- 03 Nov 2017 10:27 PM
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Back to Kitty Hawk
Exploring the Secrets of the Kitty Hawk Flyer
By Kenneth I. Swartz
It’s a long way from the windy sand dunes of the Outer Banks of North Carolina to the San Francisco Bay, but the aviation adventure that the Wright brothers launched near Kitty Hawk in 1903 now continues with new electric vertical takeoff and landing (eVTOL) aircraft being developed by Silicon Valley startups.
While several teams have presented at past AHS-led Transformative Vertical Flight Workshops, some are obsessed with secrecy, just as the Wright brothers were a century ago. But one such team lifted the veil and conducted public demonstrations of its prototype this summer.
The Flyer in Oshkosh
On the warm morning of July 28, aviation enthusiasts lined the shore of Lake Winnebago in Oshkosh, Wisconsin, to witness the first flight of a prototype Kitty Hawk Flyer eVTOL aircraft at a public forum. The annual Experimental Aircraft Association’s AirVenture fly-in convention is the world’s biggest aviation event and has long been a showcase for innovative new aircraft. This year’s extravaganza attracted nearly 600,000 people and 11,000 aircraft, including a dozen Kitty Hawk engineers and two prototype Flyers from the company’s workshops in Sunnyvale, California.
“The Kitty Hawk Flyer is an electric aircraft that flies over water that you can learn to fly in less than an hour,” said spokeswoman Ellen Cohn as the Flyer was being prepared to fly. “This is our entry into selling electric aircraft and the beginning of a new wave of aviation innovation ... and we are so excited to see what happens next.”
Cohn said that Kitty Hawk will start selling a production version of the Flyer at the end of 2017 “that will look totally different than the prototype ... and fly up to 15 ft [4.6 m] high and up to 25 mph [40 km/h] for 15 to 20 minutes.”
“With each new version we release, the aircraft will fly a little longer, go a little faster and be sleeker. Our long-term vision is to see the aircraft evolving so everyone can have access to personal flight and limitless mobility,” said Cohn.
At the waterfront, test pilot Todd Reichert slipped on a helmet and life vest as other Kitty Hawk engineers carried the Flyer to a floating dock to complete preflight and telemetry tests.
Once EAA seaplane traffic had cleared the area, Reichert hopped on the Flyer, gripped the handlebars, activated the electronic controls and powered up the eight downward-facing electric propellers to lift the pontoon-equipped aircraft into the air.
For the next three minutes, Reichert entranced the crowd as he piloted the Flyer back and forth across the lake, demonstrating stability and maneuverability in a series of hovers, banks, turns and climbs. The purr of the eight electric motors was barely audible from the shore and was drowned out by every light aircraft flying overhead.
To a first-time observer, the prototype Flyer seemed quite at home flying above the water, and it was easy to imagine a scene in the near future when Flyers might be as numerous as speedboats, personal watercraft or kite-boarders on a popular lake.
Page Turns to Kitty Hawk
A year and a half ago, the only Kitty Hawk Flyer anyone knew about was the recordsetting aircraft that created the aviation industry on Dec. 17, 1903. Then, in June 2016, a Bloomberg Businessweek article revealed that Larry Page, the wealthy co-founder of Google and a champion of autonomous and electric vehicle technology, was funding two eVTOL startups: Zee Aero Inc. and Kitty Hawk Corp.
Zee Aero was founded in 2010, supported by $100M from Page, and was secretly flighttesting a full-scale electric multicopter VTOL airplane at Hollister Airport, 50 miles (80 km) south of the Googleplex global headquarters in Mountain View, California.
Kitty Hawk, founded in 2015, is headed by Sebastian Thrun, who previously led Google’s self-driving car program and co-founded Google X, the company’s semi-secret research arm. [Zee Aero became a division of Kitty Hawk in 2016; the combined company is an AHS corporate member. – Ed.]
Few details had emerged, however, regarding Kitty Hawk’s eVTOL projects. The Bloomberg authors could only write that “Two people say Kitty Hawk is working on something that resembles a giant version of a quadcopter drone.” (Though it is now more like a giant “octocopter.”)
Then on April 24, 2017, the Kitty Hawk Flyer — a single-seat eVTOL multicopter — was revealed in a media campaign designed to stimulate interest and sales when the production version goes on sale at the end of 2017. “Our mission at Kitty Hawk is to make the dream of personal flight a reality,” said the news release.
