United Therapeutics, a biotechnology company that sponsored the development of the electric Robinson R44 helicopter, is continuing to advance the concept of a hydrogen fuel cell-powered aircraft.
5月9日，United Therapeutics子公司Unither Bioelectronics的项目管理副总裁Mikaël Cardinal在魁北克蒙特利尔举行的Vertical Flight Society's Forum 80上透露了该公司的进展。 卡迪纳尔说，他的团队已经研究了大约一年半的氢动力R44原型，它的第一次悬停“希望迫在眉睫”。
United Therapeutics began working with Southern California company Tier 1 Engineering in 2016 to develop the battery-electric R44. The project caused a stir in December 2018 when it set a Guinness World Record for the longest distance flown by an electric helicopter.
As Vertical reported at the time, the 30-nautical-mile (55 km) flight was more than just a publicity stunt. Rather, it's an early milestone in a well-thought-out strategy to develop a fleet of zero-emission vertical lifts to get organs from United Therapeutics' facilities to patients in need – an ambition that also includes partnerships with eVTOL developers EHang and Beta Technologies.
United Therapeutics has partnered with Tier 1 Engineering to develop the third generation of the battery-powered e-R44. In October 2022, the third-generation e-R250 with magniX magni44 motor made its first all-electric off-road helicopter flight from Jacqueline Cochran Regional Airport to Coachella Valley Palm Springs International Airport in California.
At the time, the partners said they were working on a Supplemental Type Certificate (STC) for battery-electric conversion. Ultimately, however, United Therapeutics decided that the 20-minute task that the battery-electric R44 was capable of was too limited for what it wanted to achieve.
"It's not an optimal system – it doesn't perform as well as a freshly designed eVTOL aircraft," Cardinal said of the battery-electric R44. Still, he said, the project "yielded a lot of valuable lessons in different aspects of the integration of electric propulsion systems into existing airframes as part of our overall strategy for our technology portfolio." United Therapeutics expects electric modifications to existing airframes to face fewer barriers to certification than all-new eVTOLs, although it has also invested in these.
As the company explores how to expand the range of its battery-electric helicopters (about 40 nautical miles (75 km) without reserves), hydrogen fuel cells emerge as a promising solution. Quebec-based Unither Bioelectronics decided to bring its hydrogen R&D in-house, procuring commercial technology and assembling it into an iron bird for initial ground testing.
"Over the last eight months, we've transitioned from this to the actual airframe and started integrating electric propulsion, as well as fuel tanks and fuel cell systems," Cardinal said. "We are currently building more datasets of knowledge that will be ...... Safe flight configuration of the experimental fuselage.
Based on what the company has learned so far, it believes a range of more than 175 nautical miles (325 km) can be achieved using liquid hydrogen as a fuel source. "With these range projections, we believe it could be a very interesting product in terms of range and payload from a commercial feasibility standpoint," Cardinal said.
The prototype consists of two low-temperature proton exchange membrane (PEM) fuel cell stacks and a booster battery pack to meet transient power demand. The hydrogen fuel tank was installed at the rear of the aircraft, aligned with the fairing under the tail boom. Cardinal said the company plans to conduct its first test flight with gaseous hydrogen later this year and transition to liquid hydrogen.
In addition to thermal management at hover, liquid hydrogen storage was one of the main challenges for the project. Cardinal said Unither Bioelectronics is using a fully customised vacuum-insulated composite tank that has shown very low evaporation rates. The system is also lightweight, with a structural weight of 35 percent, he said, "so with a total system weight of 67 pounds (30 kilograms), we are able to hold 44 pounds (20 kilograms) of liquid hydrogen," which is enough to meet the company's range target.
"In Quebec, we are fortunate that we have a green supply of liquid hydrogen, very close to where we lead our R&D activities," Cardinal noted. Going forward, he said, United Therapeutics' helicopters require relatively little hydrogen that can be met by an on-site production facility, "so we're envisioning local liquefaction hubs across the network to supply the fleet with hydrogen as we carry out organ delivery missions."
Mr Cardinal said Unither Bioelectronics sees itself as a "system integrator" rather than a technology developer and is working with a variety of external suppliers targeting the aerospace market. However, as it is still in the R&D stage, the company has not yet finalized or announced any suppliers. "We don't have a marriage with any particular player in the supply chain," he said.
As R&D has been underway in Quebec, Unither Bioelectronics has been liaising with Transport Canada about the project, recognizing that regulators will also need time to accelerate this new technology and develop appropriate certification standards.
Ultimately, the company aims to implement STC for its integrated solution, which may or may not work for R44. "We're planning to install STC on the Robinson fuselage — let's put it this way," Cardinal told Vertical.
THE FOUR-SEAT R44 RAVEN II AND CLIPPER II HELICOPTERS ARE HIGH-PERFORMANCE, RELIABLE AND EASY TO MAINTAIN. The R44 features a two-blade rotor system, T-bar cycle, streamlined instrument panel, and anti-collision fuel system. The aluminum monocoque and powder-coated steel tubular construction provide a lightweight yet sturdy airframe, while the aerodynamic airframe optimizes airspeed and fuel economy. Hydraulically enhanced control eliminates cyclic and collective feedback forces and provides responsive handling. Low tail rotor tip speed and large arc tail reduce flyby noise. The Raven II and Clipper II helicopters are powered by Lycoming's IO-540 fuel-injected engines. The IO-540 offers improved altitude performance, higher payloads, and eliminates the need for carburetor heating.
specification
| Raven II | Clippers II | |
| motor | Lycoming IO-540, six-cylinder, fuel injection | 莱康明IO-54O,六缸,燃油喷射 |
| horsepower | The take-off derating is 245 and the continuous derating is 205 | The take-off derating is 245 and the continuous derating is 205 |
| Maximum gross weight | 2500 lbs (1134 kg) | 2500 lbs (1134 kg) |
| Approximate empty weight (including oil and standard avionics) | 1505 lbs (683 kg) | 1,570 lbs (712 kg) |
| Standard Fuel (29.5 gallons) | 177 lbs (80 kg) | 177 lbs (80 kg) |
| Auxiliary Fuel (17.0 gallons) | 102 lbs (46 kg) | 102 lbs (46 kg) |
| Pilot, passengers, and baggage (on standard fuel) | 818 lbs (371 kg) | 753 lbs (342 kg) |
| Cruising speed at maximum gross weight | Up to 109 knots (202 km/h) | Up to 106 knots (196 km/h) |
| Maximum range (no reserve) | approx. 550 km (300 nautical miles) | approx. 550 km (300 nautical miles) |
| Hover ceiling IGE | 8950 feet @ 2500 pounds | 8950 feet @ 2500 pounds |
| Hover ceiling OGE | 7500 feet @ 2300 pounds | 7500 feet @ 2300 pounds |
| Rate of climb | More than 1000 fpm | More than 1000 fpm |
| Maximum working height | 14,000 feet | 14,000 feet |
| electrical system | 28 volts | 28 volts |
本文翻译来自United Therapeutics adds hydrogen to its electric helicopter plans - Vertical Mag
R44 Raven II and Clipper II Helicopters - Robinson Helicopter Company