit Airplanes

So, what’s an aircraft kit? Imagine those balsawood planes you might find at a hobby store, blow it up 200 times, replace the wood with aluminum and you can start to imagine what Zenith makes. Though highly specialized, the industry is bigger than one might expect.

“There are more kit airplanes registered with the Federal Aviation Association (FAA) every year than there are factory built ones,” Sebastien Heintz said.

Zenith designs and manufactures aircraft kits, creating the individual parts to assemble the airframe—tail, rudder, cabin, etc.—leaving customers to purchase the engine and avionics. The company tries to put out one kit per working day, totaling about 250 per year. The kits can range around $20,000, and the engine and avionics typically cost an additional $20,000 each.

Altogether, the cost of a two-seater airplane compares to a luxury automobile or boat, but the experience of building it yourself is priceless. Plus, you get to pick out the engine, paint colors, upholstery and everything yourself, resulting in a customized plane.

“We design certain features like you would with any other product, like a car or boat: the actual wing, the position and location of the wing, the tail, etc. That part of the process isn’t really customized,” Sebastien Heintz said. “That said, every individual airplane becomes a one-off airplane. That’s one of the advantages and why the industry exists. People can build their own airplane and customize their needs. They get to choose the design because there are quite a few different designs out there. Then they can truly fully customize it as they’re choosing the engine on the airplane by choosing the avionics, radios and GPS equipment, for instance.”

If the idea of building your own airplane sounds fun, but a little daunting, Zenith hosts two-day workshops at its Missouri factory, where attendees pay to take part in the hands-on construction of the rudder tail section of an aircraft. At 3-feet tall and 2-feet deep, this component can be built easily in two days.

Sebastien Heintz explained that many customers have never really built anything before, but have a keen interest in learning.

“The real takeaway for folks is not only can they build it, but that they have invested in that interest,” he said. “It becomes more of a question of enjoying the learning process and not whether or not you have the skills and experience to build an airplane.”

If you do decide, one day, to take on such a project, it will take about 500 hours of work. Fitting this into your off-hours, vacation days and weekends, Sebastien Heintz estimates that this works out to about one to two years.

Manufacturing Kit Planes in the 21st Century

Until Sebastien Heintz took over the family’s kit plane business in 1992, the operation was entirely dependent on manual labor: hand drafting and hand manufacturing.

“Back in ’92, most of our design work was basically done with pen and paper, and we were using basic sheet metal bending brakes and press brakes, cutting the parts out manually,” he said. “Little by little we started using CAD software, both for drafting purposes and, more and more, for design purposes. Now, we’ve pretty much switched all our design and parts drafting and so forth over to SOLIDWORKS.”

All of the kit parts required to build the CH750 Cruzer from Zenith Aircraft Company. (Image courtesy of Zenith Aircraft Company.)

Zenith manufactures the individual parts for its kits in-house, beginning with aluminum alloy sheet metal. The planes are first designed in SOLIDWORKS by the company’s engineers before the parts are translated into CAM for production. Zenith has several large CNC tables for cutting out the parts and CNC press brakes to shape the parts.

“That’s really where SOLIDWORKS kicks in, both on the design side and manufacturing side. It allows us to take manufacturing to the next level,” Sebastien Heintz said. “Because the design is a solid model, we can really finalize everything completely to the last definition. We can then send the SOLIDWORKS data to the CNC machine to make the part.”

Prior to adopting SOLIDWORKS about four years ago, Zenith would drill the necessary holes in individual pieces, including the rivets necessary to attach parts together, after they were manufactured. This could add up to more than 16,000 holes. Now, the team is able to drill holes while they’re in the flat stage. This also ensures that once the parts are cut and bent, they line up perfectly for assembly. Not only has this made the design and manufacturing process easier, but it’s even made life easier for customers assembling the airplanes.

“Before, we were using Mechanical Desktop and could lay out one section, but we didn’t have a full 3D model of what it was we were working on,” Sebastien Heintz said. “Now, building everything as a solid model with SOLIDWORKS, we can accurately reflect the final design, actually locate every single hole and then send that to the CNC. Even though we’re starting from flat parts, we can drill the holes and then swing them together after and the holes will translate exactly where they need to be.”

Assembly is made even easier because Zenith is able to post its SOLIDWORKS designs online. A couple of years ago, Dassault Systèmes started offering its free SOLIDWORKS Maker Edition to members of the Experimental Aircraft Association (EAA). Because most Zenith customers are members of the EAA, they can access Zenith’s designs. This also makes it easier for customers to customize their planes, finding avionics that will suit the design, for instance.

The SOLIDWORKS model for the CH750 Cruzer from Zenith Aircraft Company. (Image courtesy of Zenith Aircraft Company.)

According to Sebastien Heintz, the company continues to look at how it can use SOLIDWORKS tools in its design and manufacturing process. For instance, SOLIDWORKS has integrated CAM directly into SOLIDWORKS 2018, something that he is exploring. The company has begun using simulation tools, as well.

In the process of partnering with the EAA, Dassault Systèmes became enamored with the kit aircraft industry. Its employees present at the event had never been exposed to kit airplanes. They were so intrigued that they flew SOLIDWORKS CEO Gian Paolo Bassi to the Zenith factory, which ultimately inspired the company to purchase a Zenith kit for assembly at its headquarters in Waltham, Mass.

“[SOLIDWORKS] has managers, coders and engineers working on it. Their goal obviously isn’t to fly an airplane. It’s more of a hands-on building project that showcases what you can do with SOLIDWORKS in the everyday world,” Sebastien Heintz said. “It’s also become a fun team-building effort. Everyone I’ve talked to that’s worked on it has really enjoyed it. If you’re working in front of a computer screen all day, it’s refreshing to get in the shop, work with your hands and see how the parts come together, especially if you can connect that back to what you’re working on with the computer.”

If you’re thinking about building your own Zenith kit, visit the company’s website.

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