Electric aircraft

In 2016, Solar Impulse 2 was the first solar-powered aircraft to complete circumnavigation of the world.

An electric aircraft is an aircraft that runs on electric motors rather than internal combustion engines, with electricity coming from fuel cells, solar cells, ultracapacitors, power beaming,[1] or batteries.

Currently, flying manned electric aircraft are mostly experimental demonstrators, though many small unmanned aerial vehicles are powered by batteries. Electrically powered model aircraft have been flown since the 1970s, with one report in 1957.[2][3] The first man-carrying electrically powered flights were made in 1973.[4] Between 2015-2016, a manned, solar-powered plane, Solar Impulse 2, completed a circumnavigation of the Earth.[5]

History

Pioneers

The use of electricity for aircraft propulsion was first experimented with during the development of the airship which took place in the latter part of the nineteenth century. In 1883, Gaston Tissandier flew the first electrically-powered airship.[6] The following year, Charles Renard and Arthur Krebs flew La France with a more powerful motor.[6] Even with the lifting capacity of an airship, the heavy accumulators needed to store the electricity severely limited the speed and range of such early airships.

For a tethered device such as an air observation platform, it is possible to run the power up the tether. In an attempt to create a more practical solution than the clumsy balloons then in use, the Hungarian Petróczy-Kármán-Žurovec PKZ-1 electric-powered helicopter was flown in 1917. It had a specially-designed 190 horsepower (140 kW) continuous-rated electric motor made by Austro-Daimler and received its power up a cable from a ground-based DC generator. However electric motors were not yet powerful enough for such applications and the motor burned out after only a few flights.[7]

The problems of power-to-weight ratio for electric flight were formidable even for small models. A claim made in 1909 has since been challenged, while in more modern times success has been achieved at least since 1957.[8]

Microwaves present an alternative way of transmitting electrical power from the ground. In 1964, William C. Brown flew a model helicopter that received all of the power needed for flight from a microwave beam.[9]

NiCad batteries and solar power

Success in a full-sized aeroplane would not be achieved until Nickel-cadmium (NiCad) batteries were developed, having a much higher storage-to-weight ratio than older technologies. In 1973, Fred Militky and Heino Brditschka converted a Brditschka HB-3 motor glider to an electric aircraft, the Militky MB-E1. It flew for just 14 minutes to become the first manned electric aircraft to fly under its own power.[4][10]

Developed almost in parallel with NiCad technology, solar cells were also slowly becoming a practicable power source. Following a successful model test in 1974, the world’s first official flight in a solar-powered, man-carrying aircraft took place on April 29, 1979. The Mauro Solar Riser used photovoltaic cells to deliver 350 watts at 30 volts. These charged a small battery, which in turn powered the motor. The battery alone was capable of powering the motor for 3 to 5 minutes, following a 1.5-hour charge, enabling it to reach a gliding altitude.[11]

Into production

The first commercially available production electric aircraft, the Alisport Silent Club self-launching sailplane, flew in 1997. It is optionally driven by a 13 kW (17 hp) DC electric motor running on 40 kg (88 lb) of batteries that store 1.4 kWh of energy.[12]

In 2007, the non-profit CAFE Foundation held the first Electric Aircraft Symposium in San Francisco.[13]

The BL1E "Electra" (F-PMDJ), the first conventional light aircraft to be converted to electrical power, made its first flight in 2007.[14]

By 2011 the use of electric power for aircraft was gaining momentum. At AirVenture in that year the Electric Aircraft World Symposium was held and attracted wide attention. It was sponsored by GE Aviation and included presentations by US Air Force, NASA, Sikorsky Aircraft, Argonne National Labs and the US Federal Aviation Administration.[15]

List of electric aircraft

Experimental projects

Up to 1969

Tissandier

In 1883, Gaston Tissandier was the first to use electric motors in airship propulsion.[6]

La France

Charles Renard and Arthur Krebs flew the airship La France.[6]

Petróczy-Kármán-Žurovec PKZ-1

The Petróczy-Kármán-Žurovec PKZ-1 electrically powered helicopter flew in 1917. It was tethered to the ground and had no onboard power source, instead drawing its power up a long cable.

