Alongside those who were equipping airplanes with solar panels, while batteries still lacked the required energy density, the idea of an electrically propelled airship was resurrected. English aeronautical engineer Graham E. Dorrington, Ph.D. at Queen Mary and Westfield College, University of London, wanting to bring researchers and scientific instruments close to the crowns of forest trees, developed what he called dendronautics (from the Greek words dendron, tree, and nautica, navigation). In 1993 Dorrington built a pedal-electric airship with Yuasa lead-acid batteries to enable Dieter Plage, a celebrated German cinematographer of nature documentaries, to film above the canopy of the Sumatran rain forest. During one flight, a gust of wind caused the airship to buck and become entangled in a treetop. Plage fell to his death, having unfastened his safety belt in order to try to reach and save his camera.
Dorrington, determined to improve stability, embarked on “Project Hornbill,” designing and building Dirigible-4 with a helium capacity of 380 cubic meters, perhaps the first electric airship since La France took to the skies above Paris in 1884, over a century before. Again with energy from gas-free recombination Yuasa lead-acid batteries to provide nominal 24V DC power for about 1 or 2 hours duration, D-4’s two main motors, 24-volt 650W EMDs, were used to drive two side-mounted 0.6m diameter propellers that could be vectored through 360 degrees, to provide about 70 N thrust (combined). As a backup, for forward propulsion, D-4 was also fitted with a large 2.6m-diameter propeller that could either be electrically or human-powered, although this was rarely used.
Between January and April 1995, Dorrington flew D-4 over a reserve of pristine tropical rain forest near the Danum Valley Field Centre (DVFC) in southern Sabah, Malaysia, collecting pollinating insects as well as counting orangutan nests in a forest area of about one square kilometer. These pioneering efforts proved that controlled movement close to the forest canopy is in fact viable. A total of thirty successful and silent flights were made, ranging up to 3 km from the takeoff point, with safe return in all cases; one flight reached 450 ft (137 m) at 20 kph (12 mph), while another lasted 114 minutes. On its penultimate flight, the D-4 was soft-landed atop a flowering Merbau tree and rested there for twenty minutes, further demonstrating the effectiveness of similar platforms for canopy research. After operations began, D-4 was also fitted with two small, laterally facing Astro Cobalt electric motors (200W each) driving propellers in the tail, and two electric motors (250W each) driving propellers slung on the keel structure, to act as bow and tail thrusters. These thrusters proved to be essential for maneuvers at low speed or during hover.
If electric airplanes were to progress, they needed men of vision. One of these was Brien Seeley. After graduating from UC Berkeley, Seeley obtained his M.D. degree from UCSF in just three years, specializing in eye surgery. While a medical student, he designed and hand-built his own 70 mph, street-licensed electric car and drove it to the hospital each day as an intern. During his residency in eye surgery at UCSF, he devoted his two-week vacation to earning his pilot’s license, and this began a life-long passion for aviation. He studied aeronautical engineering and helped build two experimental homebuilt aircraft. In 1981, Seeley founded the Comparative Aircraft Flight Efficiency (CAFE) Foundation to host the CAFE 400 flight efficiency aircraft races. From 1981 to 1990, each summer’s CAFE race at Oshkosh attracted the premier aircraft designers in the U.S. to bring their sleekest aircraft to compete. Oshkosh Airshow became the focus of an annual aircraft race that emphasized fuel efficiency; the winner had to complete the 500 mile triangular race course while consuming no more than an allotted amount of fuel. Many felt that the fuel allotment was too arbitrary and constrained entries in the event. The race’s minimum qualifying speed also limited participation.
As well as vision, electric airplane builders also needed incentives.
In 1927, at the age of 25, Charles Lindbergh had emerged from the virtual obscurity of a U.S. Air Mail pilot to instantaneous world fame as the result of his Orteig Prize–winning solo nonstop flight from Roosevelt Field on Long Island to Le Bourget Field in Paris. He flew the distance of nearly 3,600 statute miles (5,800 km) in a single-seat, single-engine, purpose-built Ryan monoplane, Spirit of St. Louis. In 1997, Lindbergh’s grandson Erik, a commercial rated pilot, artist, and entrepreneur, keen to push the boundaries of electric aviation, founded the X Prize Foundation and followed up with the LEAP (Lindbergh Electric Aviation Prize), including an electric flight program and the Electric Aircraft Development Alliance. On September 29, 2011, Lindbergh stated, “The first company to produce a certified two seat electric aircraft with a 1.5 hour range will dominate the aviation training market.”
In addition, there was also need for a technical breakthrough in energy storage. Although, as we have seen, solar energy had been the mainstay of electric flights, the age-long quest continued for a lightweight battery with high energy density. The “Grail discovery” came in the form of the lithium battery, which would make the myths of aviation a reality. In the fall of 1972, M. Stanley Whittingham, an English-born chemist working with a team at the Exxon Research & Engineering Company, announced that they had come up with a new battery, and patents were filed within a year. Within a couple of years the parent company Exxon Enterprises wheeled out a 3W 45Ah prototype lithium cell and, linking it to a diesel engine, started work on hybrid vehicles. When solid-state physicist Professor John Goodenough became head of inorganic chemistry at Oxford University in 1976, his research group included assistant Dr. Phil Wiseman, Dr. Koichi Mizushima and Dr. Phil Jones. They set themselves the task of looking at the potential of rechargeable batteries, which began by simply “kicking around ideas on a blackboard.” “We looked at it in a different way using lithium cobalt oxide at the positive terminal and pulling the lithium out; this produced a huge cell voltage, twice that of the Exxon battery,” Dr. Wiseman explained. It was this spare voltage that allowed alternatives at the other terminal where Exxon had been forced to use lithium metal, which was fraught with problems. Instead lithium-ion material could compose both electrodes. The group’s research was published in the Materials Research Bulletin in 1980. In 1977, Whittingham teamed up with John B. Goodenough to publish a book, Solid State Chemistry of Energy Conversion and Storage.1
In 1979, a paper on lithium-thionyl chloride batteries with energy of 200 kw/h was presented at the Near-Surface Ocean Experimental Technology NORDA Workshop, National Space Technology Laboratories, Mississippi, by three technicians from the Naval Ocean Systems Center, San Diego, California.
Development continued. By the late 1990s, Japanese companies, in particular SONY, had made great strides in the commercialization of lithium rechargeable batteries. In 1997, Tsuyonobu Hatazawa, R&D manager at the Sony Corporation in Kanagawa, invented the polymer gel electrolyte and lithium-ion polymer battery. In 1997 Nissan Motors produced its Altra, an electric car, equipped with a neodymium magnet 62 kW electric motor and run on lithium-ion batteries manufactured by Sony. The following year, Ji Joon Kong in South Korea founded Kokam to manufacture polymer processing equipment, including polyester film and polarized film manufacturing systems, and breathable (porous) film casting systems. In the late ’90s, Kokam expanded its business to designing and manufacturing lithium-ion/polymer secondary batteries and succeeded in developing the world’s first high-capacity Li-Po batteries.
It was about this time that the lithium-ion battery went afloat and took to the air. Its first planned use was for a top-secret defense application. In 2003, Northrop Grumman had been commissioned to design and build the Advanced SEAL Delivery System (ASDS), a 65-foot (20 m) midget electric submarine for piggyback operation by the United States Navy. With power from a 67 hp (50 kW) electric motor, when it was found that the silver-zinc batteries were depleted more quickly than planned, the pioneer decision was made to develop a lithium-ion pack. Yardney Technical Products of Pawcatuck, Connecticut, was awarded a $44 million contract modification to provide four lithium-ion batteries for the ASDS program by May 2009. But in April 2006, while this was progressing, the program for new submarines was canceled and Northrop Grumman was notified of termination. The current submarine was still in development and use from Pearl Harbor when on November 9, 2008, while being recharged, the lithium batteries caught fire, and burned for six hours. The specter of inflammability would continue to haunt the Li-Po battery.
