A little over a year since its Dornier 228 testbed last flew, advanced propulsion developer ZeroAvia has disclosed plans to convert the twin-turboprop into a liquid hydrogen test vehicle.
ZeroAvia previously modified the Do 228 (G-HFZA), replacing its port-side Honeywell TPE331 turboprop engine with a 600kW electric motor and fuel cell system running on gaseous hydrogen.
First flight of the hydrogen-powered aircraft took place in January 2023 from ZeroAvia’s Kemble airfield base in the UK. A further 11 sorties followed, culminating in a 35min mission – the testbed’s longest – on 18 April last year.
Since then, the Do 228 has been laid up. Responding to questions from FlightGlobal, ZeroAvia says the aircraft is in the process of “being converted into a liquid hydrogen flight testbed”.
ZeroAvia will retain the prototype powertrain – the fuel cells and balance of plant are installed in the fuselage – but the gaseous hydrogen tanks will instead be replaced with those for liquid hydrogen, stored at -253°C (-423°F).
In the meantime, the company is readying a second Do 228 (N409VA) to serve as the testbed for its ‘certification-intent’ ZA600 powertrain.
Having arrived in the UK in June last year, the Do 228 in February performed a series of five sorties – including a long-range return flight to Braunschweig-Wolfsburg in Germany – to gather baseline performance data ahead of the conversion work.
ZeroAvia says it expects both Do 228s to return to the skies later this year.
Commencement of flight tests with the N-registered example will be a crucial step towards the eventual integration of the powertrain with a single-engined Cessna Grand Caravan – the system’s launch platform.
ZeroAvia says manufacturing the certification-intent electric propulsion system – the motor, inverters and its power electronics – is under way at its Everett site in Washington state, while a fuel-cell-based power-generation system it is already being tested at Kemble.
“We’ll bring them all together in a new engine test facility for ground testing at Kemble,” it adds.
Once ground testing is complete, the system will be retrofitted onto the second Do 228 and flown on that asset before it is installed on a Grand Caravan.
Certification of the powertrain by the UK Civil Aviation Authority is targeted for 2026, with service entry to follow later that year or in 2027.
