China Daily reports, “The world’s first electric passenger aircraft to gain an airworthiness certificate has been produced by China.”  Whether the “first” certification statement is true will probably become a matter of debate, with Pipistrel’s Alpha Electro being certified in France and seeking more general approvals from other countries including America.  Pipistrel has been selling a Taurus Electro G2 self-launching sailplane for the last several years, and makes the following claims for it.

Taurus Electro G2 is the only electric 2-seat aeroplane in serial production available on the market. Furthermore, Pipistrel believes it is the only truly useful electric aircraft out there, because the electric drive is applied to the glider airframe, where battery capacity is not a limiting factor in performance/endurance. Taurus Electro G2 represents a leap forward in performance, safety, functionality and user friendliness.”

We noted the RX1E’s certification in the blog a few months ago.  It’s in production in China with the first two aircraft delivered to Liaoning Ruixiang General Aviation Company last month.  The company reports orders for 28 of the one-million yuan ($163,000) aircraft at this point, all in China.

Zhao-lijie demonstrates the quick-change battery configuration of the certified RX1E battery-powered LSA. Photo: Willi Tacke

Zhao-lijie demonstrates the quick-change battery configuration of the certified RX1E battery-powered LSA.
Photo: Willi Tacke

It showed up as a static display at this year’s AirVenture, and part of the Experimental Aircraft Association’s report by Randy DuFault explains, “Electric power systems are part of the ASTM LSA standard. That fact allowed Chinese aircraft manufacturer Liaoning General Aircraft Manufacturing Company to certify its RX1E two-seat, composite structure LSA in their home country.”  The Light Sport Aircraft designation allows a less rigorous medical regimen for pilot certification, but limits the airplane’s weight and performance.

Because the RX1E was designed from the start as a trainer, its 12 kilowatt-hour battery pack gives it an endurance of about 40 minutes, and its six battery packs can be swapped out in minutes, similar to the six on Pipistrel’s Alpha Electro.

China's first electric plane has been delivered to its new owners in Shenyang, northeast China's Liaoning province

China’s first electric plane has been delivered to its new owners in Shenyang, northeast China’s Liaoning province

Liaoning General Aircraft Manufacturing Company is apparently working on a fuel cell program, perhaps as a way to extend the endurance and range on the machine.  Its cruise speed of 150 kilometers per hour (93 mph) and more probable pattern airspeed of 60 mph means it will live up to claims that its 12-kilowatt battery pack will give enough endurance for a series of touch-and-goes, perfectly suited to the needs of student pilots.

With Pipistrel on hold while the company searches for a supplier to replace the Siemens 85-kilowatt motor that graced Alpha Electro’s nose until a few weeks ago, America’s Aero Electric Aircraft Company has signed a deposit agreement with the Aero Touring Club De France for a “training system” that includes an unstated number of Sun Flyers and Redwing Flight Simulators.  The 100-year-old club’s 200 members fly out of the Toussus le Noble airport in the middle of a large urban area.  Quelling aircraft noise is important to the club’s continued operation.

AEAC Sun Flyer adds to endurance with solar cells, enabling up to three-hour flights

AEAC Sun Flyer adds to endurance with solar cells, enabling up to three-hour flights

Jean Billioque, ATCF President, lists noise suppression and cost of operation [one-fifth those of a Cessna 172] as deciding factors in adding the Sun Flyer to the club’s fleet.  George Bye, President of AEAC, says “It is an honor to welcome ATCF as our first international customer.  The legacy and heritage this club brings to our Sun Flyer customer group is something we hold in high regard. Our goal is to help ATCF resolve the noise challenges they, and other training schools at general aviation airports worldwide, deal with every day.”

George’s presentation at the February 28 Powering Imagination symposium at Seattle’s Museum of Flight gave a great deal of information on the Sun Flyer, its development, and the collaborative efforts through which Bye and his leadership team obtained a positive working relationship with Federal Aviation Administration (FAA) rule makers.

George explained that the airplane will be certificated under FAR Part 21.17(b):

  • 21.17   Designation of applicable regulations.

(b) For special classes of aircraft, including the engines and propellers installed thereon (e.g., gliders, airships, and other nonconventional aircraft), for which airworthiness standards have not been issued under this subchapter, the applicable requirements will be the portions of those other airworthiness requirements contained in Parts 23, 25, 27, 29, 31, 33, and 35 found by the FAA to be appropriate for the aircraft and applicable to a specific type design, or such airworthiness criteria as the FAA may find provide an equivalent level of safety to those parts.

Three-view shows 38-foot wings, wide cockpit

Three-view shows 38-foot wings, wide cockpit

This portion of the rules allows certification for aircraft above and beyond weight and performance limits imposed under LSA regulations.  George says the airplane will be certified for day and night VFR operation, again perfectly suited to initial flight training.

At AirVenture 2015, Bye announced the Sun Flyer trainer prototype was beginning construction in Shelbyville, Tennessee at the shops of Arion Aircraft, which produces its own line of LS-! Lightning aircraft, a two-seat LSA.  Flight tests will continue with the single-seat proof-of-concept machine in Denver, Colorado while the two-seat airplane is being built.


An Electric Autogyro

Combine a FIAT 500e with an autogyro and you get the Cavalon, a two-seat, side-by-side, relatively quiet electric flying machine.   Both use the same Bosch motor and inverter.  Auto Gyro The Aircraft Company, Cavalon’s maker, says the 80 kilowatt motor drives a three-blade propeller at up to 2,300 rpm and provides performance similar to that for the Rotax-powered version of the craft.

