WASHINGTON — The Sikorsky-Boeing SB-1 Defiant coaxial demonstrator hit a new speed record of 205 knots during a June 9 flight test, the companies announced Tuesday.
The test marks a major step forward as the Sikorsky-Boeing team continues to march toward a speed requirement of 230 knots, Jay Macklin, Sikorsky’s director of future vertical lift business development, said during a June 16 roundtable with reporters.
The flight, which was piloted by Sikorsky test pilot Bill Fell and Boeing test pilot Ed Henderscheid, occurred at Sikorsky’s Development Flight Test Center in West Palm Beach, Florida.
“Exceeding 200 knots is significant also because it’s beyond any conventional helicopter speed, and we understand that speed and low-level manueverabily is critical to the holistic survivability in a future FVL environment,” Macklin said, using an acronym for future vertical lift, the U.S. Army’s effort to build next-generation rotorcraft.
The Defiant is one of two rotorcraft taking place in a competitive demonstration and risk-reduction effort ahead of the Army’s Future Long-Range Assault Aircraft program. The Army envisions FLRAA as a replacement for the UH-60 Black Hawk helicopter in the early 2030s.
The Defiant, a compound helicopter with coaxial rotors, will compete against Bell Helicopter’s V-280 Valor tilt rotor when the FLRAA program of record starts in 2022.
Fell said that during the latest Defiant flight demonstration, he was able to hit speeds of 205 knots using less than 50 percent of the aircraft’s installed propeller power. “Expect a lot more in the future because we have a lot more [propeller] power to apply to this machine,” he said.
Fell added that he believes the team will fly Defiant at maximum speeds — which could be in excess of 250 knots — in a matter of “a few months,” but that will depend on the pace of ground tests using the propulsion system test bed, or PSTB. The Sikorsky-Boeing team is carrying out extensive testing with the PSTB to wring out potential issues on the ground before moving to flight demos.
“It’s a little bit different when you’re putting power on that prop and you’re going through the air at 200 knots versus statically on the ground,” Fell said. “We have to do some MacGyver engineering on the [propeller] stand to keep the loads in check because they are significantly higher here on the test stand without the airflow through it that you have in flight.
“As we clear the [propeller] on the ground stand, that gives me the added confidence when we get up there in flight.”
The Defiant has clocked in 18 flight hours since its first flight in March 2018, and it has put 113 hours of testing on the PSTB. In January, the Defiant flew for more than 100 knots for the first time.
Macklin acknowledged that the COVID-19 pandemic has had a small impact as Boeing and Sikorsky take steps to protect its employees. But for the most part the flight test program has remained on track, he said.
Added Fell: “If we fly once a week, we’re pretty happy with that, and if we fly every other week, we’re happy with that as well. But we have to continue to make progress and run the test stand.”