Sabrewing Aircraft Company this week achieved a first hover flight with its RH-1-A Rhaegal VTOL uncrewed cargo aircraft. The preproduction prototype took off carrying an 829-pound payload (374 kg), which the California-based start-up claimed to be a new “deadlift” record for any commercial, vertical takeoff uncrewed air vehicle (UAV).
Since introducing the RH-1-A Rhaegal in 2020, Sabrewing has improved the propulsion system's ducted fans to boost thrust by 30 percent compared with the original design. Development work with the RH-1-A is preparing the way for the larger, higher-capacity RH-1-B production aircraft.
The Rhaegal B model is expected to have a maximum payload of 5,400 pounds when taking off vertically, rising to 10,000 pounds if using a 300-foot runway for conventional operations. In either case, the range is expected to be 1,000 nm (1,800 km), with the aircraft operating at speeds of up to 200 kts (368 km/h) and an altitude of 22,000 feet.
The preproduction RH-1-A weighed just over 2,700 pounds for its first flight, well below its maximum gross weight of 3,100 pounds. “This is only a fraction of what this aircraft can carry,” said Sabrewing chairman and CEO Ed De Reyes. “But it proves that we’re able to lift more cargo on our maiden flight than any previous cargo UAV.”
Currently, the Rhaegal aircraft is powered by a 1,400-kW turbo-electric version of the Arriel 2E turboshaft engine produced by France’s Safran group for helicopters. The turboshaft, which can run on a 50 percent blend of sustainable aviation fuel, turns an electric generator that produces nearly 1 MW of electrical power to run the UAV’s four ducted fans. The propulsion unit does not include batteries.
Sabrewing is working to achieve FAA and EASA type certification for the Rhaegal, with deliveries now anticipated to begin in December 2023. The first 28 aircraft have been ordered by the World Food/World Health program, and the company has reported another 102 firm orders and letters of intent for over 400 units that it says collectively represent a potential value of $3.2 billion.
The RH-1-B will be able to carry four ULD-2 cargo containers in its 675 cubic feet (19 cubic meter) hold. It will be able to support refrigerated cargo containers, which will be useful for missions such as humanitarian food deliveries and medical missions. Other applications could include search and rescue and firefighting. Sabrewing also has contracts with the U.S. Air Force to explore possible military uses, such as being able to evacuate eight injured soldiers.
In addition to Safran, program partners include Leonardo (avionics), Garmin (navigation systems), Toray (composite materials), Attollo Engineering (Lidar radar), Spider Tracks (remote positioning), U.S. Cargo Systems (cargo floors), and Cal State Channel Islands (software). Ohio State University, UCLA, and Oklahoma University are also contributing to the development project.
Sabrewing had hoped to bring the Rhaegal to market in 2022, but development work has taken longer than expected as it opted to make improvements to the propulsion system. The company says it is now building the first example of the B model, but hasn't yet settled on a target date for a first flight.
“We are extremely proud to have accomplished this milestone,” said De Reyes, who founded the company in 2016. “It’s been a long journey to get here, but we were unwilling to compromise safety or design. Our design and test teams—and our development partners—invested tens of thousands of hours in such a history-making success.”