180 x 120 millimeters, the Bosch motor will fit in a backpack

180 x 120 millimeters, the Bosch motor will fit in a backpack

A Bosch 180/120 SMG (separate motor generator) with a planetary gear propeller speed reduction powers the aircraft.   Capable of regenerative braking on the little FIAT as controlled by an INVCON 2.3 inverter, it will be interesting to see if such recharging can be expected when the Cavalon glides.  The motor/controller combination powers the FIAT 500e, the electric Smart Car, and is used to help drive the rear wheels on the Peugeot 3008 Diesel HYbrid4.

Compact like the cars and autogyro it drives, the motor gets its designation from its 180 millimeter diameter, a little over seven inches, and 120 millimeter length (4.6 inches).  Its makers claim it could fit into a “typical school backpack,” although the kid might complain about lugging around its 32-kilogram (70.4 pound) heft.

The Cavalon’s battery pack is composed of Kokam prismatic cells storing 16.2 Amp-hours of energy and can feed the motor a maximum of 400 Volts.  The high voltage accounts for the motor’s 12,000 rpm top speed and its requisite reduction drive for the propeller.  For a high-speed motor, the 180/120 provides impressive torque, 200 Newton-meters (147.5 foot-pounds).

Bosch, like Siemens, seems intent on covering a range of electric vehicle needs

Bosch, like Siemens, seems intent on covering a range of electric vehicle needs

eCavalon’s first flight took place on June 24 at the Hildesheim airfield.  Company president Otmar Birkner says, “Today we flew tomorrow’s aircraft. For now we share the same challenges for endurance as the automotive industry but in time, this will increase from the current 45 minutes and the future will become the present.”

The video is a year old and depicts a flight in a Rotax-powered Cavalon, but shows off the roomy cockpit and excellent visibility to advantage.  Autogyros are also capable of autorotating down to a small landing space.

Comparable to the FIAT and Smart Cars, the Cavalon is only 4.7 meters (15.2 feet) long, 1.8 meters (5.9 feet) wide, and 2.8 meters (9.2 feet) high, topped by its 8.4 meter (27.5 feet) rotor.  Its roomy cockpit will allow occupants to enjoy the view at its 145 kilometers per hour (90 mph) cruise.  Top speed is 160 km/hr. (99.2 mph).  The 80 kW (107 horsepower) motor should rival performance by the Rotax 912 ULS with 100 hp. or the 914 UL turbo with 115 hp.

Clean lines of Cavalon autogyro lend themselves to electric flight

Clean lines of Cavalon autogyro lend themselves to electric flight

Part of the Niedersachsen Aviat, a consortium of North Saxony aviation firms, The AutoGyro Group describes itself as, “A world leader in the development, production and distribution of Gyroplanes. Since its foundation in 1999, the ultra-light aircraft specialist has enjoyed constant growth and now has a team of highly qualified specialists and engineers. With a global network of distributors in over 40 countries, AutoGyro aims to deliver unlimited and safe flying enjoyment to its clients with the versatile gyroplanes.”

If the Bosch powerplant lives up to its goal for this application, gyrocopters could become much quieter in the near future.

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Light Sport Aircraft (LSA), alas, haven’t lived up to their early hype, 100 manufacturers selling only 235 units in the United States last year.  That bothers Chip Erwin, who would like a Personal Sport Aircraft (PSA) option.  He’s working through his company, Aeromarine LSA, to do something about that.

Chip explains that high prices for LSAs, brought on by doubling Rotax prices over the last decade and quadrupling of once cheap European labor rates, has put what were to be $50,000 airplanes into the $150,000 price range, barely able to compete with used Cessnas and Pipers.

Chip Erwin (left) shows Calin Gologan his new motor.  Hollow area in middle allows inclusion of shaft to control propeller pitch

Chip Erwin (left) shows Calin Gologan his new motor. Hollow area in middle allows inclusion of shaft to control propeller pitch

Having demonstrated two-stroke engines and an Electravia motor on his imported Zigolo ultralight glider, he has displayed an alternative motor designed by Don Lineback, first at last year’s AirVenture as a mockup, then as an operating prototype at the ninth Annual Electric Aircraft Symposium in May.

Now he’s displaying it at AirVenture 2015, complete with an e-Prop four-blade, asymmetric propeller reputed to cut noise.  His video of a back-yard run-up shows that the 25-pound motor can double as a leaf blower.  Chip told attendees at his presentation in May that the motor could theoretically put out up to 75 horsepower, sufficient to make this motor useful not only in Chip’s PSAs but also in Light Sport Aircraft (LSAs).

Along with the motor, a buyer will get a controller, battery management system (BMS) and battery pack, all for around $11,000.  The batteries themselves are unique, with carbon fiber outer tubes protecting the active ingredients.  Individual tubes can be connected in different arrays using special end connectors, allowing them to be configured to fit neatly into spaces available in an airframe.

Cells in Chip Erwin's battery packs also have unique look.  Tubes can be connected in series and parallel with end connectors, configured into any end-wise shapes

Cells in Chip Erwin’s battery packs also have unique look. Tubes can be connected in series and parallel with end connectors, configured into any end-wise shapes

Don Lineback designed the motor for high torque and low speed, so propeller speed reduction drives are not necessary.  Chip reports,”I will say that our goals of very high torque at very low RPMs look to have been met. Max RPM of 1,700 with an optimized RPM of 1,200 means the prop noise at cruise will be similar to the motor noise, which is almost nothing at 150 feet.”

He explains the high torque will allow “a whisper-quiet cruise of 900 RPM on the Zigolo.”  Not only will that keep the neighbors happy, but allow the Zigolo to cut back on the number of battery tubes it carries and stay within ultralight Part 103 weight limits.

The Zigolo makes a good test bed for the motor, with its landing speed of around 26 mph and an ability to “loiter” at 46, a nice speed for quiet, breeze-in-your-face cruising.

