Pipistrel’s Velis Electro, the world’s first type-certified electric aircraft, reveals the potential of sustainable energy
AIRCRAFT
“The grand challenge of our time in aviation is carbon emissions and global warming, and if we don’t address it in every possible way, aviation will be moot,” Erik Lindbergh, grandson of Charles Lindbergh, told attendees of May’s European Business Aviation Convention & Exhibition (EBACE).
The gravity of this situation spurred the Forever Flight Alliance—supported by The Lindbergh Foundation, X Prize Foundation, The Prince Albert II of Monaco Foundation and the NBAA—to incentivize efforts worldwide to decarbonize aviation.While impassioned leaders of our industry were calling upon the EBACE audience to join in this important mission, this BCA author was given the opportunity to fly the Pipistrel Velis Electro, the world’s first certified electric airplane, at the Ecuvillens airfield in western Switzerland.Could this be part of the answer to decarbonizing aviation? The Velis Electro proves that CO2-neutral flying is already possible. In the words of Tine Tomažič, director of research and development at Pipistrel, it is now possible to turn sunshine into knots.
Solar Panels Powering FlightMarc Corpataux, owner of AlpinAirPlanes, was our host and demonstration pilot at Fribourg Ecuvillens Airport. It is noteworthy that Corpataux’s lengthy aviation experience includes 12 years as a certification engineer at Switzerland’s Federal Office of Civil Aviation prior to starting this flight operation. AlpinAirPlanes provides import, certification, maintenance and flight training with Pipistrel aircraft.
At the heart of the Velis Electro’s instrument panel is the 5.7-in. LCD EPSI 570C cockpit display. This photo was taken near the end of the second demonstration flight, indicating that the state of charge of the two batteries was at 28%. Credit: Kimberly Henneman
Two aspects immediately captivated my attention while walking to the hangar. First, the top of the hangar was adorned with rows of solar electric panels. This provides the electrical energy for their recharging station, which is available upon prior permission to other electric aircraft. Second, the sound of a Pipistrel approach to landing was so quiet that the predominant sound in the airport environment came from cowbells in the adjacent pasture.The Velis Electro is powered by a 57.6-kW electric engine with a three-blade, composite fixed-pitch propeller. The 345-VDC electric system is built around two lithium-ion batteries connected in parallel for redundancy. One battery pack is located in the nose, and the other behind the cabin. Each battery weighs approximately 70 kg (roughly 154 lb.). Corpataux explained that a single battery has enough power for standalone operation to support climbing and continuation of a flight.The powertrain is entirely liquid cooled, including the batteries. The batteries are tested to certification standards to tolerate faults, thermal runaway and crash loads. The aircraft can be operated in cold, hot and rain. The electrical system was also tested to be tolerant of electromagnetic interference and high-intensity radiated fields.
The Velis Electro is equipped with an aural angle-of-attack-based stall warning and a stick shaker. The pitot tube mounted under the wing provides airspeed and AOA sensing. Credit: Kimberly Henneman
Enhanced awareness of the aircraft is provided by the crew alerting system and an annunciator panel. At the heart of the instrument panel is the 5.7-in. LCD EPSI 570C cockpit display. This system provides information on the operational status of the electrical propulsion system. It utilizes easy-to-understand graphics to display relevant system parameters. The first page provides information on the “state of charge,” or, in other words, how much power remains in the batteries. The second page is the equivalent of a systems page. It gives the “state of health” of the batteries. This is important because an older battery will store less electrical energy.Since the primary mission of the Velis Electro is flight training, incorporating the EPSI 570C gives students their first exposure to an EICAS-like troubleshooting system and helps them transition to the next step up in aircraft complexity.Aerodynamic EfficiencyHeightened emphasis on aerodynamic efficiency was evident in the preflight Q&A as Pipistrel engineers Jozef Kovacic and Paolo Romagnolli emphasized the importance of not wasting any energy on drag. This was quickly evident when walking up close to the Velis Electro. The utilization of computational fluid dynamics (CFD) optimized the design of the wing, the choice of airfoils and the design of the empennage. The wing has an aspect ratio of 12, which integrates well with the specially designed wing airfoils optimized for cruise efficiency and therefore speed, while at the same time ensuring high maximum lift and docile stall characteristics.The attention to detail to reduce unnecessary forms of aerodynamic drag was obvious. The gaps between the flight controls are sealed with tape, which is an aerodynamic method used for several decades on high-performance sailplanes.
