Designing a New Breed of Flying Disc

By Terry Dunn

A group of engineers at Aerobat Aviation has taken a fresh look at the flying disc and are creating designs that they think will revolutionize aviation and aerospace.

Early science fiction writers were fond of imagining that flying discs would be the favorite interplanetary runabout for little green men to soar throughout the cosmos. I suppose it could be true since the flying disc is actually an airworthy design concept (Frisbee, anyone?). Earth-based aviation history has seen many types of flying discs come and go--minus the warp drives and tractor beams, of course. The Vought V-173 and Sack AS-6 are diverse variations on the theme, although neither garnered much success. More recently, a group of engineers at Aerobat Aviation has taken a fresh look at the flying disc and are creating designs that they think will revolutionize aviation and aerospace.

The Airspeed Velocity of an Unladen Geobat

About 20 years ago, Georgia-based inventor, Jack Jones, set out to build a better flying disc. He found that by removing some of the rear area in the disc, his designs exhibited much greater stability than a pure disc footprint. Based on his findings, he developed the Geobat design and earned a US patent for his efforts.

The Geobat is somewhat of a paradox of traditional aircraft wisdom. You get the benefits you would expect from a disc shape, but also other properties that are less intuitive. Without getting too technical, let’s look at a few elements of the Geobat and see what makes it special. If you can look past the legalese, the patent is very thorough in its explanation of the Geobat’s configuration and resulting performance attributes.

This top view of Aerobat Aviation’s 1M diameter UAV shows the defining characteristic of the Geobat planform: a disc with deleted area in the rear. This simple change has notable effects on its stability.

Any kind of compact airframe is typically advantageous because it allows for a lighter structure while still having adequate strength. The aerodynamic forces on a circular flying structure such as a disc (or the Geobat) are quite evenly distributed and permit engineers take full advantage of that bantamweight premise. Lighter is almost always better when it comes to airplanes. All other things being equal, a lighter airplane lands slower and flies faster than its meatier twin. The list of advantages continues.

An unmodified disc would be considered a low aspect ratio (wingspan: chord) flying wing. This type of airplane would typically exhibit high maneuverability at the cost of aerodynamic stability (a common trade-off). While the Geobat still has the circular outer profile of a disc, the cutout serves to divide it into three discrete wings: the forward section, the rear section, and the sides which bind them together. In that way, the Geobat is a hybrid of a flying disc and more conventional aircraft.

What makes the Geobat planform most appealing is that it retains the compact structure that allows it to be built lightly, but its inherent stability belies its low aspect ratio appearance. In short, you get the weight-saving benefits of a disc coupled with stability that is on par with standard aircraft. This sort of aeronautical compromise is often hard to achieve by manipulating only the planform.

Despite all of its potential benefits, the Geobat concept sat dormant for several years, at least as a man-carrying design. However, the RC community took notice of the Geobat and found the same stabilizing properties and speed range that Jones claimed. The design’s predictable flight performance and offbeat appearance earned the Geobat a loyal, cult-like following that continues to thrive at flying fields and on internet forums.

RC modelers were the first group to embrace the Geobat. Here, three models built from sheet foam are ready to take flight. (Mark Murdock photo)

The Good Idea That Wouldn’t Die

Nanobat is a 22-inch diameter UAV built on the Geobat concept. Its developers believe that the drone’s compact form factor is a major selling point.

In 2010 there was renewed interest in the Geobat’s commercial potential. Aerobat Aviation Incorporated was formed with the intent of developing Jones’ design into a wide range of vehicles. While the Aerobat team envisions man-carrying designs in many sizes, they decided to first develop a series of Unmanned Aerial Vehicles (UAV). Their three circular drones have diameters of 22 inches, 1 meter, and 2 meters.

I spoke with Aerobat Aviation’s CEO, Travis Shannon, and he explained some of the UAV-specific advantages that his group sees in the circular planform they adopted. One key point that Shannon stressed is that the lifting-body design of their UAVs packs a lot of wing area into a relatively small footprint. This translates into the ability to hoist a heavier payload and/or provide longer flight times than similarly-sized conventional UAVs.

