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Wednesday, April 10, 2013

German Start-Up Building Electric Two-Seater

By Thierry Dubois, on Twitter @aerodub

Editor’s Note: E-volo does not use the words “rotorcraft,” “rotary-wing aircraft” or “helicopter.” Yet, the author believes their concept clearly belongs to the rotorcraft family (according to the definition in Webster’s dictionary). Therefore, the author is using “rotorcraft” to describe E-volo’s concept.

E-volo, a Karlsruhe-based company that is developing the Volocopter VC200, hoped to be the first electric two-seater in the rotorcraft world, has received significant support from German authorities. A new aircraft category is being created, while subsidies are boosting the project. In 2011, E-volo flew a single-seater, thus claiming the first flight of an electric vertical takeoff and landing (VTOL) aircraft. French-Australian engineer and commercial helicopter pilot Pascal Chrétien, who flew an electric helicopter two months earlier (see "Designer of Electric Helo Reflects on 2011 Flight Tests," Rotor & Wing, November 2012), is formally contesting the claim.

 

Graphic of the Volocopter VC200. Images courtesy of E-volo

 

“The innovative concept of an electric VTOL convinced the supreme authority for aviation in Germany, the Federal Ministry of Transport, to such an extent that it has commissioned a two- to three-year program for the creation of a new category in aviation,” company manager Alex Zosel told Rotor & Wing. The German Ultralight Aircraft Association, the German Sports Aircraft Association and the civil aviation authorities will work with E-volo. They will define “a new manufacturing specification” and rules for where and when the Volocopter has permission to fly. They will also issue training specifications for future pilots.

After “extensive endurance testing of the cabin, the landing gear and the rotor array,” test flights of a VC200 prototype should begin in the middle of this year. They will take place on a glider airfield in Bruchsal. This is where the factory of DG Flugzeugbau is located. A specialist of gliders, DG Flugzeugbau will build the airframe in carbon-fiber composites.

 

 

E-volo is developing an electric two-seater that will feature an array of 18 rotors. The first version of the VC200 will be equipped with a “range extender”—a piston engine that will recharge the batteries, like in the Chevrolet Volt.

 

 

The VC200 will be lifted by an array of 18 rotors. E-volo targets a speed of “over 54 knots,” a ceiling of 6,500 feet and a maximum takeoff weight of 990 lbs. Today’s battery technology would only allow 20 minutes of electric flight. Therefore, like Chevrolet has done with the Volt electric car, the VC200 will be fitted with a “range extender.” A piston engine will run at constant rpm, driving a generator that will charge the batteries. This will make the VC200 a serial hybrid aircraft.

E-volo hopes progress in battery technology will enable reaching one hour of electric endurance within the next few years.

An optional pusher propeller will enable “an even faster flight.” Separately, the VC200 will be equipped with a rescue parachute. E-volo officials would not discuss pricing.

The federal ministry of economy and technology has granted £2 million ($2.6 million) as a subsidy. So far the company has spent “over £500,000,” or around $650,000, Zosel said.

One of the three company founders, Zosel is the entrepreneur. Physicist Thomas Senkel used to specialize in the development of electric drives and the construction of ultra light vehicles. Meanwhile, Stephan Wolf has developed the software for the onboard flight computer.

 

Alex Zosel is the manager of E-volo.

 

Right from the start of the project, they chose a configuration based on an array of rotors. “Higher redundancy offers higher safety,” Zosel explained. The Volocopter can land safely “even if some drives fail.”

However, in case of total loss of power, it can’t perform an autorotation. “Autorotation requires a variable pitch of the blades, which we do not have,” Zosel admitted. This notwithstanding, helicopter aerodynamics department at the University of Stuttgart are currently investigating the braking effect of E-volo concept's rotors.

Flight controls use a fly-by-wire system, hence a claimed easiness of piloting. “Without any steering input, it would just hover there on the spot,” noted Senkel, who piloted the proof-of-concept VC1 aircraft, commented at the time.

If the pilot moves the joystick forward, how does it translate into rotor movement? For forward flight, the Volocopter changes its pitch angle. Thus, the rear rotors increase their rotation speed and the front rotors decrease it. The same principle of differentiated speeds is applied for turns. Several independent and mutually monitoring airborne computers control the rotation speed of each drive separately.

The VC1 has 16 rotors. With its four arms, it measures approximately 17 feet by 17 feet. It has an empty weight of around 180 lbs., including the batteries.

 

 

The first flight of the single-seat E-volo VC1 prototype took place in October 2011.

 

 

It first flew on Oct. 21, 2011. In 2012, the Lindbergh Foundation awarded its annual Lindbergh prize to E-volo.

This, and the claim for the flight of an electric VTOL, caused bitter feelings for Pascal Chrétien. The electric helicopter he had designed, with the support of France-based motorsports specialist Solution F, had flown in August 2011.

Chrétien has a record from a local court-appointed bailiff (in France, a bailiff can be an official witness). The Guinness World Records 2013 do list the first flight that took place in Venelles, southeast France. E-volo’s Wolf hinted it was not a real flight because it was too low. An official at the Fédération Aéronautique Internationale, the Lausanne, Switzerland-based international air sports federation, told Rotor & Wing that there is no particular criterion to meet for an aircraft flight to be considered as such, “except taking off the ground, maybe under its own power.”

In fact, Chrétien blames the French civil aviation authorities, which would not let him fly because there was no corresponding helicopter category at the time, he asserts. He infringed the law to perform his flights. They took place on private property, far from airports, he insists.

In hindsight, Chrétien concluded on E-volo, “by contrast, the German authorities let them fly and their government even supported them afterward. Good on them,” adding: “France is one of the rare countries where you have to hide to develop innovations.”

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