Another Electric Airplane?

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It’s not easy being me. No sooner do I get my pants unsnagged from one electric airplane idea than another one comes along literally days later. How’s a guy supposed to keep up?

Mark this date on your calendar: 2022. That seems to be when the promised magic of electric airplanes will come together and, we’re assured, you’ll be able to fly to a small airport in an Uber multi-rotor then board an electric hybrid airliner to be whisked off to an airport 500 miles away. Thence to your downtown destination via another Uber air taxi. What a wondrous new world awaits.

The airliner part was announced last week by yet another Silicon Valley-style startup called Zunum Aero. Zunum has in mind a 12-passenger regional airliner with hybrid electric propulsion. The fact that Zunum is backed by venture capital from Boeing and JetBlue lends it a certain credibility. But Zunum is still a startup with no airframe experience, no aircraft propulsion development history and probably utterly no clue of what it takes to certify such systems. I’m sure there are people inside Boeing rolling their eyes, not at the concept, but at the na´ve timeline.

And the performance claims. Zunum’s whiteboard conclusion is that it can build an airplane roughly the size of a PC-12 powered by a pair of electrically driven ducted fans. Zunum aims to tap into the “lucrative” short-haul market with an airplane whose operating costs are three to five times lower than the equivalent hydrocarbon-powered aircraft. Oh, and it’s also faster than the PC-12, with a target airspeed of 295 knots on a range of 700-plus miles. Zunum thinks it can develop and certify such a thing for under $200 million. In a gesture of uncommon generosity, The Seattle Times called the company’s business plan “sketchy.” Perhaps the best Zunum can wish for is to develop impressive technology and then be bought by Cessna or Daher or Pilatus.

Business plan aside, the idea itself is not necessarily daft. The Zunum aircraft will be a serial hybrid, meaning it has a combination of batteries and a hydrocarbon-fueled generator. Zunum hasn’t gotten to the details yet, but presumably the airplane would employ what’s become a popular flight cycle concept for hybrids. Batteries for takeoff and climb phase and a small, efficient hydrocarbon engine running a generator to recharge the batteries and sustain cruise flight, where less power is needed.

This is exactly the design Pipistrel developed for the HYPSTAIR hybrid and what Airbus sees for its longer-term E-Thrust project. The HYPSTAIR has powered up, but it hasn’t flown. Its marketability remains murky. Partnered with Rolls-Royce, Airbus plans a similar concept for its E-Thrust project. E-Thrust is intended to yield a regional airliner suitable for up 1000-mile stage lengths. But there’s an important distinction between E-Thrust and Zunum’s proposal. Airbus envisions introduction in the 2050 time frame, by which time technologies it plans to use will be mature and, more important, battery capacity will be vastly greater than it is now.

Electric airplane enthusiasts argue that even at current battery energy densities at perhaps 250 wh/kg, designs like the Zunum and what Uber proposes are feasible. I’m not convinced of this and I don’t know many people who are. If it were true, Pipistrel’s Alpha Electro would have better endurance and thus better marketability than it has now. It will get there eventually, I’m sure, but it’s not there yet. By 2050, it’s possible that entirely new battery technologies will push energy density above 2000 wh/kg. Even at half that, electric aircraft will be attractive enough to enter a transitional phase for some applications, such as training and personal flight.

And speaking of personal flight, you may have missed the fact that even Airbus has pulled back its electric aircraft program. It had planned a pair of electric aircraft, a two-seat trainer (E-fan 2.0) and a four-set hybrid drive personal aircraft for the U.S. market, the E-fan 4.0. When it was announced in 2015, the latter was planned for introduction before 2020, a timeline no less aggressive than Zunum’s. At the time, Airbus wasn’t so much interested in getting into light aircraft GA as it was using the E-fan project as certification ice breaker for more ambitious project, namely the E-Thrust. This made perfect sense.

I think it pulled back for two reasons: The incoming CEO wasn’t smitten with electric airplanes and there was little evidence of a business case within the proposed timeline. But Airbus isn’t giving up on future electric aircraft projects simply because it can’t afford to not have a foot in what’s coming.

Judging the developmental pace and impact of future aircraft is a fool’s errand at best. As some point, a transitional or disruptive technology will come along because progress is not static. Allow yourself the pleasure of magical thinking and you could see how electric airplanes with low operating costs could open up small GA airports to commercial service. Since anything new will have to have the hooks for autonomous flight, perhaps we can discern the foggy outlines of a new aviation technology.

On the other hand, increasingly, I view these electric airplane programs with a how-gullible-do-you-think-I-am reaction. This is driven mainly by unrealistic timelines and overpromising on potential performance. But what hell, this is aviation, right? Would-be purveyors of new aircraft always do that and we wouldn’t respect them if they didn’t. Well, not really. I’m a believer in electric aircraft. I think it’s a good idea that’s inevitable and will be driven by economics, efficiency, climate change regulation and noise considerations. The fact that the U.S. has pulled out of the Paris accord matters not a bit. The rest of the world has already decided and will move forward with lower emission technologies. Boeing knows this and so does Airbus.

