Defiant is a joint project between Sikorsky and Boeing featuring a compound helicopter with rigid coaxial rotors
Billed as the fastest, most maneuverable and survivable helicopter in history, the SB-1 Defiant is a design being fleshed out to satisfy the United States Army’s “Future Vertical Lift” program which has since taken over the “Joint Multi-Role” requirement. Defiant is a joint project between Sikorsky and Boeing featuring a compound helicopter with rigid coaxial rotors, powered by two Honeywell T55 turboshaft engines; it first flew on 21 March 2019.
Currently SB-1 is in the development stage. It is in direct competition with the V-280 “Valor” being developed by Bell Helicopters for the same high-speed, Army transport requirements. The requirement for the SB-1 is a multi-role helicopter, intended to inherit the UH-60 Black Hawk, AH-64 Apache, OH-5 Kiowa and CH-47 Chinook models in the US Army. The similarity of parts between the new designs is also a strong suit of the family, lowering long-term maintenance and repair costs.
Central to the SB-1’s design was speed, in a world where forward flight for helicopters is typically maxed under 200 miles-per-hour. The compound approach of the SB-1 promises twice that and doubles range in the process – this not only makes a speedier and rangier platform, it also augments general maneuverability and agility – useful for when the aircraft finds itself under fire or attempts to navigate the confined spaces of a mountainous or urban environment.
A key feature of the Sikorsky–Boeing design is the coaxial main rotor arrangement, which is common with many Russian-branded Kamov models, which are used used to provide the necessary lift characteristics, while also supporting general stability along the lateral axis .The tail rotor applies the necessary thrust forward – giving the aircraft improved cruising speed.
The first prototype was unveiled in December 2018, and the first flight was pushed to early 2019. Ground runs began in January 2019. The product’s design is influenced some from Sikorsky’s previous work in the compound helicopter field – namely the “S-69” of the 1970s, and the more modern “X2”.
Sikorsky and Boeing state the design is to have a cruise speed of 250 kn, but less range due to using the “old” T55 engine. A new engine, the Future Affordable Turbine Engine, is to meet the radius requirement of 229 nmi. Sikorsky–Boeing states the SB-1 will be quick and nimble, with fast acceleration and deceleration, fast side-to-side movement, and the capability to hover with the tail up and nose down.
In January 2021, Sikorsky-Boeing announced the Defiant X variant, specifically designed for the Future Long-Range Assault Aircraft program. In February 2022, Sikorsky-Boeing picked Honeywell’s new HTS7500 engine, a derivative of the Honeywell T55 engine that powered the SB-1 demonstrator. In March 2022, Sikorsky-Boeing has selected Collins Aerospace to provide all three seating platforms and its Perigon as flight control computer.
