• 05 Nov 2020 07:09 PM
• 2

GoFly Teams Prepare to Fly Again

By Kenneth I. Swartz
Vertiflite, Nov/Dec 2020

The GoFly Prize was unclaimed in the Final Fly Off in February. Here is the story of the 21 teams who attended and their status during the pandemic. This is a follow-on to the article “GoFly Inspires Innovation.”

Gwen Lighter believed that an international competition could nurture grassroots development of a new generation of light, quiet and compact vertical takeoff and landing (VTOL) personal flying devices when she conceived of the GoFly Prize competition in 2015.

Boeing stepped forward with $2M in prize money to stimulate innovation in vertical flight, but it wasn’t until the GoFly fly-off event on Feb. 28–29, 2020 at Moffett Federal Field adjacent to NASA’s Ames Research Center in Sunnyvale, California, that it was possible to meet many GoFly teams for the first time.

The GoFly Prize set the competitive bar very high in four key areas — aircraft size, noise, speed and endurance — but this did not deter hundreds of teams from participating in the three-phase competition over the past three years.

The basic threshold requirements are for VTOL (or near-VTOL) vehicles with a maximum size in any dimension of 8.5 ft (2.6 m) that produce a maximum sound of 87 dBA at 50 ft (15.2 m), achieve at least 30 kt (55.6 km/h), and that can fly a speed run of six laps around a 1 nm (1.85 km) course as part of a 20-minute endurance demonstration.

Twenty-one teams made the trek to Moffett Field for Phase 3 to compete for the $1.6M in remaining prizes, showcase their technology and pitch to potential investors. The variety of aircraft configurations was impressive, especially when you consider that established aircraft manufacturers only develop a small number of clean-sheet designs each decade.

None of the teams walked away with the $1M Boeing Grand Prize, but the Japanese teTra Aviation team took home the Pratt & Whitney Disruptor award and a check for $100,000.

Many of the teams wished they had more time to complete and test their aircraft designs, but in hindsight the fly-off would have probably been cancelled had it been scheduled any later in 2020 because of the coronavirus pandemic.

Today, the $1M Boeing prize is still up for grabs with a new approach to be announced by the GoFly organization soon, on account of the pandemic.

Lighter was recognized for her incredible work inspiring VTOL innovation with the VFS Paul E. Haueter Award (see “76th Annual Grand Awards Ceremony,” Vertiflite Nov/Dec 2020).

Vertiflite reached out to all the GoFly Phase 3 competitors invited to California to learn more about the teams and their aircraft designs. The following is a summary of what VFS learned. More in-depth information on each concept can be found on the VFS World eVTOL Aircraft Directory: www.eVTOL.news/aircraft.

Aeroxo

Aeroxo was founded by Russian aeronautical engineers, tech entrepreneurs and venture capitalists. In 2014, the company became one of the country’s first commercial VTOL drone producers when it developed a family of small tiltrotor unmanned aircraft systems (UAS).

The innovative ERA Aviabike tilt-duct design won GoFly Phase 1 and Phase 2 awards. A full-scale functional prototype flew on Jan. 21, 2019. The second prototype was built with aluminum spars and a carbon fiber hull to meet GoFly’s size and weight requirements.

CEO Vladimir Spinko said the Aviabike is “a tiltrotor made for bikers.” The pilot is positioned on the motorcycle-style seat between four rotating blocks of ducted fans, with four thrusters per block, and two electric motors powering each fan. In total, the Aviabike has 32 motors of about 5 kW each (for an overall power of 160 kW) to provide “multiple redundancy.” Spinko told Vertiflite that aircraft requires 135 kW of power for takeoff and landing, and about 40 kW for horizontal flight.

Aeroxo developed its own tilt actuator when it could not find a supplier that could meet its reliability and cost requirements.

The company’s goal is to sell the Aviabike to thrill seekers for a price between $50,000 and $100,000, depending on the production volume.

Athena Aero

Mechanical engineering designer-researcher Dr. Gary Gress from Toronto, Ontario, began developing radio-controlled, gyroscopically stabilized, non-cyclic twin propeller “bicopters” about 20 years ago while working as a designer of lighting systems and electrical appliances.

During Phase 1, Gress received critical feedback on his first GoFly design entry that “forced me to think different,” which led to a new, winged VTOL design with a curved lifting surface above and a canard in front of each propeller; both surfaces provide bladestrike safety and the canard actually enhances lift in hover. He also moved the pilot’s seat to a safer location away from the propellers.

