That may sound like a silly question, but thin-film solar cells are pushing the boundaries of lightness and efficiency that will make them viable candidates for use on aircraft.  Looking back at earlier achievements demonstrates the great things that can be done with limited resources.  Eric Raymond, for instance, made a solar-powered flight across the United States in 1990 on amorphous solar cells that were only about two percent efficient.

His Sunseeker Duo, which he flies around Italy and Switzerland with Irena, his wife and co-builder, has modern thin-film cells that are 23-percent efficient – a ten-fold gain.  Before that, the earliest two solar-powered flights were charged by big, round solar cells, not terribly efficient and lacking full coverage of a wing because of the gaps between cells.  Fred To in England and Larry Mauro in America did what they could with these disadvantages and managed successful, but short, flights after hours of charging small on-board batteries (also relatively inefficient).

Fred To with Solar One and co-builder David Williams to right of wing. Note gaps in solar coverage with early circular cells. Plane flew in December, 1978 Photo: courtesy Fred To

An entrepreneurial outing, Konarka tried but failed to bring solar cells that could be made on home ink-jet printers.  They dropped out around 2003, losing the market they had hoped to dominate.  Factory-sized roll-to-roll printing and improved cell design have made thin film solar cells serious contenders with modern solar-powered aircraft.  Now Perovskites (calcium titanium oxide (CaTiO3), could lead to lower-cost thin film cells flexible enough to match an aerodynamic surface.

Now, according to a press release from the University of Toronto, “Post-doctoral researcher Hairen Tan and his colleagues in Professor Ted Sargent’s lab have removed a key barrier to the manufacture of low-cost perovskite solar cells.   Printing solar cells could become “as easy and inexpensive as printing a newspaper.”

Sargent explains, “Economies of scale have greatly reduced the cost of silicon manufacturing.  “Perovskite solar cells can enable us to use techniques already established in the printing industry to produce solar cells at very low cost. Potentially, perovskites and silicon cells can be married to improve efficiency further, but only with advances in low-temperature processes.”

Unlike most commercial solar cells made from crystalline silicon, the Toronto process avoids high temperatures and toxic solvents.  Instead, perovskite solar cells manufacture deposits, “A layer of tiny crystals – each about 1,000 times smaller than the width of a human hair – made of low-cost, light-sensitive materials.”  These can be mixed into a liquid “solar ink” that can be used in a simple inkjet process.

The video below shows where perovskite cells fall in efficiency, especially compared to the far more costly and complex triple-junction models.

Why have others missed the opportunity to include low-cost perovskites in their solar mix?  Something called an electron-selective layer, or ESL, that allows extraction of electrons from crystals so they can flow through a circuit, has held up progress.  High-temperature processing of an ESL-ready powder requires baking at 500 degrees Celsius (932 degrees Fahrenheit).  Tan points out, “You can’t put that on top of a sheet of flexible plastic or on a fully fabricated silicon cell — it will just melt”

The Toronto team grows an ESL made of nanoparticles in solution and deposits that directly on the electrode at temperatures below 150 degrees C (302 degrees F), “much lower than the melting point of many plastics.”  A layer of chlorine atoms helps bind the perovskite and ESL layers.  The resulting film has achieved an efficiency of 20.1 percent.  Their findings are published in the February 2, 2017 issue of Science.

Tan notes that “This is the best ever reported for low-temperature processing techniques,” adding that perovskite solar cells using the older, high-temperature method are only marginally better at 22.1 per cent, and even the best silicon solar cells can only reach 26.3 per cent.  Even better, the new cells are stable, retaining more than 90 percent of their efficiency after 500 hours of use, something not necessarily true for older perovskite technologies.

The new perovskite solar cells have achieved an efficiency of 20.1 per cent and can be manufactured at low temperatures, which reduces the cost and expands the number of possible applications. Photo: Kevin Soobrian

Professor Luping Yu of the University of Chicago’s Department of Chemistry thinks low-temperature processing is necessary to obtain ‘the best silicon solar cells.”  An expert on solution processing of solar cells, he was not involved in the Toronto research.  This cool approach promises other applications for perovskite solar cells, ranging from “smartphone covers that provide charging capabilities to solar-active tinted windows that offset building energy use.”