E/G with two-cylinder, four-stroke engine.  A more powerful unit is on its way, rumored to be from famed Weslake firm

E/G with two-cylinder, four-stroke engine. A more powerful unit is on its way, rumored to be from famed Weslake firm

While Part 103 puts weight and performance limits on American flyers, Europe has adopted broader rules. The United Kingdom developed an SSDR (Single-Seater De-Regulated) class,  which allows airplanes up to 660 pounds (300 kilograms) and higher speeds than allowed under U. S. ultralight rules.  SSDR allows pilots to avoid medicals, an added benefit.  Europe in general has fewer restrictions on single-seat recreational craft.

Electric motor on E/G requires longer motor mount, but leaves plenty of room for battery pack, controller

Electric motor on E/G requires longer motor mount, but leaves plenty of room for battery pack, controller

Chip sees his new range of aircraft, from the Part 103-compliant Zigolo, an Italian rendering of Mike Sandlin’s Goat ultralight glider, to a high-wing E/G Plane and a low-wing Stinger.  With a gasoline two-stroke engine, the Zigolo comes in at under $12,000 in kit form, $16,000 in almost-ready-to-fly form and with electric power, around $20,000.

The E/G Merlin will cost around $35,000 ready to go, and the Stinger will not be over $42,000 if Chip’s estimates he shared during his dinner presentation at EAS IX are still viable.  From his web site, it looks like the range he’s trying to achieve, somewhere in loaded Goldwing motorcycle territory.

Stinger has miniature RV look, potential for fun sport flying

Stinger has miniature RV look, potential for fun sport flying

He has nice plans for the near future, including amphibious floats that allow the E/G to remain under 800 pounds even with a ballistic parachute.  He wowed dinner guests with the idea that he would be able to produce a single-seat, electric amphibious craft that would open up the Personal Sport Aircraft market in new and exciting ways.

See his web site for the logic behind PSAs.  Chip makes a compelling argument for this new direction in aviation.

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Belite – Going Electric?

Even to the casual observer, interest in electric flight is growing.  Major news outlets followed Solar Impulse, especially as it began its journey from Japan to Hawaii.  The fluster of cross-English-Channel attempts combined daring and rivalries – great for a public appetite voracious for sensation.  With big companies investing significant sums in the new technology, and with demonstrated efficiency of small craft that won 2011’s Green Flight Challenge, designers can’t help but respond to the ongoing challenge.

James Wiebe, founder and owner of Belite Aircraft, has a response that will be welcomed by aviators who might not be able to fly because of their budget.  He’s introduced the SkyDock low-wing ultralight at Oshkosh’s AirVenture 2015 this week at an introductory price of $3,995 for the basic kit.  Basic means no wheels, tires, cables, brakes, fabric, paint, glue or instruments.  Wiebe explains on his Facebook page, “We plan to have an option package for most of that stuff. It’s all off the shelf stuff from other vendors (so you can buy it without us marking it up, if you want.”

Belite's SkyDock prototype undergoing taxi tests

Belite’s SkyDock prototype undergoing taxi tests

He takes questions on Facebook, and gives at least one surprising answer.  “I selected an electric motor for a couple of reasons: there’s been a lot of electric airplane talk in the news, so the timing was right from a market perspective. I already owned the motors and controller. (I have a nice collection of electric motors.) The use of electric would draw attention to this new design (which can fly quite nicely on gas as well).”  Happy is the man with more than one electric motor in his shop.  The Lynch-type motor currently installed is a brushed unit, not quite as efficient as brushless motors also available.

Belite SkyDock's Lynch-type brushed motor with reduction drive - which may be removed soon for weight reduction

Belite SkyDock’s Lynch-type brushed motor with reduction drive – which may be removed soon for weight reduction.  Note carbon fiber and core-based airframe structure

He plans on going beyond this initial experiment to try different motors, re-drives, and propellers.  His prototype, and the center section and wing stubs for prototype number 2 are shown at Oshkosh this week.  Number 1 weighs 247 pounds without batteries, with “a couple of things” still to add to the airframe.  He notes this is “disappointingly high, but is in the general neighborhood of what happens to first prototype airplanes. They get heavy.”

The first craft will fly using a 66.6 Volt, 30 Amp-hour lithium-polymer battery pack weighing 22 pounds.  That won’t give great endurance, but with further airframe lightening, might keep the airplane within FAR Part 103 limits – 254 pounds empty weight.

This might be doable with a light battery pack, because Wiebe’s previous efforts have shown his ability to trim weight and stay within ultralight regulations.  He explains, “We copied what was working really well from the ProCub (tail design) and married it to a completely new wing design featuring enhanced span, chord, and thickness. This was to enable higher lift at lower speeds, such as loitering while under electric power.”  His heavy use of Computer Numerical Control (CNC) machining of parts enables quick mass production of parts and may be part of the reason for the low cost of the proposed kit, available soon at the introductory price of $3,995 as part of a Kickstarter campaign.

Prototype number 2 center section and wing stubs to be displayed at Oshkosh

Prototype number 2 center section and wing stubs to be displayed at Oshkosh

Wiebe avoids a strong commitment on whether batteries should considered part of an ultralight’s empty weight.  “I am very aware that some FAA’ers think that the batteries are part of the aircraft weight, while some independent types think that the battery weight should be part of the fuel. YMMV (your mileage may vary – wise advice in so many areas of life). That’s a debate for a future point in time.”

This gives him “an incentive” to remove the re-drive and replace the current motor controller with a lighter unit.  Doubtless all the lessons learned will be incorporated in prototype number 3, now under development.

His familiarity with programming and electronics probably accounts for his line of lightweight, electronic aircraft instruments, providing digital, rather than analog feedback on engines, flight feedback, and liquid levels.