It just won’t move very fast because of the limitations of things like the laws of physics, market uptake and the glacial advance of regulation. Zunum can plug all the happy numbers it wants into a sunny-side spreadsheet and that’s not going to change. Nor, in my view, will the much-touted revision of Part 23 help much. I give Zunum a two in 10 chance of pulling this off by 2022 and an eight in 10 chance of tanking. As Otto Lilienthal was reported to have said, sacrifices must be made. Not to worry, though. Someone will do it. Eventually.

Comments (18)

I have no faith that unobtanium-chemistry batteries will appear - now or ever. Hybrid may be doable, but hydrogen fuel cells are practical. Don Quixote can work on somebody else's engineering staff.

Posted by: Tom Yarsley | October 8, 2017 4:51 PM    Report this comment

Last that I heard unobtanium was very scarce and expensive. How do these people think that the batteries will be charged? Most likely from the local grid that will still be hydrocarbon dependent. There is no free lunch but snake oil salesmen try to convince us of the opposite while raiding our wallets.

As Edison proved, you have to go down a lot of blind holes before coming upon success. That is part of the R&D cycle. The big aircraft manufacturers know that as well, so they will keep a little finger and $ in the pot in case something truly significant comes along.

H2 fuel cells for some reason have somewhat fallen off of the RADAR. I remember working on them in the late 60s and early 70s. The current commercial fuel cells are mostly natural gas fueled that crack the natural gas then use the resulting H2 and atmospheric O2 Oh yes there is that little thing of the CO2 that is also a byproduct of the cracking process. They still suffer from lack of economic competitiveness. However, they are presently more affordable than unobtanium. As H2 production becomes more cost competitive, perhaps fuel cells will be providing the electricity for these aircraft.

Posted by: Leo LeBoeuf | October 8, 2017 5:40 PM    Report this comment

FUEL-FREE TURBINES will make electric aircraft with unlimited range practical. See that heading at Look under MORE.

Posted by: Mark Goldes | October 9, 2017 2:27 AM    Report this comment

FUEL-FREE TURBINES will make electric aircraft with unlimited range practical. See that heading on the AESOP Institute website. Look under MORE.

Posted by: Mark Goldes | October 9, 2017 2:29 AM    Report this comment

" an airplane whose operating costs are three to five times lower than the equivalent hydrocarbon-powered aircraft."

Being somewhat math and technology dysfunctional, I have to ask. How do you multiply a operating cost by 3 to 5 and get a lower number? Are fractions politically incorrect, are percentages no longer taught in school?

Posted by: Richard Montague | October 9, 2017 7:53 AM    Report this comment

One interesting aspect of evolving energy storage technology is safety. We have seen what happens when thin mylar insulators break down inside a lithium battery (see Dreamliner et al); but what are the failure modes of H2 and other yet to be seen storage methods? What happens during a violent crash landing? How does this affect the safety of first responders?

Like a ever-more tightly wound rubber band, with higher energy densities there is greater risk; by the time we get to 2000 wh/kg the risks could be enormous. These are not benign devices. It's something to think about.

Posted by: A Richie | October 9, 2017 9:28 AM    Report this comment

Gravity provides mitigating protection for the ground-bound at the scene of a lighter-than-air-fuel fire. The film of the Hindenburg crash is a popular example of the phenomenon. YouTube offers more examples.

Posted by: Tom Yarsley | October 9, 2017 9:58 AM    Report this comment

Most of the people that make rosy predictions about battery technology seem to show little understanding of basic chemistry. Unless some truly miraculous discovery occurs, increasing the engergy density of batteries by an order of magnitude is unlikely. People who know the technology are pretty skeptical about that. Lithium is the most chemically active element on the periodic chart, and it is already near its peak performance with today's batteries. And, as others have said, Boeing learned the hard way about lithium's temperamental ways.

Super capacitors? Maybe. Hydrogen fuel cells? Possibly. Pure electric, long-range airliners? Don't hold your breath. They hybrid concept does hold some practical potential, just as it has done with automobiles, but don't buy any tickets for the 2022 inagural flight just yet.

Posted by: John McNamee | October 9, 2017 10:04 AM    Report this comment

The limits of battery density are somewhat more limited than you may realize. There is a minutephysics video on youtube called "Will Batteries Power the World?" which explains that we can reasonably expect battery density to improve up to 4 times better than now, but it is unlikely to get much better. So, no 2000 Wh/kg in our future.