The processing technology might allow development of hybrid perovskite/silicon solar cells.  “With our low-temperature process, we could coat our perovskite cells directly on top of silicon without damaging the underlying material. If a hybrid perovskite-silicon cell can push the efficiency up to 30 per cent or higher, it makes solar power a much better economic proposition.”

A future for such materials might include the ability to print efficient solar cells on home devices.  Aircraft homebuilding might take on an even grander level when folks start crafting their own solar-powered wings.


PAL-V Goes on Sale in America

Pal-V is a “flying car” that looks more like a flying motorcycle.  Its three wheels would make it so in many countries.  It flies as a gyrocopter, maintaining a sporty approach to its transition from ground to air.  One reader has suggested dropping the term, “flying car,” even though it has captured reporters’ (and America’s) imaginations for the last hundred years.

Dutch Treat?

The Dutch creation, under development for close to a decade, looks like a plausible contender for an all-purpose transportation device.  Its compact dimensions mimic a car on the ground, and its clever unfolding to become a gyrocopter allows quick and apparently easy transition from one mode to another.  The company calls the total experience, “FlyDriving.”

In “car” mode, its rear suspension geometry allows leaning into the corners with “Dynamic Curve Stabilizer” control, very much like a motorcycle.  The closed two-seat cabin is considerably less raucous, though, than open-air motorcycling.  In aircraft mode, its 87 mph cruising speed is not significantly different from a 1940’s Taylorcraft or Cub, but that’s good enough to overcome gridlock

World-wide, driving is becoming a frustrating series of stops and starts that belie the idea of “the open road.”  According to, “This year, according to Transport for London, London cars are driving at an average of just 16.5 miles per hour, falling to 7.4 miles per hour in the city core.”  This equals the speed of horse-drawn traffic in 1895 London.  EcoWatch cites Scientific American’s Tali Trigg that biking beats driving in many major American cities.  Austin, Texas commuters can expect to hit 6 mph in rush hour, and Los Angeles drivers might see 8 mph.  New Delhi, India seems to have a record, with traffic more congealed than flowing at 3.1 mph – average walking speed.  87 mph will really seem like flying.

Your Time has to be Worth It

The PAL-V Liberty Edition has a base price tag of $399,000 without options.  Those wanting greater exclusivity (in case a neighbor also buys one) can purchase the Pioneer Edition at $599,000, “”Including a unique interior and exterior finishing. It has a level of personalization reserved for Pioneer Edition owners only.”  For those desiring even greater personalization, extra-cost adders are available as desired.

PAL-V offers its users the opportunity to switch back and forth between ground and aerial use, with transitions taking just minutes.  Molt Taylor had the same functionality in mind in the 1950’s, but his Aerocar required a fairly laborious and time-consuming interval to make the switch.  It also required a trailer (and additional license) to haul the wings and tail cone.  PAL-V is self-contained in either form – a highlight of the cleverness involved.

The company claims the aircraft is stall-proof, and includes, “Our Human Error Proactive Counteraction (HEPC) methodology. With HEPC we addressed most of the human errors known for gyroplanes, and made those errors hard or impossible to make.”

Claiming to be the first commercially available certified “flying car,” PAL-V, “meets all the legal standards of the European Aviation Safety Agency and the Federal Aviation Administration (USA) for flight and the local road standards for driving.”  Delivery included familiarization and early flight training, with follow-up in the customer’s favorite “scenic locations.”

Being first in the certified market will test the waters for others following.  Obviously marketed at the truly upwardly mobile, the PAL-V will be interesting to watch.


Nano twins are not something Robin Williams’ Mork would make friends with.  They are destructive pairings inside alloys, and getting rid of them will apparently lead to cleaner jet flight.  Ohio State University researchers devised a technique they call “Phase Transformation Strengthening” which leads to stronger alloys and less deformation of the final products.

This is good news for jet engine and turbine designers, since an engine that can run hotter will burn its fuel more completely, resulting in a less toxic exhaust.  Nano twins “are microscopic defects that grow inside alloys and weaken them,” according to Ohio State University researchers.  These defects weaken and deform an alloy when it is exposed to heat and pressure – two things present in a jet engine or power turbine.

Michael Mills, professor of materials science and engineering and leader of the project at Ohio State, led the research.  “We found that increasing the concentrations of certain elements in super-alloys inhibits the formation of high-temperature deformation twins, thereby significantly improving the alloys’ high temperature capabilities.”

