Sikorsky–Boeing
SB-1 Defiant

The Sikorsky–Boeing SB-1 Defiant (stylized as "SB>1"; company designation S-100) is the Sikorsky Aircraft and Boeing entry for the United States Army's Future Long-Range Assault Aircraft program to replace the Sikorsky UH-60 Black Hawk. It is a compound helicopter with rigid coaxial rotors, powered by two Honeywell T55 turboshaft engines; it first flew on 21 March 2019.

Sikorsky Aircraft and Boeing are jointly producing a medium-lift-sized demonstrator they named SB>1 Defiant (also widely known as "SB-1") for phase one of the program. Originally planned to fly in late 2017, its first flight was delayed in April 2017 to early 2018. Once flight testing begins, the aircraft will be evaluated by the Army for further development. Sikorsky is leading the development of phase one with an aircraft based on their previous Sikorsky X2 design

Sikorsky and Boeing state the design is to have a cruise speed of 250 kn (460 km/h), but less range due to using the "old" T55 engine. A new engine, the Future Affordable Turbine Engine (FATE), is to meet the radius requirement of 229 nmi (424 km). Compared to conventional helicopters, the counter-rotating coaxial main rotors and pusher propeller offer a 100-knot (185 km/h) speed increase, a 60% combat radius extension, and 50% better performance in high-hot hover operations.

Sikorsky has said that the X2 design is not suitable for heavy-lift size, and instead suggests the CH-53K for heavy-lift and tiltrotor for the ultra-class. However, Sikorsky plans to build the 30,000-pound-class (14,000 kg) JMR-TD (with a cabin 50% larger than the Black Hawk) at full scale to remove doubts about the scalability of the X-2 technology.