It must be an ultralight.  Short video on Facebook page shows wing being plugged in

It must be an ultralight. Short video on Facebook page shows wing being plugged in

Wiebe’s blog shows a fascinating background story.  His firm, WeibeTech, pioneered the field of digital forensics, kind of a reverse hacking that helps track down and block the sources of malware and deconstruct hard drives in digital investigations.  His clients include federal, state and local customers interested in protecting data.  He sold the company in 2008, but is still in demand as a speaker on digital forensics.

We’re just happy he’s producing low-cost ultra-light aircraft, and becoming a pioneer in budget electric flight.

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2015 PADA Awards Dinner and Presentation

The CAFE Foundation’s announcement should capture our attention.  “The 2015 Personal Aircraft Design Academy will feature two excellent presentations: Burt Rutan on the SkiGull and Nick Borer on the LEAPTECH project. This will be followed by the ceremony to award the esteemed PADA Trophy to a surprise recipient. A reservations-only $20 hors d’oeuvre pre-reception at 6:15 PM on July 24 in the EAA Museum’s Fergus Plaza will provide an excellent opportunity to meet with aviation’s top personal aircraft designers.

“The Personal Aircraft Design Academy (PADA) gathering for 2015 will begin with a special indoor hors d’oeuvre reception for $20 per person that begins at 6:15 PM on Friday, July 24 in the Fergus Plaza lobby of the EAA Museum. This will be followed by the PADA Program in the EAA Museum’s air-conditioned Vette Theatre at 7:30 PM. You must pre-register and pay online to attend this reception as the food must be pre-ordered and no tickets will be sold at the door.

“In addition to a presentation by the 2015 PADA Trophy winner, the 2015 PADA program plans detailed presentations by Burt Rutan about his brand new long-range amphibious aircraft and by Nick Borer, Lead Conceptual Designer on the new NASA X-plane. Please purchase your tickets here now to enable you to attend the pre-meeting social reception with the assembled leaders in aviation design.”

As an attendee and participant at last year’s PADA presentations, your editor highly recommends this year’s event.  You will come away with an insider’s insights into developments at the extreme edge of current technology.

Burt Rutan testing his Skigull systems on Lake Couer d'Alene

Burt Rutan testing his Skigull systems on Lake Couer d’Alene.  Photo: General Aviation News/Mike Kinkaid

Burt Rutan will present details of his ongoing development of Skigull, an amphibious world cruiser with a combination of fossil fuel and electric power.  He plans on making “an eight-month exploration trip around the world without ever going to an airport.” Details are scant so far, but this article from General Aviation News shows some of the hands-on work Rutan is applying to the new design.

Nicholas Borer will discuss his work on the Leaptech project, something attendees can investigate in detail through the papers he has co-authored with JoeBen Bevirt, Alex Stoll, Mark Moore, and William Fredericks.  He is heavily involved in designs for transformative flight and has even contributed to devices for lunar exploration.

Leaptech wing under test at Edward Air Force Base.  Photo: IEEE

Leaptech wing under test at Edward Air Force Base. Photo: IEEE

Shortly after the PADA event, Nick will be part of the AHS (American Helicopter Society) International – AIAA – NASA Transformative Vertical Flight Concepts: Second Annual Joint Workshop on Enabling New Flight Concepts through Novel Propulsion and Energy Architectures.   That’s an imposing title, but indicative of the imposing realm in which Nick engages.

Topics at this year’s PADA event are far-reaching, but seating is limited.  Sign up today for a glimpse at personal aviation’s very bright future.

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EAS IX: Dr. Seeley’s Magnum Opus

Your editor first met Dr. Brien Seeley, founder and President of the CAFE Foundation, at the Western Workshop for the Experimental Soaring Association in 2007.  Dr. Seeley spoke about the CAFE Foundation and its many areas of research, including its first two Electric Aircraft Symposiums.  Seven years later these events and this blog are among the few resources for people seeking information on this developing field.

He spoke then about a novel idea, an aerial taxi service that would eventually become fully autonomous, hauling people on short-to-medium range trips in small, electric aircraft that would fly out of very small airports.  This seemed a bit of science-fiction at the time, but Dr. Seeley has continued to promote this idea, gaining valuable allies and convincing growing numbers that this is a practical alternative to the wasteful clogs on our nation’s highways, taking their toll on time, treasure and the human spirit.

At this year’s Electric Aircraft Symposium, he shared the mature vision of what he has refined for the last decade.  His presentation’s title, “Realizing Sky Transit,” indicated that a decade of visualization has reached fruition.  The alternatives are sobering, Joni Mitchell’s lyrics to “Big Yellow Taxi” seeming particularly relevant today:

Don’t it always seem to go 
That you don’t know what you’ve got
Till it’s gone
They paved paradise
And put up a parking lot

Parking lots, in fact, crowd almost everything else out of urban environments, each car taking up 2,700 square feet of pavement according to Todd Litman, founder and Executive Director of the Victoria (BC) Transit Policy Institute.  That’s more space than the average family home, normally shared by four or more people.  Hardscape, the asphalt and concrete required to serve new vehicles, paves over land equal to a strip 20 miles wide and 423 miles long each year.  That swath would run from Rohnert Park (very near the annual Electric Aircraft Symposium) to Newport Beach, California.  Imagine adding an equal swath each year to accommodate the nearly 90 million vehicles produced each year.

Imagine 20 mile wide paved strip from Rohnert Park to Newport Beach, then imagine adding a strip like this every year.

Imagine 20 mile wide paved strip from Rohnert Park to Newport Beach, then imagine adding a strip like this every year.  Where would we farm?

Dr. Seeley asked whether airports themselves need to be parking lots, a tremendous amount of space used to store cars of travelers who are elsewhere, probably renting cars that also need parking spaces.  As an alternative, Dr. Seeley proposed the use of driverless, electric vehicles that could be summoned on demand, much like the program being initiated on Google campuses.  Many of these alternative vehicles, in Dr. Seeley’s opinion, should be aircraft.