During the next decade, the commercial availability of these lightweight, energy-dense batteries heralded the long-awaited arrival of electric airplanes built, as we shall see, by individuals and groups all over the world. But as we have already noted with the pioneer Fred Militky, the Li-Po adventure began with aero modelers in 2004. These were very low-current models due to the small size and low current ability of the early cells as manufactured by Kokam and E-Tec in Korea, although the range was soon extended.2
The second adaptation of auxiliary electric propulsion for full-scale sailplanes was a German-Italian project (the first being the MBE-1 described in Chapter Four). In 1992, Stefan Gehrmann of AirEnergy of Aachen, Germany, teamed up with sailplane builder Mario Beretta of the Alisport company in Cremella (Lecco), located in northern Italy near Milan. Beretta had set up a program to make gliding less expensive and more accessible to young people. As part of this, AirEnergy fitted out an Alisport Silent Targa sailplane with an electric motor and battery to combine with the front electric motor and folding propeller on the nose, enabling self-launching without the need for a tow. The Silent Club AE1 was fitted with a single-blade propeller belt-driven by a 13 kW (17 hp) DC electric motor running on 40 kg (88 lb.) made up by AirEnergy using Sanyo cells that provided 1.4 kWh of power. The Silent Club AE1 was certified in Germany under that country’s light aircraft category after numerous tests published in August 1997, including the controlled destructive testing of two airframes. It first flew in 1997 and reached a height of 600 meters. Following this, Stefan Gehrmann did a tour through Germany with the NiCad Silent, introducing it to almost twenty different airfields. “We also flew it in Italy at the field near in Alzate (near Cremella the home of Alisport). We built 4 AE-1s with NiCad batteries.”3
Another who used batteries to power his sailplane was Axel Lange, based in the Rhineland Palatinate, Germany. A passionate glider pilot since his youth, Axel Lange had previously worked as an engineer at sailplane manufacturer Glaser Dirks. Here he had, amongst others, designed the highly successful motor-glider DG 800. While working at Glaser, he conceived the idea of the electric motor-glider as a way to solve many of the reliability and safety problems bothering traditional motor-gliders. Finding no backing for the idea at Glaser, he quit the job and started his own company in 1996. Lange worked in silence, and his flying testbed and technology demonstrator, the LF 20, caused a sensation when it was unveiled in 1999. The LF 20 was a heavily modified DG800 powered by the same 42 kW outrunner motor as would later power series production aircraft by Lange. The battery system in use was an experimental NiMh battery provided by Panasonic. The aircraft could self-launch and then climb up to 1900 m (6200 ft) above the airfield. This was more than enough for the mission of a self-launching high-performance sailplane.
In 2003, AirEnergy entered into the Li-ion technology market with the development of the first battery management system, and the following year they delivered the first Korean Kokam Li-Po battery system for an electric boat (220V / 40kWh). It therefore seemed natural that for the first AE-1 sailplane, they should use Li-ion polymer batteries, weighing 10 kg less than the NiCads. The examination certificate for this sailplane, dated June 15, 2005, mentions lithium batteries as a special feature. According to his logbook for AE-1 (Registration D-MFLP), Stefan Gehrmann made the first 40-minute flight with the Li-ion battery from Aachen/Merzbrück (EDKA), near AirEnergy’s base, on June 30, 2005. Two flights followed, then Gehrmann took it on a holiday trip to Fayence, France, and made twenty-two flights over the Alps, the additional energy density enabling the e-sailplane to climb even higher and achieve three times the range. Gehrmann also demonstrated it to Alisport at Alzate Airport in Italy. A total of 38 hours of flying was sure proof of the Li-Po’s efficiency.
Axel Lange flies the LF20 motor sailplane with its experimental Panasonic NiMh battery (1999) (courtesy Lange Aviation GmbH).
Meanwhile, using funds from selling his LF 20 motor glider, Axel Lange had gone ahead with his Antares 20E, a single-seat high-performance motor-glider designed from the start for electric propulsion. (Antares is the brightest star in the constellation Scorpio.) With a wingspan of 20 m (65 ft.) and a MTOW of 660 kg (1440 lb.), it first flew in 2003, and achieved full EASA certification in 2006. It is the world’s first series production electric aircraft. Rather than using NiMh batteries, the Antares 20E used new and revolutionary Li-ion batteries from Saft-Batteries in France. These batteries, which were far ahead of their time, allow the Antares 20E to self-launch and climb up to 3,500 m (16,400 ft.) on a single charge. The same cells have since then been used in many aerospace applications, including the F35 and the A350. In the years that followed, Lange Aviation GmbH continued to produce and upgrade the Antares 20E, as well as its younger sibling, the Antares 23E, which has a wingspan of 23 m (75 ft.).
During the summer of 2005, Stefan Gehrmann of AirEnergy of Aachen used the Li-Po battery to extend the range of his electric assisted sailplane Silent AE1. He logged twenty-two flights over the French Alps, the additional energy density enabling the e-sailplane to climb even higher and achieve three times the range (Stefan Gehrmann).
Axel Lange in 2006 in the series-produced e-sailplane, the Antares 20E, named after the brightest star in the constellation Scorpio (courtesy Lange Aviation GmbH).
Proving that electric propulsion need not result in a performance disadvantage, Antares sailplanes have been used to perform numerous noteworthy soaring flights. On April 8, 2007, John Williams of the UK spent some 10.5 hours flying over the Scottish highlands. When he landed that evening, he had flown 1243 km (772 mi.) over terrain not usually associated with soaring. The flight resulted in four new national records. Williams has continued to make spectacular flights, and at the time of writing, he holds 16 UK national records. For a while, he also held the world record for fastest 1500 km out and return, with 180.3 km/h. This flight was flown over the Andes.
Another example of the transition from NiCads to Li was with the RC model helicopter. Although there had been one-offs in the late 1970s, it was in 1980 that Ishimasa Company of Japan made the first production electric model helicopter, the Skylark EH-1. It had an onboard 9.6 volt NiCad battery, but power could also be supplied via a silicone/silver cable to hook up to a 12-volt auto battery to power the Mabuchi 540 S motor. Although a technological success, because the Skylark had a limited flying time, a very basic control system, and a high price, it was not bought in any great numbers. A second model electric helicopter was developed in 1989 by Hiroyuki Oki of Kalt Sangyo Co. Ltd. in Gotenba, Japan. With energy from 20 NiCad cells and an AstroFlight 40 cobalt sport motor, the Kalt 30 Baron Whisper was an immediate success. Then there was Kyosho of Tokyo, who had already introduced their gas-engined Concept 30 in 1988 then developed the Concept EP; a powerful AP36L with an 8.4V NiCad gave moderate performance for the tyro, while increases to a 9.6V NiCad battery gave it high speed and an aerobatic performance. However, the 540-sized brushed-motors were on the limit of current draw, often 20–25 amps on the more powerful motors, hence brush and commutator problems were common. With the arrival of the Li-Po battery, sales of RC model helicopters took off—such as Horizon Hobby’s Blade CX RTF Electric Coaxial Micro Helicopter, which has sold by the thousands.
Another to adapt the Li-Po battery was airship designer and pilot Graham Dorrington. Desiring even greater autonomy, the Englishman planned a more streamlined envelope with twice the capacity, to be built by Cameron Balloons, while searching for more efficient engines and batteries. For the engine he found the radial-armature permanent magnet pancake motor developed by Cedric Lynch, while for batteries he began to examine a revolutionary chemical couple—rechargeable Thunder Sky lithium-ion phosphate batteries. Dorrington first flew The White Diamond in December 2003 inside Cardington Airship Hangar in Bedfordshire, England. The operation then shifted to Guyana, where in July 2004, flights were made over the forest canopy. A Nexa hydrogen fuel cell was also briefly tested although a 28V rechargeable lithium battery with a mass of 40kg and a nominal capacity of 200Ah was used to provide most of the propulsive power. The maximum measured discharge rate of this battery was about 165A. Additional power for the bow motors and aft gondola motor was provided by either one or two pairs of 12V, 26Ah sealed lead-acid batteries (wired in series to give 24V), each with a combined mass of about 21kg. Power control was achieved using off-the-shelf MOSFET controllers. With Dorrington was filmmaker Werner Herzog, who edited his footage into a documentary film called The White Diamond.
