Will electric aircraft eventually replace today’s turbine-powered commercial aircraft?

Aside from glass cockpits and digital fly-by-wire, basic commercial aircraft technology has changed little in the past three or four decades. But the next 5-10 years could see a revolution of sorts. Researchers are racing to design, develop and commercialize passenger aircraft that reduce emissions and noise pollution with Tesla-type battery power or cruise above the congested ground traffic of megacities. What’s the status of electric aircraft dreams? Where might they fit into the future commercial aviation scheme?

AB INITIO TRAINERS?

 Despite the hype of recent announcements about regional airline-size aircraft, the initial application of electric propulsion is more likely ab initio flight training. “The transition from training on an electric airplane is ideally aligned with a turbine aircraft like an airliner,” said George Bye, founder of Bye Aerospace in Englewood, Colorado, US, and designer of the transonic Javelin advanced jet. He was also FlightSafety International’s project manager for the US Air Force T-6 turboprop trainer programme. “Electric airplanes behave much more like a turbine aircraft than an internal combustion engine Cessna or Piper. The turbine aircraft is very smooth; the electric aircraft is very smooth. We manage RPM, torque, temperatures – just like the turbine aircraft does.” Bye Aerospace subsidiary Aero Electric Aircraft Corp. (AEAC) is developing a four-seat version of its Sun Flyer, which it hopes will be the first all-electric trainer aircraft to be certified by the US Federal Aviation Administration (FAA) under Part 23 regulations. Bye told me they expect to fly the prototype “this winter” and “the certification will take a couple of years” with deliveries commencing shortly after AEAC is working with Redbird Flight Simulations (Austin, Texas, US) to offer a comprehensive training system for the Sun Flyer. Redbird founder Jerry Gregoire said, “I got interested in the project because we were looking for less expensive solutions for flight training. We loved the simplicity.” Redbird has built a couple of prototype simulators for the Sun Flyer, based on their three-axis MCX multi-crew trainer, and is developing a training curriculum. Delivering a cockpit-specific replica of the aircraft will require further aircraft performance data. “As simulators go, this is going to be a pretty simple one. It’s basically an electric fan with a rheostat on it. It ought to be a pretty easy-handling aircraft,” Gregoire said. There will, of course, be transition training required for pilots to move to a piston or turboprop aircraft. “This aircraft is a highly simplified environment. A motor with no propulsion latency or a torque curve. We don’t have to worry about how long it takes to spin an engine up or how do you keep from cold-shocking it. It can’t be over-revved,” Gregoire explained. He added: “It does, however, provide the ideal platform where a pilot can learn all the really important things about flying and aircraft handling. Then make the transition to a more complicated propulsion system afterward.” “I would think there’d be a fair amount of simulator training to get them used to a larger, heavier aircraft,” noted Bye. “But the transition is much smoother when you’re using an electric propulsion system leading into turbine than it would be managing an internal combustion engine trainer – there’s mixture, prop and a number of things that make it a challenge.” AEAC has about 100 deposits for the US$350,000 aircraft, including an order of 25 from Spartan College of Aeronautics and Technology in Tulsa, Oklahoma, US, as well as the New York-based Academy of Aviation Part 141 flight school.

A Slovenian light aircraft manufacturer, Pipstrel (from the Latin word for bat), is already producing a two-seat, all-electric trainer aircraft, the US$117,000 Alpha Electro – originally branded the WattsUp. Pipistrel reports “substantial interest” from flight training operations based in Minneapolis, Florida and Indiana. A training programme targeted for veterans and low-income youth in California’s Central Valley has ordered four Alpha Electro aircraft, but is currently stymied from starting because of a preamble clause in the FAA’s 2004 Light Sport Utility rule that requires LSA aircraft to have “a single, reciprocating engine, if powered.” A Part 61 flight school known as Aero Squad, operated by Tomorrow’s Aeronautical Museum in inner-city Los Angeles, has petitioned the FAA to change the definition to “a single, non-turbine engine, if powered” on the premise that the word reciprocating was included “to avoid the complications of turbine and jet aircraft being introduced into the light sport aircraft category … of low-performance, simple, easy-to-operate aircraft.” European Aviation Safety Agency (EASA) versions of LSA and ultralight rules make no mention of propulsion type, so electric powerplants are acceptable. Thus far, though, the FAA has not budged, claiming, “The technological and training issues for certification and operation of electric engines go beyond the intent for simple, easy-to-maintain, recreational aircraft.

X-FACTOR REVIVED

 Test pilots and engineers at NASA’s Armstrong Flight Research Center (Edwards, California, US) are flying a simulator designed to the specifications of the new X-57 aircraft, which features a unique electric propulsion system and is NASA’s first X-plane project in two decades. The X-Plane programme was introduced in the 1940s to develop a plane that could fly faster than the speed of sound, eventually achieved by Chuck Yeager in the X-1. Also known by the unwieldy name, SCEPTOR (Scalable Convergent Electric Propulsion Technology Operations Research), the X-57 “Maxwell” is named for Edinburgh, Scotland-born physicist James Clerk Maxwell, best known for his theory of electromagnetism. The X-57 design includes 14 motors, seven on each wing. During takeoff and landing, six small motors on each wing kick on for about 30 seconds. Once moving, the propellers of those 12 engines fold back flush with the wing and two larger end-wing propellers take over. The NASA Armstrong team has designed multiple failure modes into the simulation scenarios to evaluate aircraft performance, as well as reaction time. This helps develop emergency procedures specific to the experimental aircraft. Sean Clarke, principal investigator for the X-57,

said, “This is a critical activity, so that the pilots get experience with our experimental wing, and experimental motors before we actually put them on the airplane. That way, we are optimizing the time in the flight test phase of the project so that the aircraft is not tied up with the pilots learning the performance at that time.” The simulator will be updated as the X-57’s configuration goes through design transitions. The Maxwell is expected to fly as early as next year using a modified P2006T fuselage from Italian manufacturer Tecnam.