1970s and 1980s

Militky MB-E1

In 1973 the West German Militky MB-E1 became the first man-carrying, full-size aircraft to fly solely on electric power. It used Ni-Cd batteries and a 10 kW (13 hp) DC motor, which gave it a duration of over 12 minutes.[4]

Sunrise

The 27 lb (12 kg) unmanned AstroFlight Sunrise, the result of an ARPA contract, made the world's first solar-powered flight from Bicycle Lake, a dry lakebed on the Fort Irwin Military Reservation, on 4 November 1974. The improved Sunrise II flew on 27 September 1975 at Nellis Air Force Base.[16][17][18]

Solar Riser

The world’s first official flight in a solar-powered, man-carrying aircraft took place on April 29, 1979. The Mauro Solar Riser was built by Larry Mauro and was based on the UFM Easy Riser biplane hang glider. The aircraft used photovoltaic cells that produced 350 watts at 30 volts, which charged a Hughes 500 helicopter battery, which in turn powered the electric motor. The aircraft was capable of powering the motor for 3 to 5 minutes, following a 1.5-hour charge, enabling it to reach a gliding altitude.[11]

Solar One

The Solar-Powered Aircraft Developments Solar One was designed by David Williams under the direction of Freddie To, an architect and member of the Kremer prize committee and produced by Solar-Powered Aircraft Developments. A motor-glider type aircraft originally built as a pedal-powered airplane to attempt the Channel crossing, the airplane proved too heavy to be successfully powered by human power and was then converted to solar power,[19] using an electric motor driven by batteries that were charged before flight by a solar cell array on the wing.[20] The maiden flight of Solar One took place at Lasham Airfield; Hampshire on June 13, 1979.[21]

Gossamer Penguin and Solar Challenger

The Gossamer Penguin, a smaller version of the human-powered Gossamer Albatross was completely solar-powered. A second prototype, the Solar Challenger, flew 262 km (163 mi) from Paris to England.[22] On 7 July 1981, the aircraft, under solar-power, flew 163 miles from Cormeilles-en-Vexin Airport near Paris across the English Channel to RAF Manston near London, flying for 5 hours and 23 minutes. Designed by Dr. Paul MacCready the Solar Challenger set an altitude record of 14,300 feet.[23]

MIT Monarch and Monarch-B

The Massachusetts Institute of Technology Monarch[24] aircraft project was a series of two aircraft designed to win the Kremer prize for human-powered aircraft speed record. The aircraft used an electrical motor along with batteries which were charged by the pedalling action of an athlete piloting the aircraft.[25]

Aerovironment Bionic Bat

The Aerovironment Bionic Bat was an aircraft built to compete for the Kremer Speed Challenge, one in a series of Kremer prize offerings administered by the Royal Aeronautical Society. It incorporated an electric motor that doubled as a generator while on the ground, with the pilot's pedaling action charging ni-cad batteries. The stored energy was used to supplement pedal power from the pilot during record attempts. In 1984, Bionic Bat won two segments of the Kremer Speed Challenge.[26]

Solair 1

The human piloted Solair 1 was developed by Günther Rochelt and based on a Hans Farner canard design.[2][27] It employed 2499 wing-mounted solar cells, giving an output of 1.8 kilowatts (kW). This was equivalent to approximately 2.4 horsepower (hp), and 2.2 kW (3.0 hp). The aircraft first flew at Unterwössen, Germany on 21 August 1983.[2] It flew for 5 hours and 41 minutes, "mostly on solar energy and also thermals".[2] The aircraft is now displayed at the German Museum in Munich.[27] The newly developed piloted Solair II made its first flight in May 1998 and further test flights that summer but the propulsion system overheated too fast.[27] Development stopped when Günther Rochelt suddenly died in September 1998.

Pathfinder Plus (left) and Helios Prototype (right) on the Dryden ramp.
The electric-powered NASA Helios, an unmanned aerial vehicle.
NASA Pathfinder, Centurion and Helios

NASA's Pathfinder, Pathfinder Plus, Centurion, and Helios were a series of solar and fuel cell system–powered unmanned aircraft developed by AeroVironment, Inc. from 1983 until 2003 under NASA's Environmental Research Aircraft and Sensor Technology program.[28][29] On September 11, 1995, Pathfinder set an unofficial altitude record for solar-powered aircraft of 50,000 feet (15,000 m) during a 12-hour flight from NASA Dryden.[28] After further modifications, the aircraft was moved to the U.S. Navy's Pacific Missile Range Facility (PMRF) on the Hawaiian island of Kauai. On July 7, 1997, Pathfinder raised the altitude record for solar–powered aircraft to 71,530 feet (21,800 m), which was also the record for propeller–driven aircraft.[28]

On August 6, 1998, Pathfinder Plus raised the national altitude record to 80,201 feet (24,445 m) for solar-powered and propeller-driven aircraft.[28][30]

On August 14, 2001 Helios set an altitude record of 96,863 feet (29,524 m) – the record for FAI class U (Experimental / New Technologies), and FAI class U-1.d (Remotely controlled UAV: Mass 500 kg to less than 2,500 kg) as well as the altitude record for propeller–driven aircraft.[31] On June 26, 2003, the Helios Prototype broke up and fell into the Pacific Ocean off Hawaii after the aircraft encountered turbulence, ending the program.

