Sikorsky-Boeing foresees no special challenges in scaling-up the technology developed for the X2 compound helicopter into the larger SB>1 Defiant that is being built for the US Army's Joint MultiRole - Technology Demonstrator (JMR-TD)/Future Vertical Lift (FVL) effort.
Speaking to reporters on 18 April, programme leaders said that recently aired comments in the media that the X2's rigid co-axial rotor and pusher propeller technology could not be scaled-up into the Defiant were wide of the mark, and that there should be no problems in doing so.
"There have been some comments as to whether the X2 scales-up to the [Defiant]. There are some issues with regard to the loads on the rotors increasing as they increase in size, but at this time they are not a challenge. We had the Critical Design Review at the beginning of 2016, and the design was closed-out at that time. We are meeting all of the predictions, and I don't see any restrictions on what we can do to this vehicle in terms of scalability," Sikorsky Vice-President of Future Vertical Lift and Mission Systems, Dan Spoor, said.
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 that included fly-by-wire flight controls, counter-rotating all-composite rigid rotor blades, hub drag reduction, active vibration control, and an integrated auxiliary propulsion system that included a pusher propeller that was driven by the same gear box that also turned the main rotors.
Weighing 6,000 lb (2,722 kg) and accommodating a crew of just two, the X2 was significantly smaller than the 32,000 lb (14,515 kg) and up to 18-person Defiant. Partly in order to help bridge this gap, Sikorsky developed its X2-derived S-97 Raider, which weighs in at 11,000 lb (4,990 kg) and can accommodate up to eight crew and passengers.
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