Arguably the first to adapt the advantage of lithium batteries to an aircraft which could fly under power for over an hour was Randall B. Fishman of Cliffside Park, New Jersey. Even at his elementary school in Lynbrook, Long Island, Fishman would assemble little gadgets. His 4th-grade science project was a working hydroelectric powerplant that used the water faucet pressure to turn the turbine wheel. Some of the kids good-naturedly nicknamed him “Doctor Gizmo.”
During the early 1970s, Fishman was flying hang-gliders along the beach cliffs on the north shore of Long Island. During the 1990s, on nice days, he was using an electric bicycle to commute to work at a jeweler’s shop in Fort Lee, New Jersey. His bike could use either just electric power, electric and pedaling, or just pedaling. In the late 1990s he bought a Trikke 8 sports scooter. Although he could get it to go fast on a smooth surface, it did not work very well on rough pavement. In the early 2000s Fishman took the motor from his electric bike and bought some lithium-ion laptop computer batteries off eBay: “I was able to open the plastic boxes and take out the cylindrical cells. I rearranged the cells from several laptop packs to provide the voltage and capacity I was looking for. I set the whole thing up on the Trikke 8 so now I had an electric scooter. Wow! That thing was really fast and would run for a solid half hour or more. I had a lot of fun with that and took one or two serious headers when I made less than the best decisions. This was my first experience with using lithium polymer batteries for transport. I was impressed by the amount of power these batteries could hold.”4
His experience with the Li-Po batteries from the laptop computer battery packs gave Fishman confidence to wonder whether he might use the same technology on an ultralight aircraft. He wanted to take off quietly and without vibration, and also reduce his ground maintenance. He consulted Erwin Rodger, an old hang-glider friend, designer of the Cloud Dancer motor-glider. Erwin confirmed that the power available from the motor was sufficient and the Li-Po battery pack Fishman was proposing had enough capacity and discharge rate to do the job. The 53-inch folding propeller was correct to optimize the thrust for the motor power available and the speed range of the aircraft. After running the formulas, it was clear that the trike could take off and fly fully loaded with batteries and Fishman’s 200 lb. (90 kg) weight. This was in the summer of 2006. During the fall and winter of 2006–7 Fishman built his prototype in Florida, first in a boatyard, then a hang-gliding resort, and finally in a rented apartment: “I vacuumed up the aluminum drillings, filings, etc. every day from the carpet. I assembled the battery pack there as well. I finished up the trike and did a static test run with the front wheel up against the apartment building and the prop blast angled out into the field behind the place. At full power the motor was getting a little warm but the batteries were almost completely cool. Cool!”
In April 2007, Fishman took his prototype, which he had called the ElectraFlyer, to Sun-N-Fun, an event run by the Lakeland, Florida, chapter of the Experimental Aircraft Association (EAA). It was a static exhibit.
People were very interested. The motor system had run but it had not yet flown except for a little hop at the South Lakeland airport a few days before. Tom Peghiny of Flight Design USA came over to check out the trike. A couple of years later, Tom built an electric version of his old flight design aircraft in a deal with Yuneec. I also met Mike Theeke from Fly Hard Trikes of Wildwood, Georgia. He invited me to bring the trike to his location in Jasper, Tennessee. He loaned me a North Wing Stratus high-performance wing and from May 5, I made some test flights there. First I flew straight down the runway at about 10 feet off the surface. The ElectraFlyer flew as expected so the next time I made a circuit. Mike took some video of the first circuit flight and the short, 1 minute video clip on the website is from that flight. I was really excited (and probably a little bit lucky) that everything worked so well! The next day I got a little fancier and made longer flights and more maneuvers. There was a gentleman there with his son. He took a lot of photos that day. I was full of enthusiasm since the flights went well the evening before. He must have taken about 50 pics of me flying around the airport. I was doing 360s and the normal maneuvering I used to do in my gasoline powered trike. On the third day I took off and flew down the valley. I saw Mike take off in his two-seater gas powered trike with a student. I flew for over an hour at cruise speed of 25 to 30 mph (40 to 50 kph). Words won’t describe the feeling I had! Mike landed with the student, then I came in. He was amazed at the length of time I had stayed aloft. According to my analog volt meter I still had quite a bit of capacity left in the battery packs!
Having wowed the ultralight world at the AirVenture Show in Oshkosh in 2007, and winning the Ultralight Grand Champion award there, Fishman traveled back to New York, where he enjoyed silent flying around his old haunts in the Ellenville, Ulster County area. Searching for the right batteries took time, involving Fishman’s obtaining sample cells from several manufacturers. He would try five other suppliers over three years until he finally found cells that had the build quality for this demanding use, staying with the same battery cell supplier from then on.
Next came his ElectraFlyer-C. The basis for this was a gas-powered Monnett Moni motor-glider that he had built with a friend in the ’90s:
It was a nice little airplane but the gas engine with small prop was not a good match. When I converted it to electric, the power was reduced from the 25HP gas engine to the 18HP electric motor but I made some mods on the aircraft to raise it high enough to install a much larger prop turning at a much slower rpm. The static thrust increased 60% and this also changed the airplane from loud and vibrating to a smooth quiet flyer. For this project, I rented a room in the back of a machine shop in New Jersey. Much of the work was done there to convert the aircraft in the fall of 2007. I moved down to Sebring, Florida, and rented a hangar at the airport. I also rented a house nearby and built the 2 battery packs for it on the kitchen table there. Final assembly was completed just before the 2008 Sebring Light Sport Aircraft Show. I took a booth and showed the new C model and the completed trike there. I was flying the trike at the show but the C was not ready for flight yet. I moved over to the south Lakeland airport and the DAR there issued the airworthiness certificate under the experimental category.
Randall B. Fishman of Cliffside Park, New Jersey, was the first American to adapt the advantage of lithium batteries to an airplane which could fly under power for over an hour. Here he is in May 2007, flying his ElectraFlyer trike over Jasper, Tennessee (Randall B. Fishman).
In May 2008, the aluminum ElectraFlyer Model C flew for the first time at the Ellenville airport with Joe Bennis at the controls. Then it was demonstrated before the crowds on August 2 at AirVenture in 2008. Fishman and his Electric Aircraft Corporation successfully applied for the Lindbergh Aviation Award and received $10,800, which is how much The Spirit of St. Louis, Lindbergh’s airplane, cost in 1927. It was their only aviation award given that year. In 2008 Fishman won the August Raspet Memorial Award for his electric aircraft work. The award recognizes the “person who has made an outstanding contribution to the advancement of light aircraft design” each year. Fishman now used the Lindbergh grant to develop the two-seater, all-composite ElectraFlyer-X, powered by a new 40 hp (30 kW) brushless electric motor, to eventually qualify for light-sport aircraft status. Although ElectraFlyer-X was scheduled to fly in the summer of 2010, the FAA objected to its operating under the light-sport rule. He therefore sold the project to an interested builder, then turned his inventive mind to a project he had started in 2007–8 with a Slovakian aeronautical engineer, to build a ready-to-fly electric 245-lb. ULS for sale to the public under the FAA Part 103 ultralight rule. With a 20 hp direct-drive motor and 53-inch propeller, the carbon fiber/foam airplane is available with a fixed or folding prop. Fishman would eventually log 140 flying hours on his trike, and over 350 flying hours on his ULS, securing his position as one of the true pioneers of electric flight.
By eventually logging up 140 flying hours on his trike, and over 300 flying hours on his ULS, Randall Fishman secured his position as one of the true pioneers of electric aircraft (courtesy James Lawrence).
Other aviators would also make use of the lithium advantage.
The Pipistrel powered hang-glider had been built during the late 1980s by Ivo Boscarol of Ajdovščina, who then set up the first private aircraft company in Yugoslavia. Boscarol was born on April 15, 1956, in Postojna, Slovenia, at the time part of Yugoslavia. His father August Boscarol, a machine engineer, spent several young years as a test pilot at Aermacchi, an Italian aircraft manufacturer. The family lived in Ajdovščina, a town in western Slovenia near a small military airfield. After elementary and high school in Ajdovščina, Boscarol studied economics at the University of Ljubljana. From 1976 to 1986, Ivo was involved in publishing, owning a photography studio, part of the ŠOLT group, holding expositions in several countries, cooperating with several magazines. During this time he was the official photographer at the Šentjakobsko Gledališče Theatre in Ljubljana, an advertising manager of the student radio station in Ljubljana, and a manager of several musicians and rock bands. He also organized several art photo exhibitions, including nudes.
