About Experimental Lighter-Than-Air Aircraft (XLTA)
By Dan Nachbar, for Light Plane World
Ultralight balloon pilot Mike Kuehlmuss from Amherst, Massachusetts, flying at EAA AirVenture Oshkosh 2010
For people who want to build and fly their own lighter-than-air (LTA) aircraft, you’ve found the right article. To use the official parlance of the FAA, these aircraft are called amateur-built lighter-than-air experimental aircraft. This is often shortened to experimental LTA. In aviation, the designator “X” often gets substituted for the word experimental, as in X-15. As a result, these aircraft are sometimes called XLTA.
Standard vs. Experimental
The word experimental in this context needs a bit of explanation. As far as the FAA is concerned, there are (more or less) two types of aircraft: standard type aircraft and experimental aircraft. Having an aircraft classified as standard type requires a multiyear and very expensive engineering review.
Standard type aircraft are what most folks see everyday. Everything from your local hot-air balloon used for selling sightseeing rides to a Boeing 747 is a standard type. In addition to an extensive FAA engineering review, standard type aircraft are assembled from closely scrutinized parts in a carefully controlled factory setting and undergo continuous and rigorous inspections. Construction of an experimental aircraft, while done quite seriously and painstakingly, has none of these exhaustive (and expensive) safety requirements.
Almost all of the experimental aircraft in the United States are airplanes. Very few of them are anything like an X-15. In fact, there are some well-proven and highly reliable airplane designs that are routinely built by do-it-yourselfers. Some particularly popular designs have been built hundreds and even thousands of times.
By any reasonable definition of the word, these tried-and-true aircraft are now very standard designs. Yet, because they haven’t gone through the FAA’s long and expensive formal design review process, they are always classified as experimental. It would probably be more accurate to call them custom-made aircraft because there’s nothing particularly cutting edge or tricky about their design. But they’re very different from factory-built standard type aircraft in that they’re custom-made by ordinary folks. Nonetheless, given the wonders of government bureaucracy, we’re pretty much stuck with the term experimental.
Like the folks who build tried-and-true airplane designs, most people who build custom-made balloons use very (from the engineering standpoint) conventional designs. The technology for hot-air balloon design and construction is well understood and hasn't changed much for many years. In particular, the technology for sewing the fabric that makes up the hot-air envelope has remained essentially unchanged for many decades. So the creative impulses of balloon do-it-yourselfers are usually focused on the selection of the envelope colors and pattern, some variation in the shape of the envelope, and the workmanship that they bring to the task.
Ultralight vs. Experimental
Actually, I fibbed when I said there were only two types of aircraft, standard and experimental. There’s a third important classification: ultralight aircraft. (Actually, there’s also a fourth called light-sport.) Ultralights are really different beasts as far as the FAA is concerned. In fact, the FAA doesn’t actually deal directly with “ultralights” at all. That’s right. If an aircraft is light enough, there’s absolutely no FAA involvement. No required pilot training, no airworthiness certification, no fees, nothing! The other neat thing about ultralights is that you don’t necessarily have to build it yourself. You can perfectly legally buy a factory-made ultralight and fly it without any of the usual red tape that involves the FAA.
Editor’s note: The FAA classifies a free balloon as an unpowered ultralight, putting it in the same category as ultralight gliders. The empty weight without fuel must be less than 155 pounds. The popular ultralight hang-balloon of the cloudhopper type is said to meet the weight limit if the propane fuel tank is smaller than 15 gallons.
Even though they don’t have to, some folks build their own ultralights. They do this for the same reasons that people build their own experimental aircraft. But as with their factory-built cousins, do-it-yourself ultralights don’t require FAA paperwork for either the pilot or the aircraft.
Now, all that’s kind of cool. I mean, nobody likes paperwork. But keep in mind that ultralights are really, really small. As a result, for all practical purposes, you can’t take any passengers with you on an ultralight aircraft. This is particularly true for ultralight balloons.
In contrast, there’s no such thing as a factory-made experimental aircraft. By definition, factory-made aircraft (or an aircraft made by anybody except an “amateur” as the FAA defines the term) has to be standard type. (As previously stated, that’s the kind requiring the really expensive and time-consuming engineering review process.) There are a couple of exceptions to this rule. More or less, however, experimental aircraft require that you build it yourself and have an often quite brief conversation with the FAA.