The Flyer was launched a day prior to the Uber Elevate Summit on eVTOL technology (see “Charging Forward: New eVTOL Concepts Advance,” Vertiflite, July/Aug. 2017). This created a huge wave of publicity for Kitty Hawk and the coming age of eVTOLs (often incorrectly called “flying cars”).
Since then, more than 4.5 million people have viewed Kitty Hawk’s YouTube videos showing the Flyer being flown — ridden like a motorcycle, personal watercraft or snowmobile. Memberships in Kitty Hawk’s Discovery program offering a purchase discount quickly sold out.
In spite of publicity centering on the aircraft itself, it did not go unnoticed that the Flyer development team was being led by two masters of human-powered vehicle design: Dr. Todd Reichert and Cameron Robertson.
The two Canadian engineers had been graduate students at the University of Toronto Institute for Aerospace Studies (UTIAS) when they founded Aerovelo (then written “AeroVelo”) to develop innovative high-performance, human-powered vehicles. Between 2008 and 2011, the Aerovelo team developed and flew the Snowbird, the world’s first successful human-powered ornithopter.
In July 2013, Aerovelo won the AHS International Igor I. Sikorsky Human Powered Helicopter Competition with its giant Atlas quadcopter, which Reichert also piloted and powered (see sidebar).
After winning the AHS Sikorsky prize, Aerovelo developed the egg-shaped aerodynamic Eta Speedbike. Reichert set a world speed record in September 2015, and set a new one in September 2016 when he pushed Eta to an astonishing speed of 89.59 mph (144.187 km).
Page’s team approached Reichert and Robertson to join Zee Aero after Aerovelo won the AHS Sikorsky Prize in 2013, but the Canadians only moved to California two years ago — joining Kitty Hawk in September 2015, shortly after it was founded.
Human Power to Battery Power
“The exciting thing that ties the human-powered projects and the Kitty Hawk Flyer together is the constraint you put on the problem,” Reichert told Vertiflite after his EAA demo flight.
“With the human-powered aircraft program, the constraint you have is the power of a human … but outside of that you are completely free to design whatever you can think of.”
“The Atlas HPH was an aircraft … that had to reach 3 m [9.8 ft] and hover for a minute on human power. A human produces the power equivalent to a cordless drill — about 700 watts [0.9 hp] for a minute. On that teeny amount of power you need massive rotors to be able to fly.” Reichert has a unique perspective, since he was the “engine” on all of Aerovelo’s human-powered vehicles and trained for every project to maximize his power output.
“With an ultralight aircraft, the constraint is the maximum weight limit. The design challenge is how we can build an aircraft that weighs less than 250 lb that has sufficient range to do something incredible on battery power.” US Federal Aviation Administration (FAA) Part 103 regulations introduced in 1982 established limits on size, performance and configuration of ultralight aircraft, and also established that people flying them needed no pilot’s certificate or medical qualification.
The rules say that a powered ultralight aircraft must have an empty weight of less than 254 lb (115 kg) — excluding floats and safety devices — and can’t exceed 55 kt (102 km/h) in level flight. Conventional ultralight aircraft are also allowed to carry up to 5 gal (19 L) of fuel, but that’s irrelevant when you are using battery power.
“Lightweight electric motors are incredible because you have a lot more power available. Now we have eight motors and they are capable of a lot more thrust,” explained Reichert. “What this allowed us to do is scale down the rotors from a 10-meter [33- foot] radius [on the Atlas] to something smaller than one meter [on the Flyer]. And this allows us to fly in higher wind conditions and make a much more functional vehicle.”
The Flyer has just eight moving parts. Oshkosh visitors weren’t allowed to get near the Flyer prototype at the lake for a close inspection, but the electric motors were attached to four cross tubes.
A Flyer rotor on display in the EAA Innovation Center was made of carbon fiber, measured about 32 inches (81 cm) in length and was designed to spin at up to 2,000 rpm.
Flight Test
“What we will release towards the end of the year will look fundamentally different from the prototype you saw fly today,” Reichert told Vertiflite after his first Oshkosh flight.
“At Kitty Hawk, our goal is to get something flying and start testing it. We don’t try to design something that is 10 years away. We wanted to go through the entire development process with the prototype before we really sat down and started designing an aircraft that would be released to the market.”