When asked if the design uses the Custer channel wing concept, Gress said that Custer, “had his propellers at the trailing edge and generated extra lift with the low pressure ambient air entering them… What I basically have is the opposite; I have my channel above the propeller and behind it for the most part — generating extra lift with high pressure air.”

The addition of the canard and curved wing resulted in a significant performance improvement in simulations, including a fivefold increase in endurance and the ability to glide. “I’m now looking at increasing the number of propeller blades or their chords, which will help the gyroscopic control moments and also lower the tip speeds and noise. The latest props were custom made using my 3D printer; I’m no longer using stock props.”

To date, Gress has been testing the concept with a small-scale model. The next step in development is to transition the model from hover to forward flight, he said.

The Challengers

Pathipan Sivarasa has spent most of his career as an aerospace engineer in Canada working on civil and military systems, such as the Sikorsky CH-148 Cyclone maritime helicopter. When Sivarasa learned about the GoFly Prize through social media, he formed Innowings Aerospace, Inc. with friends and family in Canada and five other countries in January 2018 to enter the competition, with the name “Team Challengers.”

“We looked at more than 30 different concepts, before the team decided to pursue an electric-powered multicopter with six fixed-pitch propellers attached to a rigid frame with a pilot’s seat and skid landing gear,” he said.

The prototype was transported by road from Brampton, Ontario, to Moffett Federal Field for the GoFly competition. The aircraft received experimental aircraft certification from the Federal Aviation Administration (FAA) during the competition, but the team didn’t get all the approvals to fly at Moffett Field as a result of transportation delays.

Development of a revised prototype has been proceeding slowly due to COVID-19 and related restrictions. More recently, the team has approached the Canadian government for research funding.

Innowings has also designed a larger hoverbike called the PKOK — pronounced “peacock” — which has a motorcycle style seat and six overhead propellers, including a coaxial propeller located above the pilot.

DragonAir Aviation

Prior to the GoFly Final Fly Off, only one contender had released videos of their personal air vehicle being piloted. That was DragonAir’s Airboard and Airboard 2.0, designed by inventor Jeff Elkins and piloted by team president Mariah Cain. See the sidebar, “DragonAir Stands Tall,” for the full story.

EDEA

Simon Etlinger is an Austrian mechanical engineer and a mechatronics technician with broad experience as a designer, product manager, draftsman and programmer. In 2012, he founded EDEA to help his industrial clients move from an idea to a finished product.

Etlinger began researching VTOL aircraft designs about eight years ago and submitted the EDEA 22/1 Jay for Phase 1. It’s a two-seat, hybrid-electric VTOL aircraft with wings, which exceeded the GoFly size limit.

He then submitted the EDEA 22/2 Squid for Phase 2, which is a hydrogen fuel cell-powered electric vertical takeoff and landing (eVTOL) design loosely based on the Hiller Flying Platform which met the size criteria, “but it is a highly complex vehicle, and I’m not in a position to build such a multi-million dollar craft,” said Etlinger.

His Phase 3 submission was the EDEA 22/3 Kamino one-passenger personal air vehicle design, which incorporated a new hybrid-electric propulsion system he’s been developing.

“I decided to combine the advantages of an electric motor and an internal combustion engine in a highly redundant pod design that other inventors could also use.” The result is “a parallel hybrid drive which combines four electric motors and a Wankel rotary engine. The engine is geared and equipped with freewheel clutches, which means only the strongest of the driving engines powers the propeller,” said Etlinger.

The propulsion system weighs more than an electric motor with a propeller but is much lighter than an all-electric system with its batteries.

“The technical design of the engine is done and some of the parts are already on the workbench. I have applied for a grant from the Austrian Federal Research Agency to partially fund my work. If the decision is positive, I can immediately start the build and testing,” said Etlinger.

Garudeus Aviation

Rishav Shrestha of Garudeus Aviation is a Nepal-born, Singapore-based entrepreneur who started his career as a physician and became the CTO of a medical technology company after earning his PhD in nanotechnology.

“I’ve been following crowdsourcing platforms like HeroX and then one day GoFly just popped up,” said Shrestha. The Phase 1 entry was a now-abandoned exoskeleton-based flying contraption that evoked a comparison with Garuda, a mythical being with wings that could fly (which gave the team its name).

