eCSTOL: Longer Range Commutes on Less Power

Competition is growing in the electric Vertical Take Off and Landing market, with 407 potential builders listed in eVTOL News.  Vertical flight takes power, though, and with available batteries limiting range, most such vehicles can make only short hops.  Alternatives that allow speedier, longer flights, in the form of electric Conventional Short Take Off and Landing (eCSTOL) aircraft are in development.

Such craft offer the benefit of requiring less power for takeoffs and climbs, being more aeronautically-based than power-based.  Airflow, for instance, claims operating costs for their eCTSOL craft is one-third that of an eVTOL or helicopter.

We will look at three eCSTOL craft that seem to making headway at this time.  The infrastructure (in two cases below) to support their flight may already exist.


Curt Epstein, writing in Future Flight, under the headline, “Infrastructure Needs for eSTOL and eVTOL Aircraft May be Closer than Imagined,” notes the “intense study” being undertaken.  Speaking at the Vertical Flight Society’s  Electric VTOL Symposium, Airflow co-founder and CEO Marc Ausman, “Described the runway needs of his proposed blown wing aircraft as being 150 feet of ground roll with an overall requirement of 300 feet in length. That is roughly three times the length of the currently [prescribed] touchdown-and-liftoff (TLOF) area plus safety zone, for a helipad.”

Airflow’s Virtual Tailhook program will assist pilot, enable very short, precision landings

This would open up thousands of potential landing zones.  A Massachusetts Institute of Technology (MIT) study, “…examined several major cities and found that Los Angeles had 6,200 such potential sites, while New York had 5,700, Dallas and Chicago around 3,800 each, and Boston 2,500.”  David Ausman explains, “So even if one percent of those were actually viable, you would still have dozens of rooftops plus other areas around the city and suburban areas where these aircraft can land.”

Ausman believes such a runway length will enable flight from the roofs of existing buildings, and reasonable integration into “urban environments.”  The single-pilot aircraft’s proposed 250-mile range (with reserves) and ability to carry 500 pounds of low-density cargo could lead to profitability because of low operating costs.

Airflow is testing subscale aircraft to prove concept for Cessna 210 eCSTOL demonstrator

Airflow is building a demonstrator based on a Cessna 210 what will feature (according to the company’s illustration) eight electrically-driven fans across the width of the wingspan.  This is similar to the David Ullman’s experiment in distributed electric propulsion, part of his IDEAL (Integrated Distributed Electric-Augmented Lift) concept.

The final craft will not be purely electric, but a hybrid powered by Eric Lindbergh and Eric Bartsch’s Verdego Diesel-electric system.  Combining a 184 kilowatt (247 horsepower) piston-engine driven generator with the DEP motors providing enhanced lift on Airflow’s wings will give economical operation and short-field potential.


Taking a similar demonstration step to Airflow, Electra pledges its mission is, “To turn flygskam (flight shaming) into Flugvergnügen” – the joy of flying. wants to bring Flugvergnügen” – the joy of flying, back

Charles Alcock, in Future Flight, writes, “Electra is on track to complete the preliminary design phase of its eSTOL aircraft technology demonstrator this month with most of the vendors and suppliers having been selected, including Blue Force Technologies, which will be the lead designer and manufacturer for the airframe.”

Langford foresees expanded possibilities for landing sites for eCSTOLcraft

Program manager James “JP” Stewart will oversee the program, building and test flying a Cessna 172-size craft.  The two-seat craft, weighing about 3,000 pounds, will be powered by a “custom turbogenerator” that will serve as its hybrid-electric powerplant and drive eight electric motors with an installed power of 260 kilowatts.  That kind of power should ensure true STOL performance.

First flights in 2021 are intended to show takeoffs and landings in “as little as 100 feet.”  A later production aircraft will carry up to six people and perform “a variety of missions once it achieves type certification in 2026.”

Founder and CEO John Langford, winner of the 2019 Personal Aircraft Design Academy trophy, was leader of Aurora Flight Sciences, which investigated different eVTOL technologies and extremely large remotely-piloted vehicles, among other things.

Langford, a graduate of the Massachusetts Institute of Technology (MIT), is teaming with his alma mater on a Small Business Technology Transfer (STTR) project.  This project includes a contract to join the U. S. Air Force’s Agility Prime program for “Innovative Control and Configurations for ORBs [Organic Resupply Busses] with Distributed Electric Propulsion.”

Note the video never defines the term “ORB” but lets us know what they are and what they are not.  Since the video was made in mid-2020, the working definition of such vehicles may have changed in the official lexicon.

Note also that Langford’s team and Airflow’s were previously heavily involved with multiple rotor eVTOL projects, and are familiar with the many difficulties of such systems.  They have both switched to eCSTOL projects.

Metro Hop

Like John Langford, Bruno Mombrinie helped develop and fly human-powered aircraft at MIT.  Bruno is now involved with Metro Hop, and ambitious project that incorporates aircraft and infrastructure design.  The eCSTOL aircraft and its systems can support passenger or cargo operations.

Like Airflow and Electra.Aero mechines, the Metro Hop aircraft is speedier and more far-ranging than most multi-rotor machines, with a cruising speed of up to 400 kilometers per hour (250 mph) and a 200-kilometer (125-mile) range “with current battery technology.  A highly specialized skyport and service facilities shown in the video seem essential to the clockwork timing of Metro Hop’s operations.

Currently, Metro Hop has received grants through the ESA (European Space Agency) and BIC Bavaria, and is looking for more investors.

All these eCSTOL machines feature intermediate ranges and the speed to perform longer trips in the same time urban air machines make cross-city hops.  Coupled with what will become longer commutes to more affordable enclaves, these machines open many possibilities for a future that looks very different from what we may envision for our cities.


