Hingeless rotor systems. You have to love it. (In German but the video is sweet)
http://wmt.e-tv.t-bn.de/ondemand/e-tv/ondemand/tvtotal/2005/03/21/0698-00-06-wm_midband.wmv
http://wmt.e-tv.t-bn.de/ondemand/e-tv/ondemand/tvtotal/2005/03/21/0698-00-06-wm_midband.wmv