Beta Technologies revealed its new eVTOL prototype on Friday during a 30-mile (50-kilometer) airlift from its headquarters in Burlington, Vermont, to the flight test facility in Plattsburgh, New York. There, the new aircraft will continue the ground testing already begun in Vermont, with on-the-wing and hover tests and finally transitions between the two — all expected within the next few months.
The fixed-rotor Alia, as the aircraft is presently code-named, succeeds the tilt-rotor Ava prototype, which was revealed in January 2019 and which the company used to validate propulsion and flight-control systems as well as better understand the aerodynamics of eVTOL in small aircraft. (Though Alia is relatively large compared to its eVTOL competitors.) The new 6,000-pound (2,720-kilogram) airplane is completely fly-by-wire and uses a 50-foot (15-meter) arched wing for lift in horizontal flight; four fixed rotors, mounted high at wing-level, for vertical flight; and a rear pusher prop to speed it along more efficiently in while moving forward. In that phase, the four rotors would be locked in their lowest drag position.
According to founder Kyle Clark, Alia already has months of tethered hover tests under its belt, along with a few high-speed taxi tests using a wheeled landing gear assembly — affectionately known as “the shopping cart” — in place of the airplane’s normal skids. “We completed high-speed taxi tests the other day, and that was a huge boost,” Clark said. “We were able to ensure that we have pitch stability in the airplane and can lift the nose wheels off the ground and put them back down. We’re penetrating the aerodynamics just in time for the move to Plattsburgh, where we can continue in earnest.”
The airplane was built at Beta’s hangar on the grounds of Burlington International Airport, but the steady cadence of commercial flights there, as well as Vermont’s Air National Guard unit flying Lockheed Martin F-35s twice a day, means that conducting a proper flight test program with several flights each day would be virtually impossible amid the ever-present risk of a new aircraft type needing occasional tows to and from the runway. Beta’s plan has all along been to transfer Alia to Plattsburgh, just as it did with Ava. That airport, a former U.S. Air Force base, has ramps and runways built to accommodate Boeing B-52 bombers, and thus plenty of room. It only has limited daily service and no control tower.
Throughout the flight test program, Beta will effectively serve as a private air taxi service, with company pilots shuttling personnel back and forth across the lake several times each day. Its 15-aircraft flight department includes five pilots total — most ex-military — with several additional team members in training. Clark and Nick Warren, a former U.S. Marine Corps pilot who flew Marine One for President Barack Obama, will be the initial test pilots for Alia.
Following Friday’s airlift (via a Sikorsky S-61 helicopter operated by Helicarrier), the flight test program will continue at Plattsburgh with more tethered hover test and high-speed taxi tests, then progress to horizontal flight while still on the wheeled landing gear, to fully understand the aircraft’s behavior as a conventional airplane, Clark said. Only then will it proceed to vertical flight, via untethered hovers initially then controlled ascents and descents, before folding in the transition from horizontal to vertical and back.
The team hopes it will validate the work to make a clean, simple design. This was initially inspired by the Arctic tern, a bird with the longest migration on earth, with annual distances averaging around 45,000 miles (72,000 km). Its hyper-efficient aerodynamics are reflected in Alia’s arcing wings and tapering surfaces. Aerodynamicist Mark Page, of DZYNE Technologies, then helped hone Alia’s configuration and overall aerodynamics to meet the efficiency challenges of combined vertical and horizontal flight capability — absent the furious wing-flapping a tern can use to spring into flight.
“We selected a wing that would allow us to go slow enough to enable a compromise design between dedicated hover props and dedicated cruise props,” Page said. “If you want an airplane to both pick itself up in the air and push itself forward, you need to either change the pitch of the prop drastically, or it has to have that compromise between the two.”
Using variable-pitch propellers felt as off-limits as tilting props, as both required significant, heavy hardware, especially if there were eight, 10, or more propellers on the aircraft. Tilting wing systems proved even more problematic, introducing unappealing, asymmetrical stall characteristics as well awkward transitions to backward flight in hovers. The final product had to answer to all these challenges. “Because it’s VTOL, it’s no-joke loads — not just some secondary aerodynamic load,” Page said. “You’re picking up the whole damn airplane and contorting it around in gusty winds.”
To zero in on a viable design, Page focused on mitigating drag, increasing the tail size, and using a bigger wing, all of which improved stability and efficiency at low speeds. The engineers also created more robust propeller designs and torquier motors to enable immediate, precision control of the aircraft as it progressed through multiple phases of flight, as well as the ability to hover on low power, reducing the draw on the battery. The final design is extremely “economic,” Page said, with the least amount of moving parts while still enabling the transition, and the computer-controlled quad-rotor configuration allows for easy movement in all directions while in the hover mode.
Making Alia efficient in forward flight meant counteracting as much as possible all the tactics they deployed to optimize vertical flight, including the two outriggers on which the four rotors are mounted. They are aerodynamic in both directions, in that they don’t introduce their own turbulence or vortices, and they’re also designed to not amplify the acoustics, which protrusions that large that tend to do.