That may be a tough sell.  Last year, Light Sport Aircraft sales, for instance, numbered a disappointing, and disappearing 255.  Spending $150,000 or more for a machine that most of the time will take up lots of expensive space going nowhere is not appealing.  One solution is to improve that duty cycle, so the aircraft are flying a majority of the time.  This probably won’t work with conventional machines as we know them, with their down time for inspections, regular servicing and unplanned repairs.  Their noisy passage requires that they stay at airports at some distance from most centers of commerce or residence, making them even more inconvenient.

What if aircraft were ultra quiet, could lift off in 90 feet and climb swiftly, barely causing notice in the nearby neighborhoods?  The FAA requires that no more than 40 percent of a neighborhood can be annoyed for an airport to be allowed in its vicinity.

Lden (day evening night sound level must be low to gain neighborhood acceptance

Lden (day evening night sound level must be low to gain neighborhood acceptance

This proximity to residential and commercial areas would allow access to small aircraft that would carry two to a selected destination – on demand.  The frequency of their coming and going, and their ability to land at small pocket airparks within walking distance of other transport would enable travelers to travel conveniently, and without a Transportation Security Administration pat-down to delay them.

Hopping in an autonomous aircraft might cause concern, but human hands on the wheel might cause even more.  Driver error accounts for 92 percent of road accidents, and pilot error causes 83 percent of all air accidents.  This adds up to a catastrophic 60 million deaths from auto collisions alone in the 20th century.

Imagine avoiding this when you want to go 200 miles

Imagine avoiding this when you want to go 200 miles

Dr. Seeley envisions a hub and spokes arrangement of pocket airparks similar to the efficient setup used by UPS and FedEx to deliver packages.  Passengers would fly the spokes from one hub to another.  Because runways would be a little more than 400 feet long, two airparks could be contained in San Francisco International (SFO), and enable 1,000 landings and takeoffs per hour between them.

These transit hubs would complement other transport, with arriving Sky Taxi riders entering a major airport for more distant destinations, or taking arriving airline passengers directly to their neighborhood.

Two-seat Sky Taxis would provide quiet, clean, fast door-to-door transport

Two-seat Sky Taxis would provide quiet, clean, fast door-to-door transport

To carry out this kind of mission and be available in the numbers required for on-demand, low-cost transportation, Dr. Seeley’s ideal machine would be mass produced, a rarity in aviation. It would be capable of a 36 mile-per-hour stall, a calm pace less nerve frazzling than the thrust-reversing, heavy braking arrival of larger craft.   Self-preflighting airplanes, ready to launch every 10 seconds, could allow an arriving passenger to be lined up for takeoff 90 seconds after arrival at an airpark.  Such flights, with steep angles of climb and moderate speeds, would enable separations of only 700 feet between aircraft.

This could lead to rooftop airparks, 80 meters (about 263 feet) square and a few stories up from one’s departure or destination site, would increase the convenience and efficiency of air traffic.

Other than the relatively low cost of each airpark, infrastructure costs are almost non-existent, Sky Taxis taking advantage of existing air traffic control and navigation aids.  By comparison, Bay Area Rapid Transit (BART) tracks – often tunneled through the city and under the bay, can cost $1 billion per mile, versus $0 for sky taxi air space.

Sky Taxi potential market would dwarf that for current General Aviation craft - justify mass production and deployment

Sky Taxi potential market would dwarf that for current General Aviation craft – and justify mass production and deployment

Sky Taxis won’t have to be blazingly fast, since they will compete against a 28.87 mph average transit speed in American cities.  Just to make us all feel better, Beijing registers 7.5 mph, giving extra time to wipe one’s eyes from the persistent smog.

Green Flight Challenge II will initiate a series of competitions for wheel-motor-assisted takeoff runs, short-field landings and takeoffs, and hushed liftoffs and arrivals.  Putting all of this together, the $2 million prize money CAFE seeks to bring about its future aviary could make a profound difference in our commuter culture.

Good as Dr. Seeley’s presentations are, they may be topped by his latest accomplishment, publication of his paper, “Regional Sky Transit,” by the American Institute of Aeronautics and Astronautics.   Dr. Seeley presented the paper at the 15TH AIAA Aviation Technology, Integration, and Operations Conference.  AIAA members can find the paper here, and in a few weeks, in the CAFE Foundation’s technology library.


Solar Impulse Stays in Hawaii until Next Year

A sign on the climb from Salem, Oregon to the Redmond/Bend area indicates that no gas or services exist for the next 52 miles.  It’s worth heeding, since the route goes over mountain passes, and in winter can require tire chains and sometimes long passages behind a snow plow.  Range anxiety happens even for those of us still plugging along in fossil-fueled vehicles.

One of the ostensible advantages of Solar Impulse’s ability to charge itself, is that it has an endless supply of solar fuel and its batteries can make it through the night – depending on the relative lengths of day and night.  Making the longest flight of the round-the-world trip at high latitudes and during summer months was well planned, subject only to obstacles presented by weather.  Even those impediments were handled brilliantly by the team’s meteorologists and mission director.

What couldn’t be foreseen and must have caused moments when Andre’ Borschberg’s discipline, yoga and powers of meditation were put to the extreme test, was the overheating of some of the batteries, reducing their performance and jeopardizing the mission – and Borschberg.

Since the first signs of trouble occurred on the first climb from Nagoya, Japan, that meant each day’s climb to 28,000 feet or more was a tenuous effort, many eyes doubtless scanning the instruments showing temperature and charge.  This was a courageous press onwards.

The team’s announcement postponing further flights this year reflects their disappointment, but adds an optimistic overtone typical of the entire program.

Despite the hard work of the Solar Impulse team to repair the batteries which overheated in the record breaking oceanic flight from Nagoya to Hawaii, the solar powered airplane of Bertrand Piccard and André Borschberg will stay in Hawaii until early spring 2016.