Due to legal restrictions imposed by the Yugoslavian government during the 1980s on flying alternative and ultralight aircraft, Boscarol and his friends had to fly their first hang-gliders secretly in the evening, between dusk and dark and using lights at the front of the aircraft. Since powered hang-gliders had triangular shaped wings, the local people started to call them “bats”—and “Pipistrellus” is a Latin word for a bat. Boscarol decided to name his company Pipistrel, and during the first 10 years they produced over 500 hang-gliders and exported them all over Europe. In 1991 he also organized the first national championship for ultralight aircraft.
In the mid–’90s the market started to change and new composite materials appeared, resulting in the 503 Rotax engined Pipistrel Sinus ultralight motor-glider, of which some 600 were built and sold. Sinus is still one of Pipistrel’s best-sellers. In 1999 the closed-cabin Virus was added, having shorter wings and built for higher speeds, not so much for gliding.
Then the Taurus self-launched microlight glider made its first flight in 2003, again Rotax-engined. As the world’s first microlight class two-seater with parallel seats, the Taurus was much wider than conventional two-seat gliders; with its wider nose and its wingtips turned up like horns, it seemed appropriate to call the glider Taurus (Latin for bull). In 2007 Boscarol and his team decided to electrify the Taurus, installing a 30 kw Sineton motor with Li-Po batteries. On December 21, 2007, Ivo Boscarol took off in the modified airplane, silently climbed to 1,000 m (3,250 ft), and flew for 20 minutes at speeds of up to 150 kph (90 mph). They were delighted that their electric bat behaved exactly as predicted and that they could now go into serial production. On their website, they posted: “First flights of the Taurus Electro, the first two (2) seat self launching glider with electric engine in the World are behind us. We are happy to announce that the bird behaves exactly as predicted and that we will publish additional information shortly. For now, let the pictures do the talking! Merry ELECTRO Christmas and an ELECTRO New Year everybody!”
In 2008, Popular Science magazine named the Taurus Electro one of the ten best innovations of the year. In 2010 the Pipistrel team won both a gold medal at the Biennial of Industrial Design and the European Business Award for Innovation from among 15,000 competitors.
One of the team was Tine Tomažič. He learned to fly at age 15, became an instructor at age 19, and in 2001 became test pilot at Pipistrel. A deep believer in electric flight, Tomažič dedicated his Ph.D. thesis at the Faculty of Electrical Engineering, University of Ljubljana, Slovenia, to “the development of control strategies and systems to optimize flying with hybrid-powered aeroplanes,” researching technologies to identify the future of electric flight, including distributed electric propulsion architectures, power train modeling, and flight mission optimization. One of his first projects was to electrify the Taurus G2 as a two-seat side-by-side self-launching sailplane. Its motor peaks at 40 kW for takeoff and allows continuous climbing at 30 kW power. It is controlled by a specially developed power inverter/controller and governed by the cockpit ESYS-MAN instrument. All components are networked via CAN-bus, feature proprietary multilayer protection logic, and produce a true throttle-by-wire experience. Alongside this Pipistrel had developed their Solar Trailer, which offers 1 kW of usable energy; this means charging time of 10 hours for 30-Ah batteries and 12 hours for 40-Ah batteries. Powered endurance was 17 minutes, intending to allow for self-launching to an altitude of 2000 m (6500 ft), after which the engine is retracted and the aircraft then soars as a sailplane.
On December 23, 2007, Ivo Boscarol took off in the electrified Pipistrel Taurus airplane, silently climbed to 1,000 m, and flew for 20 minutes at speeds up to 150 km/h (Pipistrel).
In 2011, for the NASA Challenge, Pipistrel now linked two G2 hulls into a four-seater one-off, the Taurus Electro G4. All components of the aircraft were developed and made by Pipistrel. Aerodynamic studies were carried out by to Dr. Gregor Veble, head of research at Pipistrel. The construction of the aircraft was accomplished by Vid Plevnik in cooperation with structural specialist Rado Kikelj. The development of composite technology parts and systems was done by Sašo Kolar and Franci Popit with their teams. The most challenging parts, namely the development of electronic systems and their regulation as well as the system for charging the batteries, were developed by Jure Tomažič. With a 75-ft. (22.9 m) wing, the G4 had a gross takeoff weight of 3,300 lb. (1,497 kg), making it the heaviest manned electric-powered aircraft built to date. It had a glide ratio of over 30:1 at 100 mph (161 km/h). The 145 kW (54 hp) engine powered the aircraft from internally-mounted Li-Po batteries, weighing 1,100 lb. (499 kg) for a 17-minute climb.
In 2011, Pipistrel developed a unique four-seater, the Taurus Electro G4. It made its first flight at 7 a.m. on August 12, at AirVenture, Oshkosh, Wisconsin, winning the $1.35 million CAFE Green Flight Challenge prize. It would later be used as a testbed for fuel cell propulsion (Pipistrel).
In April 2011, the Taurus G2 won the 2011 Lindbergh Electric Aircraft Prize for “best electric aircraft” at the aero show held in Friedrichshafen, Germany. It was first presented to the American public at the Oshkosh AirVenture in July. According to the informal vote by the visitors, it was amongst the 10 most attractive aircraft on display among 15,000 exhibited airplanes; each year, the EAA awarded a virtual “Dead Grass Award” prize (for the most viewed exhibit) to the ten aircraft with most votes.
Taurus G4’s first flight was at 7 a.m. on August 12, 2011, at AirVenture, Oshkosh, Wisconsin. NASA had put up for the CAFE Green Flight Challenge (200 miles at 100 mph) the largest aviation prize of all time, $1.35 million, which was also won by the Taurus G4, with the Pipistrel-usa.com team led by Jacob W. Langelaan, covering 403.5 passenger miles per gallon (649.4 km) gasoline equivalent. During the challenge, at the Santa Rosa airport, there was no power supply to charge the G4 and the e-Genius overnight, so Google sponsored a basic charging point.
Because of all these achievements, the president of the Republic of Slovenia, Dr. Danilo Türk, decorated the Pipistrel team in 2011 with the highest civil award in the country, the Golden Order, for services to the Republic of Slovenia! The Design Museum in London chose the Taurus G4 as one of the nominees in the transport category for the “Designs of the Year 2012” exhibition. Taurus G4 was nominated for the prestigious Colli Trophy, the “Greatest Award in Aviation.” Because of all the achievements of this aircraft, a scale model of Pipistrel’s Taurus G4 is displayed hanging in the main hall of ICAO’s headquarters building in Montreal.
By an extraordinary coincidence, the first flight of a French electric airplane had also taken place on Christmas Eve 2007. In the Hautes Alpes, one start-up company had also realized the potential of lithium-ion polymer batteries. It was set up by Anne Lavrand, a business executive and keen amateur pilot. Beginning with an SME manufacturer of ULMs, Lavrand heard about the Li-Po batteries produced by Kokam. In 2007, she applied for a grant to modify a wooden ultralight Souricette, a Michael Barry design, and retrofitted it with an 18-kW (24 hp) disk-brushed Lynch electric engine, a golf cart–type controller, and a 47 kg (104 lb.) Kokam Li-Po battery power pack. There would be no solar panels. Electra made its first test flight on December 23, 2007, at Aspres sur Buëch airfield, Hautes Alpes. Test pilot Christian Vandamme flew the strut-equipped aircraft (officially registered as BL1E Electra F-PMDJ) for 48 minutes, covering 50 km (31 mi) cruising around the southern Alps at about 90 kph (55 mph). It was the first time since 1887 that a French battery-electric flying machine had taken to the skies. The French team was unaware that the Slovenian team had also flown on the same day.