A Rose by Any Other Name
I use the term “experimental LTA” to include all LTA aircraft except standard type LTA. In this sense, the term includes both those aircraft that are officially experimental in the FAA’s view as well as ultralight LTA. Perhaps it might be clearer to call them unconventional LTA or even nonstandard LTA. But then the next thing you know is that people would start quibbling about what’s unconventional and what’s not, etc. So I’ll just continue using the term in the inclusive sense. Actually, I kind of like the term custom-made aircraft. But that doesn’t cover factory-built ultralights.
The Mystery of the Missing 2 Percent
Building and flying custom-made aircraft (or whatever you want to call them) doesn’t mean that you have to be a macho “right stuff” test pilot or some sort of daredevil. In fact, there are lots of ordinary folks – something like 23,000 of them – flying various experimental aircraft today. And as many of you already know, there’s the Experimental Aircraft Association whose main focus is using its considerable resources in helping people build custom aircraft.
As it happens, in total there are 625,000 or so pilots in the United States. So that means about 3 percent of them are flying custom-made airplanes (23,000 divided by 625,000 equals about 3 percent). Compared to airplanes, ballooning is a very small niche in the world of aviation. According to the U.S. national organization for balloonists – the Balloon Federation of America – there are about 7,000 or so folks who fly balloons in this country. The number of people who fly custom-made balloons in the United States is very small indeed, probably less than 100. That means that only about 1 percent of balloon pilots are flying custom-made aircraft.
Frankly, it seems weird to me that, percentage-wise, there are three times as many custom airplane builders as there are custom balloon builders (3 percent versus 1 percent). The financial advantages, joy of creation, and other benefits of flying custom aircraft apply to balloons as much as they do to airplanes (and in some cases, more so). Yet, the difference persists.
Perhaps my website XLTA.org will encourage some of “the missing 2 percent” to give custom-made ballooning a try. Presented on the plans page is an open content reference design for a homebuilt balloon suitable for first-time amateur builders. The project is being supported by a generous grant from the Wolf Aviation Fund. Rick Jones wrote a very nice overview that appeared in the 2008 January/February issue of Ballooning magazine. Click here for a PDF of the article.
The design is for a 54,000-cubic-foot balloon envelope. The envelope uses a classic 16-gore, 13-panel structure. This design was chosen because it’s very straightforward to build and modestly sized for a first project. Comparable designs have been completed by first-time builders in less than 200 hours of work. The plans focus on the design and construction of the balloon envelope. This includes the fabric, webbing, “parachute” opening at the top, skirt at the bottom, and cables to connect the envelope to the basket.
Most people who build their own balloon choose to have them classified by the FAA as experimental/amateur-built aircraft. In order to qualify for this classification, the “major portion” of the aircraft must be built by persons “solely engaged in education or recreation.” In every case that we know, the envelope is treated as the “major portion” of the balloon for certification purposes.
We don’t cover the construction of an appropriate bottom end (burners, basket, fuel system, etc). Working with these components, in particular the burners and fuel systems, requires great care and experience. Most homebuilders, even the most experienced ones, use an FAA-certificated balloon repair station to inspect and repair these components. In addition to the safety issue, we also believe that first-time builders are best served by concentrating their efforts on building an envelope. After you’ve successfully built and flown your own envelope, you might then consider turning your attention to building a bottom end.
Envelope construction is much more straightforward than bottom-end construction. Further, envelopes usually wear out much more quickly than bottom ends. So, used basket/burner/tank configurations that have outlived their envelopes can be readily purchased from any number of reputable sources. Also, be sure to check the XLTA links page for pointers to many other websites with useful experimental LTA information.
And one more word of caution: As every pilot knows, anytime you take command of an aircraft, you are literally taking your life and lives of your passengers into your hands. This is particularly true of a flight in an aircraft that you have built yourself. So you would be wise to take your work seriously and seek the advice of experienced people to help you.
If you need help finding experienced people, contact me at firstname.lastname@example.org, and I’ll be glad to assist you in connecting with trained and competent advisors. If you build and fly an aircraft without availing yourself of such expertise, you are a fool. And aviation isn’t kind to fools. With all that said, building and flying your own aircraft can be one of life’s truly wonderful experiences. It certainly has been for me. So quit stalling and take the plunge.
Photo<sewing.jpg> caption: Dan Nachbar at the sewing machine. Photo by Janice Doyama.