The Sikorsky–Boeing SB-1 Defiant is the Sikorsky Aircraft and Boeing entry for the United States Army's Future Vertical Lift program, succeeding the Joint Multi-Role initiative. It is a compound helicopter with rigid coaxial rotors, powered by two Honeywell T55s, and made its first flight on 21 March 2019.
Sikorsky Aircraft and Boeing are jointly producing a medium-lift-sized demonstrator they named SB-1(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.

Boeing plans to lead phase two, which is the mission systems demonstrator phase.The Boeing-Sikorsky team is seen to have an advantage with their large industrial base that may result in wider support from Congress. Their transport helicopter designs are the most-used in the Army now, and the US Army has had little interest in the tiltrotor technology in Bell's submission.

Up to 2013, Sikorsky and partners have spent $250 million on X2 and Raider.[5] The team and aircraft will be separate from the S-97 Raider.[9] The team feels confident in the SB-1 Defiant and is paying for more than half of its design costs. The last project the companies teamed up for was the RAH-66 Comanche, which started in the 1980s and cost $7 billion before being cancelled in 2004. They say that factors outside their control, like budget cuts, "requirement creep", and a long development period caused problems with the Comanche and not team dysfunctionality. Under the Comanche program, each company built different parts of the aircraft. For JMR, employees from both companies will work together. The team named the suppliers in 2015. Swift Engineering Inc. supports the program with a major portion of the airframe structure designed and manufactured at the company's facility in San Clemente, California by an integrated team of Swift and Boeing employees.

The timeline for the first flight has slipped several times. Originally scheduled for 2017, delays arose due to a requirement to implement automated fiber placement blade manufacture at the request of the U.S. Army. Further delays resulted in the first flight slipping past summer 2018. Dynamic systems like turboshafts, transmission, and rotors were scheduled to be tested at West Palm Beach, Florida, by the end of October 2018, before ground runs in November, then first flight to reach 200 knots (230 mph; 370 km/h) within six months.

The first prototype was unveiled in December 2018, and the first flight was pushed to sometime in early 2019.[16] Ground runs began in January 2019; 15 hours of ground tests were needed before the first flight.

The first flight took place on 21 March 2019 at Sikorsky West Palm Beach site in Florida.In the summer of 2019, flights were suspended to address a bearing issue with the main rotor. Flight testing resumed 24 September 2019. The aircraft reached a speed of 211 knots in October 2020.

El Sikorsky–Boeing SB-1 Defiant (acortado como "SB-1") es la propuesta de Sikorsky Aircraft y Boeing para el programa Future Vertical Lift del Ejército de los Estados Unidos, como sucesor de la iniciativa Joint Multi-Role. Es un girodino de rotores coaxiales, propulsado por dos Lycoming T55s. Su primer vuelo ha tenido lugar el 21 de marzo de 2019 en las instalaciones de Sikorsky en West Palm Beach, Florida.

El diseño tendrá una velocidad de crucero de 460 km/h, pero un menor rango a causa de utilizar el "antiguo" motor T55. Un nuevo motor, la futura turbina afordable (FATE), conseguirá el rango necesario requerido 229 nmi (424,1 km).1​2​ Comparado con helicópteros convencionales, los rotores coaxiales, copiados a la rusa Kamov, y la hélice tractora ofrecen un incremento de velocidad de 342 km/h, un 60% más de radio de combate, y un desenlace un 50% mejor en zonas altas y calientes.

Sikorsky Aircraft ha dicho que el diseño X2 no está diseñado para grandes cargas, y sugiere para esa tarea el CH-53K, que es un helicóptero pesado y convertiplano.

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