Encouraged, Ann Lavrand created a start-up she called Electravia, based at Sisteron airfield, in France. Further developing their prototype, by 2008 they had developed the Electravia Electro Trike, a single-seater delta trike with an electric propulsion system from Electravia. With a 26 hp GMPE 102 electric motor supplied by a 3 kWh pack of Li-Po batteries, the ElectroTrike could fly for an hour. One ultralight sailplane which benefited from the Electravia motor was the Alatus-ME, built by Aerola of Kiev in Ukraine. The electric motor gave the Alatus a half-hour endurance. Another spin-off from Electravia’s initiative was the E-Fenix, the first electric two-seater paratrike in the world. Developed by Planète Sports & Loisirs, headquartered on Re Island, off the coast of La Rochelle, France, the trike would carry visitors on discovery flights over the scenic island. Equipped with a 35-horsepower GMPE 104 motor, an E-Props QD2 four-blade propeller, and a 6 kWh Kokam Li-Po battery, the E-Fenix made its maiden flight on May 12, 2011, with Michaël Morin at the controls, circling around Electravia’s Sisteron airfield. With its Bulldog wing, the E-Fenix can fly for 35 minutes with two people on board.
With no further funds for his electric airships, Graham Dorrington turned to electric airplanes with Project Orion. A group of ten master of engineering 4th-year students at Queen Mary and Westfield College, University of London, were electrifying a 335 kg (739 lb.) “Optimist” glider. To do this, they added eight under-wing pylons attached by moveable straps that carried 16 Graupner/Ripmax Li-Po battery-powered wireless link activated electric motors that drove sixteen 280mm (11-in.) diameter propellers. Such a configuration is known as displaced electric propulsion. On September 20, 2008, Derek Piggot piloted the EA9 for its maiden test flight at RAF Tibenham Airfield, Norfolk, England. It was towed to 2,500 ft (760m) and then released; it made two further flights. This was the first time that a manned e-airplane had taken to English skies. Further development work was halted through lack of sponsorship, and the British Isles are still waiting for a second electric aircraft to take to the skies.
Since the 1980s, ICARO, located in Sangiano, North Italy, had been making Atos and Swift hang-gliders, and by 2008 sales totaled almost 9,000. This is largely due to the innovative Manfred Ruhmer, holder of the absolute hang glider distance world record at 701 km and 4 times rigid world champion with a Swift. Ruhmer decided to equip the rigid-wing Swift with an electric assist. In April 2008, a 10kw Werner Eck-design para-motor weighing just 3.7 kg, powered by a small Li-ion phosphate battery, enabled Ruhmer to reach a height of 600 meters. Building a slightly larger battery enabled him to fast-charge in 15 minutes between 20-minute flights. In 2011, series production of the Electric Swift, with its 1.4 m folding-blade carbon fiber propeller, began with both new eSwifts while existing ones were retrofitted. Using battery swap systems, to date almost 40 Electric Swifts are in use. Ruhmer also experimented with an electric trike fitted with two rear-facing Eck motors.
September 20, 2008: Derek Piggot pilots the EA9, designed by a University of London Queen Mary and Westfield College team led by Graham Dorrington for its maiden test flight at RAF Tibenham airfield, Norfolk, England (courtesy Graham Dorrington).
During this time, Sweden had been developing its own electric airplane. In 2001, the Swedish Defense Administration asked Saab, who had been building aircraft since 1937, to produce a demonstrator for practical education in More Electric Aircraft technology. The project, led by Lars Austrin, was to buy and modify a flying platform, the 12m wingspan Windex 1200C motor-glider designed by Sven Olof Ridder and built by Windex Air AB in Åtvidaberg. The task was to retrofit the glider with a 20 kW, 11 kg custom-designed Stridsberg PM electric motor in the tail plane. The plane modifications were by Kåre Ljung at Windex, including a custom carbon fiber propeller. SAFT provided 44 lithium-ion MR39 cells weighing 1.1 kg each, with 22 fitted into each wing. The total electric power was 6kWh @ 176VDC. The central electric distribution system was designed by Jonas Larsson and Lars Austrin at Saab. In March 2005 the Saab MERA 01 was delivered to Saab, and in 2008 the airplane was ready for taxiing trials at Saab/Linköping airport.
Following trials being towed into the air, it made its first powered flight of 45 minutes in June 2009, piloted by Fredrik Müchler, a Saab Gripen fighter test pilot, reaching a speed of 150 kph (93 mph) and an altitude of 1,100 m (3,600 ft). Throughout its short career, the MERA 01 clocked up a total of 5 hours. By 2012, when it was put on static display at the 2012 Malmen Airshow, Sweden, its flight career was over. During the project a study of electric actuators for aileron control was initiated. This was continued with a demonstrator program including a prototype actuator based on Stridsberg’s PM-motor and a test rig. As a spinoff from these programs, a business concept was proposed for the Boeing 787, the “Dreamliner.” As a result, the high lift system in the Dreamliner is based on the SAAB electric actuators.5
In 2009, the Swedish team stand proudly behind their e-airplane; among them, their positions unidentified, are Jonas Larssen, Lars Austrin, Sven Olof Ridder, Kåre Ljung and pilot Fredrick Müchler (Saab).
The Saab 20 kW, 11 kg custom-designed Stridsberg PM electric motor derived its energy from 44 lithium-ion SAFT MR39 cells weighing 1.1 kg each with 22 fitted into each wing. Its custom carbon fiber propeller was made at Air AB in Åtvidaberg (Saab).
For Brazilians, the Father of Aviation is not the Wright Brothers, but Brazilian-born Alberto Santos-Dumont. In 1906, Santos took off in his 14-bis and made the first officially observed flight of more than 25 meters (27 yd), certified by the Aéro-Club de France, and won the Deutsch-Archdeacon Prize. Remaining in Paris, he continued to develop his airplanes, which he called Demoiselle. A century later, it seemed natural for the Brazilians to produce an electric airplane. The SORA-e (Portuguese for “sister”) is a two-seater developed and built by Alexandre Zaramella and a team at ACS (Advanced Composites Solutions) from an original design created by Professor Claudio Barros of Universidade Federal de Minas Gerais (UFMG). With support from the state financier of studies and projects (Finep) in 2010, an electrical system was developed by the Electric Vehicle Research & Development Center (CPDM-VE) at Itaipu; two Emrax motors of 35 kW each, produced by the Slovenian company Enstroj, were powered by six sets of Li-Po polymer batteries, which together provide 400 volts. Following taxiing trials from ACS’s runway, the SORA-e made its first public flight on May 18, 2015, at Professor Urbano Ernesto Stumpf Airport, São José dos Campos, in the interior of the state of São Paulo. Its rate of climb was 1,500 feet (460 m) per minute. Its flight range was from 90 minutes to 190 kph (120 mph) and it was designed for a top speed of 340 kph (200 mph). In April, the airplane went to Iguaçu Falls, in the state of Paraná, where it was put through a second and final series of tests, performed by ACS-Aviation. The next challenge will be to develop a commercial version of the SORA-e.
Canada’s first gas airplane, the Silver Dart (or Aerodrome #4) had been flown off the ice of Baddeck Bay, Nova Scotia, in February 1909. Now, one hundred years later, on December 8, 2012, Canada’s first electric airplane, Green 1, took to the skies above the Pitt Meadows Airport in British Columbia. Behind the project were Randy Rauk and John McClintock of eUP Aviation in Lumby, British Columbia. Rauk, of Freedom Flight School, Inc., piloted the glider trike, with its complete Electravia electric solution: a 19 kW (25 hp) electric motor and a 3.9 kWh lithium polymer battery. Bench and ground testing had been completed in the Vancouver and Okanagan areas during the previous months. In 2013 Green 1 was flown across western Canada, then up and down the Pacific Coast, demonstrating its self-launching and soaring capabilities over California deserts, at Torrey Pines, and in the mountains of Oregon.