Posted by: Rick Woods | October 9, 2017 10:10 AM    Report this comment

Didn't the Hindenberg achieve buoyancy because it used hydrogen instead of helium? So we'd be flying around in aeroplanes (or driving cars) with fuel tanks filled with high pressure hydrogen gas. Give me a break! The malevolent among us will quickly figure out a way to use that technology to harm us.

It irks me to no end when people who've never seen the inside of a Physics 101 classroom start pontificating that battery powered airplanes or cars are gonna save the planet. I guess they'll charge them up by plugging them into "energy" trees that grow electrons. Leo is right ... plugging an electric anything into a charger means that the energy is produced elsewhere, that's all. And Richie is right about winding up the rubber band tighter, as well.

Just last evening I was watching an interesting program about diesel-electric locomotives up in Alaska having to have their electric motors overhauled because they wear out. Well ... so would an electric motor in an airplane. TBO might be higher but it isn't infinite. A hybrid propulsion system might achieve slightly higher energy efficiency but ... at what cost. No one talks about the raw materials involved in building some of those devices.

I think about the amount of money being spent by NASA at NASA Armstrong at Edwards AFB on the X-57 Maxwell / Tecnam P2006T idea. Ridiculous! 14 electric motors ... for what? At least they innocuously say they're trying to achieve zero "IN FLIGHT" emissions. Translated ... the electrons will come from someplace else. They're spending millions of OUR tax dollars so that someone can write a technical report ... that's about it. Unless and until we start building atomic power generating facilities again ... electric powered vehicles aren't going anywhere fast.

Posted by: Larry Stencel | October 9, 2017 11:47 AM    Report this comment

"plugging an electric anything into a charger means that the energy is produced elsewhere, that's all."

Generating, for example, 50MW of power at a central location is more efficient than 1MW at 50 locations. Even after transmission loss, it's still more environmentally clean.

"I think about the amount of money being spent by NASA at NASA Armstrong at Edwards AFB on the X-57 Maxwell / Tecnam P2006T idea. Ridiculous! 14 electric motors ... for what?"

I just view that as a means to explore an unknown. Sometimes, you don't know what you don't know. There were a lot of crazy ideas tested out before we got to a workable heavier-than-air powered vehicle.

Posted by: Gary Baluha | October 9, 2017 1:07 PM    Report this comment

Hypstair did fly. No press release. Check in with Tine!

Posted by: Serena Ryan | October 9, 2017 1:10 PM    Report this comment

Hydrogen fires burn upwards; the entire fuel cloud quickly climbs away from the scene of its release. Filament-wound aramid tanks are remarkably robust. Vary their typically cylindrical profile into a conic one, and you've got a lightweight spar. You can package the catalyst elements as additional elements of the wings - ribs and skins. It's actually serendipitously convenient geometry. Make it a high-wing, to more-benignly position the PAX/cargo "oven." ;-)

Posted by: Tom Yarsley | October 9, 2017 2:12 PM    Report this comment

Larry, what you say makes sense.

Posted by: Rafael Sierra | October 9, 2017 3:22 PM    Report this comment

Yeah, Tom ... maybe BRS can make some sort of downward ejection apparatus for those H2 powered electric airplanes. When they blow, the cloud goes up and the PAX go down ... kinda like the early F-104's. Now that'd be a real "E" ticket ride !!

Posted by: Larry Stencel | October 9, 2017 7:53 PM    Report this comment

You have to seriously wonder why there are so many investors ready to back charlatans spouting flapdoodle, and too few with the smarts, discipline, and patience to invest in what works.

It looks like Airbus and Boeing are cynically pretending to lead the way in "green" energy by following the pack on the latest tech fads. One might cynically respond that they appear to be looking for free PR in the aviation media. Unless Boeing has deep and spectacular proprietary knowledge of a fully mature, low risk, high capacity, and low weight electrical energy source, their recent involvement with GoFly and Zunum ought to be huge embarrassments to the adults in their organization.

In recent years, the Chinese have bought several important, credible US companies with excellent track records and a sustainable future, while the Americans and Europeans mostly seem to be chasing unicorns. This can't end well.

Posted by: S. Lanchester | October 9, 2017 11:41 PM    Report this comment

This morning, someone sent me a pic of a BMW electric car (with Euro plates on it) 'dead' on the side of the road. Next to it is a gas engine car pulling a trailer with a generator inside and it plugged into the BMW and charging it up. MY point exactly. Too bad Mr. B doesn't allow small .jpg pics on the blog ... I'd post it ... it's THAT good !! I'll see if there's a URL for it ?

Posted by: Larry Stencel | October 10, 2017 12:12 PM    Report this comment

Maybe Boeing or Airbus will come up with an "electric recharger" aircraft, that can become the AAA of the skies - rescuing discharged e-birds in-flight. Better be REALLY fast, though..... ;-)

Posted by: Tom Yarsley | October 11, 2017 1:16 PM    Report this comment

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