Starting with two commercially-available superalloys, Mill’s team simulated conditions found in jet engines, and “compressed samples of the alloys with thousands of pounds of pressure at around 1,400 degrees Fahrenheit.”  Turning to the electron microscopes at Ohio State’s Center for Electron Microscopy and Analysis (CEMAS), they had access to, “One of the largest concentrations of electron and ion beam analytical microscopy instruments in any North American institution.”  Examining the two samples under “atomic-level imaging,” researchers found divergent paths related to the elements in the alloys.

In the first alloy, “Atoms of cobalt and chromium filled the fault… weakened the area around the fault, allowed it to thicken and become a nano twin.  In the second, titanium, tantalum and niobium “tended to diffuse into the faults instead.”  This diffusion stabilized the area and resisted the formation of nano twins.  The second allow turned out stronger and more stable than in its original form.

Timothy Smith, a former Ohio State student and lead author of the team’s Nature Communications paper wrote, “’We discovered that when the amount of titanium, tantalum, and niobium in the alloy was increased, while decreasing cobalt and chromium, we could actually strengthen the region around the faults and prevent the fault from widening into a nano twin.”

Such metallurgy should enable future turbines to last longer and be more economical in operation.  Until we come up with sun-powered jumbo jets, this is progress we can all applaud.

A big thank you to Colin Rush for the lead on this story.


Will Dubai Beat Everyone to Jetson World?

What do you give the country that has everything?  Perhaps the world’s first aerial taxi service.

An Excess of Riches

Dubai is a fabulously rich country, with an air conditioned beach, the world’s largest shopping mall and an indoor ski center complete with a good base and a layer of powder.  Disappointingly, it’s only the third largest indoor skiing area in the world.  The largest is in the Netherlands, with the second largest in Germany.  At least those countries don’t have to overcome the desert’s heat to drop the temperature below freezing.

Visitors to Dubai can be excused for wanting to commute between these tourist attractions in an equally extravagant way.  Buzzing down on them in an eHang 184 passenger-carrying drone will ensure a grand entrance.  An Associated Press report says the Dubai officials are already pushing forward on test flights.

“Mattar al-Tayer, the head of Dubai’s Roads & Transportation Agency (RTA), announced plans to have the craft regularly flying at the World Government Summit. Before his remarks on Monday, most treated the four-legged, eight-propeller craft as just another curiosity at an event that views itself as a desert Davos.

“’This is not only a model,’ al-Tayer said. ‘We have actually experimented with this vehicle flying in Dubai’s skies.’”

Enthusiasm vs. Dubiety

Enthusiasm seems high, with publications such as Conde’ Nast Traveler touting the possibility that tourists might hop flights around the Burj Dubai or other popular sites this summer.  Others are less enthusiastic, exhibiting touches of dubiety about Dubai’s aerial adventures. takes the promise that Dubai will be lofting these pods skyward by July seriously.

Wired showed its skeptical side last year, doubting the eHang 184 would get past the testing stage.  “Wherever there are rich people with somewhere to go and maybe a little bit of a danger streak, EHang will be there. Maybe.”  DroneLife expanded on that skepticism with a late December report noting that although Nevada had granted permission for flight testing in June, no tests have taken place to date.  Ehang co-founder and CMO Derrick Xiong has assured the press that the vehicle seen on display at the Consumer Electronics Show last year was the real deal and not just a stage prop.  This comes despite the loss of 70 workers and apparent financial problems for the Chinese firm.

DroneLife reports, “However, Xiong is reassuring the public that the Ehang 184 has performed over 200 test flights in China, and that the drone has proved its stability and accuracy.  The company continues to develop the drone: improving the propeller, motor, motor driver, and battery.”

With China and Dubai allowing test flights, the Emirate seems to be ready to start passenger service in July.  Engadget reported on the eHang Flight Command Center – or at least the imposing-looking artist’s renditions of the proposed Center.  Engadget adds that the 200 test flights are not enumerated by the number of passenger-carrying flights, or how many were fully autonomous.  In the meantime, the company reports having flown several flights from the Center with the Ghost drone, the small consumer item one might have registered with the FAA.

eHang’s Flight Command Center seems larger than necessary, perhaps indicating future growth

The Center can monitor, “Speeds, altitude, individual propeller power, location, drone camera feed and video feed of the passenger — plus communicate with passengers and schedule air traffic.”  Engadget says they received press photos that show place-holders in place of actual data input on control center screens, indicating not all functions are yet up and running.