By Phase 2, development shifted to KiiRA, the “world’s first reverse trike-hexacopter.” It’s a compact single-seat, electric/ gasoline hybrid-powered VTOL vehicle that can also be driven on roads.

KiiRA means “insect” in Nepali, and “our design is focused on having something compact, so everything folds up (including the propellers),” said Shrestha. “In Nepal we have very narrow roads and we need to have small cars when we are driving in the mountains.”

The team found it hard to procure the best quality high energy density batteries and propulsion systems since suppliers were charging $300,000–$500,000 for the latest technology and “were not really interested in the small guys.” The solution to cutting costs was lots of creativity and the selection of the hybrid-propulsion system that could meet performance and cost targets.

The aircraft has an epoxy-impregnated carbon fiber cabin, touchscreen displays, pedals and a joystick, a 5.5-gallon (20.8-liter) fuel tank and 40 kW battery, with an empty weight of 414 lb (188 kg). The flight control system uses open source drone technology.

The team displayed a mockup in California and hopes to fly a full-scale prototype later this year or early 2021. Garudeus has developed a working collaboration with M4 Engineering, an Uber Elevate partner. Work on building a hangar is on-going in Kathmandu and the team is recruiting talents within Nepal.

“We are planning for a complete move to the US by 2022 as Garudeus is a US company. Right now, we’re pushing for fundraising, collaborations, and product development side-byside,” Shrestha said.

Gyrobikers

Civil engineer Guillermo Villabrille of Madrid, Spain, founded the PRADES Research and Development Company in 2011 to create a family of VTOL aircraft featuring a tip-driven “concave lenticular shaped rotary wing.” Gyrobikers SLU was spun off in late 2018 for the GoFly competition.

The team’s GyroPack features a rotating overhead disk with blades that is powered by a tip jet system using compressed gas from a turbine. During takeoff and landing, the blades on the disk are open and allow the aircraft to operate like a helicopter with the help of two electric-ducted fans mounted on either side of the pilot that can tilt.

“In straight and level flight the blades close hermetically and the disk turns like a frisbee; the aircraft hangs from the disk which then functions as a flying wing and is pushed by the ducted fans which are in the horizontal position allowing the vehicle to fly like an airplane,” said Villabrille. The Kevlar disk “behaves like a flying wing with the added stability that gyroscopic stiffness provides.”

“Finally, in the emergency case, if the aircraft runs out of batteries or the power or electric system stops working, the aircraft goes into autorotation operation, opening the blades of the disk so the air pushes the blades and rotates the disk in autorotation, allowing a gliding descent until landing.”

The hybrid propulsion system features two electric-powered ducted fans and an unspecified turbine. At full power, the 17.7- inch (450-mm) diameter ducted fans each generate 133 lb (60 kg) of thrust and the turbine driven compressor produces the same amount of thrust through the tipjets.

A sponsor stepped forward in late 2019 to help finance the construction of the GyroPack prototype. Safran also recently became a supporter of the project.

JAYU

JAYU was formed in Boston in February 2018 by aerospace engineers Ben Sena and Soojae Jung while they were working for different VTOL companies.

Their GoFly entry is a VTOL tailsitter with “three sets of independent rotors, each counter-rotating with the clockwise on top and the counter-clockwise on the bottom… and a Y-frame constructed from the wing dihedrals,” said Sena. He added, “during flight it will pitch 90 degrees down… and be able to transition very smoothly between the multicopter hover and fixed-wing cruise on the same motor set.”

Several elements provide improved efficiency in cruise flight, said Sena. “First, we get out of the static thrust regime of the propellers and into the dynamic thrust where the effective angle of the propeller is reduced. So, you are in a higher lift-to-drag regime. And then by using the lift of the wings, we don’t have to provide pure thrust upwards (on a continuous basis) but can use the momentum and the lift effect to maintain the altitude and increase our range significantly.”

They started flying a quarter-scale model in July 2018 and logged 120 flights totaling more than three hours before they began building a half-scale model in December 2019.

JAYU was one of four teams that was able to fly at Moffett Field to compete for the Pratt & Whitney Disrupter Prize. Participation in the GoFly competition has been very positive, said Jung, adding that “It’s like realizing a dream.”

Phattony’s Rock & Roll Flying Motorcycle Circus

Anthony “Phattony” Windisch designed and tested 25 engine, airframe and subsystems models in his quest to produce a radio-controlled BAE Systems Harrier jump jet before he learned about the GoFly prize and decided that this, “might be a way to develop a human scale aircraft; even if I didn’t win.”

