Robinson refines fuel cell system ahead of hydrogen-powered R66’s first flight

Manufacturer continues initiative to develop a zero-emission version of its best-selling turbine helicopter.

Robinson Helicopter has begun “up-and-away” flights of a hydrogen fuel cell-powered version of its R44, with the modified rotorcraft leaving the confines of its base airport in Bromont near Montreal in Canada for the first time.

Having carried out “pattern work” along the airport’s runway since its first flight last year, latterly to allow Robinson’s test team to balance the power provided between the fuel cells and batteries, the R44 is now flying “all around the region”, chief executive David Smith told FlightGlobal at this week’s Aero Friedrichshafen show.

Much of the hydrogen powertrain is hidden inside the fuselage, but to provide thermal management for the fuel cells, the R44 features distinctive nacelles “that look like turbofan engines” mounted above the skids. These house the cooling fans and other heat exchanger elements.

A key target of the expanded flight-test regime is to assess the effect of those nacelles “on stability during higher speed flight” and the magnitude of drag penalty they incur, a figure Smith says will likely be “meaningful”.

In the latter case, a better understanding of the effects of higher drag on performance will allow Robinson to work through its proposition for operators, who may be prepared to trade speed for more payload or endurance.

Although a prototype configuration, an eventual product will still require a substantial thermal management system to deal with the “pretty high thermal loads” generated by the long periods a helicopter spends hovering.

Improvements in fuel cell technology, particularly of high-temperature systems, may also be needed to ensure a hydrogen-powered helicopter can be operated globally, suggests Smith.

“This design has worked in our test facility in Montreal, we are not sure it will work yet in Arizona or in more equatorial regions,” he says.

In development since 2024 in partnership with United Bioelectronics, the work on the R44 demonstrator will pave the way for a hydrogen-powered version of the larger R66.

Conversion of that helicopter will take place this year, ahead of a first flight planned for 2027, says Smith.

While it will use a similar heat-exchanger system to the R44, the design has been refined, says Smith: the intakes will be positioned higher on the fuselage and more integrated with the airframe, improving drag performance.

Another significant change between the two aircraft will be a switch from gaseous to liquid hydrogen due to its better volumetric density.

Robinson also intends to retain the two 85kW-output fuel cell stacks used in the R44, although it may look for a higher power rating if an increase in maximum gross weight is wanted. Power will come from a 250kW Magnix HeliStorm electric motor.

Additionally, tests so far have shown that while the hydrogen-electric R44 is significantly quieter than the standard piston-powered version, absent the noise from the engine  “what you end up with is the [sound from] the tail rotor”.

As such, one of the firm’s “focus areas” is to refine the shape of the two-blade tail rotor to “reduce the noise signature” – potentially adding swept tips and an improved aerofoil design.

“We looked at multi-bladed, but it adds complexity to the design and weight and cost,” he adds.

Certification of the fuel cell-powered R66 under a Transport Canada supplemental type certificate is targeted for 2030.

“We believe this can fly 200 nautical miles, with zero emissions, producing just water,” says Smith.

“This is a technically feasible design, it just needs to go through the rigour of a certification programme.”