1990s

Solar Flight's Sunseeker flying over Southern California's high desert
Sunseeker

During the summer of 1990, the solar-powered airplane Sunseeker, piloted by Eric Raymond, became the first solar-powered airplane to cross the United States.[32] It used a small battery pack charged by solar cells on the wings for takeoff, and then was able to fly directly on solar power.[33]

The Sunseeker II, built in 2002, was updated in 2005–2006 with a more powerful motor, larger wing, lithium battery packs and updated control electronics.[34] As of Dec, 2008 it was the only manned solar-powered airplane in flying condition and was flown regularly by Solar Flight.[33] In 2009 it became the first solar-powered aircraft to cross the Alps, 99 years after the first crossing of the Alps by an aircraft.[35][36]

Soaring
Test Flight of Soaring in 1994
Summary of Configuration and Performance Parameter of "Soaring"

China's first solar-powered aircraft "Soaring" was designed and built by Danny H. Y. Li and Zhao Yong in 1992. The body and wings are hand-built predominantly of carbon fiber, Kevlar and wood. The design uses winglets to increase the effective wing span and reduce induced drag.[37][38]

Icaré II

The German solar-powered aircraft "Icaré II" was designed and built by the institute of aircraft design (Institut für Flugzeugbau) of the University of Stuttgart in 1996. The leader of the project and often pilot of the aircraft is Rudolf Voit-Nitschmann the head of the institute. The design won the Berblinger prize in 1996, the EAA Special Achievement Award in Oshkosh, the Golden Daidalos Medal of the German Aeroclub and the OSTIV-Prize in France in 1997.[39]

LF20

Built by Lange Flugzeugbau GmbH, the LF20[40] was a heavily modified DG800. First flown on 7 May 1999, the aircraft was used as a flying testbed and technology demonstrator. Powered by NiMh cells and using the same EA42 propulsion system as the later Antares 20E, the LF20 could climb 1725 m on one charge.

2000s

Lange Antares

The Lange Antares 20E is an electric, self-launching 20-meter sailplane with a 42-kilowatt DC/DC brushless motor and lithium-ion batteries. It can climb up to 3,000 meters with fully charged cells.[41] The first flight was in 2003. The Antares 20E was the first aircraft with an electric propulsion system to obtain a certificate of airworthiness. In 2011 the aircraft won the 2011 Berblinger competition.[42]

Alan Cocconi and the SoLong

In 2005, Alan Cocconi, who founded the California (USA) electric-propulsion research company AC Propulsion, flew, with the assistance of several other pilots, an unmanned airplane named "SoLong" for 48 hours non-stop, propelled entirely by solar energy. This was the first such around-the-clock flight, on energy stored in the batteries mounted on the plane.[43][44]

Solar Impulse
The Swiss solar aircraft Solar Impulse 1 made its first "flea hop" test flight on December 2009. Solar Impulse 2 achieved the longest non-stop solo flight in history and planned to make the first solar-powered aerial circumnavigation of the globe in 2015.
Main article: Solar Impulse

The first short-hop (350 m) test flight of the Solar Impulse prototype was made on 3 December 2009.[45] The prototype and its successor, Solar Impulse 2, are each powered by four electric motors. Energy from solar cells on the wings and horizontal stabilizer is stored in lithium polymer batteries and used to drive propellers.[46][47] In 2010 it completed the first manned 24-hour flight completely powered by solar power.[48][49][50]

In 2012, the Solar Impulse successfully completed an intercontinental flight, the first-ever by a solar plane, flying a 19-hour trip from Madrid, Spain, to Rabat, Morocco.[51][52] The following year, the aircraft set a new world distance record for solar aviation on a flight from Phoenix, Arizona to Dallas-Fort Worth International Airport as part of its multi-segment trip across the United States.[53][54]

A second aircraft, completed in 2014 and named Solar Impulse 2, carries more solar cells and more powerful engines, among other improvements. In March 2015, the plane began a circumnavigation of the Earth, departing from Abu Dhabi in the United Arab Emirates.[5] It was originally scheduled to return to Abu Dhabi in August 2015, upon the completion of its multi-stage journey.[55] However, due to battery damage, continuation of the flight beyond Hawaii was postponed until April 2016.[56]

