Zero-emission propulsion pioneer ZeroAvia has completed the initial flight-test campaign with a Dornier 228 fitted with a prototype of its ZA600 hydrogen-electric powertrain.
The company will now finalize the design for certification of the powertrain and its installation on the initial application, Cessna’s Caravan.
ZeroAvia completed 10 flights of the 228 testbed with the 600-kW ZA600 replacing the 19-seat regional aircraft’s lefthand Honeywell TPE331 turboprop. The demonstrator powertrain tested included a fuel cell system and battery pack in the fuselage powering an electric motor in the nacelle.
The testbed made its first flight from Cotswold Airport in Kemble, England, on Jan. 19. The 10-flight test campaign saw the aircraft fly to 5,000 ft., perform a 23-min. endurance flight and operate over a temperature range from just above zero to 30 C (86 F), ZeroAvia says. The 10th flight was a cruise test.
While the initial test campaign is complete, “we have a lot of plans for the 228, like A to B flights. We’re now finalizing the airports we want to fly to,” ZeroAvia Founder and CEO Val Miftakhov says. “Other plans include testing some of the advanced technology for the ZA2000.”
The ZA2000 is ZeroAvia’s planned larger, 2-4-megawatt hydrogen-electric powertrain for Part 25 aircraft. The startup is intending to flight-test a prototype ZA2000 in 2024 in a 76-seat Bombardier Q400 (now De Havilland Canada Dash 8-400) regional turboprop donated by Alaska Airlines.
“The 228 is our largest and most capable test vehicle and it’s already in flight. We’re getting our Q400 ready to go, but it will probably take at least 9-12 months before that’s flight capable with hydrogen technology,” Miftakhov says.
The next step with the ZA600 is type certification of the powertrain with the UK Civil Aviation Authority (CAA), with concurrent validation by the FAA and European Union Aviation Safety Agency, followed by Part 23 supplemental type certification on the Caravan with Textron’s assistance. ZeroAvia is aiming for entry into commercial service in 2025.
“The test data is substantiating a lot of decisions that are going into the final design and we are happy that we didn’t have any real surprises,” he says. “The design is progressing as expected, so I think in the next 3-4 months we’ll be in a position to submit the project with the CAA.”
For installation on the Caravan, the ZA600 will be repackaged. The electric motor, inverters, fuel-cell stacks, compressor and heat exchangers will be mounted in the nose, replacing the Pratt & Whitney PT6A turboprop, while elements of the fuel system will be in the forward section of the cargo pod. There will be no battery in the production system.
The production ZA600 will have a liquid-cooled, direct-drive electric propulsion system that ZeroAvia is developing internally. With a peak power of 700 kW, this has four three-phase cores and four inverter/controllers, providing multi-engine redundancy in a single-propeller aircraft, Miftakhov says.
The ZA600 uses pressurized, 350-bar (5,000 psi) gaseous hydrogen storage and low-temperature proton exchange membrane (PEM) fuel cells supplied by Sweden’s PowerCell. The larger ZA2000 will use liquid hydrogen (LH2) and high-temperature PEM fuel cells developed internally by ZeroAvia.
The startup is already ground-testing the larger motor for the ZA2000. This is a liquid-cooled, high-speed machine that runs at 20,000 rpm and drives the propeller via a gearbox. The four-core motor is designed to produce 900 kW peak power and 750 kW continuous. Up to six can be stacked in the same shaft to produce up to 6.5 megawatts to power larger turboprops and regional jets.
For initial flights of the ZA2000 in the Q400 testbed, ZeroAvia plans to use two of these motor units to replace one of the Pratt & Whitney PW150 turboprops and power the propeller via the existing gearbox. Initially, electricity for the motors is likely to come from existing ZA600 power systems, Miftakhov says.
ZeroAvia is working with a partner to develop the LH2 tank for the Q400 demonstrator. This will be a composite, vacuum-insulated dewar. “We’ve already done a number of tests on a small version of the tank that holds 3 kg [6.6 lb.] of hydrogen,” he says.
The startup is aiming for the first application of the ZA2000 to enter service in 2027. This will not be the Dash 8-400, Miftakhov says but instead a 2-megawatt powertrain to re-engine the ATR 42/72 or Dash 8-300. The -400 could follow 1-2 years later, he says.
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