Longer Aerial Commutes to Affordability

Exurbs and Extended Range

Urban Air Mobility (UAM) may be only a small part of electric aerial transport in the next decade.   Longer-range vehicles may enable longer aerial commutes to affordable country homes. Cities are becoming too expensive for most families, and examples abound of commuters traveling over 100 miles to and from work.  Two years ago in San Francisco, for instance, the cheapest home (a true “fixer-upper”) was listed at $699,900, a sum that used to include significant acreage and servants’ quarters.  A “typical” home price in SFO is over $1,400,000.  As a result, workers travel from places like Manteca, 76.4 miles downtown to downtown and one hour, 35 minutes in a car on a good day.  Manteca’s homes average less than $400,000.

During the 2019 Sustainable Aviation Symposium at UC Berkeley’s Pauley Ballroom, Susan Dell ‘Osso, President of River Islands Development LLC, talked about Planning Sustainable Communities for California’s Future. She didn’t sell condos and single-family dwellings, but, “Cited the untenable commute times that affect people who work in the Bay Area but have to live in the Central Valley. She explained that just three small airparks could serve the entire 5,000 acre community of River Islands near Tracy, California.  If such airparks were served by electric aircraft, pollution caused by long automotive commutes could be a thing of the past.

1940’s light aircraft were designed for grass runways and rural settings. Today’s electric craft could perform on runways or farm fields

William T. Piper, President of Piper Aircraft, saw such a future with craft such as J-3 Cubs and Aeronca Champions linking small towns in rural areas, and regional airports bringing goods and commerce to the areas served.  Ms. Dell ‘Osso’s vision includes master planned communities with affordable housing, “green” buildings, resource conservation, quality education, and jobs creation and “game-changing transportation innovation” showcasing the “benefits benefits of disruptive technology in transportation systems to tie large areas together.”

Commute distances from River Islands development. These would all be shorter by air, saving even more time.  Relaxation factor would be enhanced enormously over grueling highway commutes

This fits Piper’s vision with cleaner, less costly operations (avgas was 25 cents per gallon in the 1940s, and closer to $5.00 in 2021).  A no-wind, well-leaned trip in a Cessna 150/152 would consume $25.00 each way on the daily commute, and all the concomitant costs for maintenance, licensing, etc.  Given that traditional aircraft are subject to weather delays, winds, and other forces of nature, a self-flying or shared electric commuter vehicle would be preferable for costs and reliability.

Expanded Horizons

Perhaps reflecting Piper’s never-realized future, planned developments like River Islands, or designated facilities such as Lake Nona herald the medium-distance commute that fits neatly with the range and capabilities of Lillium, Dufour Aerospace’s aEro 3, Jaunt’s Rosa, and Joby’s certified machine.  All can meet regional range requirements and are faster than the light aircraft promoted by Piper and others in the 1940s.

Swiss-built Dufour Aerospace’s aEro 3 could emulate rural flying of 1940s with greater safety and speed

Beyond that, a quick aerial trip from work to home (perhaps even with a rooftop to doorstep ease) would cut drive times in half, enabling more and better home life, and the enjoyment of a an environment (physically and spiritually) being healed by conscious decisions.

Jaunt Journey, much like other modern designs, includes autoflight and communications systems to enhance safety

We’ll do an entry soon on the longer-range eCSTOL (electric Conventional Short Take Off and Landing) aircraft that will enhance transportation over 300- to 600-mile journeys.   The market is heating up and designers are advancing the technology.


Siting  and Building Considerations at the 2019 SAS

As we see an inrush of capital to finance new electric Vertical Takeoff and Landing (eVTOL) machines and now electric Conventional Short Take Off and Landing (eCSTOL) machines, we are on the cusp of seeing newly envisioned landing zones for these machines.  With the departure of Uber from the aerial scene, we probably won’t see the grandiose platforms the firm promoted.

Uber’s urban air mobility landing zones were perhaps a bit grandiose, meant to “hype” future plans.  One wonders if neighbors would be happy with up to 1,800 planned passengers per hour adding ground traffic to the area.

Your editor poked fun at these visions in his talk at the 2019 Sustainable Aviation Symposium at UC Berkeley, doubting that urban centers would welcome hundreds of arrivals and departures overhead day and night.

Luckily, presenters who had worked on real-world re-imaginings of Uber’s grander vision helped talk your editor down.  Byron Thurber, an ARUP architect, discussed “A Practical and Sustainable Transit Hub for Urban Air Mobility –the Uber Elevate Skyport.”  Following LEEDS, or Leadership in Energy and Environmental Design criteria, the sustainable building would retrofit an existing parking garage at the edge of the downtown core.  Formed from sustainable building materials, it would support landings and takeoffs for eVTOLs and, “…function as a true transit hub, providing accommodation for a network of other modes, including e-bikes, e-scooters, electric cars, and… rideshares.”  The vision was considerably more restrained than that of Uber’s corporate futurism.

Darrel Swanson, Director of the Swanson Aviation Consultancy, held that, “UAM will succeed in areas where the noise control is achieved, high capacity vertiports can operate, and certification obstacles are solved.”

With competing needs for safety, quiet, and access creating problems for downtown cores, Dr. Jasenka Rakas, Co-Chair of SAS 2019, UC Berkeley CEE Faculty, and Board Member of the Sustainable Aviation Foundation suggested “Air Piers for Urban Air Mobility.”  Using waterfront locations to position landing zones, air operations would be less likely to draw the ire of local residents.  Her talk highlighted the many alternatives possible, including Vertiports and Short Take Off and Landing (STOL) facilities, Skyports, converted helipads and piers. Retrofitted rooftops and garages, and new structures above highways and highway intersections.  All of these would have the benefits of existing roads and transit means leading to them.

Short-Range Drop-In Sites reports that Hyundai and Urban Airport, an aptly-named startup, are partnering to build a Air One in Coventry, England.  Air One is a pre-fabricated, squat truncated cone that will provide shelter for, launch and retrieve Hyundai’s SA 1.  This transportable unit can be taken elsewhere as demands for drop-in air service change.  Others involved in the project include the city and University of Coventry, the drone company Maloy Aeronautics, but also Hyundai Motor Groups themselves

In somewhat marked contrast to a year ago, Hyundai’s immediate vision seems to have contracted to more immediately plausible levels.