On April 23, 2016 the plane completed its flight across the Pacific and landed in California. It was scheduled to make 3 more stops in the U.S. and will then continue by crossing the Atlantic Ocean.[57]

On 20 June 2016 the plane departed from New York JFK and landed successfully in Sevilla, Spain on 23rd.[58]

Electravia BL1E Electra
French BL1E Electra F-PMDJ : the first registered electric aircraft in the world. First Flight in Dec, 2007

The Electravia team, with the APAME Association, first flew its "Electra" electric-powered open-cockpit airplane on Sunday, 23 December 2007 at Aspres sur Buech airfield, Hautes Alpes, France. Test pilot Christian Vandamme, Electravia technical manager, flew the strut-equipped aircraft for 48 minutes, covering 50 km (31 mi). The BL1E "Electra" is powered by an 18-kW (24 hp) disk-brushed electric engine driven by a 47 kg (104 lb) KOKAM Lithium-Polymer battery power pack.[59][60] The BL1E "Electra" is the first registered aircraft in the world powered by electric engine and with batteries. It was the first electric realization of the French company Electravia.

Electravia Electro Trike
E-Trike : French electric delta trike

The Electravia Electro Trike is a single-seater delta trike with an electric propulsion system from Electravia. First flight in June 2008 in Aspres sur Buëch, Hautes Alpes, France. Engine GMPE 102 of 26 hp. The 3 kWh pack of Lithium-Polymer batteries allows 1 hour of flight with ElectroTrike. Charge of a 3 kWh battery takes 1 hour 30 minutes.[61]

First manned AA-battery-powered aircraft

Matsushita Electric Industrial Co. and undergraduates at the Tokyo Institute of Technology teamed up to build an aircraft powered by 160 AA battery cells and successfully flew it for a distance of 391 meters (1,283 ft) in July, 2006.[62]

Boeing-FCD Project
In 2008, The Boeing Fuel Cell Demonstrator achieved straight-level flight on a manned mission powered by a hydrogen fuel cell.[63]

The FCD (Fuel Cell Demonstrator) is a project led by Boeing that uses a Diamond HK-36 Super Dimona motor glider as a test bed for a fuel cell–powered light airplane research project.[64] Successful test flights took place in February and March 2008.[64] Boeing's partners in the project are Intelligent Energy of Britain (fuel-cell); Diamond Aircraft of Austria (Airframe); Spanish Sener (control system); Spanish Aerlyper (integrate motor with airframe); Advanced Technology Products, a U.S. company (motor, batteries, flight testing).[65]

QinetiQ Zephyr

The QinetiQ Zephyr is a lightweight solar-powered unmanned aerial vehicle engineered by the United Kingdom defence firm, QinetiQ. As of 23 July 2010 it holds the endurance record for an unmanned aerial vehicle of over 2 weeks (336 hours).[66] It is of carbon fiber-reinforced polymer construction, the 2010 version weighing 50 kg (110 lb)[67] (the 2008 version weighed 30 kg (66 lb)) with a span of 22.5 metres[67] (the 2008 version had 18 metres (59 feet)). It uses sunlight to charge lithium-sulphur batteries during the day, which power the aircraft at night. The aircraft has been designed for use in observation and communications relay.[68]

The 2008 Zephyr version flew for 82 hours, reaching 61,000 feet (19,000 m) in altitude in July 2008, the then unofficial world record for the longest duration unmanned flight. In July 2010 the 2010 version of the Zephyr made a world record unmanned aerial vehicle endurance flight of 336 hours, 22 minutes and 8 seconds (more than two weeks) and also set an altitude record of 70,742 feet (21,562 m) for FAI class U-1.c (Remotely controlled UAV: Weight 50 kg to less than 500 kg).[69][70][71]

SkySpark
Skyspark in flight 2009

The SkySpark is a joint project of engineering company DigiSky and Polytechnic University of Turin. The two-seat Pioneer Alpi 300 has a 75 kW (101 hp) brushless electric motor powered by lithium polymer batteries. The aircraft achieved a world record of 250 km/h (155 mph) for a human-carrying electric aircraft on 12 June 2009.[72][73]

Green Pioneer Ι
Test flight of "Green Pioneer I" in 2004

The Green Pioneer solar-powered aircraft research programme was announced at the 4th China International Aviation and Aerospace Exhibition in 2002. The experimental programme was intended to provide research data for future Chinese solar-powered aircraft. The programme was run by New Concept Aircraft (Zhuhai), the China Aviation Industry Development Research Center, and China Academy of Space Technology. The project leader and chief designer was Danny H. Y. Li.[74][75]

