The Sikorsky/Boeing SB-1 Defiant demonstrator, the team’s entrant for the U.S. Army’s Future Long-Range Assault Aircraft (FLRAA), has flown to a speed of 247 kt., with the engine showing some limited power left to go faster, the companies said Oct. 12.
The companies have said they hope to exceed 250 kt. with the aircraft, which uses rigid coaxial rotors and a pusher propeller to reach high speeds. The aircraft has also flown a 56 kt. side flight and lifted a 5,300-lb. training pod, the companies said during an update at the Association of the United States Army conference in Washington.
So far in testing, the SB-1 Defiant demonstrator has flown 41 flights totaling 39 hr., along with 42 ground run hours. The team will keep the demonstrator flying through the end of this year and into next year, with another flight planned for Oct. 15. That is when pilots plan to test efficiency at speed through steps such as moving the aircraft’s elevator and flying at different pitch attitudes to experiment with “a lot of variables” in flight, said Bill Fell, Lockheed Martin-Sikorsky’s principal test pilot. During the 247 kt. flight, test pilots aimed to reach 240 kt., and continued before deciding seven more was enough of an overshoot.
“We were designed to achieve the Army goal of 230 knots. We’ve already significantly exceeded that,” Fell said. “I think anything above 250 knots will put a smile on my face when I get home. There’s not a lot of speed remaining in it, but we have some.”
The Defiant X is an underdog for the speed goal as part of FLRAA, with Bell’s V-280 tiltrotor having exceeded 300 kt. in test. The V-280 demonstrator has flown 214 flight hours in test, and the company is reviewing data on its performance.
Fell said the Defiant X’s 250-kt. goal will be a “dash speed,” as opposed to a cruise speed. There is not a complete performance chart for the aircraft with its two Honeywell T55 turboshaft engines yet, with Sikorsky/Boeing working out the best range speed and cruise speed. The rear propeller, which can switch from push to pull, will help the helicopter go from 200 kt. to a hover in about half a mile, Fell said.
“We’ve got some pretty good ideas, but we’re still narrowing in on them,” Fell said.
The Army wants the FLRAA effort, part of its Future Vertical Flight program, to replace more than 2,000 Sikorsky UH-60 Black Hawks. The aircraft could also be part of the Marine Corps’ Attack Utility Replacement Aircraft program, though that requires an aircraft that can cruise at a speed of at least 280 kt.
Sikorksy and Boeing delivered their proposal in September. The Army plans to award a development contract in the third quarter of fiscal 2022. The entrants are continuing Phase 2 of the Capability Development and Risk Reduction program, during which Sikorsky/Boeing are working to refine the design, said Jay Macklin, Lockheed Martin-Sikorsky’s business development director for Future Vertical Lift.