The platform planned for Coventry is simpler still, but one can see a network of the planned 200 Urban Air Ports worldwide varying in size and complexity.

Ricky Sandhu, Founder and Executive Chairman of Urban Air Port, explains Air One’s place in the scheme of things.  “Cars need roads. Trains need rails. Planes need airports. eVTOLs will need Urban Air Ports. Over a hundred years ago, the world’s first commercial flight took off, creating the modern connected world. Urban Air Port will improve connectivity across our cities, boost productivity and help the UK to take the lead in a whole new clean global economy. Flying cars used to be a futuristic flight of fancy. Air-One will bring clean urban air transport to the masses and unleash a new airborne world of zero emission mobility.”

Meanwhile in Florida

In the meantime, German firm Lillium has cemented plans for making its advanced air mobility (AAM) solution into Florida’s civil transportation network.  According to eVTOL News, The city of Orlando, the Tavistock Development Company, and Lilium held a virtual press briefing to announce that Lake Nona — adjacent to Orlando International Airport — would be the site of what it called the first eVTOL vertiport in the world.  “First” is probably arguable since eHang in China has what appears to be a place, at least, that might match that description.

With Lillium’s claimed maximum range of 300 kilometers (186 miles), over 20 million Floridians could enjoy quick, low-altitude trips around the state.  That brings us to the next level of longer-range commuting – something that may become as big a factor in electric flight as urban air mobility.  We’ll be back with a look at exurban flight becoming a necessity as families move further away from major urban centers.  Coming soon.


Hydrogen as a Goop? Fraunhofer’s Powerpaste

Not Gwyneth Paltrow’s Goop

What if a different approach to storing hydrogen as a fuel gave benefits that are easily disbelieved?  Would this new fuel find approval and widespread adoption?  Ask the Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM) in Dresden, Germany.  The Institute has come up with something called Powerpaste, claimed to be, “A safe way of storing hydrogen in a chemical form that is easy to transport and replenish without the need for an expensive network of filling stations.”

(Fraunhofer describes the paste as a “goop,” not to be confused with the very different fluids marketed by Gwyneth Paltrow under the “Goop” trade name.)

We’ve seen hydrogen flying for several decades, with Michael Friend leading a Boeing project to launch the first fuel-cell powered craft in 2008 and Gérard Thevenot flying his H2 fueled “trike” across the English Channel in 2009 using only 550 grams per hour on his crossing, which took a little over an hour.

Some problems prevent adaptation of this technology a decade later.  Less than 50 hydrogen “filling stations” exist in the United States, mostly in southern California.  Only relatively local trips are practical at this time, and the number of hydrogen-fueled vehicles is not that significant.   As of March 21, 2020, “The U.S. has only 300 hydrogen cars (mostly in California) and only 48 retail fueling stations (43 are in California).  Only three H2 fueled cars are made by major manufacturers – the Toyota Mirai, the Hyundai Nexo, and the Honda Clarity.”

Only 6,500 H2 cars exist in the world.   That would mean no profit margins for their makers, and therefore almost negative incentive to push forward.  Obviously, lack of a supporting infrastructure is a big reason for lack of demand, just as hampering as the low number of charging stations was to battery electric vehicles 15 years ago.

Powerpaste in its raw form, as possibly packaged for consumers, and as produced by an industrial machine at room temperature and relatively low pressures.

Today, most hydrogen for vehicles has to be stored in high-pressure cylinders.  Transporting the gas is fraught with problems (if not dangers) and thus is costly.  Fraunhofer sees a change coming, however.  “Gasoline and diesel engines, which are powered by fossil fuels, will soon be sidelined by climate change. Instead, new propulsion systems will be required. One fuel with a big potential is hydrogen. Hydrogen vehicles are equipped with a reinforced tank that is fueled at a pressure of 700 bar (10152.6 pounds per square inch). This tank feeds a fuel cell, which converts the hydrogen into electricity. This in turn drives an electric motor to propel the vehicle.”

Obviously, anything stored at 700 times atmospheric pressure is an explosive threat in itself without adding the flammable nature of hydrogen.

Fraunhofer offers a different new way to avoid those hazards, while offering energy and power densities several times those of lithium batteries.

Powerpaste – Just Add Water

A Fraunhofer press release promotes the stuff.  “’POWERPASTE stores hydrogen in a chemical form at room temperature and atmospheric pressure to be then released on demand,’ explains Dr. Marcus Vogt, research associate at Fraunhofer IFAM. And given that POWERPASTE only begins to decompose at temperatures of around 250 °C, it remains safe even when an e-scooter stands in the baking sun for hours. Moreover, refueling is extremely simple. Instead of heading to the filling station, riders merely have to replace an empty cartridge with a new one and then refill a tank with mains water. This can be done either at home or underway.”

Power Paste, which includes magnesium hydride, reacts with water to form hydrogen gas

This blog examined the idea of cartridge storage and replacement as early as 2012.  A Hawaiian operation that offered scooter rentals with H2 tank swaps at their stopping points is apparently no longer in business, but similar operations in Taiwan are growing.  Taiwan is small enough that scooter company Gogoro has hundreds of battery swap stations all over the island, negating range anxiety.  Perhaps H2 swaps could work as well, with some makers looking at that option.


Could Powerpaste follow the Gogoro model?

Fraunhofer’s video includes a wealth of information on manufacturing the material, distributing it, and using it.

Most promising, Powerpaste promises energy density equal to or greater than that of gasoline.  This would enable long-distance trips without range anxiety or the need to find charging stations.  Fraunhofer explains the energy density would allow higher ranges than compressed H2.

Fraunhofer notes there are not hydrogen stations in all locations, even in a small country like Germany with its 100 hydrogen stations currently.  Because the paste can be pumped without a high-pressure, lock-nozzle arrangement, a fueling site could have a simple drum of Powerpaste with a hand pump to serve scooter or motorcycle customers.  This could be expanded to more complex storage and pumping outlets as demand grew.