Lungs by Air

The Verge, verging on disbelief, reports the possible use of eHangs to fly pig lungs to human patients.  Their subhead, “A wild vision of the future that should be taken with a grain of salt,” shows an editorial slant Derrick Xiong might not appreciate.  The client, Lung Biotechnology, is a subsidiary of United Therapeutics, a multi-billion dollar biopharmaceutical firm.

The firms’ press announcement explains the approach.  “Lung Biotechnology specializes in manufacturing lungs and other organs for transplant using a variety of technologies, including pig-to-human xenotransplantation, as well as regenerating them from stem cells. It plans to station the MOTH (Manufactured Organ Transport Helicopter) rotorcrafts outside of its organ manufacturing facilities, and use preprogrammed flight plans to hospitals and re-charging pads within the MOTH radius so that the manufactured organs can be delivered within their post-production window of viability.”

With a potential patient base of 200,000 people who would die every year without a lung transplant, the approach could save lives and be highly profitable for those making the organs and the deliveries.  Between shuttling wealthy tourists in Dubai and making timely deliveries to hospitals, eHang certainly has incentive to step up its game.


Dale Kramer’s Lazair was one of the most popular ultralights in the 1980s, selling over 1,200 units.  He re-engineered it a decade ago and flew the electrically-powered version in both land and amphibious versions.  Appearances at AirVenture saw him making daily flights over the area.  Your editor was privileged to visit Dale’s home, once owned by Glenn Hammond Curtis in Hammondsport – who also flew his creations from Keuka Lake, one of New York’s Finger Lakes for which the region is named.

Ever an inventive soul, Dale has returned to the drawing board, in his own way answering the question of how to perform vertical takeoffs and landings in a small, light, personal aircraft.  To overcome pilot’s getting cricks in their necks, The VLazair has a constant-frame-of-reference seat.  The seat swings around during takeoffs and landings to keep the pilot upright, avoiding the rear-view mirror technique used in previous such craft from Convair and Lockheed.

VLazair will have a 100-horsepower Rotax engine driving a 15-kilowatt generator, which in turn feeds six Joby JM-1 electric motors – one at each wing and tail tip.  Performance sounds wonderful for the VTOL craft.  Able to fly horizontally at 200 mph, its 15-gallon fuel tank, 25 pounds of batteries and semi-hybrid configuration would allow up to a 600 mile range (or three hours endurance), according to Dale.  Considering others are projecting lower cruise speeds and lesser range, the VLazair would be a game changer.

He’s built 1/32-scale, 3D-printed models and a quarter-scale model to test the viability of the final product.  His calculations show that scaling the model to full size will provide the thrust necessary to lift-off from the owner’s backyard – a long-term dream for all readers of Popular Science or Popular Mechanics.

Pilot remains upright while descending into backyard landing spot – a dream for many since the beginning of flight

His crowdfunding efforts did not bring in sufficient funds to get the project off the ground, but knowing Dale Kramer’s ability to innovate, though, he’s certain to come up with something – and it will be great.


NASA’s Mark Moore Joins Uber

You must really be somebody when Fortune Magazine notices you’re taking a new job.  Mark Moore is indeed somebody, and remarkably self-confident in leaving a 30-year NASA career to sign on to a startup – even if it is run by Uber.  He will be Director of Aviation for the on-demand ride company, tackling the problems inherent in taking such services into the third dimension.

Lockheed XFV-1 Pogo operated much the same as Mark Moore’s Puffin concept, but with unusual attitude for pilot on landing

His decade-long work in electric propulsion for aircraft has led him to conceive of some interesting possibilities for Personal Air Vehicles, a term he engaged early.  His Puffin vertical takeoff and landing vehicle, for instance, seemed to use elements of Lockheed’s XFV-1 Pogo and Aerovironment’s Sky Tote – both tail sitters.  Ben Rich’s book, Skunk Works, details the problems pilots “faced” while trying to land the Pogo on its tail  lying on their backs and looking straight up.

Moore’s design allowed the pilot to take off and land while standing upright, and then transitioning to a prone position for high-speed horizontal flight.  The design went “viral,” garnering huge numbers of “hits” on Facebook, Twitter, and YouTube and numerous articles in the technical and popular press.

