Piasecki targets light helicopter market with hydrogen-powered PA-890
By Oliver Johnson | April 29, 2022
Estimated reading time 15 minutes, 21 seconds.
Piasecki Aircraft is developing what it believes will be the first FAA-certified hydrogen-powered helicopter, with plans to fly a scale system of the potentially revolutionary propulsion system on a surrogate helicopter early next year.
As well as producing no direct emissions, the Piasecki PA-890 Pathfinder promises a 50 percent reduction in direct operating cost over traditional turbine-powered helicopters, as well as reduced noise.
The PA-890 features a slowed-rotor winged compound design, with a large four-bladed main rotor, a “variable incidence” wing that rotates up to 90 degrees to minimize download in hover, and a swiveling tail rotor that provides anti-torque and yaw control.
When in forward flight, the aircraft’s wing moves to a horizontal position, providing additional lift to offload the rotor; while the tail rotor swivels to offer forward propulsion. The combined effect lessens the lift and thrust demands of the main rotor, which can then be slowed. This reduces drag and increases the aircraft’s range (Piasecki Aircraft’s design mission is 200 nautical miles, plus IFR reserve), while reducing noise.
The company says the low disk loading of the PA-890 will deliver excellent hover performance and allows for safe autorotation landing. Using a conventional rotorcraft architecture for its main components will reduce the complexity of the certification process.
Piasecki is aiming to certify the PA-890 under existing Part 27 standards, reducing the technical, cost and schedule risk of bringing it to market, the company believes.
The aircraft is being designed to carry a pilot and seven passengers, and have a cabin size that would allow for “multiple configurations” for different missions, including emergency medical services (EMS) operations.
The hydrogen fuel cells, being developed in partnership with HyPoint, provide power through a chemical reaction between hydrogen and oxygen across a membrane, generating electricity and water vapor as a by-product. The cell runs at a relatively high 160 C/300 F (compared with existing “low temperature” hydrogen fuel cells), and use ambient air to regulate the system’s temperature.
Piasecki said this approach reduces the fuel cell’s complexity and weight compared to low-temperature hydrogen fuel cells, and will allow it to achieve two or three times the energy density at the system level; and six times the energy density of lithium-ion batteries.
The PA-890 aircraft is being developed in parallel with the hydrogen fuel cell, but it is the latter that will dictate the program’s pace.
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“The big push right now is getting the hydrogen fuel cell developed and into test in as realistic an operating environment as possible,” John Piasecki, president and CEO of Piasecki Aircraft, told Vertical. “We’re going to take the fuel cell test units, integrate them onto a surrogate aircraft helicopter, flight demonstrate them, and learn a lot in the process.”
At the same time, the company will be designing a full-scale hydrogen fuel cell system for the PA-890. This will run in a ground test rig; and once qualified on the ground, will be integrated into the PA-890 itself.
The timelines for this program are ambitious: flight demonstration of the scale system in the first half of 2023, ground tests of the full system by the end of 2023/early 2024, and certification flight testing of the PA-890 with the fuel cell integrated by 2027.
Piasecki said the Pathfinder is “really focused on a real market,” using many technologies the company has already developed.
“We wouldn’t be trying to target that existing market without some major step increase in value,” he said. “From our perspective, the most compelling area that needs to be addressed with helicopters is cost. I know there’s a lot of enthusiasm about zero emissions — and that is a really important component of it — but in order to penetrate a very well established mature market, you’ve got to be offering something that is compelling, and reduction of cost is the most important thing.”
The promise of hydrogen
While there is currently a huge amount of industry excitement about — and significant global investment in — the urban air mobility industry, Piasecki said his company is targeting the traditional light helicopter market with the ground-breaking new system.
Founded by industry pioneer Frank Piasecki in 1955, Piasecki Aircraft has a long history of developing new technology and approaches for the vertical-lift market.
“We are vertical lift enthusiasts and we are always looking out to the future — but we also are realists,” said Piasecki.
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“Our ability to endure has been based on a realistic assessment of technology’s potential, the timeline to develop it, and then the applicable markets. In looking at the lay of the land, and engaging customers directly, we feel that the most near-term realistic market isn’t the UAM market, it’s going to be the existing light helicopter turbine market, for which there are real customers that are paying real dollars.”