2010s

Airbus E-Fan

Airbus has been co-developing an electric aircraft with Aero Composite Saintonge. The aircraft, called the E-Fan, uses on-board lithium batteries to power the two electric engines and can carry two crew. A test flight was conducted in April 2014 at Mérignac Airport, France, landing in front of a large audience, the French Minister of Industry Arnaud Montebourg being one of them. Airbus has stated that there are plans for development of a commercial regional aircraft in the near future.[76][77]

EADS Cri-Cri

In June 2010 European aerospace company EADS unveiled an electric version of the 1970s vintage Colomban Cri-cri ultralight aircraft powered by four electric engines. The Cri-Cri will have lithium batteries and will be able to fly for 30 minutes at 60 kn (111 km/h) or 15 minutes of aerobatics at speeds up to 135 kn (250 km/h), with a climb rate of 1,000 feet per minute. The aircraft is a demonstrator for future technology, as Jean Botti, EADS's chief technical officer explained: "The Cri-Cri is a low-cost test bed for system integration of electrical technologies in support of projects like our hybrid propulsion concept for helicopters." The Cri-Cri first flew on 2 September 2010 at Le Bourget airport near Paris.[78][79]

Hugues Duval MC15E Cri-Cri
The MC15E electric Cri-Cri during world speed record - 2011 Paris Airshow in Le Bourget

On 5 September 2010, pilot Hugues Duval established a world speed record for electric aircraft with his twin engine MC15E CriCri “E-Cristaline”. This aircraft has been equipped with Electravia engines, controllers, batteries and propellers. During the Pontoise Air show, a top speed of 262 km/h (141 kt) was recorded by Aero Club de France organizers. Then, on 25 June 2011, during the official flight presentation at 2011 Paris Air Show (Salon du Bourget), Duval established a new world record of 283 km/h (176 mph).[80]

e-Genius

The battery-powered e-Genius was designed and built by the Institute of Aircraft Design (Institut für Flugzeugbau) of the University of Stuttgart Germany for the 10–17 July 2011 Green Flight Challenge in Santa Rosa, California. The design has similarities to their earlier solar-powered aircraft Icaré II and seems to share most of the components with the fuel-cell–powered Hydrogenius. The aircraft is a converted motorglider and uses a tail-mounted 80 hp (60 kW) electric motor. The e-Genius performed its first 20-minute flight on 25 May 2011. In July 2011 the aircraft flew for over two hours between two points near Mindelheim, Germany, at an average speed of more than 100 mph (161 km/h).[81][82][83]

ENFICA-FC

The ENFICA-FC is a project of the European Commission, to study and demonstrate an all-electric aircraft with fuel-cells as the main or auxiliary power system. During the three-year project, a fuel-cell based power system was designed and flown in a Rapid 200FC ultralight aircraft.[84]

Paratrike E-Fenix
E-Fenix: the first electric 2-seater paratrike in the world. Flying at Re Island

The E-Fenix was the first two-seat electric paratrike flown. Developed by Planète Sports & Loisirs, headquartered on Re Island, off the coast of La Rochelle, France, with an Electravia electric drivetrain, this paratrike has been used since the summer of 2011 for tourist flying. The first flight took place on 12 May 2011 at Sisteron's airfield (South of France, headquarters of Electravia), with Michaël Morin as test pilot.[85]

Puffin

The NASA Puffin is a proposed hover-capable, electric-powered, low-noise, personal, vertical takeoff and landing (VTOL) technology-concept, proprotor aircraft. It would be capable of flying a single person at a speed of 150 miles per hour. Range is expected to be less than 50 miles with initial battery technology. The design has a 13.5-foot wingspan and stands 12 feet tall on the ground in its take-off or landing configuration.[86]

As of January 2010, a one third–size, hover-capable Puffin demonstrator was planned for March 2010. Future designs might incorporate additional rotors to provide redundant systems.[87]

As of August 2010, the one-third scale model of the Puffin was on display at the NASA Langley campus for filming for the Discovery network series “Dean of Invention.” The Puffin simulator was also demonstrated. As of August 2010, the Puffin was planned to appear in the eighth and final episode of the show.[88]