Shannon also noted that the compact layout of Aerobat’s UAVs allows them to be transported and readied for flight more easily than many other UAV platforms. For instance, the 22 inch-diameter model can be carried in a backpack and launched with virtually no field assembly required. Shannon feels that such rapid deployment capabilities offer a significant selling point to both the military and civilian emergency response agencies.

UAVs in the field take a beating. In fact, most small UAVs are considered expendable. During testing of their models, Aerobat has found that without conventional cantilevered wings jutting out, their UAVs are surprisingly resilient. Shannon notes, “They tend to roll when they crash.” Even their 54 pound, two meter prototype has seen several hard knocks during its testing regimen, but none have delivered a KO punch. In fact, this mostly carbon fiber ship was flown on the same day that I spoke with Shannon.

This two meter diameter UAV is built primarily of carbon fiber. It has proven to be surprisingly tough.

Aerobat’s engineers hope to take advantage of their UAVs’ circular outline by integrating a mobile platform of cameras and sensors. In this fashion, a single package of sensors can continuously reposition itself anywhere along the perimeter of the UAV to gain the best vantage point for whatever it’s looking at. This would virtually eliminate blind spots while avoiding the mass and volume penalties of utilizing multiple cameras.

Between the three sizes of UAVs, Shannon feels that Aerobat has a wide range of potential drone duties covered. The team is also developing proprietary autopilot devices to further enhance their capabilities. Currently, Aerobat is focused on attaining FAA certification for their designs.

Get In and Buckle Up

While Shannon and the Aerobat Aviation crew see much potential in the Geobat as UAVs, they also perceive extraordinary scalability in the planform. Next up the size ladder would be a Light Sport Aircraft (LSA) called the FS-7. LSAs are a relatively new breed of private aircraft recognized by the FAA. They are a notch above Ultralights in terms of weight and complexity, but have far less overhead and pilot scrutiny than the Pipers and Cessnas that presently fill the general aviation ranks.

This rendering of the FS-7 illustrates Aerobat Aviation’s concept for a Light Sport Aircraft variant of the Geobat.

The FS-7 makes sense as a LSA because its intended flight performance would cater to the breed of recreational pilots who are flocking to buy them. Recall the Geobat concept’s light structure and resulting low stall speed. When you apply that to an LSA, pilots are able to land at a slower, safer speed (LSAs must stall at 45 knots or less). The natural aerodynamic stability of the design would also come in to play, making the LS-7 approachable for less experienced pilots. Furthermore, the compact circular footprint could pay dividends for LSA owners looking to save a buck (hangar space isn’t cheap).

By far the most extraterrestrial-appearing concept in Aerobat’s portfolio is the Sultan Jet. This biz-jet would utilize a single jet engine on an upsized Geobat airframe. Perhaps the expected wide speed envelope of the Sultan Jet would allow executives to fly in to smaller regional airports (with relatively short runways) without sacrificing the top-end speed coveted in Lear Jets and the like.

Although it looks decidedly less sexy than a Lear Jet, the Sultan Jet could open up more rural destinations for executive travelers.

Looking Skyward

Engineers see a wide range of potential applications for the Geobat planform. This image depicts a fleet of large, jet-powered Geobats next to their more conventional counterparts.

Aerobat Aviation’s website illustrates many of the large-scale projects that they have visualized. All are centered on the Geobat planform. One rendering shows a line of conventional jets astride their Geobat-themed counterparts. Even that does not encompass the full scope of the company’s ambitions. Shannon revealed that they have even worked on design studies for a super-sized reusable spacecraft that would have unprecedented payload volume.

There is no doubt that Aerobat Aviation has grandiose visions for the Geobat. Yet, they also have numerous supporters and interested parties who think they are on to something big. It has been said that the Geobat planform could be the secret ingredient for the next significant jump in aircraft performance. Time will tell if that prediction rings true. I just wonder how the little green visitors are going to take it when we tell them they did it wrong.

Photos courtesy of Aerobat Aviation Inc. unless otherwise noted.