AlpinAirPlanes, utilizes photo voltaic panels mounted on the southern-facing portion of their hangar’s roof. Pipistrel’s SkyCharge charging station is designed to provide fast and secure charging for two or four aircraft. Credit: Kimberly Henneman
The Velis Electro’s wingspan is 35 ft., 1 in., so it fits easily into a hangar. At a basic empty weight of 428 kg (941 lb.) it was easy for one person to move the aircraft out of the hangar. The maximum takeoff weight of 600 kg (1,320 lb.) creates a maximum payload of 172 kg (378 lb.).After strapping in it was time to continue with the start-up process. The Velis Electro was clearly designed to be simple to operate. The aircraft has four cockpit switches. A safety guard in the powertrain will not activate the propeller unless the throttle is fully in the idle position. Unlike a conventional reciprocating engine where the propeller immediately begins to spin when the starter is engaged, the Velis Electro’s propeller doesn’t begin to spin until the throttle is moved forward to begin taxiing.Another unique aspect of electric propulsion is the lack of warm-up time needed for takeoff. This was amply demonstrated as a Beechcraft Bonanza sat short of the runway for several minutes doing its pre-takeoff checks. We sat for multiple minutes as the Bonanza did its engine run-up, leaned the mixture, checked the magnetos and checked the propeller. Our engine wasn’t running while we waited.
Recharging the Velis Electro’s batteries is as simple as plugging the power cord into this receptacle. An aircraft that returns from a training flight with 35% of the “state of charge” (power remaining in the batteries) will require up to 60 min. for recharging to attain 95%. Credit: Kimberly Henneman
After a quick check of the windsock, prepositioning the flight controls for the slight crosswind, and making a position call “en Francais” on CTAF, I moved the throttle forward. Power is delivered instantly and without hesitation. The noise level within the aircraft was remarkably quiet, and there were essentially no vibrations. This was especially noticeable since my last light aircraft flying was predominantly done in a restored PT-17 Stearman and a Robinson R-44 helicopter. The lack of noise and vibrations in those aircraft would be cause for concern. Flying in relative quiet and without vibrations is a refreshing experience.The aircraft’s flight manual predicts a takeoff run of 791 ft. at sea level, standard-day conditions. The warmer-than-standard temperature conditions produced a slightly longer takeoff run using one notch of flaps (8 deg.). Quickly, we were climbing out toward the scenic mountains surrounding the famous village of Gruyeres at a brisk climb rate of 600 fpm.We set the throttle to approximate 35-kW power, which resulted in 90 KCAS of cruise performance. This normally results in an endurance of up to 50 min., which leaves a 30-min. VFR reserve.The high-aspect-ratio wing reminded me of a sailplane as we cruised through the thermal activity. The ailerons and elevator control forces were enjoyably light with the control stick. The Velis Electro has full-span flaperons, thus a turn made without coordinated use of the rudder will produce adverse yaw. The rudder movement required to make a coordinated turn was quite manageable.Next, we explored the slow-flight handling characteristics. The Velis Electro is equipped with an aural angle-of-attack-based stall warning and a stick shaker. This was deliberately included in the aircraft design because of its intended mission as a training aircraft. As we slowed down, the aircraft gave plenty of warning of the usual characteristics of high AOA. The flight controls became sluggish, and some tactile vibration was noticeable from the empennage. As the AOA increased, the stall warning system activated and then progressed into the stick shaker close to the book value of 51 KCAS in the clean configuration. The aircraft still exhibited plenty of control and did not have a tendency to “drop off.”
The 345-VDC electric system is built around two lithium-ion batteries connected in parallel for redundancy. One battery pack is located in the nose, and the other behind the cabin (shown here).Credit: Kimberly Henneman
It was then time to return to the traffic pattern so that our photographer could grab inflight videos. The aerodynamic sleekness of the aircraft was immediately apparent on downwind. The lack of drag kept the aircraft sailing along with only a minor decrease in the speed even with the throttle fully back at idle. While on base leg it was evident that a slip would be needed to bleed off enough airspeed to get the final notch of flaps (19 deg.) deployed. Even with the second notch of flaps the aircraft does not bleed speed. This handles more like an aerodynamically sleek sailplane in the pattern.Again, the lack of noise and vibrations was a remarkable difference from conventional reciprocating-engine aircraft. This provides a wonderfully quiet cockpit environment, enabling a pilot to easily listen over the headsets without the shaking, rattles and loud noise. This improves the ability to maintain situational awareness.I couldn’t help but grin while taxiing into the ramp. At my home airport I would be taxiing into the self-serve refueling rig where the cost of aviation gas is excessive at the FBO, which is “unfriendly” to general aviation.
The Velis Electro’s takeoff noise signature is a mere 60 dBA. It was possible to still hear the cowbells in the adjacent pastures.
