Deutsche Aircraft has begun the early stages of modifying a legacy Dornier 328 twin-turboprop to serve as a flying testbed for a new hydrogen-electric powertrain.
Dubbed “Alpha” by the German company, the aircraft will retain its two Pratt & Whitney Canada PW119 engines but gain a pair of 1MW GE Aviation electric motors on outboard wing stations. A 1.5MW fuel cell system running on liquid hydrogen will be located inside the fuselage.
Riaan Myburgh, chief engineer, future projects and demo at Deutsche Aircraft, says the configuration was selected to “segregate the systems under test from flying the aircraft”.
In addition, the performance characteristics of the Do 328 will allow it to “lift the equipment under test to the appropriate flight conditions”.
Initial modification work on the airframe (MSN3015/D-CSNC) has begun at Deutsche Aircraft’s Oberpfaffenhofen facility in Bavaria, southern Germany to support a first flight in 2025 or 2026.
In particular, the fuel system will be slimmed down as the aircraft no longer needs to carry the same volume of jet fuel, reducing the wing loading sufficiently to allow installation of the two outboard electric motors.
With fuel cell technology still in its relative infancy compared with that of the electric motors and power management system, Deutsche Aircraft has deliberately oversized the overall electrical system, says Myburgh. This will allow the aircraft to support a higher-power fuel cells as these are developed in future “without redoing the whole electric system”.
“A total of 2MW is sufficient to power the aircraft in cruise. It gets us to the power classes for the electrical system, integration, fuel cell management and thermal management that is relevant for future aircraft,” he says; around 4MW would be required to power an aircraft the size of a Do 328, he adds.
Ultimately the airframer intends to bring a hydrogen-powered aircraft to market as a successor to its developmental D328eco which is scheduled for certification in the second half of 2026. However, it has yet to decide on what the follow-on design will look like.
“We don’t know yet,” says Myburgh in reference to the future aircraft. “This architecture is interesting, that’s why we selected it.”
To reach a 4MW-class system there are “lessons we still need to learn”, he says. “This aircraft enables us to learn them in order to make that decision.
“The precise hybrid architecture will depend on how fuel cells develop over the years.”
However, he stresses there is no immediate need to finalise the architecture for the “N+1 aircraft” until the D328eco arrives later in the decade.
Technology evaluation work on the platform is supported by two separate research programmes funded by the German Federal Ministry for Economic Affairs and Climate Action: one covers the propulsion system and includes GE and TU Berlin, while the second is focused on the power system and features H2Fly, Diehl Aviation, Premium Aerotec and aerospace research centre DLR.
Deutsche Aircraft recently announced a delay to the certification of the D328eco – a stretched and modernised variant of the original Do 328 – pushing the milestone back until the second half of 2026 from an earlier 2025 target.
Peter Spyrka, director of programmes, says the revision followed discussions with the aircraft’s supplier base. “We had to adapt the schedule to the ramp-up… and build-up of the supply chain,” he says.
Production of the first flight-test article using a lengthened fuselage and wing retained from the original Do 328 programme will begin in 2023, leading to the aircraft rolling out in 2024 and first flight in 2025.
Final assembly of serial aircraft will take place at a new facility to be constructed in Leipzig. Deutsche Aircraft says the D328eco will be able to carry up to 40 passengers on flights of up to 600nm (1,110km). A high-density 43-passenger layout is an option but this will trim the range slightly.
A significant part of the aircraft’s green credentials will come from the ability of its twin PW127XT-S powerplants to run on 100% sustainable aviation fuel – either standard biofuel or that produced through the power-to-liquid (PtL) process.
“Our objective is clearly to make the Eco 100% compatible with PtL fuel by service-entry,” says Dr Regina Pouzolz, head of sustainability. “It is a really, really efficient way to have an impact on climate change.”
Deutsche Aircraft on 22 June struck an agreement with South African fuel producer Sasol to advance the use of PtL fuel in aviation.