Sikorsky's unofficial 258 mph run last week of its X2 counter-rotating coaxial rotor technology demonstrator bests a previous record set by a Westland Lynx in 1986, but is still short of the X2's goal. Sikorsky aims to cruise the X2 at 288 mph by late this year. The helicopter itself is far from traditional. It includes a six-blade rear-facing propeller that relieves the main rotors of certain aerodynamic and engineering hurdles created by high-speed rotor-wing flight. Normally, traditional helicopters rely on the main rotor for all forward propulsion and lift. At high forward speeds, the rotor blades meet increasing stresses as they advance and retreat. At some point, the retreating blades can stall or the advancing blades can achieve tip speeds that reduce their efficiency. Those complications, among other things, effectively create a speed barrier for traditional helicopters. The X2 approaches the problem differently.
This is a companion discussion topic for the original entry at https://www.avweb.com/news/sikorsky-x2-goes-faster