Our photographer then jumped into the seat. I was surprised when the Velis Electro slipped past us on the takeoff roll. The noise level is a mere 60 dBA. It was possible to still hear the cowbells in the adjacent pastures. This would be a game changer at an airport such as Santa Monica with its restrictive noise abatement procedure where residents have the airport authority on speed-dial to register their complaints of aircraft noise. The lawn mowers and leaf blowers of those residents are far louder than the Velis Electro.This will be a great asset for all of aviation because it will lessen the sound signature. Flight schools that operate in noise-sensitive communities will benefit from the quietness of the Velis Electro.The transition for an already-certified pilot into the electric aircraft is a simple four-flight process, according to Corpataux. The first flight is an introduction to the engine characteristics and management of the batteries’ energy. The last flight is a cross-country to demonstrate the pilot’s proficiency in energy management.There are currently 11 e-grid recharging facilities in Switzerland at partner flight schools that similarly operate electric aircraft. There are also recharging facilities at the Bern and Luzern airports. An aircraft that returns from a training flight with 35% of the “state of charge” (power remaining in the batteries) will require up to 60 min. for recharging to attain 95%. Pipistrel recommends a three-phase, 380-VAC connection to enable quick charging.Reliability And MaintenanceThese aircraft are game changers in terms of technological innovations and cost efficiency. Pipistrel’s Tine Tomažič explained that electric aircraft are much more upgradable. For example, the inevitable improvements in batteries will be easier to incorporate into the same aircraft.Reciprocating engines are more complicated and prone to problems such as pre-ignition and detonation. Starting a reciprocating engine in excessively cold temperatures should normally be assisted by pre-heating the engine. And, of course, in excessively hot temperatures it is possible to vapor lock a fuel-injected engine, or with improper leaning procedures cause problems with the magnetos. An electric engine will have none of these issues.The Velis Electro’s service ceiling is 12,000 ft., which brings up another advantage of electric aviation. The power output of its batteries or the engine does not diminish with increases in altitude. This is a contrast to the considerable loss of engine power in a normally aspirated reciprocating engine at higher density altitudes. Advisory materials for pilots venturing into high-density-altitude destinations such as the Rocky Mountains have warned for decades about the diminution of engine power.The Velis Electro’s drivetrain has only one moving part, a ball bearing, which explains the lack of vibrations from the engine. The reduced number of moving parts dramatically increases the ease of maintenance and simultaneously decreases maintenance costs. The risk of malfunctions is further minimized due to a continuous health-monitoring system.The TBO of the motor is 2,000 hr. There is an initial limitation of 500 hr. on the batteries, but as additional testing and operational experience are accumulated this will increase significantly. The batteries are replaceable without special skills. An exemption with the European Union Aviation Safety Agency (EASA) sets forth the requirements for licensed AMTs who complete a different training course specific to the Velis Electro.Pipistrel’s engineering knowledge of electric propulsion dates to before 2007. It has two-plus generations of considerable in-house R&D experience, and its team has already won multiple awards.The electric drivetrain is just one of the engineering specialties within the Pipistrel team to produce an efficient aircraft. This team evaluated propeller efficiency by analyzing two existing propellers during ascents and descents, and comparing the number of traffic pattern circuits performed with one fully charged battery. When a propeller designed for piston engines was replaced with a propeller tailored to electric drive, the net energy consumption within ascent and descent was decreased by 19%. Similarly, a 27% increase in the number of traffic pattern circuits (endurance) was achieved.In 30 years of activity, Pipistrel has proven its expertise in working with metal and composite materials. The majority of the Velis Electro’s structure is made from carbon-fiber composites. Composite construction is superior to achieve the surface shapes necessary for efficient aerodynamics. Composite structures have further advantages in corrosion resistance and fatigue resilience. They also allow engineers to build strong structures at the lightest possible weights. Pipistrel’s in-house prototyping facility offers one of the largest eight-axis robots in Slovenia for milling, a five-axis waterjet cutter, 3-D printers and scanners with a wide selection of computer numerical control (CNC) machines.International AwardsThe Pipistrel team has been recognized with noteworthy international accolades and awards for its accomplishments in sustainable aviation. In 2011, NASA launched a competition with a $1.3 million prize to develop an electric-powered aircraft capable of flying 200 mi. in less than 1 hr. using the energy equivalent of 1 gal. of fuel per passenger. The innovative winning aircraft, Pipistrel’s Taurus G4, featured a twin-fuselage concept with a large central wing housing the most-powerful electric aviation motor ever developed (145 kW) at the time. The minimum efficiency criteria figure—in passenger miles per gallon (pmpg)—was 200, but Pipistrel won the competition by totaling 403 pmpg. This impressive recognition illustrates that out-of-the-box thinking can set new performance milestones previously thought impossible.The American Institute of Aeronautics and Astronautics (AIAA) recognized the Velis Electro’s technical team with the renowned Aircraft Design Award in 2021 for creating the world’s first certified electric