SB>1 Defiant coaxial helicopter speeds past 100 knots in latest test flight

Sikorsky and Boeing have started the new year by speeding up flight testing of the SB>1 Defiant, which bested 100 knots in forward flight on Jan. 13.

As the Defiant team has done announcing previous flight test milestones, the revelation of the compound coaxial helicopter’s fast flight came in an edited video that hit social media early Jan. 17.

The aircraft is seen to lift off from the Sikorsky Development Flight Test Center in West Palm Beach, Florida, on Jan. 13. During takeoff and hover, Defiant’s rear pusher propulsor is not spinning.

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The video then cuts to a 30-degree angle of bank turn, where the propulsor is spinning. The camera next zooms in on the twin, counter-spinning coaxial rotors before focusing on the spinning rear prop during forward flight that “exceeded 100 knots,” according to a caption.

All the while the rear propulsor is engaged, but the landing gear remain extended throughout the flight.

“The Sikorsky-Boeing team is focused on program performance and continues to advance SB>1 Defiant’s rigorous test flight program,” the team told Vertical in an email. “We are very encouraged by the data we are collecting from our flights and from the feedback we are receiving from our pilots.”

Defiant has the same basic configuration as its smaller brother, the S-97 Raider. The 33,000-pound Defiant is aimed at fulfilling the Army’s need for a Future Long-Range Assault Aircraft, or FLRAA.

The Sikorsky-Boeing SB>1 Defiant exceeded 100 knots and performed maneuvers at 30 degrees angle of bank at the Sikorsky Development Flight Test Center in West Palm Beach, Florida, on Jan. 13. Lockheed Martin Photo

Since it first flew in March 2019, Defiant has flown at least five times. Testing began slowly, though deliberately, in Florida through three flights until the engineering team disassembled and inspected the ground-based propulsion system test bed — which mimics the stress put on Defiant’s drive train — and found the main rotor gearbox was grinding some of its bearings. So-called “bearing creep” was not found on the Defiant itself, but flight testing was halted for weeks while the issue was corrected.

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Defiant returned to flight in late September 2019 and by December had achieved 20 knots in all directions, according to Sikorsky. The Defiant team said it plans to expand the aircraft’s performance envelope in 40-knot increments out to at least 250 knots.

The team “continues to expand [the Defiant’s] flight envelope through sorties each week,” according to a Sikorsky spokesperson.

Defiant was developed and is flying under the sundowning Joint Multi-Role Technology Demonstration (JMR-TD) program. Its primary competitor, the Bell V-280 advanced tiltrotor, has logged significantly more test flight hours since its first flight on Dec. 18, 2017. Two years to the day in 2019, the V-280 Valor flew an autonomous test flight at Bell’s test flight facility in Fort Worth, Texas.

Valor has logged more than 150 flight hours and in 2019 met its namesake speed of 280 knots.

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