US-UK hybrid-electric aircraft propulsion system development company ZeroAvia has reported that it has successfully completed its first flight test programme, using a Dornier Do 228 twin-engined testbed aircraft. In feederliner configuration, a Do 228 can carry 19 passengers. This testbed aircraft has had one of its turboprop engines replaced with an electric motor, part of ZeroAvia’s ZA600 propulsion system.

The ZA600 system is composed of a hydrogen fuel cell, currently fitted (for convenience) in the aircraft’s cabin, which generates the electricity which is used to drive the electric motor mounted on the aircraft’s port (left) wing. The only emission produced by this system is low temperature water. Studies indicate that hybrid-electric propulsion would reduce the climate effects of aviation by more than 90%.

“Zero-emission flight technologies are moving from promise to delivery and our amazing team is leading the way with this testing programme,” affirmed ZeroAvia founder and CEO Val Miftakhov. “We do not have to push the unappealing choices on passengers of paying more or flying less to deliver climate-conscious air travel. We instead can adopt this technology quickly to reduce climate impact and air pollution.”

This first flight test programme lasted six months and involved ten test flights. These saw the aircraft operate across a temperature range from just above freezing point to just under 30 °C, carry out a 23-minute endurance test, and reach the maximum speed limit assigned to it, by the UK Civil Aviation Authority, in its Permit to Fly. The aircraft also reached and flew at an altitude of 5 000 feet (1 524 m).

The company reported that, throughout all these tests, both the fuel cell and the electric motor performed at, or above, expectations. The ZA600 propulsion system matched the power of the conventional, fossil fuel, turboprop on the other (starboard, or right) wing. On certain tests, the aircraft was flown using only the power produced by the ZA600.

The tenth and last flight in this first test series was a cruise test. The data from this will be used to predict the ranges that the ZA600 system will be able to achieve. This will prepare the way for the second flight test series, which will include the first cross-country flights with the aircraft.

The ZA600 testing programme is part of the UK’s HyFlyer II project. This is partly funded by the UK government through the Aerospace Technology Institute (a public-private partnership), jointly with funding agency Innovate UK and the UK Department for Business and Trade.