Stralis Aircraft Co-founder and CEO Bob Criner has said that his company will offer hydrogen-electric (HE) retrofits for Beechcraft Bonanzas, and is taking expressions of interest as system development proceeds.
Stralis is developing technology to power an A36 Bonanza using a 240-kW electric motor drawing from Stralis fuel cells fed from wingtip tanks.
Speaking at Avalon 2025, Criner said system development had been proceeding in A36 iron bird Clyde, but he expected it would move to flight-test article Bonnie for the first flight later this year.
"If anyone is flying a Bonanza and is interested in retrofitting it, we're certainly getting interest from Bonanza societies in Australia and the US."
"If you're interested, this is an exciting way to get your hands on the technology and see how it works."
The Stralis system uses an H3X electric motor coupled to Stralis in-house hydrogen-electric fuel cells, which are fed from Fabrum wingtip tanks.
"The Bonanza is designed for wingtip tanks, which we like for a number of reasons: the structure can already take a load out on the wingtip and it's easier to refuel and interface on the ground," Criner explained.
"With our fuel cells you can fly 10 times further than using batteries, but you can also fly twice the distance of a fossil-fuel-powered Bonanza with a 300-kg payload.
"You reduce the size of your radiators by a factor of five and the weight of the system by a factor of six. This really is the step-change that is needed to unlock hydrogen flight for commercial applications."
Importantly, Criner said that installing the Stralis system will keep an A36 within its existing weight-and-balance envelopes.
Although retrofit systems won't be available until after certification, Criner said that development was progressing at a steady rate.
"We're pushing towards upgrading the system," he said. "We've completely that first phase of testing, we've learnt a number of things and we're now upgrading the system towards the flight-ready state.
"We'll get the system into flight-ready state about Q3, do some ground testing, move from Clyde into Bonnie and prepare for high-speed taxi testing towards the end of the year and hopefully the first flight before Christmas."
Stralis is currently developing the HE powertrain using hydrogen gas, but is aiming for the certified product to use liquid hydrogen. Criner said the technology already existed, but that it needed to be brought into the aerospace sector and certified.
Once the technology is finalised, Criner said it will easily scale-up to larger aircraft.
"We're really excited about taking this technology from the Bonanza scale and moving it up to the Beech 1900," he said. "We think that's a great aircraft: it's the right size, it's Part 23, which is where we think this technology will enter the market.
"We don't think it makes sense to go straight to 150-seat single-aisles, it's just too much of a leap.
"The tech that's in the Bonanza is very scalable. The Bonanza is about 240 kW, the Beech 1900 is two 1 MW systems, so we increase the power by a factor of four."
Stralis is aiming to have the first commercial HE systems available in the second half of next year, after which it will begin work on the Beech 1900 project with a target entry into service of 2030.