Fraunhofer claims Powerpaste outdoes even gasoline for energy and power densities

A Powerpaste pumping system would cost perhaps, “…Several tens of thousands of euros. By way of comparison, a filling station to pump hydrogen at high pressure currently costs between one and two million euros for each fuel pump. POWERPASTE is also cheap to transport, since no costly high-pressure tanks are involved nor the use of extremely cold liquid hydrogen.”

Alternately, Powerpaste could be delivered in ready-to-use, swappable containers like the battery packs Gogoro employs.  A driver could carry a spare, for instance, and trade used containers for new ones at service outlets.

Extending Drone Endurance

Powerpaste would not only make electric scooters and motorcycles long-range vehicles, but could also provide extended endurance for drones.  Important in applications like survey work or medical delivery to remote locations, such fuel-cell powered vehicles could have great impacts on their respective fields.

A First Batch

Now under construction, a production facility at the Fraunhofer Project Center for Energy Storage and Systems ZESS should be operational by the end of the year.  Somewhat disappointingly, it’s scheduled to produce only four tons of Powerpaste per year.  Depending on public acceptance, let’s hope for success and expanded production soon after that.  Planes, trains and automobiles could grow the market enormously.


Airflow Moves toward Full Scale eCSTOL, AI

Airflow, a recent entry into the electric conventional short takeoff and landing (eCSTOL) market, is pushing forward into fielding a full-scale demonstrator.  They are also testing the limits of Artificial Intelligence (AI) in nailing their landings.

Airflow’s mission is spelled out in big ideas and bold fonts.

“Freight without the wait. 

The first electric Short Take Off and Landing (eSTOL) aircraft for middle-mile logistics. 

1 pilot, 500 lbs of cargo, 0 lbs of CO2.”

Airflow’s concept illustrations show a twin-boom pusher with 10 distributed electric motors along the wing’s leading edge.  Trying out their ideas for extremely short takeoffs and landings will fall to a modified Cessna 210.  In the meantime, the team is advancing its concept at this time with a model Cessna 150 and showing some success at nailing their landings.  Airflow calls its pilot assistance program, “Virtual Tailhook,” and it seems to serve that purpose in making landings possible in a tight space.

Videos show the progress being made with their model 150, and the firm’s press release explains their full-scale ambitions.

“For the last year, Airflow has been utilizing a sub-scale model for test flights that have helped develop eSTOL flight control technology. The next phase will transform a Cessna 210 into an eSTOL with Distributed Electric Propulsion (DEP). DEP enables operations into and out of very short runways by providing more control at slower airspeeds.”

In one week, Artificial Intelligence enabled tighter landings within a prescribed area,  Dispersion dropped from 41 feet to 21 feet

Peter Kalogiannis, co-founder and CTO of Airflow, explains shortcuts taken to expedite testing of power and control systems.  “Selecting the Cessna 210 saves us the effort to design and build the pieces that already work, such as the cockpit, fuselage, landing gear, etc. We’ll concentrate on changing the rest to make it an eSTOL aircraft. This aircraft represents the first step towards bringing to market aircraft designed for sustainability and reducing carbon emissions.”

Seeing a Different Landscape

eVTOL and eCSTOL flyers (human or automated) will see a similar visual, but very different operational landscape.  Rooftops and open areas that allow vertical liftoffs and landings will be able to accommodate craft that can land within the same types of space constraints.  Although eCSTOL flight may require sites with longer approach corridors, the same general landing areas will suit both vertical and conventional operations.

Even helicopters and eVTOLs use angled approach and departure paths to save power, increase range

Surprisingly, approach angles seem to favor eCSTOL aircraft and allow their use in a possibly wider selection of “airports.”

New Partners

Having pulled members from Airbus, Eclipse Aviation, Northrop Grumman, Uber Elevate, Airware, and Scaled Composites, Airflow has an awareness of the strengths and weaknesses of a variety of flight technologies.  This may have helped inform their decision to partner with VerdeGo Aero, an aerospace electric powertrain technology company. They are teaming up to explore using the VerdeGo Aero hybrid-electric powertrain system in the Airflow eSTOL (electric short takeoff and landing) aircraft.

VerdeGo Jet-A hybrid system combines a 180 kilowatt generator with a high-power battery pack that reduces emissions. Airflow Photo

VerdeGo Aero’s diesel (Jet-A) hybrid system combines a 180 kilowatt generator with a high-power battery pack that reduces emissions and fuel burn by 35 per cent compared to conventional turbine powertrains. Integrating VerdeGo’s hybrid-electric powertrain to the eSTOL platform enhances the aircraft’s mission capabilities by extending range to four to ten times that of a battery-electric system.

Marc Ausman, Airflow CEO, explained, “Our ability to rapidly move cargo from a warehouse directly to another warehouse helps e-commerce companies centralize inventory and reduce carrying costs. These capabilities are made possible by continued strategic partnerships like VerdeGo Aero.”

Eric Bartsch, CEO and co-founder of VerdeGo Aero confirmed. “VerdeGo Aero is excited to be applying its hybrid-electric powertrain systems for the Airflow eSTOL aircraft. VerdeGo’s hybrid powertrain will enable the Airflow eSTOL to play a significant role in cargo and logistics missions around the world.”


Work Begins on Production eFlyer 2

For the last year or so, Bye Aerospace has grown a burgeoning order book, with over 700 aircraft on call, but only one or two real-world examples flying.  That’s changing now, with a new motor from Safran and Composites Universal Group (CUG) assembling an actual production eFlyer 2 fuselage.

Parts of the video may seem like comparing apples and bananas, or even cumquats, with aircraft of different missions and levels of development (the Airbus eFan having left the building years ago), but several points of interest remain.  Where are 92 kilowatt-hours of battery hiding in the 662 kilogram – 1,459 pound airframe (empty weight)?  That’s equivalent to the energy of an early Tesla S and probably a significant chunk of the total aircraft weight.