While Puffin remains a concept, other Moore projects are being turned into real vehicles, the best known being the X-57 Maxwell, with a string of 14 small, electrically-driven propellers gusting over a high-aspect ratio wing with multiple high-lift flaps to allow both slow and high speeds – while reducing operational costs by as much as 40 percent, according to NASA.  Maxwell uses Joby motors, and some of Joby’s approach to VTOL operation are seen in Uber’s conceptual renderings.

Moore’s Linked In profile helps us understand why he will probably be a good fit for Uber.  “Currently his research efforts include advanced concepts relating to On-Demand Mobility, Personal Air Vehicles, Aerial Robotics, Atmospheric Satellites, and Airborne Wind Turbines.”  That, and his work with power, control and the logistics of operating a viable transportation network will doubtless help Uber in its great leap upward.

His approaches to solving terrestrial gridlock may involve VTOL flight to pads on freeway interchanges and a structure of nodes instead of airports.  This might free valuable real estate and permit true on-demand operations – very much like the ground-bound Uber.

Mark Moore excited public interest through his years with NASA.  We can’t wait to see what comes next with Uber.


Time-to-Climb is a tough record to beat, requiring an airplane with an excess of power, a skilled pilot, and just the right weather.  Your editor was supremely lucky a few years ago to meet Bruce Bohannon, holder of 25 records, including altitude and TTC marks to 20,000, 30,000 and 40,000 feet.  He managed these records in a modified Van’s RV-4 with a Lycoming IO-540 engine pumping out a nitrous-oxide assisted 425 horsepower.  The normal gross weight of an RV-4 is 1,500 pounds, for a power loading of 8.33 pounds per horsepower with a 180-horsepower engine.

Bohannon BO-1 Exxon Tiger set 25 records in its career

Since the RV-4 normally flies with 180 to 200 horsepower, the additional 225 ponies helped Bohannon achieve some big numbers.  His rate of climb to 3,000 meters (9,842 feet) was 4,407 feet per minute, besting the P-51D’s 3,600 feet per minute or the F-8-F Bearcat’s 4,500 feet per minute.

An IO-540 weighs 199 kilograms, or 438 pounds (depending on configuration and accessories.  An O-360 with 200 horsepower weighs 117 kilograms, or 258 pounds.  Bohannon’s airplane would have weighed 180 pounds more than a stock RV-4, depending on fuel load and other variables.  The IO-540 would have been pulling a little less than four pounds per horsepower sky ward.  This background helps us understand the significant achievement Walter Extra and Siemens Motors recently scored.

On November 25, 2016, a Siemens-powered Extra 330LE aerobatic aircraft set a new world record for time to climb.  It reached 3,000 meters in just four minutes and 22 seconds, climbing at 11.5 meters per second or 2,263 feet per minute.  This is the best so far for an electric airplane, beating Chip Yates’ five minutes and 32 seconds in his modified Long-Eze in 2014.  Walter Extra did a great job of designing an airplane worthy of his piloting expertise, and flew it with precision.

Although no video seems to be available for the record flight, YouTube includes this record of the July 4, 2016 test, in which Walter Extra flies his new creation and Dr. Frank Anton of Siemens congratulates him.

Note the 260 kilowatt (motor (348 horsepower) weighing only 50 kilograms, or 110 pounds) pulls an airplane weighing around 1,000 kilograms (2,200 pounds), the powerplant’s lightness compensated by the large battery pack.  This gives the airplane a power-to-weight ratio of 6.32 horsepower per pound – a considerable disadvantage against the best fossil-fuel climber.

Such comparisons will go away in time, probably with the advent of improved batteries.  Several new cells promise two times greater energy density, for instance, which would improve the power-per-pound considerably by cutting battery weight.  Still light but even more powerful motors will come, so the current record set at the Dinslaken Schwarze Heide airfield in Germany, will fall, just as early records in any contest tend to fall.


Intel Drones Back Lady Gaga

Seeing Lady Gaga perform with 300 Intel Drones at this week’s Super Bowl was the highlight of the evening for this editor, who doesn’t share the national passion for watching men in Spandex crunch helmets together.  The Lady does have a way of attracting attention, and this year, Intel helped contribute to the half-time excitement.  The literally over-the-top show didn’t hurt Lady Gaga’s revenues, as noted in this report.