“Following the longest and most difficult leg of the round-the-world journey which lasted 5 days and 5 nights (117 hours and 52 minutes), Solar Impulse will undergo maintenance repairs on the batteries due to damages brought about by overheating.

“During the first ascent on day one of the flight from Nagoya to Hawaii, the battery temperature increased due to a high climb rate and an over insulation of the gondolas. And while the Mission Team was monitoring this very closely during the flight, there was no way to decrease the temperature for the remaining duration as each daily cycle requires an ascent to 28’000 feet and descent for optimal energy management.

“Overall the airplane performed very well during the flight. The damage to the batteries is not a technical failure or a weakness in the technology but rather an evaluation error in terms of the profile of the mission and the cooling design specifications of the batteries. The temperature of the batteries in a quick ascent / descent in tropical climates was not properly anticipated.

“Irreversible damage to certain parts of the batteries will require repairs which will take several months. In parallel, the Solar Impulse engineering team will be studying various options for better cooling and heating processes for very long flights.

“The University of Hawaii with the support of the Department of Transportation will host the airplane in its hangar at Kalaeloa airport. Post-maintenance check flights will start in 2016 to test the new battery heating and cooling systems. The Round-The-World mission will resume early April from Hawaii to the USA West Coast. From there Solar Impulse will cross the USA to JFK in New York before making the Atlantic crossing to Europe and then returning [to] the point of departure in Abu Dhabi.

“Solar Impulse is attempting a historic first of flying around the world only on solar energy. And while Solar Impulse has completed 8 legs, covering nearly half of the journey, setbacks are part of the challenges of a project which is pushing technological boundaries to the limits. Solar Impulse will try to complete the first ever round-the-world solar flight in 2016 and this delay will in no way influence the overall objectives of this pioneering endeavor.”

Despite the disappointment for all concerned that the flight will be postponed, a few good elements shine forth.  Borschberg and Piccard can attend the December COP21 climate conference in Paris as true heroes; perhaps eliciting more support for their Future is Clean initiative.

And, the lucky Solar Impulse team members remaining to work on the airplane will be wintering in Hawaii.  It’s all good.


Solar Impulse – Tougher than it Looked

The record-breaking flight from Nagoya, Japan to Kalaeloa, Hawaii by Andre’ Borschberg in Solar Impulse had more difficulties than were immediately apparent to even the most involved observer.  During the first climb out of Nagoya, some of the cells mounted behind each motor experienced overheating, now attributed to over-insulation.  High-density foam packed around the cells was apparently too effective for even the freezing temperatures at altitude and caused the batteries to become warmer than desired.

Location of Solar Impulse batteries - one pack behind each motor

Location of Solar Impulse batteries – one pack behind each motor.  That’s the combined weight, each individual pack being 158,25 kilograms or 348,15 pounds

As explained on the Solar Impulse web site, “The energy collected by the solar cells is stored in lithium polymer batteries, whose energy density is optimized to 260 [Watt-hours per kilogram]. The batteries are insulated by high-density foam and mounted in the four engine nacelles, with a system to control charging thresholds and temperature. Their total mass amounts to 633 [kilograms] (1,393 pounds), or just over a quarter of the aircraft’s all-up weight.

“In order to save energy, the aircraft climbs to 8,500 meters (27,887 feet) during the day and descends to 1,500 meters (4,921 feet) at night.”

This sawtooth profile allowed the airplane to climb in the sunshine and descend in darkness, using less power and conserving the cells so Solar Impulse could greet the dawn with at least partially charged batteries.

What the public could view during the flight, among other data

What the public could view during the flight, among other data, a commercial operation which wholesales 18650 cells has a technically astute writeup by Anton Doos, one of the group’s cofounders, about the batteries on board HB-SIB.

Energy storage represents the plane’s primary inefficiency, but also is a very achievable goal to improve upon. [Bertrand] Piccard has this to say on the state of battery technology for aircraft:

“‘The batteries we have used have been specially developed for optimal maintenance but are still 10 times heavier than kerosene. I would imagine that we are still 20 years away from attaining parity on this point.’”  CAFE Blog readers would love to see a more optimistic projection, but even modest improvements in energy density and pack weight are welcome.

For instance, Solar Impulse 1 used Kokam batteries with an energy density of 243 Watt-hours per kilogram.  Solar Impulse 2 flies with Kokam batteries  with an energy density of 260 Wh/kg., a modest gain, but significant out over a dark ocean.  Both aircraft used battery housings designed and built by Air Energy, a German firm.  The four battery packs were housed in the same insulating materials used in the cockpit to protect the pilot from temperature extremes.

Pouch cells as installed in Solar Impulse 2

Pouch cells as installed in Solar Impulse 2

Commenting that the four 8-kilowatt motors are operating at a level that does not allow for errors, the site explains the choice of Kokam pouch-type cells used in the Solar Impulse.

“This solar-powered aircraft Solar Impulse uses four main lithium-ion batteries, each containing 70 lithium-polymer cells. It does not use a commodity cell like the 18650 that Tesla uses. There are several reasons, foremost being weight. An 18650 battery is in a steel housing, and a lithium-ion polymer battery like what is in this aircraft or in a cell-phone is housed in a soft, thin, flexible material. That is why nearly all drones, RVs, and electric planes use polymer (soft-packs). The polymer pack used by Solar Impulse is completely custom-built.”

Battery University, another on-line resource, has a brief history of pouch-type cells as used on Solar Impulse.  Its main benefit is weight savings, but the lack of a metal enclosure as in a cylindrical cell requires the use of some form of protective housing for the pouch or pouches.  Despite this the pouch cell attains 90-95 percent packaging efficiency, the highest among battery packs.  No standard pouch cell exists like an 18650 battery – each manufacturer designing its own version.