Concept Aircraft, LLC was formed in Edmond, Oklahoma, to compete in the prize and Phattony’s Rock & Roll Flying Motorcycle Circus established “to operate as a race team to facilitate construction and operations.”

Windisch describes his Aircycle as a “sleek canard-delta wing light aircraft with VTOL capabilities. It is powered by a hybrid electric engine coupled to our patented Hover-Jet Vectored Thrust Compressor (VTC) and is EPA compliant. The VTC has dual inline multi-stage tandem fans in a thrust vectoring duct. A 34-hp [25- kW] Predator 670cc gas engine provides 45N [10,100 lb] at 3,600 rpm and is connected to the VTC and a generator by a transmission.”

“The duct directs the thrust generated by the fans to four exhaust nozzles. The nozzles can be rotated. This unique configuration provides for operations of vertical lift and horizontal propulsion using a customized Navio/Raspberry Pi flight computer and integrated electric in flight and hover control subsystems.”

Windisch said the biggest technical challenge to date has been integrating the analog/digital flight control system, which is made from commercially available parts, components, circuit boards and sensors.

Since February, the team has been “feverishly pushing to finish a viable prototype.” Engine ground tests should begin soon, followed by flight testing in the spring of 2021.

Helium

Helium Aero, a startup based out of Ryerson University and the Design Fabrication Zone was one of five university teams and one of three teams from Canada invited to participate in the fly-off.

The team was founded by six friends during their second year of school. Though they had already envisioned larger vehicles, “it took the validation of Boeing and GoFly to say, ‘we believe in people making these aircraft and we want to give you money to do it,’” said co-founder Amin Ismail.

The team grew to 35 students and was divided into functions working on different subsystems, including a user interface to ensure the eventual autonomous eVTOL caters to passenger comfort.

Helium’s Paragon is a dodeca-copter with a pair of coaxial propellers on each of six arms powered by a modular, electric power system to avoid the use of a single battery pack and large-gauge wires.

“A key consideration is that we wanted to use the biggest propellers we could and still stay within the size constraints prescribed by the competition,” said Keith Watts, the team’s aerodynamics lead. “We used ANSYS simulation software and CFD to determine the various interactions between our propellers. Since we were using a coaxial configuration, we wanted to minimize the interactions and maximize our lift. We also built a test rig where we could vary the distance between the motors to minimize noise.”

The team started building a full-scale airframe from carbon fiber and fiberglass after flight-testing a half-scale proof-of-concept model. The target weight is 474 lb (215 kg), including a passenger/pilot.

The team displayed the uncompleted airframe in California and still had to optimize the propulsion system and avionics before the aircraft could start test flights. Helium Aero envisions a world where large drones occupy the skies and do far more than just carry humans around.

Raven

The Raven team was founded by Irakli Shengelia and is based in Tbilisi, the capital city of the Republic of Georgia. They named the first prototype “Raven,” because the raven is considered a very smart urban bird and “a great pilot.”

The team displayed a hang glider with a pair of electric motors at the GoFly event. The operational concept is circular-wing tailsitter with eight ducted fans, four on each surface of the wing. Raven has been seeking investors to help develop its aircraft design.

rFlight

rFlight was formed by members from rLoop, a global crowdsourced volunteer engineering team originally founded in 2015 to compete for the Hyperloop Pod Competition sponsored by SpaceX.

The rWing design on Phase 1 was a delta-wing VTOL tailsitter concept with a pair of side-by-side, 48 inch (122 cm) diameter counterrotating propellers. This was followed by N271RL in Phase 2, which is a delta-wing tailsitter with 145 hp (108 kW) two-cycle gasoline engine powering a single set of 68 inch (173 cm) diameter counter-rotating propellers.

The delta wing incorporates features found on short takeoff and landing (STOL) aircraft, said designer Keith Stormo of Moscow, Idaho. There are six fixed slats on the leading edge to maintain laminar flow over the wing at high angles of attack and generate significant lift, even at 40 degree angle of attack, which means “a shorter transition from vertical to near vertical flight and a lower stall speed,” said Stormo. The sloped drooped Hoerner wingtips, “give the wing an effective length that is six-to-eight inches [15–20 cm] longer at each tip, providing a 15 percent gain” in wingspan.