960 percent

Lady Gaga’s digital song sales are up about 960 percent compared to the day before the Super Bowl, according to Nielsen Music. Seems like her Super Bowl halftime show was a hit. [USA Today]

Considering that the company began last May by schmoozing the FAA into permitting 100 drones to fly in a remote desert location – a first mass flight in the United States with such permissions – they have made remarkable speed in staging larger and larger demonstrations in more well-populated areas.  300 drones larked about over the Magic Kingdom in November.  Note, though, that they were positioned above a large lake for this display.

Some critics have scoffed that the Super Bowl flying was done days before the game, and that the pre-recorded segment was inserted into the actual live half-time show.  This was at the FAA’s request, since the large display would need to have been timed meticulously to match the action on the stadium floor (and weather might have played a factor).  Regulators were concerned about the safety of those below and wanted the fewest possible distractions during the recording of Lady Gaga’s rooftop portion of the show.

300 drones provided a red, white and blue backdrop for the singer’s performance of a patriotic medley, finishing with her leap from the Houston Superdome roof.  This was matched to the interior shot of her dropping on two cables and doing a number of flips on the way down to her first landing spot.  The illusion was fairly credible for TV viewers, and set off 13 minutes of frenetic performance by over 1,000 dancers and well-staged performers.

Intel has sent 500 drones into the sky for earlier displays, and the 300 at the Super Bowl were controlled by a single operator, a sign that unmanned aerial systems traffic management may be possible with the programming and logistics skills now available.  Your Amazon package or pizza may be coming to a front-yard landing zone soon.  New Zealand already has demonstrated Domino’s drone delivery, a sure-fire way to increase national obesity levels.

As one might guess, Intel is not the only enterprise interested in mass drone flights.  Syncdrones staged this display in 2012.

Such showy demonstrations make it clear that controlled flight within carefully set parameters will be possible in the near future, using near-term programming.


Your Flying Car is on Its Way – How Soon?

Uber is projecting real-world approaches to personal transport in urban environments.  Their work with Airbus affiliate A3 could help unlock gridlock for all of us.  Gridlock wastes millions of hours of otherwise productive time, a key measure of “the good life.”  With eVolo having demonstrated that 16 rotors can carry the weight of two people, and eHang showing a drone-like device that can carry one passenger on a 20-minute hop, urban mobility may soon become less depressing and more uplifting.  Other vehicles wait in the wings, so to speak, with the main impediment being regulatory gridlock.

Uber Elevates the Discussion

Uber Elevate, a project on which Uber and Airbus are collaborating, published a 98-page white paper last November, Fast-Forwarding to a Future of On-Demand Urban Air Transportation.  Written with contributions from Uber personnel (including Airbus’ A3), NASA, and private individuals, the paper outlines the aerial possibilities Uber intends to follow.  In the meantime, Uber notes, “A study in the American Journal of Preventative Medicine, for example, found that those who commute more than 10 miles were at increased odds of elevated blood pressure.”

A Marketplace of Disgruntled Drivers

Uber’s white paper indicates a large and growing “silent majority” seething in their seatbelts.  “According to the US Census Bureau54, 123M of America’s 143M workers (86%) commuted to work in 2013 via private vehicle; 89% of those drove alone. Of these, 18.9M (15.0%) had a commute exceeding 30 miles and 7.9M (6%) longer than 60 minutes – this includes 27.4% of all D.C. workers, the highest of any state.”  (page 37)

An Uber Vertiport atop a downtown office building – similar to current heliports

In presentations at different symposia, Sebastian Thrun, one of the founding members of Google’s self-driving cars, suggested that getting three percent of drivers into the air would mean never having to build a new freeway, road, or parking area, that being enough to alleviate gridlock.  The savings would perhaps boost investments in research toward more efficient, effective modes of transport – something private enterprise might fund if the rewards are apparent.  Your editor thinks that economic rewards are incentive enough for even the short-sighted.

Plausible vehicles

As noted above, eVolo has demonstrated “dynamic handling” capabilities, and eHang is showing its ability to lift a single-passenger load in and maneuver in a controlled manner.  Joby Aviation has the S2 concept able of taking off vertically and carrying two passengers to destinations up to an hour away.  Each of these could fulfill the requirements for an Uber craft, but Uber and A3 apparently have their own design that emulates – to some extent – the layout of the Joby S2 but would carry only one passenger.