Equally the Czech Republic developed an e-airplane using the SportStar EPOS. Financed by the Technology Agency of the Czech Republic under the guidance of the company Evektor, based in Kunovice in the Czech Republic. Evektor is one of the biggest design companies in Central Europe, with activities in aerospace and automotive industries. In 2012, Evektor developed its SportStar EPOS (“Electric Powered Small Aircraft”) powered by a Rotex Electric RE X90–7 50-kW electric motor, which directly drives the three-blade composite propeller manufactured by VZLÚ Prague. Engine performance was controlled by an electronic control unit, developed by MGM COMPRO, manufacturer of the motor control unit, and the Faculty of Information Technology of Brno University of Technology, supplier of the display unit for motor parameters. The system was divided into “airborne” and “ground” sections to reach the lowest possible weight of its Kokam 90S, 330-volt, 40Ah battery. The first test flight, in cooperation with the Czech Light Aircraft Association, was made by factory pilot Radek Surý on March 28, 2013, from Kunovice Airport. After taxiing tests at 8:25 a.m., the aircraft took off for its first test flight. After a short, approximately ten-minute flight, it landed successfully, and a second flight, lasting 30 minutes, followed immediately afterwards. The Czech SportStar EPOS was presented to the public for the first time at Europe’s largest aviation exhibition, Aero Friedrichshafen in April 2013. By 2014, power output had been stepped up to 75 kW, more than the most powerful Rotex 914.
In July 2010, with the success of his Antares e-motor-gliders, Axel Lange was honored with the prestigious Lindbergh Award, presented by Lindbergh’s grandson, Erik Lindbergh. In 2011 Lange and the Antares 20E won the Berblinger competition for electric aircraft, which was held in Ulm, Germany, and in 2017, Lange received the OSTIV award for his pioneering work on electric propulsion in sailplanes.
Lange Aviation’s Antares 20E and 23E propulsion system was also adapted by the Holighaus family of the Schempp-Hirth sailplane firm based in Kirchheim-unter-Teck, to produce their Arcus-E self-launch two-place glider. After Lange had installed the propulsion, following a first flight in 2010, the Arcus-E entered series production shortly afterwards, with several now delivered. Kirchheim-unter-Teck, it may be recalled, was the home of Fred Militky, who had pioneered electric model airplanes half a century before.
What if powered sailplane pilots could use an electric motor installed just behind the nose propeller to launch themselves into the sky? Once the plane was airborne, the propeller blades would fold back flush with the nacelle. In 2008, Luka Znidarsic and his father Matija Znidarsic, both experienced sailplane pilots and mechanical engineers in Logatec, Slovenia, developed their FES (Front Electric Sustainer). This a power system that provides a climb of 1.5 meters (5 ft.) per second (198 feet per minute) for their prototype configuration on an 18-meter (60-ft.) LAK 17 sailplane. The Znidarsics developed their own brushless DC synchronous permanent magnet electric motor and controller for the application, which is light, small and mounted on top of the main well box. The motor is 7.3 kg (16.1 pounds), and puts out 22 kW (30 horsepower) at 116 volts. Total weight for the power package is 45–50 kg (99–110 pounds), with Kokam Li-Po batteries in two packs (each behind the rear spar, balancing the weight of the motor and propeller in the nose). If batteries are discharged during flight using the motor, they are easily accessible from the top of the fuselage so that you can take them out for charging. To date more than 70 sailplanes of 7 different types are already equipped with the FES propulsion system. The maximum endurance in powered flight is almost 1 hour or 100 km (60 mi).6
In 2010, another American e-airplane took to the skies. The Sonex Waiex could trace its origins back to 1994, when John Monnett, a builder of aircraft kits based in Oshkosh, Wisconsin, teamed up with Pete Buck, who had spent two semesters of his engineering degree analyzing and building the battery/power system for a hybrid electric vehicle (HEV) sponsored by Ford Motor Company. Together they came up with a feasibility study for a project dubbed Flash Flight for a small, electrically powered, and manned aircraft that would be capable of a short duration flight in order to set or establish speed records for this new class of aircraft. Built of many off-the-shelf components at relatively little risk, it would only have a 10-minute autonomy. Sonex Aircraft was founded in 1997 with John Monnett building a succession of Moni sailplanes and gasoline-motor gliders, and the electric was put on hold. In 2007 Monnett and Buck got round to building the e-Flight Waiex, complete with a 54 kW brushless DC-Cobalt motor. The motor was designed be very lightweight, at only 50 lb. (23 kg), to operate at 90 percent efficiency, and to use a 14.5kw-hr Li-Po battery system. It was displayed at AirVenture in 2009 and made its maiden flight at Wittman Field, Oshkosh, on December 3, 2010. With John Monnett as pilot, the yellow N270DC made a short hop on runway 27, intended to be a conservative non-pattern flight to break ground-effect and analyze in-flight system performance as the next step in testing. On March 30, 2011, the e-Flight Waiex made its second flight, achieving a full circuit of the Wittman Airport traffic pattern, as planned. A third flight was also conducted on April 13, 2011, in which a full pattern was again flown. The electrical system would be 270 volts and 200 amps, and adjustable to different power outputs. At the time of writing, Sonex, like others, is waiting for the increase in battery energy density.
In 2010, Calin Gologan, a Bucharest-trained aeronautical engineer formerly at Aerostar Bacau, and his team at PC-Aero of Nesselwang, Bavaria, Germany, teamed up with composites expert Carbon Wacker GmbH of Hurlach, to develop a 660-lb. advanced glass/carbon-fiber composite single-seater aircraft for electric propulsion. Powered by a 16 kW motor and ultra-lightweight Kreisel battery units, the Elektra One sailplane, complete with retractable main wheel, made its first flight on March 21, 2011; it won the Lindbergh electric aircraft prize presented at the EAA AirVenture airshow in July 2011. With help from Solar Hangar and Solar World, equipped with molded solar panels, PC-Aero’s Elektra One Solar motor-glider was projected to have an endurance of almost four hours/400 km with a top speed of 100 mph (160 kph). PC-Aero was 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. Two- and four-seaters are envisaged. On June 25, 2015, Elektra One Solar took off from Unterwössen (Germany) for the Alps, crossed over the Grossglockner, and landed in the sunny town of Lienz in East Tyrol (Austria). The flight took around 2.5 hours. After the successful flight on the south side of the Alps, Elektra One Solar started on the way back on July 2 (a few days before the e-Genius of the University of Stuttgart also flew over the Alps) in quite difficult weather conditions. Despite headwinds and strong gusts, the plane crossed the Alps at an altitude of more than 3,000 m (9,800 ft) and landed after a flight of about 2 hours and 190 kilometers (120 mi), as planned at the airfield in Zell am See, Austria. It used only 18 kilowatt-hours of electricity for the complete trip.
In 2011, researchers at Nottingham University, England, published a paper concerning the feasibility of equipping the main landing gears with electric motors for the aircraft traction during the taxi phase. Those electromechanical wheel actuators make possible a “Green Taxi” operation by considerably reducing the on-ground carbon emission. Moreover, this would enable important fuel saving for short-distance flights with high frequency of landing and takeoff. In this work, a direct-drive wheel actuator was considered for energy efficiency and mechanical reliability. Two possible locations of the actuator were examined and the weights of the corresponding electric machines compared. The most weight efficient location was then selected. A high torque density permanent magnet machine was then designed to fit in this envelope to satisfy peak torque, weight, and flux weakening capability requirements.
The Cri-Cri (English: the chirp-chirp sound made by a cricket) is the smallest twin-engined manned aircraft in the world, designed in the early 1970s by French aeronautical engineer Michel Colomban. In 2004, Didier Esteyne, designer and amateur pilot of Aero Composites Saintonge in the Charente Region of France, had thought about an electric Cri-Cri. The Kokam Li-Po batteries and 4 electrical model engines weighing about 7.5 kW could come from aeromodeling. But with the batteries’ total weight of 40kg (88 lb.), Esteyne calculated that the airplane could only stay airborne for around 13 minutes with five as aerobatic! So he decided to wait. But Esteyne was not one used to giving up. In 1979, as the son of a pilot in the French Air Force, Esteyne had been training in fine arts, including technical drawing, in Bordeaux. Following his first flight, at age 25 he caught the flying bug and obtained his pilot’s license the following year. From then on he combined his passions, designing, building and flying his first aircraft three years later. He went on to design and fly a succession of eight aircraft in France, Mexico and the USA, improving each aircraft based on his own experience as a pilot.