Pipistrel Taurus G4

In July 2011 Pipistrel unveiled their Taurus G4 dual fuselage, four seat, single engine experimental aircraft that demonstrated the equivalent of 400 passenger miles per gallon efficiency. The aircraft joins two sailplane fuselages, with two seats each, with a single tractor configuration electric motor mounted between the fuselages. The aircraft carries 1,100 lb (499 kg) of Lithium polymer batteries. The aircraft has a 75 ft (22.9 m) wing and has a gross take-off weight of 3,300 lb (1,497 kg), making it the heaviest manned electric-powered aircraft built to date. It has a glide ratio of over 30:1 at 100 mph (161 km/h). The G4 first flew on 12 August 2011 and won the NASA Green Flight Challenge on 3 October 2011.[89][90][91]

Luxembourg Special Aerotechnics MC30E
The MC30E during flight test campaign of August 2011

On 13 April 2011, during the AERO Friedrichshafen show, the Luxembourg Special Aerotechnics MC30E proof-of-concept aircraft[92] piloted by Jean Luc-Soullier, using Dow Kokam Li-Po batteries, set a record for electric aircraft of 135 km/h (73 kn) over a return 15 km (8 nmi) circuit in the FAI RAL1E category (FAI ID 16214) which was not approved solely for file format reason. This aircraft was later retrofitted with a more efficient engine from Electravia, in order to pursue further records in 2011.[93] Since this time the FAI registered four records in speed, distance and altitude, flown 27 February 2012[94] (FAI ID 16 495,16496 and 16497) and 29 September 2012 (FAI ID 16638).

Electric Lazair

In 2011, Ultraflight Lazair designer Dale Kramer introduced an experimental electric-powered Lazair on an amphibious mono-float, with outrigger floats at AirVenture. The aircraft is powered by twin Bevirt JM1 Joby model aircraft powerplants and dual 16 cell 4 amp-hour battery packs that produce 63 volts, mounted in the wings. The aircraft won Antique Ultralight Champion and Best Ultralight Amphibian at AirVenture. The aircraft is an experimental project and no production is planned.[95]

Electric Rotorcraft

The Solution F/Chretien Helicopter the world's first man-carrying, free-flying electric helicopter was developed by Pascal Chretien. The concept was taken from the conceptual computer-aided design model on September 10, 2010 to the first testing at 30% power on March 1, 2011—less than six months. The aircraft first flew on August 12, 2011. All development was conducted in Venelles, France.[96][97]

Pascal Chretien hovering world's first manned electric helicopter on 12 August 2011

The electric Sikorsky S-300 of the Project Firefly was a project to flight test an electric rotorcraft, but the project was put on hold due to battery limitations.[98] The world's first large-scale all-electric tilt-rotor was the AgustaWestland Project Zero unmanned aerial vehicle technology demonstrator, which performed unmanned tethered fights on ground power in June 2011, less than six months after the company gave the official go-ahead.[99]

A Robinson R44 was converted and flown for 20 minutes in 2016.[100][101]

SORA-e

The first Brazilian manned electric aircraft flew on 18 May 2015. Powered by two electric engines with a total of 70 kW and with a Li-Po battery package the SORA-e flew from São José dos Campos airfield. The project was developed by ACS Aviation with funds from FINEP and the support and partnership of Itaipu Binacional.[102][103]

Battery-Powered Robinson R44
High voltage battery system being prepared for installation in a Robinson R44.

In September 2016, Martine Rothblatt and Tier1 Engineering successfully tested an electric-powered helicopter which took flight at Los Alamitos Army Airfield. The five minute flight reached an altitude of 400 feet with a peak speed of 80 knots. The helicopter, a modified Robinson R44 had Its 500 lb Lycoming IO-540 internal combustion engine replaced by electric motors, weighing a 100 lb, plus 11 Brammo Lithium polymer batteries weighing 1100 lb. The flight controls and drive train were unchanged, although a digital cockpit display was added for pilot management of torque and power, as well as for data logging. Two three-phase permanent magnet synchronous motors were stacked together for redundancy in the event of a motor failure.[104][105][106]

Others

NASA is converting a Tecnam P2006T to be powered by 18 electric motors in a project called LEAPTech[107] and an aircraft designated X-57 Maxwell.[108]

The European Commission has financed many low TRL projects for innovative electric or hybrid propulsion aircraft. The ACHEON Project[109][110] couples electric or hybrid propulsion with ultraSTOL performance produced by nozzle that deflects exhaust jet gas by the Coanda effect. It involves developing two hybrid propulsion aircraft[111][112] and an electric aircraft for operating in urban areas.[113]

Several other electric aircraft are now being created for the Green Flight Challenge. These include:

Production aircraft

1990s

Alisport Silent Club

The first commercially available production electric aircraft was the Alisport Silent Club self-launching sailplane. It was first tested in 1997. It is optionally driven by a 13 kW (17 hp) DC electric motor running on 40 kg (88 lb) of batteries that store 1.4 kWh of energy. As its name implies the aircraft has a low noise footprint, creating a maximum of 42 dB in climbing flight.[12]

Commercially successful, the electric version was still in production in 2015, 18 years after its introduction.[12]

Air Energy AE-1 Silent

The Air Energy AE-1 Silent came on the market in 1998.