Four sets of three vanes behind the propellers function as flaperons (combined flaps and ailerons) and can deflect the thrust in any direction by up to 30 degrees.

The propulsion system has been tested on a 600-lb (2700-kg) “iron bird” tethered beneath a crane. The prototype featuring an aluminum wing was displayed at Moffett Federal Field and will be remotely piloted during planned test flights at the Pendleton UAS test site in Oregon.

“Our normal flight profile will be to climb vertically to 2,000 feet [600 m] in about 30 to 45 seconds and then nose over and swoop down 1,000 feet [300 m], gaining speed, and then fly horizontally. In the event of trouble, we could fire the ballistic parachute and recover our vehicle with very little damage,” said Stormo.

Since February, “we have been developing an alternate hybrid power system to install in the aircraft after we complete testing with current gasoline engine,” said Stormo, adding that the team is also seeking additional funding.

RMIT’s X-Aero

Students at RMIT University in Melbourne, Australia, got their first taste of the GoFly Prize about two and half years ago when a Phase 1 team was formed under the mentorship of Glenn Neal Martin, the designer of the original Martin Jetpack (which used ducted fans). It was a single-duct counter-rotating propeller, hybrid-electric configuration.

A new Phase 2 team built a full-scale quadcopter as a proof of concept aircraft after conducting lots of small model tests only to discover that “the biggest limitation was that the aircraft had only three minutes of battery life, so we decided to build an aircraft with larger rotors,” said Stephen Hardiman, the RMIT team leader (who has since graduated).

This coaxial rotor design had two three-bladed, 72- inch (182-cm) diameter propellers inside a carbon fiber duct powered by two 30 kW motors to provide lift and yaw. Pitch and roll authority were provided by eight 5-inch (13-cm) diameter thrusters, each powered by pairs of 5-kW motors attached to the outside of the duct.

The team then added a 10-inch (25-cm) diameter thruster producing 35 lb (156 N of thrust to increase the cruise speed for the competition. A subscale model was used to validate the control system “because no one had done this before. We succeeded and it flew really well, which was really, really exciting!” said Hardiman.

The four-member RMIT team completed building the vehicle two days before they flew to California to attend the GoFly competition. The aircraft remained in Australia and has been locked away at RMIT because of the coronavirus.

“GoFly has been such a driving part of my life for the last 2.5 years. It’s the best experience I have ever had in my life… it’s been life changing,” said Hardiman.

Most of the members of the Phase 3 team have since graduated. A new team of students is working on eVTOL designs at the university and may form a new competition-compliant company to pursue the GoFly prize if funding is forthcoming.

RMIT’s Dr. Graham Dorrington provided this update, “Prof. Pier Marzocca remains the overall lead for this activity within RMIT University. We regard our involvement in the GoFly competition as an inspirational educational activity with some useful research aspects, e.g., applying our expertise in high fidelity CFD modelling and digital twins.”

Scoop

Alex Smolen bought his first DJI Phantom 3 drone when he was a sophomore at the University of South Carolina and dreamed about building larger drones that would carry people, but “I was told if it was a good idea then Elon Musk would already be doing it!”

He was signed up to compete in the GoFly Prize when he heard it had a series of master lectures to assist people, like himself, who didn’t have a background in aerospace.

His Pegasus was one of 10 Phase 1 winners. This was a “Y6 multirotor with the front four motors tilting to provide forward thrust, a small wing to provide some lift, and a series hybrid generator to provide enough energy to complete the mission.”

For Phase 2, he added a small canard wing in the front of his design to maximize the wing area in the 8.5 ft (2.6 m) sphere, “even though I knew we wouldn’t be able to get totally wingborne,” said Smolen.

During Phase 3, Smolen determined that he was not going to be able to create a vehicle that could complete the GoFly challenge, but decided to create an eVTOL business in any case.

“Six subscale prototypes later, I found a configuration that had great handling characteristics in hover, transition and forward flight.”

Smolen’s now building a full-scale multi-passenger composite eVTOL aircraft with a large wing and tilting electric-powered propellers.

He’s now based out of Patuxent River, Maryland, where “it has been easier to find interested people and those willing to help here or there” and there is a growing eVTOL community.

Silverwing

Silverwing was founded by a group of friends at Delft University of Technology (TU Delft) in the Netherlands and quickly grew to 35 students when “we found out quickly that in order to build such a complex vehicle you need a lot of expertise,” said Silverwing’s Ruben Forkink.