Five years later, Didier Esteyne felt more positive about the weight and energy of batteries. During the Le Bourget Air Show in June 2009, with his friend Gérard Feldzer, the Director of the Musée de l’Air et de l’Espace, Esteyne decided to create an association “GREEN CRICRI” and try to find money for this exciting idea. With Gérard Feldzer’s contacts, they met staff from “EADS (European aerospace company) Innovation Work” in Paris and convinced them to support them technically and financially. A classic 2-stroke Cri-Cri was modified by Esteyne and his 9-strong team at Saint-Sulpice de Royan, including Marc Faure and Alain Bugeau.7 Four Czech Republic-built Free-Air electric engines each developing 5.5 kW each weighing just 2.2kg (5 lb.) derived their energy from 26.5 kg (58 lb.) of Kokam, Li-Po batteries. The Green Cri-Cri had a flight potential of 30 minutes at 86kn (160 kph) or 10 minutes of aerobatics at speeds up to 120 kt (222 km/h) with a climb rate of 1,000 feet (300 m) per minute. 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.”
In September 2013, electric aviation had its first fatality. At the practically disused airport of Marville in Northern France, two recently fitted Electravia electrical motors in a Colombian MC-15E Cri-Cri were being given a high-speed taxi test when the aircraft became airborne unintentionally, and during the landing, it bounced several times. The aircraft left the runway, flipped over and caught fire, killing its 70-year-old Belgian amateur builder and pilot, Toon Jacobs. He had been the fourth to own an electric Cri-Cri, which he had recently shown at the Federation RSA (Network of Sport Air) Rally in Vichy, France.
In 2014, Chip W. Erwin of Aeromarine LSA, based in South Lakeland Airport, Florida, equipped a 220 kg (485 lb.) Zigolo MG12 ultralight kit-built motor-glider built by Aviad in Italy with an electric unit and flew it over to the Sun’n Fun Fly-In Expo. Through his PSA or Personal Sport Aircraft, Erwin’s mission is to bring an affordable airplane to the market.
Now it was the turn of the amphibian aircraft, able to use both land and water for takeoff and landing, to be re-engined electrically. Amphibians are not new. In 1920 the British Air Ministry organized a Commercial Amphibian Competition at Martlesham and Felixtowe; entrants must take off from the land and touch down on the water, then vice versa. Four prototypes took part and so kick-started a category which during the 1920s and 1930s would challenge aircraft builders from France, Germany, Canada and the USA with such amphibians as the Keystone-Loening K-85 Air Yacht, an eight-seat biplane amphibian (1930).
Back in 1977, Dale Kramer, an aircraft engineering student at the University of Toronto, got his inspiration to design the 5.5 hp 100 cc Pioneer chainsaw-engined Lazair, a majestically slow ultralight aircraft with an average speed of only about 70 kph. The plane was sold in kit form, and between 1979 and 1984 more than 2,000 were built, making it the most produced Canadian-designed aircraft. In 2010, Kramer decided to “electrify” his plane, using twin Bevirt JM1 Jobymotors with Jeti SPIN Pro 300 controllers and dual 16-cell 4 amp-hour battery packs that produced 63 volts, mounted in the wings. He moved to Hammondsport and bought the estate of Glenn Curtiss, the father of naval aviation. In July 2011, Kramer took off from a field behind his house and made the first-ever landing on water with an electric-powered amphibian Lazair after a 7-minute maiden flight. Past the historic flight, after one hour of recharging, he took off again, this time from water. The aircraft won Antique Ultralight Champion and Best Ultralight Amphibian at EAA AirVenture, Oshkosh. The aircraft has remained an experimental project with no production planned.8
Since 2013, E. Brian Robinson and his team at Lindsay, in the Kawartha Lakes region of southeastern Ontario, have been developing the 6 PAX Horizon X2 to operate from land, water, ice, or snow. The company envisions a hybrid with 700 hp powered from two advanced axial-flux electric motors, coupled with a range-extender high-efficiency gas engine, and designed around system redundancy. Traveling at speeds up to 200 mph (320 kph), the X2 will be able to carry 2,000 lbs. (900 kg) of useful load over 1,000 NM (1850 km) at altitudes up to 18,000 feet (5000 m).
It was perhaps inevitable that prolific aircraft innovator Burt Rutan of Coeur d’Alene, Idaho, would direct his innovative genius to electric propulsion. In 1986 Rutan had designed the record-breaking Model 76 Voyager, which was the first plane to fly around the world without stopping or refueling, and the sub-orbital space plane SpaceShipOne, which won the Ansari X-Prize in 2004 for becoming the first privately funded spacecraft to enter the realm of space twice within a two-week period. During 2014, although technically retired, working as an individual out of his one-car lakeside garage, 73-year-old Rutan conceived a new two-seater seaplane which would fly up to 2,100 NM (3,890km) nonstop, survive a 10g impact on rolling seas, and fit inside his garage. The SkiGull can cruise at 200 mph (320 kph), taking off or landing in about 400 feet (120 m) on challenging surfaces including rough terrain, seas, grass, snow, or ordinary runways, fueled by ordinary automotive or marine gasoline, and having small auxiliary electric motors for 30 percent power assists or emergency landing. It can also can fly in cruise mode for about 7 NM using electric power alone. In water, the electric power system can also be used to maneuver the aircraft to the dock. It is designed to resist corrosion, even in salt water, and will have a docking system using two 12 hp electric motors driving a folding propeller. Its autonomy will enable it to travel from California to Hawaii, or from Boston to Iceland, without having to pick up fuel along the way. Rutan has said the SkiGull will be his last design and, having spent more of his life developing new airplanes than flying them, he wants to fly this one around the world with his wife Tonya. In October 2015, Rutan’s pilot Glenn Smith made the SkiGull’s first flight test at Hayden Lake north of Coeur d’Alene; on November 24, further flights were made from the Coeur d’Alene Airport.9
The 2014 CAFE Electric Aircraft Symposium saw an incredible meeting of experts and thought-leaders in the areas of electric and sustainable aviation. Dr. Qichao Hu of MIT presented a multi-fold advance in energy storage density, Dr. Ajay Misra of NASA presented super-magnets made by nanotechnology, and Dr. Gecheng Zha of Miami University presented high-efficiency forward-swept ePropellers. Brien Seeley wrote the seminal AIAA paper in 2015 on Regional Sky Transit.
In 2015, after Seeley’s 34 years as president of the renowned CAFE Foundation, including the setting up of the Personal Aircraft Design Academy (PADA), an annual gathering of prominent aeronautical designers at Oshkosh AirVenture, this visionary left to found the nonprofit Sustainable Aviation Foundation (SAF). Its aim is to advance technologies and innovations pertinent to environmentally friendly, electrically-powered aircraft and to help bring forth their implementation into safe, quiet, useful aircraft that can benefit the public, the environment and the transportation system. In May 2016 the SAF Symposium, a global group of renowned presenters focused on the future of quiet, electrically powered aircraft, was held in San Francisco. It focused on early entry practical market opportunities in all-electric, hybrid, and autonomous flight. With its history of drawing together green aviation leaders from industry, government, and academia worldwide, EAS had now become the go-to conference for electric flight.
Erik Lindbergh continued to work towards electric flight. In 2013 with Eric Bartsch, Lindbergh founded a private company, “Powering Imagination—the Future of Flight.” One of the first moves was to enter into a partnership with the Museum of Flight in Seattle to help graduate students from the Embry-Riddle Aeronautical University in Daytona Beach, Florida, design The e-Spirit of St. Louis, an extremely light (1,700 pounds), 52-foot (15m85), 100-horsepower two-person prototype that can soar in near silence. The design is based on the Austrian Diamond HK-36 motorized glider. There is the potential for more than 200,000 sightseeing flights over the USA’s parks every year. And while the views are spectacular, the noise spoils the show. The National Park Service has been concerned about the racket, and its effects on wildlife and visitors, since the 1970s.
For a decade, experienced airplane builder Brian John Carpenter of Adventure Aircraft Inc. at Corning Municipal Airport, California, has been working on a low-cost electric motor glider kit using complete video instruction for the build and incorporating over one hundred 3D-printed components. The EMG-6 began development in March 2013 from the lessons learned on the EMG-5 after the FAA’s response to the manufacturer’s request for clarification on Li-Po weight and the maximum ultralight empty weight specified in FAR 103. Power is from twin Plettenberg Predator 37 electric motors developing 16 hp (12 kW). Carpenter gave EMG-6 its first test flight on December 20, 2013. Those wishing to build their own EMG-6 were able to visit an Internet website and blog to get guidance.