Before Uber can become Uber uber alles, the white papers sees some clouds ahead – starting with the certification process.  The FAA has limited certification for electric aircraft at this point to effectively allow only single-seat operation – a deterrent to the two-seat trainer market.  Uber’s paper suggests (page 45) that because “flight-based ridesharing is a very specific use case,” that the company’s understanding of the market, and “pull” exerted by the demand side of the market will help expedite new rule-making.  Consensus-based standards, according to Uber, will replace the sometimes sluggish process of rulemaking, and FAA and EASA (European Aviation Safety Agency) will work with one another to standard rules for both Europe and America.

Vertiports and Vertistops

A large part of the paper discusses the need for infrastructure compatible with the operation of VTOL-type craft.  The white paper suggests vertiports, areas capable of handling up to about a dozen VTOL craft at once, with landing areas and space for parking the vehicles for extended periods.  Vertistops would allow one vehicle to land and take off on a much smaller area.

As Mark Moore has shown, freeway off ramps might serve as vertistops, using existing infrastructures to facilitate aerial activity.  One potential problem might be providing parking for those waiting for rides, although that might be alleviated by siting these stops near public transit.

Airbus A3 Vahana awaiting its Uber passengers

Flying This year?

Reuters reported on January 16, “Airbus CEO Tom Enders told the DLD digital tech conference in Munich, adding he hoped the Airbus could fly a demonstration vehicle for single-person transport by the end of the year.

“’We are in an experimentation phase, we take this development very seriously,’ he said, adding that Airbus recognized such technologies would have to be clean to avoid further polluting congested cities.”  Airbus’ Urban Air Mobility division is “exploring concepts such as a vehicle to transport individuals or a helicopter-style vehicle that can carry multiple riders. The aim would be for people to book the vehicle using an app, similar to car-sharing schemes.”

Vahana in flight

“He said using the skies could also reduce costs for city infrastructure planners. ‘With flying, you don’t need to pour billions into concrete bridges and roads,’ he said.

“Enders said Airbus, as the world’s largest maker of commercial helicopters, wanted to invest to make the most of new technologies such as autonomous driving and artificial intelligence, to usher in what amounts to an era of flying cars.

“’If we ignore these developments, we will be pushed out of important segments of the business,’ he said.”

With corporate giants such as Airbus and Uber willing to invest in serious research and development in autonomous aerial taxis, we may have our flying car sooner than we might expect.


Mike Friend’s Hybrid Electric Solution

Electric airplanes currently can give 15 or 20 minutes of intense aerobatics, or about an hour of more sedate cruising.  What if you had a lovely little airplane that invited flinging it about the sky, but you still wanted to visit distant places?  In 2005, Mike Friend owned a Silence Twister, a Spitfire-like single-seater registered as N787M, a nod to Mike’s employer, Boeing.  He thought about making it a hybrid craft.

Waiting for Batteries

An early effort around 2010 by a German company to electrify the Twister did not produce a surge of orders, and Mike presented a 2011 symposium feature on making a hybrid out of the Twister to reduce its fuel burn while retaining its frisky character.  That approach would have used a pod under the belly of the Twister, making it look like a fighter with an auxiliary fuel tank.  Aerobatics combined with long-range seemed like a potential winner.

Cute as it was, the concept was still a single-seat aircraft – and many of us enjoy taking our friends and family for flights.  The major barrier to making a pure electric craft is still, after a decade of breathless announcements of great progress, the battery.  Mike Friend explains,” I have been involved in the design of electric airplanes since 2001, when I first proposed that Boeing build a fuel cell demonstrator aircraft powered by a hybrid electric power plant. 15 years ago, I was assured that within ten years the power density of batteries (and the cost of fuel cells, but that is another story…) would improve to the point where electric flight could become practical. Here we are 15 years later, and the energy density of batteries that you and I can go out and purchase is only slightly better than it was at the turn of the century. So what do we do about this?”

Still Waiting

Recent announcements and video of the Hamilton aEro Electric Twister flying in Switzerland show the sleek cowling made possible by the compact Siemens motor.  A three-blade scimitar propeller graces the airplane’s nose.  But the one hour endurance at cruise and roughly fifteen minutes battery availability for full-out aerobatics demonstrates Mike Friend’s premise that we really haven’t progressed very far with real-world battery performance.

