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Electric aircraft engines

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Established companies and start-ups alike envision an electrified future.


Owen Davies
Contributing Writer

For environmentally friendly aviation, one technology is critical. It is not sustainable aviation fuel (SAF), or better batteries, or hydrogen fuel cells. It’s the motors that convert energy into usable power.

Unfortunately, today’s best batteries hold about 1/50 the energy per pound as Jet A, and DoE’s Advanced Research Projects Agency – Energy (ARPA-E) says that aircraft motors need to put out more than 7 hp/lb (12 kW/kg) continuously for practical flight. Conventional electrics deliver only 1.8 to 3.0 hp/lb (3 to 5 kW/kg).

For a few special cases, electrics are practical today. In 5 years, they will drive commuter and regional
aircraft.

Aerospace innovators have recognized this market, and some companies are already building electric aircraft motors. Several are clearly heading toward a prosperous future. Small aircraft makers are buying electric motors for their designs and hope to have them airborne soon.

Established engine manufacturers are also entering this market. Here is a look at some of what lies ahead.

Harbour Air de Havilland Beaver seaplane is a testbed for magniX certification.

magniX

The largest and most successful single-business maker of electric aircraft motors to date, this Washington state company offers 2 models – the 470-hp (350 kW) magni350 and the 870-hp (700 kW) magni650.

They weigh in at 282 lb (128 kg) and 454 lb (206 kg), respectively, including the inverters and cables needed to run them. For comparison, the Pratt & Whitney Canada (P&WC) PW123E turboprop weighs 992 lb (450 kg) and churns out 2380 shp.

The turboprop has better power density, but electrics offer 3 compelling benefits. Firstly, it’s a lot cheaper to charge a plane with electricity than to fill a tank with avfuel. Secondly, the motors need only a relatively simple and inexpensive overhaul every 10,000 hours. Lastly, they spew no carbon-rich exhaust.

These features have brought magniX many customers. Vancouver’s Harbour Air famously operates an all-electric de Havilland Beaver seaplane with a 750-hp magni500 motor. Similarly, Sydney Seaplanes, an operator in Australia, has converted a Cessna Caravan floatplane to magniX power, and plans to electrify the rest of its fleet. And Eviation’s Alice 9-passenger regional airplane is propelled by 2 magni650s. The aircraft made its first flight in September 2022. The company hopes deliver its first planes in 2027. Eviation should be a lucrative customer for magniX. As of May 2023, they already had orders for 255 airplanes.

Furthermore, NASA’s X-57 electric twin demonstrator is being fitted with magni650s. Test flights are scheduled to begin in 2025.

Faradair’s Bio Electric Hybrid Aircraft will carry 18 pax or 5 tons of cargo. A Honeywell turbogenerator will power the prototype, giving a range of 1000 nm, but it can be swapped out for batteries or hydrogen fuel cells. Wherever the energy comes from, 2 magni650s with counter-rotating props will convert it to thrust.

In March 2023, a magni650 replaced one engine of a 40-passenger de Haviland Dash 8-300 test flown by Universal Hydrogen. It was the largest fuel-cell aircraft flown to date.

Canada’s Air Tindi is working with magniX on an electrified 50-pax de Havilland Dash 7. Plans call for extension to short-haul turboprops with up to 70 passengers and a single-aisle regional airliner with up to 180.

NASA plans demonstration flights as part of its Electrified Powertrain Flight Demonstration (EPFD) program by 2028, with commercial flights to follow in the early 2030s.

A magni250 motor propelled a modified Robinson R44 helicopter on a 20-min hop from TRM (Jacqueline Cochran, Palm Springs CA) to PSP (Intl, Palm Springs CA). Lung Biotechnology BCP will use the helicopters to deliver organs for transplant.

Safran Electrical & Power

EcoPulse modified TBM 900 maintains altitude with Safran turboelectric power.

EcoPulse took to the skies last November. It is a Daher TBM 900 with batteries and a flight control computer developed by Airbus and powered by 3 Safran electric motors on each wing. It lifted off from LDE (Tarbes–Lourdes, France) with its standard turboprop, then spent 20 minutes at altitude using only Safran’s turboelectric power.

Safran already has 2 NGINeUS aircraft motors ready for market, and a 3rd in development. The line offers a power density of 3 hp/lb (5 kW/kg) – considerably less than ARPA-E’s estimate for regional carriers. Yet aircraft makers are lining up to buy.

Nearest to certification is the NGINeUS 100, which covers the 134 to 240 hp (100 to 180 kW) range. The Aura Aero Integral E and Diamond eDA40 trainers, CAE’s electrified Piper Archer trainer, VoltAero’s hybrid-electric Cassio 330 4-seat canard design, and the E20 eVTOL vehicle by Chinese startup TCab Tech all will use it. Safran expects EU certification in Q1 2024.

The GENeUS 300 puts out 400 hp (300 kW) with a power density of 6 hp/lb (10 kW/kg) and 1/5 the weight of an equivalent piston engine. It also can function as a generator, occupying about 1/3 the volume of a conventional generator of the same capacity.

The GENeUS XL has been tested to exceed 675 hp (500 kW), and is expected to deliver twice that in future development.

Safran has already committed to installing 4 new automated production lines – 2 in France and 2 in the UK. They are slated to open in 2025. By 2026, they should be turning out 1000 motors per year.

Honeywell Aerospace/DENSO

Propelled by 30 electric motors designed by Honeywell and made by Denso, the Lilium Jet is on track for 2025 certification in the US and EU.

Germany’s pioneering Lilium Jet is propelled by 30 electric motors mounted on its wing and canard. They are remarkable little motors, each weighing about 8.8 lb (4 kg) and turning out 134 hp (100 kW.) Yes, that is a staggering power density of 15.2 hp/lb (25 kW/kg.) If they can be scaled up, the race to power regional airliners may already be over.