aircraft and leading the marketplace in a new era of green aircraft design and technology.Aviation Week’s editorial team selected the Velis Electro in 2021 for the prestigious Laureate Award in the business aviation category. The editors augmented their choice with the following words: “Slovenia’s Pipistrel redefined general aviation by becoming the first company to certify an electrically powered aircraft—cutting emissions, noise and operating costs along the way. Pipistrel received EASA type certification for the battery-powered Velis Electro in July 2020, and the quiet aircraft has allowed the reintroduction of flight operations during weekends and holidays.”The Velis Electro also has a string of world records to add to its list of notable accomplishments. A team of five electro-mobility enthusiasts demonstrated its capability of cross-country flight with a noteworthy trip from Zurich to the North Sea island of Noderney. The team wanted to show that there are alternatives to traditional fuel. The flight broke seven world records: highest average speed over 700 km, highest altitude reached by an electric plane, lowest energy consumption per km per person, longest distance flown electrically, fastest climb performance, lowest number of intermediate stops over 700-km distance, and longest electrically flown distance in 24/48/56 hr.‘Leading Edge’ Certification ChallengeOne of the major difficulties for design engineers who are utilizing “leading edge” technologies is the learning curve for both the manufacturing engineers and certification authorities. For example, many aspects of Beechcraft’s Starship were certainly noteworthy for being forward thinking. However, years into the process questions occurred regarding how to test composite structures for impact damage, detection and repair. What were the acceptable methods to detect underlying delamination? Then there was the question of how to design and certify a structure for lightning protection. Even though the Starship offered remarkable aerodynamic performance, being on “the leading edge” added significantly to the time delays bringing the design to the market.
Pipistrel’s aerodynamicists highlighted the importance of not wasting any energy on drag. The utilization of computational fluid dynamics (CFD) optimized the design of the aircraft’s wing and empennage to minimize drag. Credit: Kimberly Henneman
Pipistrel’s Tine Tomažič remarked that in an ideal world an electric aircraft design would begin with a clean sheet. For practical reasons, Pipistrel built the Rotax-powered version first, the Virus SW 121. European certification authorities were already familiar with the powerplant, so this version was easier to get certified in a timely manner. For speed into market, it is quicker to start with an already existing aircraft.The second factor is social acceptance, and this harkens back to the Starship’s unconventional design. Potential buyers were not comfortable with the new, radical design. Aviators as a group are rather resistant to new ideas. Thus, in the case of the Velis Electro the only novelty was the propulsion system.Numerous flight schools throughout Europe are now utilizing the Velis Electro. Unfortunately, a Velis Electro currently operating in the U.S. will carry the “Experimental” status. Under current certification regulations in the U.S., it is not possible to certify a light sport aircraft (LSA) with an electric propulsion system. The process of changing regulations in the U.S. is lengthy and complicated, and the workload is only getting worse for the FAA as the drone and advanced air mobility sectors seek to create entirely new concepts in U.S. airspace.The FAA is developing a new set of standards that will deal with the airworthiness certificates given to a broad range of airplanes, to include warbirds, amateur-built, LSA, drones and eVTOLs. It is hoped that this new set of standards, which are called the Modernization of Special Airworthiness Certification, can be published by 2023.Where Is the Future Going?Textron recently purchased Pipistrel as part of its strategy to focus on the development of sustainable aircraft. This will benefit Pipistrel with access to greater resources, technical and regulatory expertise and a global aircraft sales and support network.Another exciting project by Pipistrel will soon captivate attention. The Panthera is a sleek, efficient aircraft with retractable gear envisioned to carry four people for 1,000 nm at 200 kt. Hybrid and electric models are major goals of the project.Pipistrel has also contributed to the “HY4” project, which developed the world’s first four-seat passenger aircraft powered by a zero-emission hydrogen fuel cell. The first public flight was on Sept. 29, 2016 at Stuttgart Airport. The airport authorities stopped all other air traffic during the 15-min. performance so that spectators could listen to the nearly silent flight.The most striking impression left after this opportunity to fly the Velis Electro was a realization that electric aviation is truly a viable option as a climate-neutral source of power for aircraft. This article was initially proposed as an opportunity to get a hands-on flying opportunity with a new aircraft. It turned out to be much more thought-provoking.Think back a mere 15 years to your first smartphone. Who would have thought that in 15 years these devices would become indispensable with their exceptional capabilities? To paraphrase Tomažič’s words, “Without innovation there is no future. Yes, electric aviation can be done. If you like this airplane today, it will only get better.” Perhaps an even more apt description of the Velis Electro is that it is showing the potential for a sustainable future.
—Upon his retirement as a non-routine flight operations captain from a fractional operator in 2015, Dr. Veillette had accumulated more than 20,000 hours of flight experience in 240 types of aircraft, from balloons, rotorcraft, sea planes, gliders, war birds, supersonic jets and large commercial transports. He is an adjunct professor at Utah Valley University.