The team won Phase 1 and 2 of the competition and is financially backed by many sponsors.

The team developed a tailsitter VTOL design with two large fixed-pitch propellers attached to a wing. It flew a half-scale model during Phase 2 of the competition and then built a fullscale aircraft for Phase 3.

The entire 35-member Silverwing team — including 10 full-time members — flew to California with the first arriving a month before the competition to start flight testing the full-scale aircraft.

The Silverwing S1 aircraft was shipped by airfreight to San Francisco, but for safety reasons the batteries had to be shipped by sea from Rotterdam to Oakland, California.

The team conducted indoor tethered test flights in a hangar at Hayward Executive Airport before moving 40 miles (65 km) inland to Byron Airport where the first outdoor free flights of the S1 prototype took place just prior to the competition.

Silverwing wasn’t able to fly their aircraft at Moffett Federal Field because the S1 had not accrued enough flight time to compete. However, after the GoFly event, the team’s supporters and sponsors were invited to see the aircraft fly inside the Patriots Jet Team hangar at Byron Airport in early March.

Teledrone

Three British professionals with backgrounds in aviation, IT and real estate decided to name their GoFly team after an iconic red British phone booth.

Colin Hilton is a former airline captain with over 15,000 flying hours and who previously worked in IT, while Peter Day is a private pilot who sold his software business to distribute Velocity kit aircraft and develop combined hangar-homes. Finally, house builder and drone enthusiast Mark Andrews joined the team temporarily after being matched by the GoFly organization.

Hilton said they set out to develop the cheapest possible vertical lift aircraft, “and so the original plan was for a tic-tac-toe planform of nine squares, with the operator occupying the center square and surrounded by eight ducted propellers.”

“As the tightest possible means of containing the operator was standing in a booth, the notion of teleporting an individual — familiar from programs like Star Trek and Doctor Who — led to the project being called Team Teledrone.”

Eventually, the team selected T-Motor’s U13 and open propellers on the prototype, “which is a motor below what they normally provide for human carriage.” With 32-inch (81-cm) propellers, each is designed to produce 55 lb (25 kg) of thrust when running at 45 V on seven-cell batteries — for a total of 220 lb of thrust — “though I would reduce that by around a third for practical purposes.”

In California, the team showed a two-thirds-scale model of the Teledrone with a pilot seat suspended in a box below a single quadcopter. The aircraft was test-flown in a gymnasium before the competition in February 2020, and it was sufficiently compact to travel to the event as checked-in baggage.

Hilton said the GoFly Prize represents a considerable challenge and he believes it will be difficult to meet the size, weight and flight duration requirements on the existing budget.

Nonetheless the team remains focused on the competition: “We’re still in the game.” Accordingly, the team is flight-testing a prototype featuring quad-propellers around both the base and top of the phone booth.

teTra

Team teTra won the $100,000 Pratt and Whitney Disruptor Prize at the GoFly Fly Off event in California with their “MK3” vehicle, which made a short, unmanned flight due to the high winds at the event. teTra is an acronym for “technology for transportation.”

The team is led by Tasuku Nakai, a doctoral student in the department of mechanical engineering at the University of Tokyo. The vehicle was developed at Toda City, Saitama Prefecture and flight tested at Fukushima Robot Test Field. The teTra MK-3 has two pairs of ducted propellers set at 50–70° to one another. A small windscreen on the upper surface of the wing protects the pilot.

“The banked rotor layout enables this vehicle to fly in a vertical and horizontal [attitude], without any change in the configuration or any change in control. So, it doesn’t really have a transition state,” said former teTra Chief Operating Officer Akihiro Mizutani.

Simulations were used to determine the optimum angle between the propellers for stability and other features. Then teTra built and flew a one-eighth-scale model followed by a half-scale model with a fixed wing.

Full-scale flight tests began in mid-2019 using three vehicles, the last of which was brought to California and featured a small wing that was restricted in size to meet GoFly’s 8.5-ft (2.6-m) size limit. The team plans to sell a kit version of the aircraft with a larger more efficient wing when it exhibits for the first time at the Experimental Aircraft Association (EAA) AirVenture 2021 in Oshkosh, Wisconsin.

teTra recently signed an agreement with the Japan Aerospace Exploration Agency (JAXA) to collaborate on the development of quiet ducted fans to make the aircraft more socially acceptable.

