Another Electric Airplane?
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.