Air Platforms

Defiant makes maiden flight

21 March 2019

The first flight of the Sikorsky-Boeing SB>1 Defiant co-axial compound helicopter for the JMR-TD FVL programme took place on 21 March. Source: Sikorsky-Boeing

The Sikorsky-Boeing SB>1 Defiant co-axial compound helicopter made its maiden flight on 21 March.

The flight, which took place at Sikorsky's West Palm Beach facility in Florida, came some three months after the aircraft was rolled out in late December 2018, and marked a major milestone for the platform that has been developed under the Joint MultiRole - Technology Demonstrator (JMR-TD) programme to inform the US Army's Future Vertical Lift (FVL) effort.

Along with the Bell V-280 Valor tiltrotor, the Defiant was downselected in October 2014 to help the US Army develop its requirements for the new utility rotorcraft expected to enter service in the early 2030s. Based on an upcoming 'fly-off', the army will downselect to one platform for further development of the FVL family.

The Defiant and Valor are geared towards the Capability Set 3 (Assault)/FVL-Medium requirement, for which the US Army has laid down a number of key performance parameters. In terms of speed, the service stipulated the competing designs be able to fly at more than 230 kt while carrying 12 fully equipped troops. The Defiant is said to be able to attain 250 kt with 18 fully equipped troops.

To achieve this the SB>1 Defiant uses the same co-axial rotor and pusher propeller technology that Sikorsky developed for its X2 high-speed demonstrator and later its S-97 Raider. Developed by Sikorsky to cruise comfortably at 250 kt while retaining excellent low-speed handling, efficient hovering, and safe autorotation combined with a seamless and simple transition to high-speed flight, the X2 incorporated a number of advanced technologies, including fly-by-wire flight controls, counter-rotating all-composite rigid rotor blades, hub drag reduction fairings (not fitted during the first flight), active vibration control, and an integrated auxiliary propulsion system that included a pusher propeller driven by the same gearbox that turned the main rotors.

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