Texas A&M Harmony

When Assistant Professor Moble Benedict first heard about the GoFly Prize in 2017, he thought it would be an exciting project for his graduate students at the Advanced Vertical Flight Laboratory at Texas A&M University, but “it was not a trivial task to integrate this into the normal activities we do.”

In June 2018, Prof. Benedict, eight of his graduate students, Dr. Eric Greenwood (then at NASA Langley but now a professor at The Pennsylvania State University), and Dr. Vinod Lakshminarayan (a researcher at NASA Ames) formed Harmony Aeronautics to compete in the GoFly contest. Their Aria eVTOL design was a winner in Phase 1 and Phase 2 of the competition.

“Physics tells us that a coaxial system is the optimal solution to meet GoFly’s quiet, compact, and efficiency requirements,” said team member Farid Saemi. “Big rotors with large blades are always more efficient,” said Benedict, noting that NASA’s Ingenuity Mars Helicopter has a coaxial rotor.

Saemi said the team went through “hundreds of thousands of simulation cases trying to optimize the rotor.” They built a 22-lb (10-kg) one-third-scale model to validate their concept.

The team outsourced fabrication of the machined and composite parts, including the complex wide-chord rotor blades. They relied on commercial off-the-shelf solutions for the motor, motor controller and battery. In October 2019, Aria was tested attached to an indoor gimbal stand so the team could fine tune the control system without the aircraft leaving the ground.

Between December and February, the team conducted more than 14 hours of tethered flight testing, both indoors and outdoors in a variety of weather conditions. Specially shaped swept rotor blade tips were designed and optimized for low noise signature.

The team recorded a hover noise for Aria of 73 dBA at 50 ft (15.2 m), well below the GoFly cutoff of 87 dBA. Team member David Coleman said, “the quiet rotor technology is broadly applicable to eVTOL platforms.”

Untethered flights began in February 2020, but the aircraft crashed just as the team prepared to leave for California. At Moffett Field, the team flew their scale model to compete for the Pratt & Whitney Disrupter Prize.

Trek Aerospace

In 1994, aerospace engineers Rob Bulaga and Mike Moshier formed Trek Aerospace, Inc., based in Folsom, California, to develop personal air vehicles using a novel ducted-fan design. The company developed the Dragonfly UMR-1, the Springtail EFV, the SoloTrek XFV (Exo-skeletal Flying Vehicle) and the OVIWUN, all of which used its ducted propellers, which were also the subject of several Defense Advanced Research Projects Agency (DARPA) contracts.

About 20 years ago, Trek developed a proprietary computational fluid dynamics (CFD) software program called Trek Aerospace Shrouded Propeller Analysis (TASPA) to design optimal shrouded propeller modules.

When owner Rob Bulaga heard about the GoFly Prize, he recognized “the requirements were almost exactly what we were shooting for with our FlyKart 1 and a perfect fit for our technology, so we modified FlyKart 1 to enter the GoFly competition.”

Trek built four versions of FlyKart 2 — FlyKart 2.1 to 2.4 — to pursue the GoFly Prize.

Material changes and a progression from 10 to 12 ducts helped achieve a 10% reduction in empty weight, a 20% increase in power, a 15% increase in endurance, and a 50% reduction airframe weight — from 18 to 9 lb (from 8.2 to 4.1 kg) — with a switch from aluminum to carbon fiber tubes.

Bulaga said there are three reasons to use a shrouded propeller: it increases static thrust by up to 40% compared to a free propeller, it can reduce noise by up to 50%, and improves safety.

The FlyKart 2.4 uses 12 fixed-pitch propellers powered by 5.6- kW motors that produce a maximum of 47 lb (21 kg) of thrust each, providing over 500 lb (227 kg) of capability. This means that with a 200-lb (91-kg) pilot, the 230-lb (104-kg) FAR 103 ultralight aircraft will have 120 lb (54 kg) of excess thrust.

Bulaga said his ducts are achieving figures of merits of 85% efficiency, with about 45% of the thrust coming from the shroud and 55% from the propeller itself.

Trek hoped to compete at the GoFly fly-off in February, but an electronic speed controller fire damaged FlyKart 2.3 and FlyKart 2.4 wasn’t ready in time to fly. The flight test program was further delayed by the coronavirus restrictions in California.