Development of the PA-890 began in late 2017, with a broad configuration study where Piasecki Aircraft evaluated 25 different vehicle types against various criteria the company felt reflected the market needs.
The end result was a decision between two designs: a low disk loading tiltrotor and a compound helicopter coupled with a wing and auxiliary thruster. While the compound configuration was heavier, it was still within the Federal Aviation Administrations Part 27 7,000-pound (3,175-kilogram) gross weight limit.
“We felt the lower certification risk of a compound helicopter and its simplicity — which directly extends into both acquisition and operating costs — really gave that platform a leg up,” said Piasecki.
The company looked at lithium-ion battery power “very intently,” but its analysis predicted diminishing returns in that technology’s future rate of growth, as well as dramatically degraded cycle life from rapid charging and discharging. The latter also pushed the potential operating cost of the aircraft close to that of a turbine helicopter.
Piasecki said lithium-ion battery technology was also unlikely to be able to provide the performance — in terms of range — to compete with turbine helicopters.
“When you look at the distribution of ranges in the market for various missions — I’m talking EMS and oil rig support, utility functions, etc. — the 50 or so miles that Uber talked about [in its market-defining 2016 Elevate White Paper] as being the requisite spec range for electric vehicles is not adequate,” said Piasecki. “We’re really not designing the aircraft to meet that requirement; we’re designing it to meet what we feel is a useful capability in the existing marketplace.”
This left hybrid electric power and hydrogen fuel cells under consideration. While Piasecki was keen to stress the benefits of a hybrid system — including a significant reduction (potentially 25 percent) in operating cost, it still requires the complicated machinery of an internal combustion engine.
“Hydrogen fuel cells showed a lot of promise and they delivered the required performance — not quite as good as the hybrid — but it met our mission objectives,” said Piasecki. “Furthermore, there are growth opportunities in fuel cells that will allow us to be better than hybrid, ultimately.”
That growth in energy density could be two or three times the figures the company’s current projections, he said.
And, as hydrogen fuel cells use an electrochemical reaction, there are few moving parts — and this is one of the key reasons the operating cost is anticipated to be so much lower than that of a turbine helicopter.
“It is a budding technology, and it still has a long way to go,” said Piasecki. “As technology developers, we are very clear-eyed about the challenges in front of us, and we have a crawl-walk-run approach. The hybrid propulsion is always available for us to exploit, but we’re going to shoot for the moon with hydrogen fuel cells.”
Piasecki announced a partnership with HyPoint — a developer of turbo air-cooled hydrogen fuel cell systems for aviation and urban air mobility — in August 2021. At the time, the two companies said they planned to deliver a customizable FAA-certified, zero carbon-emission hydrogen fuel cell system to the global eVTOL market.
The cell uses compressed air for both cooling and oxygen supply, and HyPoint believes it will be able to achieve up to 2,000 watts per kilogram of specific power.
The agreement calls for the development of five 660kW hydrogen fuel cell systems for the PA-890.
At HAI Heli-Expo 2022 in Dallas, Texas, in March, Piasecki Aircraft announced it had signed a memorandum of understanding with Metro Aviation to further develop the PA-890.
“We wanted to have the benefit of somebody that has an innovative culture and also the operational experience to be able to inform the design while it is still in the malleable stages of development,” said Piasecki.
In addition to getting Metro’s input as an operator, Piasecki said his company would also be able to leverage their experience to commercialize the PA-890, as well as Metro’s other services — such as interior installations and training.
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In a press release detailing the move, Metro Aviation CEO Mike Stanberry said his company was “glad to be a part of” bringing carbon-free, quieter technology to the rotary-wing world.
“We look forward to a long-term partnership with Piasecki, sharing our expertise in helicopter completions, flight operations, maintenance, training, and support to help make the Pathfinder a truly transformational product for our industry and customers,” he said.
While the agreement with Metro at Heli-Expo represented the first public announcement to the commercial market about the PA-890, Piasecki Aircraft has been quietly working with several operators for a little while on the program. “The most important thing is the validation that we’ve received from the marketplace about how positive the reception would be if we could reduce operating cost by 50 percent,” said Piasecki. “That is game changing for the whole industry. The market size for the application of vertical lift is, in large part, restricted by its cost — and if you can reduce the operating costs by 50 percent, a whole bunch of different applications in the market will expand to take advantage of it.”