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In its most recent test flight last week, the Sikorsky-Boeing SB>1 Defiant coaxial helicopter flew faster than 200 knots and with another 50 percent power in reserve is set to “well exceed” the target speed of 230 knots in coming months.
In a June 9 test flight at the Sikorsky flight test facility in West Palm Beach, Florida, Defiant reached 205 knots in forward level flight.
“Two hundred and five knots is just a number, but it’s a number that you’re not typically accustomed to hearing with respect to a helicopter,” Bill Fell, Sikorsky’s chief test pilot, told reporters during a video conference call June 16. “Expect a lot more in the future because we have a lot more prop power to apply in this machine. . . .
“If we have it our way, the only thing that will limit us is the amount of power that those engines can produce to put thrust into that pusher prop,” Fell added.
The Sikorsky-Boeing team as of June 16 has 113 hours on the ground-based propulsion system test bed, 20 hours of ground run on Defiant itself and 18 hours of flight time. The aircraft has flown at 10,000 feet (3,048 meters), performed a 45-degree angle of bank turn and done some “side-slip work,” Fell said.
Defiant is one of two aircraft competing to become the Army’s Future Long Range Assault Aircraft (FLRAA), which should fly at least 230 knots. Its competition, Bell’s V-280 Valor advanced tiltrotor, has flown at 300 knots.
The U.S. Army is emphasizing speed as a critical capability for future rotorcraft that are expected to fly in “contested” environments where enemies possess guided anti-aircraft munitions. In those environments, helicopters flying low and slow are vulnerable. FLRAA and its smaller counterpart, the Future Attack Reconnaissance Aircraft (FARA), will fly below air defense systems or fly through them faster than an enemy is able to detect, target and shoot them down.
“Exceeding 200 knots is significant also because it’s beyond any conventional helicopter speed and we understand that speed and low-level maneuverability is critical to the holistic survivability in the future [vertical lift] environment,” said Jay Macklin, Sikorsky’s business development director for FVL. “The key takeaway is we’re seeing exactly the performance our analytical tools predicted. This gives us even greater confidence as we continue to expand the speed envelope and maneuvers in Defiant.”
Macklin’s Boeing counterpart, Randy Rotte, said the 200-knot benchmark validates the digital modeling and data gathered on the ground-based propulsion system test bed (PSTB) that shows the basic X2 coaxial technology is scalable and performs in the real world the same way it does in simulation.
“It’s another point along the way that helps refine our models, that gives us . . . continued confidence in them, that they are telling us exactly what we’re going to be able to do,” Rotte said. “If you go back in time, talking about X2 and then Raider and now Defiant, there were definitely those who were not convinced that you would be able to scale this technology up to the size we have and the capabilities we are showing.”