The Sikorsky X2 Demonstrator is an experimental compound co-axial helicopter under development by Sikorsky Aircraft.

Sikorsky will incorporate decades of company research and development into X2 Technology helicopters, including: the S-69/XH-59A Advancing Blade Concept Demonstrator which showed high speed was possible with a coaxial helicopter and auxiliary propulsion, the Cypher UAV which expanded company knowledge of the unique aspects of flight control laws in a fly by wire aircraft that employed coaxial rotors, and the RAH-66 Comanche, which developed expertise in composite rotors and advanced transmission design.

The X2 first flew on 27 August 2008 from Schweizer Aircraft's facility at Horseheads, New York. The flight lasted 30 minutes and began the flight test program.

On 4 May 2009, Sikorsky unveiled a mock-up of a Light Tactical Helicopter derivative of the X2.
(source :
http://en.wikipedia.org/wiki/Sikorsky_X2)