A New Motor

Bye has been busy formulating the design of is two- and four-seat aircraft, dropping its original plan to bedeck its wings with solar panels, and running though a gamut of available power plants.  Originally finding Siemens motors to be a viable choice, the team underwent a branding change when Rolls-Royce bought out the Siemens aero-motor line.  This did not require changing anything other than the decals on the nose of Bye’s aircraft.  Now, however, a major change involves some actual re-engineering.

Bye Aerospace and Safran Electrical & Power have signed a Cooperation Agreement to equip eFlyer 2 and eFlyer 4 aircraft with ENGINeUSTM (ingenious, no?) electric smart motors.  Emissions and cost benefits are almost a given for electric propulsion.

Safran’s  ENGINeUS TM 100 product line will power the eFlyers.  The motors feature air cooling (with liquid cooling as an option), an integrated motor/controller configuration, and a structural design that withstands all propeller shaft loads.  All motors seem to be based on modular components and manufacturing techniques that enable high levels of automation, including automatic winding (presumable for coils and other wire-wound components).

George E. Bye, CEO of Bye Aerospace, explains, “Bye Aerospace has concluded that Safran’s ENGINeUS TM 100 smart electric motor is the optimal production solution to meet the requirements of our rigorous FAA and European Aviation Safety Agency (EASA) certification schedules for eFlyer 2 and eFlyer 4.  Our list of future eFlyer purchase agreements, currently at 711 units, continues to grow, and we must continue forward at a high-tempo pace to meet the demands of aviation enthusiasts worldwide who have been waiting years for all-electric airplanes to come to market.”

An Airframe on Which to Hang a Motor

Bye has chosen, “Composites Universal Group (CUG) to begin assembly of the production eFlyer 2 fuselage, the first major component being assembled.”  Serial number 001 will proceed even while FAA Part 23 certification for the eFlyer 2 goes forward.

Bye explained, “We continue to make advances in the certification process,” “These activities commence production of the first conforming eFlyer 2, the first of three planned conforming eFlyer 2 aircraft that will be used to help complete final FAA certification.  We look forward to working with Steve Ruege and the team at CUG.”

Steve Ruege, CEO of CUG, added, “Composites Universal Group is extremely proud to have been selected by George and the team at Bye Aerospace to begin tooling and construction for the all-carbon fiber fuselage for Serial #001 of the eFlyer 2 aircraft.  We all feel here at CUG that Bye Aerospace has absolutely hit a home run with this next-generation all-electric aircraft design.  We are very excited about working collaboratively with the Bye Aerospace team to achieve FAA certification and commencing production.”

CUG’s ability to manage large objects is evidenced by its Space X command module

CUG is no latecomer to the party, having been in operation since 1994 and having partnered with Airbus’ A3 on its Vahana test vehicle, for example.  They build composite components for wind turbines, have a contract to make 34-foot long carbon-fiber seaplane floats for Kenmore Aviation, and have provided components for the Navy’s autonomous Anti-Submarine Warfare (ASW) ship, Sea Hunter.

Their facilities include a 45-foot long oven that can heat multiple small parts or very long large ones.  A large paint booth matches that capability, and they are soon to have an equally large autoclave.  They have an array of high-tech measuring equipment to ensure quality fit and finish for their products.  With their facilities only 28 miles from his home, your editor is looking forward to a visit when COVID clears up.

With new power and skilled manufacturing available, Bye Aerospace can look forward to getting those 711 airplanes to eager customers.  Bye’s statement of their hopes says a great deal about the benefits for all of us.  “All of Bye Aerospace’s current and future families of aircraft feature exemplary engineering, research, and electric aircraft solutions producing no CO2 and are designed to answer compelling market needs. These needs include five-fold lower operating costs, no CO2 emissions, and decreased noise. Bye Aerospace estimates the eFlyer will eliminate the release of millions of metric tons of CO2 each year for flight training alone.”


Happy Velis Electro News from Pipistrel

Taja Boscarol, Public Relations Manager for Pipistel Vertical Solutions, and Michael Coates, Master Distributor for USA, Australia & New Zealand, shared a lot of happy news this week about their Velis Electro.

Electric Outsells Gasoline Powered

Michael puts his news in enthusiastic, all-caps context.  “The US has a new president, Europe is under siege from new Covid varieties, and Pipistrel is adding a SECOND SHIFT TO KEEP UP WITH PRODUCTION!

“Did you know that in 2020 Pipistrel DELIVERED 111 (one-hundred and eleven) of the certified Pipistrel Velis electric aircraft, as well as many more Pipistrel ALPHA Electro aircraft?  In fact, this year for the first time ever, Pipistrel produced more electric aircraft than gasoline powered!”

Pipistrel’s Velis Electro is becoming a popular trainer, especially where quiet operation is a must

More than 70 Pipistrel Velis aircraft are already on 2021’s order books, with many more anticipated through the remaining 11 months of the year.

The second shift essentially means doubling production, and this of course leads to increased demand from suppliers.  Michael adds, “Pipistrel is cooperating with dozens of OEM manufacturers, implementing Pipistrel electric propulsion into their fleets.

“The future really looks good for electric aircraft and the Pipistrel Velis, which is going from strength to strength in both sales and use.”

Mechanics Need Training

Taja Boscarol has two related news items.  With many electric aircraft coming into play, it’s only natural that there will be a big need for newly-trained mechanics for the new technology.  Taja announces, “We are happy to let you know that Pipistrel organized a maintenance type-training course for Pipistrel Velis Electro, for Part-66 licensed aircraft mechanics.”  (Part 66 is the European Aviation Safety Agency’s set of regulations for aircraft mechanics.)

First-time mechanics might have a hard time convincing themselves that IS the motor

This is an historical first, training mechanics for the maintenance of a certified electrically-powered airplane, the Pipistrel Velis Electro.  Pipistrel can thus train “other organizations’ “Part-66 licensed aircraft mechanics for the purpose of maintenance and repair of our Velis Electro (which is at the moment the only certified fully electric aircraft in the world).”

