Sikorsky X2 breaks helicopter speed barrier

http://www.flightglobal.com/articles/2010/05/20/342211/sikorsky-x2-breaks-helicopter-speed-barrier.html

Sikorsky reports that its X2 advancing blade concept technology demonstrator has achieved 168kt (311km/h) forward speed, putting the dual counter-rotating pusher-prop compound beyond the typical maximum speed for traditional helicopters and outside the reach of the company's S-76 chase vehicle's 155kt capability.