Meanwhile, Yuneec of China had also been adapting good designs. One of these, an ultralight, was by Martin Wezel of Germany, renowned for his ultralight motor gliders such as the Condor, Star, Sting and Sirius. The build-it-yourself Apis 2 wing design, with its upper wing telescopic air brakes as well as flaps, was initially intended to be powered by a 50 hp (37 kW) Rotax 503 two-stroke or 60 hp (45 kW) HKS 700E four-stroke powerplant. The rights to this motor-glider were purchased by Yuneec in 2011 with the intention of making an electric version. The standard engine fitted is the 40 kW (54 hp) Yuneec Power Drive 40 electric motor, controlled by a Yuneec Power Block 40 400-amp power controller and powered by two Kokam Li-Po battery packs of 31 ampere-hours (Ah) each 62 Ah total. But in June 2012, Wezel announced that the production move had been delayed indefinitely. In 2013, the Yuneec eSpyder 24kw electric propulsion system received the world’s first electric aircraft engine certification from DULV.
In the Netherlands, during the air combats of World War I, among the aircraft doing battle was a Dutch-built bus called the Spyker-Trompenburg V.2, a low-powered, tandem-seat gasoline biplane. Now 100 years later, Spyker linked up with the American electric-aircraft startup Volta Volaré, to produce the SpykerAero, powered by an electric motor weighing just 32 lb. (14 kg) but delivering upwards of 680 pound-feet of torque.10
Axel Lange’s Antares sailplanes continued to satisfy their pilots. On November 10, 2015, Ludwig Starkl (Austria) flew a cross-country flight over Namibia. He flew 1104.5 km (686 miles) with a very high average speed of 165.6 km/h (89.4 kts). On December 17, 2016, Anja Kohlrausch of Eberbach (Germany), also flying in Namibia, set a new (female) world record for free distance using up to three turn points of 1141.7 km in an Antares 20E.
There is also a requirement for a reliable e-airplane for training pilots. On August 8, 2014, Pipistrel’s WATTsUP two-seater electric trainer made its maiden flight. As part of its 25th anniversary celebrations, that month Pipistrel displayed the airplane at the Salon de Blois Airshow, France.
In November 2015, Contra Electric Propulsion (CEP) was set up by Nick Sills, formerly technical director of the Electric Lightning P1 single-seat pylon racer, to develop an electrically powered version of the Falco composite Furio kit plane designed by legendary Italian engineer Stello Frati, fitted with two electric motors driving twin contra-rotating propellers. The CEP development, manufactured by Potenza Ltd., a Coventry-based company, a leader in electric and hybrid power units, is a bolt-on self-contained twin-engine contra-rotating fixed-pitch 300hp system for existing piston engine light aircraft. The contra-rotating props will be supplied by Hercules Propellers, which has already manufactured similar items for the Bugatti 100P project. The Furio has a carbon fiber monocoque airframe light enough to allow 400kg of Li-Po battery to be added and enable an autonomy of 1 hour. The component parts, fixed-pitch contra-rotating propellers, twin YASA 750 series motors, their inner and outer coaxial shafts and splined drive rings, were next assembled in a ground test vehicle to undertake both static and mobile tests to simulate aircraft taxing and ground maneuvering at up to 60 mph. This would lead to a design using 4 motors to offer a 500kW (625 shaft horsepower) system.11
Following Graham Dorrington’s Dirigible D4, the return of the electric lighter-than-air ship continued. Indeed in April 2013, French pilots Pierre Chabert and Gerard Feldzer of transoceans.fr flew their electric-powered lenticular blimp, Iris Challenger 2, across the English Channel from France to Dymchurch in Kent, covering 45 km (30 mi) in 2 hours and 23 minutes. It was built by Chabert’s company, Airstar Space Lighting, which won an Academy Award for technical achievement in 2003, specifically given for “the introduction of balloons with internal light sources to provide lighting for the motion picture industry.” Chabert’s balloons have illuminated Titanic, Pirates of the Caribbean, and countless other films. The e-airship’s envelope contained 568 cubic meters (20,059 cubic feet) of helium, and could carry a payload of 200 kilograms (440 pounds). Equipped with two electric motors of seven kilowatts (9.38 horsepower) each, and two counter-rotating 1.3 meter (51.1875 inch) propellers made by E-Props, the 14-meter (46-foot), six-meter-high Iris Challenger 2 navigated at a cruising speed of 20 kph (12.4 mph). An air-filled floater gives amphibious capability to the airship. They set a world record for distance, duration and speed, which was certified by the FAI (the World Air Sports Federation) in the 400-m3 to 800-m3 balloon class.
The French are not alone. By 2015, researchers at the University of Lincoln (UK) School of Engineering had completed a three-year investigation into stratospheric passenger airships as part of a multinational engineering project designed to provide a future sustainable air transport network. They were members of a pan-European research team that believed airships may be the “green” answer to the future growth of aviation. The Multibody Advanced Airship for Transport (MAAT) project aims to position airships as the solution for future air transportation that is safe, efficient, cheap and environmentally friendly. The EU-funded MAAT project, made up of eight nations and led by the Universita di Modena e Reggio Emilia in Italy, envisages the design of a cruiser which can travel across the globe on a set route. Smaller feeder ships carrying people and goods would then be able to dock onto the cruiser while it is still moving. The primary energy source for the MAAT is through harvesting sunlight from photovoltaic arrays mounted on the upper airship surface to provide sufficient electric power during the day to operate the airship’s systems and provide life support, propulsion and control, while also producing sufficient excess energy that can be stored to facilitate continuous MAAT operation at night.12
The electric airplane had come a long way thanks to the Li-Po battery. But could it be made even more efficient? In March 2017, after four years of R&D, South Korean battery manufacturer Kokam launched XPAND, a nickel-manganese-cobalt (NMC) drone battery pack for EVs including a ceramic separator and battery pack thermal containment technologies; its energy density of 265 watt-hours per kilo would increase operating time by 20 percent over the average Li-Po battery.
Elon Musk of Tesla announced that their Model S P100D automobile would be equipped with a 100kWh battery, extending range up to 300 miles. Backing this up, Musk invested in building a “Gigafactory” outside Sparks, Nevada, with the aim, by 2020, of mass-producing more lithium ion cells annually than were produced worldwide in 2013. Musk revealed having his own design for a VTOL electric plane, and says that such a system becomes possible once battery energy density reaches over 400 Wh/kg, while his Tesla vehicles are believed to be powered by battery cells with ~240 Wh/kg.
Then there is Ann Marie Sastry of Sakti3 in Ann Arbor, Michigan, who discovered that Li-ion batteries could be improved by a factor of 2 to 3 by replacing the liquid electrolyte with a thin film of solid material. Though Sakti3 batteries are not yet on the market as a stand-alone product, the company has announced that it has achieved an impressive energy density of 1,143Wh/liter.
One serious player in the quest for greater specific energy density is OXIS of Oxfordshire, a team led by Huw Hampson-Jones, with their Lithium-Sulfur (Li-S) battery. When the Li-Po battery was first presented in the 1990s, it showed 80 kw/h per kg, and this has increased to 220. The OXIS battery lighter, safer and maintenance-free, is already showing an energy density of 400Wh/kg. Sulfur represents a natural cathode partner for metallic Li and, in contrast with conventional lithium-ion cells, the chemical processes include dissolution from the anode surface during discharge and reverse lithium plating to the anode while charging. As a consequence, Li-S allows for a theoretical specific energy in excess of 2700Wh/kg, which is nearly 5 times higher than that of Li-ion. In view of the price of cobalt mounting, and the toxic nature of the Li-Po, the Li-S stands a greater chance for the future. As a demonstrator, OXIS has built a UAV called Centurion fitted with Li-S batteries. The craft is so named because during World War II the iconic Centurion tank was built by the MG car company at Abingdon, where OXIS is based.
Whichever comes out the winner, it can only prove beneficial. Meanwhile other solutions are being investigated and tested to give the electric airplane its much-needed autonomy range.