The five-day course had an enthusiastic reception on its first outing, was repeated, and is now going to be repeated for interested parties.

Taja concludes, “Organizing a training course of this kind is a great achievement and honour for Pipistrel. The road to this point was very long and required cooperation of many individuals and institutions, especially the European Union Aviation Safety Agency and the Slovenian Civil Aviation Agency, who stood by our side during the entire process and gave us their help and support.

“Apart from the two organizations, a great credit also goes to the entire teams of the two companies: Pipistrel Aircraft d.o.o., which is the holder of the authorization, and Pipistrel Vertical Solution, which participated in the entire phase of preparation of manual and training program. The teams showed diligent internal cooperation on every step of the process and contributed to the joint success of the project.”

50 Electric Aircraft for Lease

Taja’s next announcement is straightforward and concise.  “We are happy to announce that in order to accelerate the transition of the aviation to sustainable, zero-emission kind and to enable flight schools and clubs to use electric aircraft without a large initial investment, the French organization Green Aerolease, subsidiary of the W3 group, Pipistrel Aircraft company from Slovenia and with the support of the French Federation of Aeronautics, formed a partnership to offer the first 50 Pipistrel Velis Electro aircraft for rent to French aeroclubs and flight schools, from this season onward.”

Ivo Boscarol, Founder and CEO of Pipistrel Aircraft,adds, “I am delighted to see the confidence given to us by Green Aerolease who decided to commit with us to participate in the reduction of the environmental impact of the aeronautical sector.

Green Aerolease can find the use of electric aircraft rewarding.  Europe has over 100 small airports with “severe flight restrictions,” or where flight patterns don’t allow training circuits because of noise.  Pipistrel’s Velis Electro emits only 60 dB of noise, making it welcome at many otherwise touchy venues.  The 50 Velis Elctros headed for France will bring many operations back from the brink, and expansion to 200 trainers in the next three years will encourage further operations in other EU countries.

Charles Cabillic, Founder of W3 and Green Aerolease, said: “We are particularly proud to make this partnership with Pipistrel Aircraft, pioneer of breakthrough innovation in the light aviation sector.”  Velis Electros have demonstrated over 200 hours of reliable service, and enabled next steps into a future of “green aviation.”

“I am convinced that the aeronautical sector has a great future, with the progressive arrival within two to three years, of light electric or hybrid aircraft designed for business travel or leisure aviation, because it will permit to revive the French aviation.”  Let’s hope we can celebrate the same spirit in America soon.


Michael Friend’s Spark Solo

“The Quest for a Truly Practical Electric Touring Motor-Glider”

Mike Friend is not your typical retired aircraft executive.  As Technical Director for Boeing, he oversaw “the first manned fixed wing aircraft powered by a hydrogen fuel cell/lithium ion battery powerplant that first flew back in 2008.”  He’s been associated with green energy projects since then, including work on the Boeing-supported Zunum project, a set of 10- to 50-passenger electric hybrid airliners.  On the personal front, he hopes to design and build the Spark Solo, a single-seat electric motorglider that will enable cross-country flights from his home base of Bremerton (Washington) Regional Airport.

Spark Solo in rendering by Shawn Cvetezar depicting a good soaring day

Working with Gabriel DeVault

Motorgliders make a good combination with battery power.  Their clean lines enable using low power at cruise, and as this video from Gabriel DeVault shows, even a respectable takeoff and climb with power limited to 25 kilowatts (33.5 horsepower) in this instance.

Normally, DeVault’s Sonex would make full use of its Zero Motorcycle motor’s full 52 kilowatts (69.7 horsepower), but this self-limited output puts into perspective the importance a long wingspan’s low span loading.  Being able to fly safely in “econo-mode” would allow longer flights by limiting the battery drain during takeoff.

Shawn Cvetezar rendering shows general layout of motor, batteries. Spark Solo upholds Mike’s support of Stelio Frati’s dictum about beautiful airplanes

Mike was lucky enough to meet Gabriel on one of his outings, and that might have led to his choosing a Zero Motorcycle motor for his projected bird.  Financial considerations play a part, too, with Pipistrel’s 40 kilowatt package, batteries and all, totaling $27,000.  Wrecked Zero Motorcycles can be found for $9,000 or less, giving a prospective builder motor, controller, batteries and even cabling and instrumentation.  The only extra needed is a propeller speed reducer, a simple item designed by Mark Beirele for his Zero-powered eGull.

The Airplane’s Design

 Mike is a self-admitted “fan” of “touring motor-gliders,” machines capable of self-launching and as implied – touring to distant places.  He particularly likes the Schleicher ASK-14, a German craft that used the wings and tail surfaces from the popular KA-6 sailplane.  It used a raspy little four-cylinder Hirth two-stroke engine, which thankfully went silent in soaring mode.  The engine didn’t have an electric starter, so the pilot had to yank on a pull-cord if he or she wanted to relight the motive power.  Two-strokes being what they are, the engine sometimes balked, and forced a landing.  That is what makes electric motors so ideal for self-launching sailplanes or touring motor gliders.  They rarely refuse to go when requested.

Mike has a set of requirements for the craft.  They start with having enough space inside to accommodate a 6-foot, 2-inch person like Mike.  It should allow single-person operation – enabling rigging and de-rigging, and all operations by the owner/operator alone.  One of the off-putting aspects of sailplane operation is the large crew required to assemble, launch and retrieve an airplane.  This would allow flights when the owner desired with no need to coordinate with others.

Practicality reigns in most respects for the Spark Solo.  It can be kept in a standard hangar and operated from a 1,500-foot grass strip.  It will meet FAA glider requirements for maximum weight/wing span squared of less than 3.0 Kg per meter squared, (0.62 pounds per foot squared).  Spark Solo will be registered as an FAA Experimental Amateur-built Glider – Self Launching.

The light wing and span loading will enable an initial rate of climb of at least 1,000 feet per minute, and the electric motor will produce quiet operation.