2000s

Electraflyer

In April 2007 the Electric Aircraft Corporation began offering complete electric ultralights and engine kits under the ElectraFlyer brand name, to convert existing ultralight aircraft to electric power, in what was the first commercial offering of an electric aircraft. The 18 hp (13 kW) engine package weighs 26 lbs and an efficiency of 90% is claimed by the company. The battery consists of two lithium-polymer battery packs which provides 1.5 hours of flying in the trike application.[114][115]

In January 2008 the company introduced their new ElectraFlyer-C at the Sebring Light Sport Aircraft Show. This aircraft is a converted Monnett Moni motor glider equipped with an 18-hp electric motor, regenerative-braking-capable controller package and two lithium polymer battery packs. The engine weighs 29 lbs and the battery packs weigh 78 lbs total. The aircraft has a climb rate of 500 ft/min, cruise of 70 mph and an endurance of 90 minutes. It is capable of being recharged from a 110-volt source in six hours or from a 220 volt source in two hours. The aircraft began flying in May 2008 and was demonstrated before the crowds on August 2 at AirVenture 2008.[116]

In April 2009 the ElectraFlyer-C prototype was offered for sale on eBay. The designer intended to use the funds from the sale, plus a Lindbergh Foundation grant of $10,580 to complete the two-place Electric Aircraft Corporation ElectraFlyer-X design that will eventually qualify for light-sport aircraft status. The new design will incorporate composite construction, detachable wingtips to aid storage and will be powered by a 50 hp (37 kW) electric motor. Its design goals include a 28:1 glide ratio and a cruise speed of 80 mph (129 km/h) for two hours.[117] Electraflyer president Randall Fishman announced in April 2010 that the company's latest model, the Electraflyer-X, would fly in May or June 2010. The aircraft will be a two-seater and will utilize a new 20 hp (15 kW) single rotor electric powerplant. Fishman is also developing 40 hp (30 kW) two-rotor and 60 hp (45 kW) three rotor engine designs.[118]

Sonex Aircraft

During AirVenture 2007 Sonex Aircraft announced that they are working on a series of alternate power initiatives, including an electric-powered aircraft. The electric-powered Waiex motor glider was first flown in December 2010 and is powered by a 54 kW (72 hp) brushless DC electric motor, managed by a newly designed controller. Power is from a collection of 14.5 kW-hour lithium polymer batteries, giving the aircraft an endurance of one hour at low-speed cruise or 15 minutes of aerobatics.[119][120] This power system is being developed for the Sonex Electric Sport Aircraft, which will be available as a kit.[121]

Yuneec International E430

A new Chinese aircraft was announced in 2009. The Yuneec International E430 is a two seat, V tailed, composite aircraft with a high-aspect ratio wing. Take-off speed is 40 mph and top speed is 93 mph. The aircraft is being developed as a homebuilt aircraft for the US market.[122][123]

The prototype E430 was displayed at EAA AirVenture Oshkosh in July 2009, by which time it had flown over 22 hours. Powered by a Yuneec Power Drive 40 electric motor, the company claims that the battery packs have an expected lifespan of 1500 hours and cost US$7000 each, with the aircraft carrying 3–5 battery packs, giving two to two and half hours' endurance. The batteries can be recharged in 3 hours. The company projects that by the time the first customers require replacement battery packs that improved and less expensive ones will be available. Projected price for a commercially available light sport aircraft production version of the E430 is US$89,000.[124]

Lange Antares 20E
A Lange Antares 20E in a hangar

The Lange Antares 20E is a self-launching motor glider with a 42-kW electric motor and SAFT VL 41M lithium-ion batteries. The motor actuates 2-blade fixed pitch propeller. It can climb up to 3,000 meters with fully charged cells. After launch it can function as a conventional, though heavy, glider. As of January 2010, over 50 had been built.[125]

2010s

GreenWing eSpyder (formerly Flightstar e-Spyder)