The batteries operate at a high voltage range of 210-304.5 Volts DC, which must generate some heat of its own.  Batteries have a total capacity of 38 kilowatt-hours. (Corrected July 15.)

Solar Impulse’s blog says their new Kokams are “particularly revolutionary,” in having a new chemical composition that has improved the oxidation issue which ages batteries and causes them to lose efficiency.   This technology is two years ahead of the industry, according to the blog, and “allows Solar Impulse to have batteries able to guarantee 2’000 flight hours, versus 500 in HB-SIA’s case.”  To gain energy density, Kokam added Monoflourethylencorbonat solvent developed by Solvay Chemicals.

The 70 cells in each battery pack don’t work well in extreme heat or extreme cold, and the insulation made by Bayer Material Science is intended to help maintain an optimum temperature of around 25°C (77°F – or around room temperature) inside the motor gondolas.  This involves an active heating mechanism to counter the effects of low temperatures at altitude, -40.5°C (-40.9°F) at 28,000 feet and an even more grueling -44.4°C (-48°F) at 30,000 feet, which the airplane exceeded on at least one climb.

According to Solar Impulse, each battery pack is an independent element, but a balancing controller can transfer power between cells in case of motor failure.  Each battery is fed by a particular solar panel associated with a given motor.

Monitoring available to the public did not show the battery temperatures during the flight, but did show the overall energy available from each pack in percentage of the total potential for that pack.  Some observers asked questions about one of two packs that seemed to lag behind the others.  Whether this was a function of temperature issues is unstated at this time.

Our hopes are with the Solar Impulse team as they sort out the heating issue, perhaps in time to meet the weather window that will allow their flight from Hawaii to the U. S. before summer’s end.

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e-Genius spent July 4 crossing the Alps both ways from Germany to Italy, a first for a two-seat, battery-powered airplane.  Although the Elektra One Solar from PC-Aero GmbH is lighter and seats only one, its flights starting two weeks before and ending two days before e-Genius’s journey are equally proud accomplishments.

The outgoing flight started in Unterwössen, Germany on June 25, crossed over the Grossglockner and landed, according to PC-Aero’s description, “In the sunny town of Lienz in East Tyrol, Austria.  The flight took around 2.5 hours. After the successful flight on the south side of the Alps, Elektra One Solar started [on its next trip] on 2 July (few days before the eGenius of the University of Stuttgart also flew over the alps) in quite difficult weather conditions. Despite headwinds and strong gusts the plane crossed the Alps at an altitude of more than 3,000 meters and landed after about 2 hours and 190 kilometers (117.8 miles) [in] flight, as planned, at the airfield in Zell am See, Austria.”

Not exactly severe clear, weather for the flights was windy and turbulent

Not exactly severe clear, weather for the flights was windy and turbulent.  Photo: PC-Aero

280 series production solar cells from the German company Solar World fed an 11.5 kilowatt-hour battery pack, and provided about 30 percent of the energy needed for the flights.  Maximum range for the Elektra One Solar is about 500 kilometers (310 miles).

For the southerly flight the pilot was Klaus Plasa, an experienced test pilot with thousands of flight hours on the Transal (a twin-engined transport craft), gliders, and as a test pilot for vintage airplanes and aerobatic aircraft.  Norbert Lorenzen made the return flight. He has more than 10,000 flight hours on light airplanes, gyrocopters, aerobatic airplanes and helicopters, and has the most experience on Elektra One.

After the landing in Lienz the batteries were at about 25 percent – even though Plasa loitered about one hour for the chase airplane used for photos and videos.  Had he landed following a direct flight he would have had about 50-percent battery capacity left, according to PC-Aero.  The pilot recharged the batteries for the next flight.

Takeoff from Lienz shows effects of strong crosswind

Takeoff from Lienz shows effects of strong crosswind.  Photo: PC-Aero

On the flight from Lienz to Zell am See Norbert, Lorenzen landed with about 30 percent battery capacity, notable after flying against a “quite strong head wind.”

The Elektra One Solar is a very light aircraft, weighing only 300 kilograms (660 pounds) all up, battery weight accounting for 60 kilograms (132 pounds), and a 100 kilogram (220 pound) maximum payload leaving a 120 kilogram (264 pound) airframe, motor, retractable landing gear and everything else – not bad for a 13-meter (42.7 foot) wingspan airplane.   It will be certified in the German Ultralight Class (LTF-UL) by the end of this year.

Pilot happy to be in the sunshine shares a thumbs up with the camera plane.  Photo: PC-Aero

Pilot happy to be in the sunshine shares a thumbs up with the camera plane. Photo: PC-Aero

The Elektra range of aircraft is intended for multiple missions, so this flight carried a special high resolution camera for 3D landscape mapping (up to five centimeter (just under two inches) resolution. The system was developed by the partner company Elektra UAS GmbH for use in upcoming unpiloted versions of the aircraft.

Calin Gologan, CEO of PC-Aero GmbH and its unmanned aerial vehicle spinoff, says, “We need not reinvent the aircraft for clean mobility, we need only integrate and optimize existing technologies.”

Double motor, rather than 16kW single, might have been welcome here.  Photo: PC-Aero

Double motor, rather than 16kW single, might have been welcome here. Photo: PC-Aero

He points to the integration of light-weight structures, highly efficient motors and controllers, modern lithium-ion batteries, and solar cells on his aircraft as proof of his practicing what he preaches.

In the meantime, PC-Aero forges ahead in its design, prototyping and certification work, both for its own products and for clients.  The firm entered the electric-solar aircraft business five years ago, and has since build five Elektra One electric/solar aircraft in sizes ranging from 8.6-meter (28.2-foot) to 15-meter (49.2-foot) wing spans.