Base Spark Solo uses Pipistrel wings, tail, Zero motor, controller and batteries. Proposed flight would require recharging at KORS

Mike is adamant that, “The appearance of the aircraft shall comply with the dictates of my hero, Italian aircraft designer Stelio Frati who is rumored to have said – ‘There is no use for an ugly aircraft when a few minutes of thought will produce a beautiful one.’”

Mike is using the wings and tail section from a Pipistrel Sinus Flex, but it would seem that many other standard-class size flight surfaces would work, although they would take different approaches for their assembly into a completed airframe.  Wings and Wheels has on-line classifieds for used gliders and parts.

Economy of Operation

 Time and money are often conflated, and a small airplane can save time at a usually high cost.  Electric aviation may help with that equation, however.  The shortest car trip from Bremerton to Orcas Island, according to Google Maps, runs 118 miles on the most direct route and requires passage over one toll road and a ferry trip.  The fastest automotive passage runs 167 miles, runs north on I-5, and still has toll roads and a ferry trip.  Either takes about four hours.  On the Anacortes to Orcas Island ferry, fees run from $14.50 for a single adult to $34.50 for a compact car and driver and $44.50 for a vehicle under 22 feet and its driver.

Alternative configuration would employ e-Genius approach, probably require different motor from base configuration

Considering an average of $3.00 per gallon for automotive gas, and an average of 25 miles per gallon, a car would use a little over $28 worth of gasoline for the shorter trip and just over $40 for the longer route.  It’s impossible to avoid a ferry trip to the island, for a another $69 for the round trip.  Even Mike’s Aeronca Champion, average 5 gallons an hour, would take about an hour to make the trip and a round trip would consume about $55 in avgas.  In the Spark Solo, with electricity costing about 9 cents per kilowatt hour in Washington (among the lowest rates in the world), the trip would cost around $3.14 for the round trip.

A more shocking comparison comes from looking at charter aircraft rates for the 73 mile trip from KPWT to KORS.  The trip for a single passenger in a chartered Cessna 172 is $1,264.  The price for “premium air charter” in a Cirrus SR22 climbs to $3,828!

See the chart below for Mike’s calculations based on energy usage for this clean single-seater.

Spark Solo Energy Usage – KPWT to KORS and return
Mission Phase Power  Duration Energy Used This Segment Total Mission Energy
(kW) (Hours) (kW-hrs) (kW-hrs)
Taxi from hangar to end of runway at KPWT 5 0.1 0.5 0.05
Takeoff and climb to 500 feet 40 0.017 0.68 0.73
Climb from 500 feet to 2000 feet 30 0.25 7.5 8.23
Cruise at 70 Knots – 73 Nautical miles 8 1.04 8.32 16.55
Descent and Landing 1 0.15 0.15 16.7
Taxi to parking at KORS 5 0.1 0.5 17.2
Taxi from parking to runway at KORS 5 0.1 0.5 17.7
Takeoff and climb to 500 feet 40 0.017 0.68 18.38
Climb from 500 feet to 2000 feet 30 0.25 7.5 25.88
Cruise at 70 Knots – 73 Nautical miles 8 1.04 8.32 34.2
Descent and Landing 1 0.15 0.15 34.35
Taxi to parking at KPWT 5 0.1 0.5 34.85
NOTE: cruise power based on scaled Pipistrel Taurus data, maximum takeoff power limited to 1 mile

Mike is currently working on articles about this promising aircraft.  For the time being, we can see that a well-designed motor-glider can promise grand adventures and reasonable operating costs.


Stemme Goes Electric with its New Elfin

Reiner Stemme designed his namesake sailplane 30 years ago and the overall design and his new Elfin retains the original pop-out nose cone, folding propeller configuration.  The 50:1 glide ratio means this 20-meter (75-foot) span motorglider offers less than 40 pounds of drag at its maximum takeoff weight 0f 1984 pounds.  That is a significant benefit for the new electrically-powered version – which can fly further and save its batteries for retrieval and go-arounds.

In its latest iteration, the Stemme configuration is a totally new airframe being built by a totally new company, Reiner Stemme Aero GmbH.  As explained on the new firm’s web site, “The Elfin design is a complete new development and [is] not base[d] upon the existing S10. GmbH, the present company of Dr. Reiner Stemme, is not connected to STEMME AG.”

A High-Flying Heritage

Earlier Stemme designs have accomplished much in the way of efficient, high-performance flight.  In 2014, Klauss Ohlman accomplished one trans-continental trip from Europe to Asia, followed by the surmounting of Mount Everest in an SV-10T.

That accomplishment is recounted even in the new company’s web site. “A highlight in its history was the successful mission “On Top of the World” in the Himalaya region using an underwing 3D camera system from DLR. We have the ambitious objective to continue this story in a new generation of planes; therein we rely on radical innovations. We cooperate with German research institutes and the industry – so we can best incorporate today’s knowledge in this project.”

New Name, New Propulsion

The REINER STEMME elfin 20.e name represents the 20-meter (75-foot) wing and its electric (e) power system.  A further refinement, the “ex,” has a range extender that will allow flights up to six hours and 1,000 kilometers (540 miles) under power.

Elfin’s battery system, with 21 kilowatt-hours nominal value can provide a flight profile that uses four kWh for three minutes of taxiing and a take-off and climb to 500 meters (1,600 feet).  It could then, on the same charge, fly level for an hour at 130 kilometers per hour (70 knots or 80.5 mph) on another 12 kWh.  70 knots is Elfin’s best glide ratio.  A climb to 3,000 meters (10,000 feet) would require 16 kWh.

Nose-mounted Siemens motor simplifies power train of gas-powered Stemmes, eliminating propeller shaft that ran through cockpit

The liquid-cooled Siemens motor can produce 72 kW peak (96.5 hp) and 55 kW continuous (73.75 hp).  Two 60-kilogram (132-pound) 600 Volt battery packs of three modules each sit behind the cockpit.  Stemme expects 1,000 full cycles from the packs, which can be replaced at a cost of 18,000 euros ($21,700).  With at least 1,000 hours of flight from each cycle, and more in soaring mode, cost of operations would be under $20.00 per hour.