VertiCycle

The Electric Jet Aircraft, Inc.’s VertiCycle was one of only two full-size VTOL aircraft to fly at Moffett Federal Field in the competition for the Pratt & Whitney Disrupter Prize. A serial entrepreneur, founder Pete Bitar “has been interested in personal flight since I was six years old.” He founded Electric Jet in 2018 to develop an electric-powered jetpack he hopes to commercialize.

When Bitar set out to compete for the GoFly prize, he started by analyzing performance data for the VertiPod 4 heavy-lift drone made by AirBuoyant, LLC, a company he founded in Anderson, Indiana, in 2006.

For the GoFly competition, he opted for a quadcopter configuration with four ducted propellers for increased thrust, with the power provided by Tesla Model 3 batteries modified with the help of the Battery Innovation Center, which is sponsored by the State of Indiana. The modular eVTOL design allows additional ducts to be added to carry more payload.

Once funding was secured, Bitar ordered all the components in October 2019 and began assembling the aircraft in January 2020. The VertiCycle made its first indoor flight on Feb. 6 in Anderson, Indiana, as Bitar raced to update his FAA biennial flight review so he could fly the VertiCycle remotely under his 14 CFR Part 61 manned pilot certificate.

Unfortunately, the aircraft was damaged just prior to Bitar driving through snowstorms from the US Midwest to demonstrate the VertiCycle in California. This meant he couldn’t use his full-scale battery pack for the short showcase flight at Moffett Federal Field, but he said, “our Tesla packs would actually allow us to fly 32 minutes with a 200 lb [91 kg] pilot and up to 50 miles an hour [80 km/h].” The VertiCycle flew briefly unmanned at Moffett Field during the Fly Off.

Since February, Bitar has developed a new version of the VertiCycle with larger propellers, no ducts, and a deflector screen above the propeller to protect the pilot and bystanders. The aircraft produces the same thrust but now has a faster forward speed. Bitar plans to market the VertiCycle as a kit and his Electric Jetpack as a FAR 103 ultralight aircraft.

ZEVA

ZEVA Aero was founded by consulting electrical engineer Steve Tibbitts in Tacoma, Washington, in 2017 to compete in the GoFly competition. The team has grown to 25 people from various disciplines.

Tibbitts said the GoFly Prize provided him with an opportunity to revisit electric vertical flight almost 15 years after he submitted his first grant proposal to NASA to develop an electric-powered tiltrotor aircraft in 2005 while working as a consulting electrical engineer. He didn’t get the grant, but built a scale model anyway; however, “it was overwhelming to get the control system worked out,” he said.

The Zero — ZEVA Aero’s first design — is a blended wing body tailsitter octocopter, with four pairs of electric propellers attached to the upper and lower surfaces of the wing. The design philosophy was to “keep it simple and maximize our wing area in the allotted space. And the prone position [for the pilot] was really driven by the requirement to have an unobstructed 90-degree view cone,” said Tibbitts.

The design was refined using Ansys tools, CFD studies, a review of earlier circular-wing aircraft designs and one-sixth-scale model testing that began two years ago.

The carbon fiber airframe was made in sections to reduce tooling and layup costs. The propulsion system was developed using off-the-shelf 32 inch (81 cm) diameter multi-blade propellers, electric motors, batteries and open source flight control software.

However, ZEVA suffered supply chain issues when the motor selected for Zero was discontinued in late 2019. Sourcing a new 25-kW motor had a ripple effect through the entire electrical architecture and drivetrain since they had to transition from 120-Volt to 240-Volt batteries and source new motor controllers that could handle the increased voltage.

ZEVA suspended testing when the coronavirus arrived in Tacoma in March and turned its attention to making masks and face shields for medical workers. ZEVA resumed flight testing in July. Tibbitts sees a future market for the Zero as an ideal air vehicle for emergency services.

What’s Next?

As this article went to press, the GoFly competition was expected to heat up soon. Stay tuned for news from the GoFly team: www.goflyprize.com.

UPDATE: GoFly announced its approach to continue the competition on Nov. 12, 2020: “Given the global pandemic, GoFly has adjusted its format to reflect this new normal. While the Grand Prize remains $1,000,000, we will now provide for an individual team demonstration rather than a large event gathering. The requirements of the competition have not changed, only the process to a flight demonstration to be eligible for the Grand Prize.” More details are available on the competition website: www.herox.com/GoFly. 

Note: More than 150 photos of the GoFly Final Fly Off are posted in the VFS Vertical Flight Photo Gallery: www.vtol.org/gallery