The motors are a collaboration between Honeywell Aerospace and DENSO, a maker of auto parts well versed in mass production. Honeywell designed them and DENSO will build them. They are destined to sell a lot of motors.

In mid-June 2023, Lilium already had orders for 745 of its eVTOL jets with 22,000 motors. The first manned flights are due this year, and the company is on track to receive certification in the US and EU simultaneously in 2025.

ZeroAvia

Founded in the UK in 2018, this firm was testing its first 134-shp (100-kW) motor as early as that July, test-flying a 6-seat Piper M-Class aircraft with a hydrogen fuel-cell motor by February 2019. Today, it has 2 powertrains ready for market.

Dornier 228 has flown with one engine replaced by a ZeroAvia powertrain.

The ZA600 delivers 670 to 1000 shp (500 to 759 kW) continuous power. Last July, the company flew an initial 10 flight tests of a Dornier 228 with one turboprop replaced by a ZA600 powertrain.

The ZA2000 offers 2700 to 6700 shp (2 to 5 mW.) Fueled by liquid hydrogen, it will be able to carry passengers on routes up to 1000 nm. ZeroAvia expects it to begin replacing turboprops in 40- to 80-seat regional airliners by 2027.

The ZA motors are already attracting customers. Ecojet, a British startup airline, has ordered up to 70 ZA600 powertrains for retrofitting to its aircraft as soon as the motors are certified.

Target date is 2025. Ecojet also placed “a larger order” for the ZA2000, which they intend for aircraft up to 80 passengers by 2027. Japan Airlines, which operates more than 50 regional aircraft, has signed an MoU to develop the ZA2000 for use in Japan. In California, Air Cahana has already ordered 250 ZA200 motors. And Monte Aircraft Leasing has ordered up to 100 ZA600 powertrains for 9- to 19-seat aircraft.

Collins Aerospace/P&WC

This Raytheon division has designed a 1350-hp (1-mW) electric motor and associated electronics for sister company P&WC. It will be paired with a P&WC turbine in a hybrid-electric propulsion system. The companies are targeting a 30% improvement in fuel efficiency and CO2 emissions. Compared with Collins’ most advanced electric motors now in the air, the motor will deliver 4 times the power at half the weight. Flight testing of a 2700-shp (2-mW) parallel system in a Dash 8-100 is expected to begin this year.

GE Aerospace

By 2025 or so, a souped-up Saab 340B in blue and white livery will fly as part of NASA’s electric aircraft demonstration program. It will be powered by a megawatt-class hybrid electric propulsion system developed by GE Aerospace. With Boeing subsidiary Aurora Flight Sciences, they plan to install the system in parallel with the original CT7 gas turbines to demonstrate the electric motor and associated technologies.

In 2022, GE and NASA tested a pair of 1-mW powertrains, representing the left and right engines on a twin, in the space agency’s large high-altitude simulator at the Neil A Armstrong Test Facility in Sandusky OH. The motors performed flawlessly at simulated altitudes up to FL450.

H3X
H3X HPDM-30

H3X

This 3-year-old Denver CO company’s 36.6-lb (16.6-kg) HPDM-250 delivers 335 hp (250 kW) peak power and 268 hp (200 kW) continuous.

That is 12 kW/kg continuous power and 15 kW/kg peak. Lockheed Martin has invested in H3X. It says the company’s technology could eventually power 50- to 100-seat aircraft.

H3X is also putting the finishing touches on 2 new motors – the HPDM-30, designed for drones and similar applications (9 lb [4.1 kg], 29 hp [22kW]), and its big brother HPDM-3000 (3750 hp [2.8 mW]).

With a continuous power density in excess of 12 kW/kg, it should weigh only 500 lb (230 kg) or so. H3X plans to deliver test units this year.

Duxion

ejetNewfoundland-based Duxion Motors is working on a new kind of electric jet motor. In most fans, the axle is attached to a motor – or is part of it. Duxion’s eJet is driven by a ring of electromagnets mounted in the duct surrounding them. The magnets are the stator, the fan blades are the armature.

One big benefit is the air gap between the stator and the fan blades, which is typically less than 1 mm. Call it 1/25 of an inch.

This near-perfect seal helps convert an extra 7% of energy to thrust. Those tolerances, however, are also the challenge, as keeping the blades running within them is not easy. At large sizes, central bearings are omitted, as they tend to deform the blades.

Duxion carried out a successful ground test of the eJet last October. The eJet attracted its first customers even before the test.

In September, Dymond Aerospace signed a C$500-million agreement to equip its forthcoming fleet of unmanned cargo planes with 200 eJet motors. They are expected to deliver more than 8000 lb of thrust.

RogersEV

electric
RogersEV HaloDrive

The HaloDrive is this company’s alternative to the eJet. RogersEV solves the air-gap problem by arranging the magnets in a way that keeps the blades in line.

This allows a 2.5-mm-wide channel – almost 1/10 of an inch. This is said to improve propulsive efficiency by up to 35% compared to a turbine while cutting noise by 40%.

Conclusion

This has been only a narrow look at a broad field of aviation development. DARPA and ARPA-E are sponsoring some 30 research and development projects. At least 3 universities have developed motors in the 1350-hp (1-mW) range. Some companies are working on better magnets and other technologies that will make electric motors more efficient, cheaper, and free from expensive rare earths.

The next few years should see short- and medium-range aviation transformed. Eventually, younger Pro Pilot readers can expect to pilot electric bizjets across continents. By 2050, they will probably be carried across oceans by electric fans.


OwenOwen Davies is a veteran freelance writer specializing in technology. He has been a futurist at Forecasting International and TechCast Global.