Elfin range extender allows up to 1,000 kilometer flights under power

For those wanting a longer mission profile, the Elfin can be fitted with an auxiliary range extender. The 60 kilogram (132 pound) under-wing mounted internal combustion engine and generator setup can deliver 30-35 kW continuously.  At a normal cruise of 185 km/hr (100 knots or 115 mph) at 10,000 feet, the Elfin can carry its two passengers 1,000 kilometers, or 540 nautical miles – roughly six hours endurance.  Fuel is carried in the center wing and the pod carrying the engine/generator can be mounted or demounted by a single person with a “rigging aid.”  In operation, a single on/off switch enables or disables the range extender.

Comfort and Safety

Pilot and passenger share a wide side-by-side cockpit in front of the wing.  A centrally-mounted instrument cluster and single-lever power control makes operation simple.  A directly-coupled Siemens motor in the fuselage nose turns the folding propeller which neatly tucks in behind a retractable nose cone.  (Current versions use a manual extension/retraction handle, but Stemme says the electric version has automatic operation.)  Your editor has been astounded at how easily the small-diameter prop pulls a large Stemme into the air.

Reiner Stemme has designed a “specific wing airfoil 20e-143 without premature lift plateau, seamlessly optimized over the entire wing span.”  Their long center section, fixed to the fuselage, avoids the problem of separate wings which plug in and have to be taped along their chord to avoid extra drag.  What the company describes as an “ambitious wing-to-fuselage-intersection design with fillets for drag reduction” is meant to overcome at least some of the drag from aerodynamic interference between joining components.  Outer wing sections pivot and allow the large craft to be stored in a conventional hangar.

If all were to go wrong (an unlikely event) the Elfin can be lowered safely be a whole-airplane ballistic parachute.  As an indication that authorities are betting that won’t happen, Elfin can be certified under EASA (European Aviation Safety Administration) or FAA equivalent rules.

We look forward to seeing this latest example of Reiner Stemme’s creativity in the air soon.


Archer Aviation Gets Fiat Chrysler Backing

Another eVTOL?  Among the many battery- and solar-powered entries at this year’s (virtual) Consumer Electronics Show, Archer Aviation has entered the electric Vertical Takeoff and Landing (EVTOL) market with Fiat Chrysler backing.  It’s being discreet about it, however, and reveals little detail.

The company willingly shares its mission statement, though.  “To fix traffic and create a fully renewable transportation solution, we’re designing, manufacturing, and operating advanced electric aircraft that can travel 60 miles at 150 mph, all with today’s technology.”

They present only one picture of their design, a head-on shot on a black backdrop.  We can see the six large rotors blanketing the leading edge of the wing, but wonder how and where the six vertical lift rotors are hiding.

Most used image gives “glamor shot” approach used in high-end car ads, but provides little detail

eVTOL Insights provides more information on the planned craft’s specifications:

  • Aircraft type: eVTOL
  • Piloting: Will be piloted in the beginning and will have autonomous capability in the future
  • Capacity: 4
  • Cruise speed: 150 mph (241 km/h)
  • Range: 60 miles (nearly 100 km)
  • Propellers: 12
  • Maximum takeoff weight: 7,000 lbs (3,175 kg)
  • Windows: Panoramic window spectacular views
  • Wing: High wing
  • Tail: V-tail
  • Safety features: Distributed Electric Propulsion (DEP), provides safety through redundancy for its passengers and/or cargo. DEP means having multiple propellers and motors on the aircraft so if one or more motors or propellers fail, the other working motors and propellers can safely land the aircraft. In addition, the company is increasing the safety of their aircraft by eliminating critical parts, increasing component reliability and designing safe aerial batteries.

(Archer’s wording on “eliminating critical parts” might be reconsidered.  Do they mean eliminating unnecessary parts?)

Graphic explains expected performance with math overlay

Big Money Backing

Fiat Chrysler America (FCA) has announced it is investing in Archer.  The partnership should allow Archer to press forward with its plans to have an 80-percent scale test vehicle flying in 2021. reports, “In a January 12 announcement, FCA, which makes Chrysler, Dodge, Jeep, and Ram vehicles, did not say whether it will actually manufacture Archer’s aircraft. ‘Archer will benefit from FCA’s low-cost supply chain and advanced composite material capability, and design and engineering expertise,”

“A spokesman for Archer told AIN. ‘We have already tapped into FCA’s extensive design expertise, collaborating with the company on elements of the cockpit design of our first full-scale aircraft.’

Benefitting from expertise of Airbus’s A3 Vahana program engineers and designers, co-founders and co-CEOs Brett Adcock and Adam Goldstein have been accused of “poaching” other talent in the area.  The former “headhunters,” having come from the financial talent recruiting firm they built and sold, know how to attract skilled employees.  According to Forbes, the pair, “Have lured dozens of top engineers away from electric air taxi startups like Joby and Boeing-backed Wisk with rich compensation packages that include signing bonuses of two to three times annual salary and talk of connections to deep-pocketed investors.”

One with particularly deep pockets sees a future in the company.  Marc Lore, Walmart’s e-commerce chief and founder of, has apparently invested a substantial but undisclosed amount.  (Emulating much of the rest of the program.)

Coming: A Possible Name Change

Piper Aircraft’s Archer has been around since 1976, giving it seniority in the flying world.  It’s understandable then that Piper would sue this new, upstart company for infringing on its federally-registered trademark name.  AIN reports, “In a case filed in the U.S. District Court in Delaware, where California-based Archer was incorporated, Piper alleges that the use of the name for the four-seat, fixed-wing eVTOL infringes its federally-registered trademark and also its legal rights in the state of Florida, where the longstanding general aviation manufacturer is headquartered.”

Archer has yet to name its eVTOL craft, and we hope this kerfuffle over naming rights abates in time for the first flight later this year.