“We have already conducted over 1,000 flights on this aircraft as well as many flights on the new aircraft,” said Riechert, refusing to elaborate further about the new aircraft.
“We have tried to create a type of feedback loop between the test pilots and the engineers. And a lot of the engineers are actually flying the vehicle as well. We try to get as much time as we can in the air in as many different environments as we can. Every time we fly there is something new that we can learn.” Reichert added, “As with any engineering process things are very iterative. And you work through the iterations.”
The prototype Flyer was developed in a little more than a year, and Kitty Hawk has recently invited people from outside the company to flight test the aircraft, including journalists and others who have never flown an aircraft before.
Flight Controls
“On the prototype, you hold on to the handle bar with two hands and use two thumb sticks on each grip to control the aircraft. The right hand controls roll and pitch and the left hand controls altitude and yaw,” said Reichert. “We have taken a complex hardware problem and are turning it into software. The fundamental basis of the design is to simplify the mechanics and use computational power for stabilization and control. The onboard computer stabilizes the aircraft and that gives us the ability to make it incredibly easy to fly.”
The first flight demonstration at Oshkosh was conducted in winds gusting up to 10–12 kt (19–22 km/h), “which limited the ability to go exactly where you wanted to go,” said Reichert. “This aircraft flies on attitude command mode. If I had to take my hand off the stick the aircraft will level but it will not be fighting the wind. It will be drifting with the wind since the aircraft has a limit to how much you can bank for a variety of technical reasons. It is very easy for me to go downwind but I cannot make as fast progress flying upwind.”
“The power from the eight engines is synchronized through the central flight computer. The beauty of being totally electric is … the amount of computational power we can put inside there,” he continued. “The computer has almost the same sensors you find in your cell phone, including accelerometers and gyros.” To maintain attitude, the sensors “can tell the instant the plane starts to tilt and it speeds up those rotors before I can even feel it move. If I had four levers and I was trying to control them manually I couldn’t move them fast enough.”
“Envelope expansion is a huge thing we are working on, such as the ability to fly in heavier wind conditions,” he added.
The production version of the Flyer will have redundancy in the motors, battery controllers and computer, which means that, “if you lose one engine it will still be able to fly,” said Reichert. The aircraft also has an auto-land capability for safety.
Reichert added that the production Flyer will be fitted with a GPS that will hold the aircraft position such that “when you take your hands off the controls it will just sit there.”
All of the Flyer’s flights on YouTube and at Oshkosh were within about 20 ft (6 m) of the surface of the water, which begs the question, “Can the Flyer fly out of ground effect?”
“As far as the physics go, this aircraft could definitely fly out of ground effect. However we have limited the altitude and speed of this aircraft to 10–20 feet [3-6 m] above the water and 20–30 miles an hour [32–48 km/h]. These are [safety] limits that are not set by the aircraft or limited by the technology,” said Reichert. “If this aircraft is a few feet off the water it only uses 70% of the power required at a height of 10 feet [3 m]. At the higher altitudes we were flying today we were about 90% out of ground effect.”
Plans for Tomorrow
Kitty Hawk’s initial sales will be to a small group as it slowly enters the eVTOL market and builds production. Initially, the aircraft will only be delivered to customers in the US, including those who intend to use it in other countries. “In the future, Kitty Hawk is likely to be developing other products that will serve other markets, but for now our Flyer team is focused on the ultralight market,” Reichert noted.
Selling a production aircraft that flies for 15 to 20 minutes means that Kitty Hawk is planning a five- to seven-fold increase in flight endurance compared to the prototype. This will probably require the use of more expensive high-capacity batteries that can be recharged or swapped out between flights. Obviously, though, improvements in batteries over the years will allow future models to achieve ever-improving performance.
The price of the Flyer has not been released, but the high-end BRP Sea-Doo personal watercraft starts at $16,000, while a Mosquito XEL ultralight helicopter “ready to fly” on floats is priced at $45,000. A range of accessories, likes covers and trailers, will also be available when the eVTOL aircraft hits the market.
Kitty Hawk’s first step is to enter the recreational market, but “the long-term vision is that this is going to be the next form of transportation. When that happens will depend on a lot of factors,” said Reichert.
“I’m not going to predict the future, but it’s moving fast,” he concluded.
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