Design of the two-seat side-by-side version, the Elektra Two Trainer, is finished and construction will start this year with a license contract signed by U. S. Partner George Bye and his firm, Aero Electric Aircraft Company.

A two-seat tandem version, Elektra Two Record, was designed for high altitude stratospheric record flights up to 24 kilometers (over 78,000 feet) altitude. One prototype was just ordered by the Swiss company SolarXplorer.

Calin says the prototype is under construction and the first flight will take place in the first part of next year.  Fuselage molds are ready for use.

Less high-flying Elektras are also under development.  Calin announces that the HPD-25D motor will fly on one of his craft in the next week.  This is the dual motor that will power the American Sun Flyer, a good choice for a training craft since the redundancy of what is essentially two motors will provide additional safety.

In the next few weeks, the team hopes to fly the 15-meter span Elektra with solar cells, with the hopes of going after some distance records.

Showing the versatility of the basic design, Elektra UAS is responsible for the unmanned (also Optional Pilot) applications of the aircraft platforms designed by PC-Aero. Applications include 3D landscape/city mapping and communications such as internet and mobile phone networking.

Congratulations to Calin and his pilots on their adventures over the Alps, and continued best wishes for ongoing success.  Thanks to Calin and his wife, Birgit Weissenbach, for their help in providing information and photographs for this blog entry.

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106 years after Louis Bleriot took off into a foggy morning and pointed the nose of his Model XI toward the Dover coast, Airbus celebrates the event with an anniversary flight of their e-Fan prototype,  now sporting a bigger, more powerful battery pack, lightened airframe and lighter electrical components.

French pilot Didier Esteyne lands after crossing the Channel with his European planemaker Airbus E-Fan prototyp, at the Calais Airport, northern France, Friday, July 10, 2015.  (AP Photo/Michel Spingler)

French pilot Didier Esteyne lands after crossing the Channel with his European planemaker Airbus E-Fan prototyp, at the Calais Airport, northern France, Friday, July 10, 2015. (AP Photo/Michel Spingler)

Their press release carefully avoids mentioning Hugues Duval’s flight the day before, apparently done to upstage the e-Fan’s trip.  It does claim credit for making the first cross-channel flight in a “twin-engine electric plane,” even though Duval’s Cri-Cri was powered by twin Electravia motors.

“At 11am on a calm, sunny summer morning, the Airbus E-Fan touched down in Calais to enter its name in the record books. The all-electric plane became the first twin-engine electric plane taking off by its own power to negotiate the English Channel, more than 100 years after Louis Blériot had first made the intrepid journey.

“Travelling in the opposite direction to the pioneering Frenchman and powered by lithium-ion batteries, the E-Fan took off from Lydd on the English south coast, completing the 74 kilometre flight east to Calais, France, in around 37 minutes. Flown by test pilot Didier Esteyne, the all-electric plane weighs around 600 kilogrammes and travelled at an altitude of about 1000 metres [3500 feet].”

Bleriot’s three-cylinder Anzani clattered out about 25 kilowatts (33.5 horsepower) to its 2.08-meter (6.82-foot) diameter propeller.  Top speed of the Bleriot was 75.6 kilometers per hour (40.8 mph), which accounted for the 36 minute flight required to cross the 22-mile channel.

A bit sleeker and speedier than the best aeronautical science could manage a century ago, the e-Fan’s twin electric motors put out 60 kilowatts (80.4 hp.) through its ducted fans.  Its maximum speed of 220 km/hr. (119 mph) will enable a shorter flight time and its sleekly faired cockpit will provide a comfort level Louis Bleriot would envy.

e-Fan's battery placement helps distribute loads on wings

e-Fan’s battery placement helps distribute loads on wings

To ensure sufficient energy levels for the flight, Airbus has created a heavier, but more energy-dense battery package.  They’ve compensated for the added battery weight by reducing aircraft structural weight and using much lighter electrical components in some instances.  The airplane’s original battery package weighed 137 kilograms (301.4 pounds), while the new system adds 30 kilograms (66 pounds) for a new total of 367.4 pounds.

The original pack was good for 30 minutes of flight, while the new extends that to 53 minutes, more than enough for the jump from Lydd, a few miles south of Dover, Bleriot’s original destination from Calais.  The southerly location required the e-Fan to fly due east to Calais, where Bleriot’s route had been more north by northwest.

Francis Deborde is CEO of Aero Composites Saintonge, builders of the e-Fan prototype.  He reports E-Fan’s total weight has been reduced by some 38 kilograms (83.6 pounds) in countering the increased battery weight.  Part of that came from removing the electric motor system that drove the landing gear for taxiing.  A significant amount came from redesigning the motor controllers, originally industrial units totaling 12 kilograms (26.4 pounds) and dropping their weight to 1.5 kilograms (3.3 pounds) each.  The original controllers sat behind the pilot, requiring heavy cabling to the motors: the new units “are integrated into each of the E-Fan electrical engines’ shrouds, with an aerodynamic fairing on the exterior and a heat-dissipating radiator on the interior.”

To appreciate the heavy hitters involved with Airbus projects like this, consider that the battery array came from a collaboration between CEA Tech (the French Atomic Energy and Alternative Energy Commission’s technology research unit), Airbus Defense and Space, and Airbus Group Innovations.

Projected e-Fan factory in Pau, France will mirror airplane's shape

Projected e-Fan factory in Pau, France will mirror airplane’s shape

Airbus Airbus Group has begun development of the E-Fan’s Pau, France assembly site, which it will lease to its wholly-owned Voltair subsidiary responsible for the electric aircraft’s development, production, sales, delivery and customer support.

Plant construction is expected to begin in 2016, and the swoopy-looking facility will begin aircraft production the following year, expected to be only 10 e-Fans per year initially.  This small initial offering will enable Airbus to evaluate interest in the machine and plan future production of the 2.0 two-seater and 4.0 four-seater.



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