Another key challenge has been developing a control system that feels balanced, natural, and predictable for pilots in all modes of flight, with none feeling unstable and the controls never mushy or uncertain. Persistent control authority is key, as is harmony between all the control surfaces activated in each mode and during the transition. “The goal is a wide transition envelope, so that it transitions smoothly at a variety of speeds, altitudes, air densities, wind gusts, and controller forces,” Page said. “It has to accommodate imperfect conditions and imperfect piloting. Control harmony allows you to have that without becoming unstable. It makes it much more enjoyable for the pilot to fly, and much safer.”
Further tuning of the airflow helped achieve what Page thinks will prove to be a smooth, laminar aircraft with low drag and minimal aerodynamic interference from various interfaces on the airplane — such as landing gear, the tail assembly, and the intersection of the wing and the fuselage. The latter is a particularly problematic area, as it tends to cancel out efficiencies achieved elsewhere. To manage it, Page made the wing and body connection extremely blended. Not so much that it could be called a blended-wing-body airplane, but enough to diminish the losses.
All of this was validated through computer simulation, in particular via the X-Plane software developed by Laminar Research — a program that’s renowned for its highly accurate physics simulations. Creator Austin Meyer serves as an advisor to Beta, and contributed to its control system designs. Test pilot Camron “Arlo” Guthrie, who flew General Dynamics F-16s for the Air National Guard, has been leading the integration of this simulation technology to ensure it’s smoothly deployed for training as well as aerodynamic modeling and flight-control development.
“We have a totally new propulsion system and aircraft configuration, and these need unique avionics, displays, control interfaces, and more,” Guthrie said while demonstrating Alia’s flight simulator. “We’re now in our 10th iteration of our flight controls, and we’re constantly testing it all out here to see how it works. It’s a truly immersive, visual environment to work in.”
Guthrie said the advance to aggressive flight test will allow them to hone the algorithms and aircraft responses to pilot inputs — as well as help them make sure pilots can intuitively grasp what the airplane is doing. So far, flying the simulator has suggested that Alia should be an easy bird to fly. “It’s a light touch, just as you’d expect in a very high-performance airplane,” Guthrie said. “But it’s also a very low-workload airplane and has excellent handling qualities. To land you just get down to the stall speed of conventional airplanes, and then lean into it and you’re in horizontal flight.”
Beta’s first application for Alia will be to accommodate the mission of United Therapeutics, the pharmaceutical company that provided initial funding for Beta. United Therapeutics is developing manmade organs for human transplant, and founder Martine Rothblatt — herself an accomplished aviator who also sponsored the development of an electric version of the Robinson R44 helicopter by Tier One Engineering — wanted a reliable, green system for distributing those organs on-demand. Clark said the urgency of that mission compelled the Beta team to select a configuration that would generate the greatest range and be the most safe and reliable feasible system — that is, with the fewest amount of breakable moving parts, and also the most redundancy.
The motors Beta developed are essentially two motors in one for each rotor, so the likelihood of failure is dramatically reduced, and the minimization of moving parts will help speed certification — a challenge faced by all eVTOL manufacturers. It has also made the development process filled with far fewer unknowns. “We’re not trying to break the laws of physics,” said mechanical engineer Manon Belzile. “You might not be able to find the most lightweight solution right away, but we can certainly find solutions that will make this aircraft fly. Then the more we fly, the more we’ll be able to optimize everything. It’s an engineering challenge, but we know we’re going to get there.”
Fast on the heels of the United Therapeutics adoption, Alia will be adapted for commercial and industrial use, a role as an air taxi, and military applications. Beta is already proving integral to the U.S. Air Force’s Agility Prime effort to spur the development of electric aircraft. Along with Joby Aviation, it’s one of just two companies to recently advance to the next stage of development support from the Air Force in that effort.
Beta hasn’t estimated Alia’s range and other specifications formally yet, though it will say it’s targeting 250 miles (400 kilometers) and charge times under one hour. Its battery technology is still not fully disclosed, though its packs are designed and manufactured in-house from commercially available lithium-ion cells. Propulsion engineer Herman Wiegman, a former energy storage specialist for GE Global Research, said the program is viable with existing battery technology, albeit with careful integration.
“The battery pack is fundamental, and very integral to the success of the aircraft,” he noted. “But you have to be careful about the presence of the mass in the aircraft, how much frontal area is dedicated to the battery packs, how much drag will be induced because of their presence. One doesn’t simply purchase a battery pack off the common market and integrate it into an aircraft.” He added, however, that their mass can be advantageous, helping stabilize the aircraft against wind gusts while in a hover, for instance.
Finally, Beta has also declined to place a timeline on flight test for Alia or its likely entry into service, something eVTOL manufacturers are routinely stung by as those timelines slip. But if the company’s prior track record is any indicator — it achieved its experimental airworthiness certificate for Alia just 16 months from program inception — the wait likely won’t be very long.