IN THE INTERIM, HYBRIDS.

 Boeing has put a toe into the electric waters via its HorizonX jointventure capital backing of Zunum Aero (Kirkland, Washington, US), which hopes to certify and deliver a hybrid-electric 12-passenger aircraft by 2022 to serve regional point-to-point and hub feeder routes. “Back in 1980, there were close to 300 small carriers in this country. They averaged about 20 seats and about 150-mile stage lengths. A lot of secondary cities have seen their air service decline as the airlines have pulled out of hubs or combined their hubs,” said Matt Knapp, Zunum Aero chief technology officer and co-founder. JetBlue’sTechnology Ventures arm is another investor in Zunum, whose name comes from the Mayan word for hummingbird. Airbus has a roadmap for future electric-powered aircraft designs, including the E-Fan 2.0, a hybrid/electric collaboration with Siemens, and eventually “an electrically powered airliner.” Airbus Group’sE-Aircraft System House near Munich, Germany is planned to open by late 2018. EasyJet announced in September a partnership with US firm WrightElectric (Cambridge, Massachusetts) for a battery-powered aircraft to handle flights under two hours, or 335 miles, which represent 20 percent of the European regional carrier’s flights. Wright has built a twoseater prototype; the next step is a 10-seater aircraft, then a single aisle with 120-passenger capacity. Timeframe? “Within a decade.”

 

Director of Embry-Riddle Aeronautical University’s flight research center and professor of aerospace engineering, Richard Anderson, , noted, “A lot of the technical advances that happen start in smaller airplanes. There will be a market for smaller, fully electric airplanes.” Teal Group Vice-President Richard Aboulafia calls the electric aircraft concepts “1950s Popular Mechanics cover stories.” He added, “The essence of futurism is the tendency to overstate the impact and readiness of exciting new technologies.” Aeronautical consultant Bjorn Fehrm predicted, “Electrical aircraft will come, just not as fast as many think.” He cautions that current Battery technology “leaves a lot to be desired. A battery needs 20 times more space than jet fuel for the same energy content. The inefficiencies make the battery virtually impossible as an energy store for longer-range aircraft. In addition, the battery has four times higher maintenance costs than gas turbines; it needs replacement after 1,500 charge cycles. The consequence is a battery-driven aircraft can only be used for short-range operations.” 

‘ROUND THE NEIGHBORHOOD

 “Electric aircraft (and quad-copters) will make sense as urban commuters at first,” Fehrm opined. “They can be made quieter and more neighborfriendly than gas turbine or piston aircraft (no noise, no fuel or exhaust odors).” Indeed, in October, the Volocopter VC200, claiming to be the world’s first certified multicopter, flew its two-seat, all-electric 18-rotor “flying taxi” in Dubai, UAE, for the first time (in an unmanned flight). Volocopter GmbH (Bruchsal, Germany) has attracted Florian Reuter as CEO (formerly Siemens) and CTO Jan-Hendrik Boelens (formerly Airbus Helicopters), along with investments from Daimler and Intel. Dubai aims to have 25 percent of its passenger transportation via “autonomous means” by 2030. Singapore has also announced its intent to deploy air taxis. Others in the race for urban airspace are Chinese company Ehang, which has had one-seater, 100-kilometre per hour passenger drones hovering above the sand dunes near Dubai during test flights, and the Russian flying motorcycle, Hoversurf Scorpion. On-demand ride service Uber, which has been experimenting with autonomous automobiles, ambitiously aims to deploy Electric vertical takeoff and landing (VTOL) “Uber Elevate” air taxis by 2020 in Dubai and Dallas, Texas, US. Uber is partnered with Pipistrel, Brazil’s Embraer, Mooney International (Kerrville, Texas), and Bell Helicopter (Fort Worth, Texas), as well as Aurora Flight Sciences (Manassas, Virginia), which is being acquired by Boeing. Aurora has a US Defense Department contract to develop an unpiloted electric VTOL, the LightningStrike, which generates 3 megawatts (4,000 horsepower) to power 24 ducted fans on its wings. Airbus is developing an e-VTOL aircraft for its CityBus initiative called Vahana through A3, its Silicon Valley outpost. The Airbus air taxi uses multiple rotors for hover capability, plus wings and a rear-mounted propeller for forward flight. Few experts expect aviation authorities to approve free flight of low-altitude “commuter aircraft” in urban canyons. Most likely, air taxis will operate similar to aerial rail systems – passengers will board an aircraft at one “station” and be deposited at another station or heliport in the network. However, a California company known as Passenger Drone will allow you to “take over any time via the joystick on board or using the touch avionics displays.” Normally, a passenger would simply input their destination and leave the driving to the computer. “Our aerial vehicles can be 100 percent remotely controlled by 4G technology, allowing an operator located as far away as the EU or Asia to fly a North America-based aircraft safely and efficiently,” the company claims. The car-size aircraft with 16 rotors has a range of 25 minutes at speeds up to 45 miles per hour. This article is reprinted by permission from The Journal of Civil Aviation, Halldale Media.