Mike’s Hybrid Solution

Mike sees a workaround that employs current technology.  “Range-extender hybrids having a relatively small battery pack used for takeoff and climb, with a gasoline powered range extender putting out enough power for cruise flight.”  This is similar to the solution Stuttgart University came up with for the e-Genius – with a power pod on the right wing.  It also follows the power system used on the Equator P2.  With available batteries able to produce half of the 350 Watt-hours per kilogram needed for practical power for a light aircraft, Mike turns to a hybrid solution.

Mike spoke at the Powering Imagination Symposium at Seattle’s Museum of Flight – an event organized by Erik Lindbergh and Eric Bartsch.  He reflects on the consensus among speakers there regarding the energy storage capacity needed to enable practical pure electric aircraft. “The number we agreed on was 350 watt-hours per kilogram. This is a number that is not only for the battery cells, but also for the Battery Management System, and for the battery housing.  Upon hearing my story on battery performance, I often hear the words “but Mike, that is so depressing! I thought we were just months away from being able to buy an electric airplane.” I, on the other hand, don’t find it depressing at all, but rather a grand engineering challenge! As my first boss at Boeing told me many years ago, ‘Physics is a harsh mistress.’”

Mike notes that electric aircraft, to win converts, must perform at least equally to available fossil-fuel driven aircraft.  He explains that Teslas are popular because their performance exceeds that of many conventional cars.  He points to his 70-year-old Aeronca L-16A (a military version of the Champion), which carries two people, can take off in 200 meters (650 feet), climb at three meters per second (590 feet per minute), and cruise 140 kilometers per hour (87 mph) for two hours (with a 30-minute fuel reserve).

NG Aero Stellar One – Mike’s concept for hybrid power

He posits that a modern electric example would need at least 75 horsepower, but with a sleeker design, could cruise at 140 kph on only 15 kilowatts (20 hp).  It would use “a relatively small lithium-ion battery pack, combined with a gasoline motor capable of providing the 15 kW needed for cruising flight.”  Since Mike and his wife cruise around Puget Sound on a MotoGuzzi cycle, he suggests the 850 cc MotoGuzzi V9 as a drive unit for both the propeller and range extender.  It weighs a mere 43 kilograms (94.6 pounds) and can put out “slightly more than 15 kW of power at the low 2500 RPM that a quiet propeller should turn. Why turn the engine so slowly? Because a direct drive is much lighter and simpler than a gear reduction drive, and turning the engine slowly should keep it quiet and reliable.

“If more power was needed from the sustainer motor, a gear or belt reduction could be installed. My plan is to mount the electric motor directly to the clutch side of the Guzzi engine. The Spanish firm Axter has already done something similar, mounting an electric motor to the front of a Rotax 912. A clutch is placed between the gasoline motor and the electric motor. For quiet electric operation, the clutch is open and the electric motor directly drives the prop. For cruising operations, the clutch is closed, starting the gasoline motor, and the gas motor drives the prop through the electric motor shaft. As the gasoline motor takes over at cruise, the electric motor becomes a generator, slowly charging the battery pack that was drained during takeoff and climb. The Guzzi motor burns about 1 gallon (4 liters) per hour of operation at 15 kW, so a 2 gallon (8 liter) tank would provide 2 hours of cruising flight at 140 kilometers per hour.”

Mike’s hypothetical example airplane is based on a Swiss design by Bernard Clausen and Cristophe Bourban called the Stellar One.  In their concept, a BMW motorcycle engine sat behind the pilot and passenger, with power transmitted to the propeller by a shaft passing between the two.  Mike’s alternative approach puts the electric motor at the propeller end and the sustainer engine in place of the original BMW.

Mike concludes, “Why, you might ask, go to all of this trouble just to match the performance of a 70 year old antique? For starters, I believe that electric power is the future, and we need to start finding a way to that future with the technology at hand today. Until the long-anticipated improvement in batteries to the 350 watt-hr per kilogram level becomes a reality, I think a hybrid is the best way forward.”

Mike is president of Experimental Aircraft Association 406, serving the Bremerton/Puget Sound area near Seattle, Washington.  He retired from his position as Technology Director for Boeing last year and is obviously still pursuing the hope of improving light aircraft economy and making such craft good environmental citizens.