The GreenWing International eSpyder is a single-seat electric airplane sold as a kit for construction as an amateur-built airplane.[126] It is based upon the Flightstar Spyder ultralight, developed by Flightstar Sportplanes president Tom Peghiny of South Woodstock, Connecticut, USA in cooperation with electric motor manufacturer Yuneec and first flew July 17, 2009.[127] It has a Yuneec 24-kW electric power system that can lift a 220-pound payload at an initial climb rate of 375 feet per minute. Maximum speed is 56 mph; economy cruise is 37 mph. Flights as long as an hour are possible, with a 30-minute reserve still available upon landing. Batteries can be charged in about two hours.[128] German DULV certification was awarded in February 2013.[126] GreenWing began taking orders at the 2013 EAA AirVenture show in Oshkosh, WI at a cost of $39,990 and kits are scheduled to begin delivery the end of 2013.[129]

Icaro 2000 Trike

Icaro 2000 Trike is a single-seat ultralight trike, with a conventional hang glider and the Flytec HPD 10 10 kW (13 hp) engine, developed by Manfred Ruhmer.[130]

Schempp-Hirth Flugzeugbau Arcus-E

The Schempp-Hirth Arcus-E self-launch two-place glider first flew in 2010 and entered series production shortly afterwards, with several now delivered. Arcus was designed to accommodate electric, gas-self-launch, gas-sustainer, or no motor. Arcus E is a collaboration between Schempp-Hirth and Lange Aviation, and uses the identical propulsion system as the Lange Antares 20E and 23E.[131]

Cessna 172

In July 2010 Cessna announced it was developing an electrically powered Cessna 172 as a proof-of-concept in partnership with Bye Energy. Then Cessna CEO Jack Pelton stated that the project reflects "encouraging news for the future of mainstream general aviation." Pelton pointed out "the electric power plant offers significant benefits, but there are significant challenges to get there."[132][133] On 19 October 2012 Beyond Aviation announced that it had flown an electric Cessna 172 Skyhawk multiple times, using Panacis lithium batteries.[134]

PC-Aero Elektra One

The PC-Aero Elektra One is a development of a commercial electric aircraft design by PC-Aero of Germany. The single seat composite aircraft had its first flight in early 2011.[135] The Elektra One is powered by a 21 hp (16 kW) electric motor and is expected to have an endurance of three hours, with a 100 mph (161 km/h) top speed.[136] The company is planning a whole line of aircraft including a version of the Elektra One with longer wings and built-in solar panels and an aerobatic version with double Elektra One's power and airframe strength. The company is also planning two and four seat developments.[136]

Pipistrel Taurus Electro G2

First made available commercially in February 2011, the Taurus Electro G2 is a two-seat self-launching sailplane. The 40 kW (54 hp) engine powers the aircraft from internally mounted lithium batteries for a 17-minute climb, after which the engine is retracted and the aircraft then soars as a sailplane. In April 2011 the Taurus won the 2011 Lindbergh Electric Aircraft Prize for "best electric aircraft" at the Aero show held in Friedrichshafen, Germany.[137][138]

Electravia ElectroLight 2
Electric Motoglider ElectroLight2

ElectroLight 2 is an ultralight motorglider with an Electravia electric propulsion system and a silent propeller. First flight was 21 December 2011 at Sisteron's airfield (Provence, France). With a Lithium-Polymer pack of 5.55 kWh (weight: 34 kg), the endurance was 1:35 and the altitude gain about 3,000 m (9,843 ft) at a best glide ratio speed of 90 km/h (56 mph).[139][140]

Volta Volare GT4

The Volta Volare GT4 was announced in April 2012, but has not flown. It utilizes a standard canard pusher airframe and is expected that it will be able to fly up to 300 miles (480 km) on electric power alone. In hybrid mode, a supercharged 1.5-liter displacement gasoline engine with a 23 US gallons (87 l) fuel tank will back up the electric system and extend the GT4’s range up to 1,000 miles (1,600 km).[141]

APEV Pouchelec

The French APEV Pouchelec is an electric development of the APEV Pouchel Light, powered by a 15 kW (20 hp) Agni Motors AGNI 119R electric motor and a Kokam Lithium-ion polymer battery pack, which gives a 30-minute flight endurance.[142][143]

eUP Green1

The Canadian Green1 electric motor glider trike was developed by eUP Aviation with a complete Electravia electric solution and had its inaugural flight on 8 December 2012 at Pitt Meadows Airport in British Columbia. Powered by a 19 kW (25 hp) electric motor and a 3.9 kWh lithium polymer battery, the single place ultralight with a hang gliding wing is capable of one hour of power flight which can be supplemented for greater time and distance with power-off soaring. Production delivery is forecast for the spring of 2013.[144]

Aero Electric Sun Flyer

The Aero Electric Sun Flyer is an American electric aircraft intended for flight training use, first shown on 11 May 2016.[145]

See also

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