The two prototypes use very different approaches to high speed helicopter flight. The Sikorsky approach uses a pair of counter rotating main rotating main rotors and a pusher prop on the tail. Eurocopter’s X3 hybrid design uses a pair of turbine engines to power the main rotor as well as a pair of forward facing propellers mounted on small wings.

The push for high speed helicopters is being driven by military demands, though both companies cite civilian applications including search and rescue and medical evacuation flights.

The X3 – and yes, apparently Eurocopter subscribes to the Nigel Tufnel school of thought of using a number that is just one more must be better – made its first flight on September 6, but it was only unveiled to the public this week. Eurocopter says testing will continue through the end of the year and the plan is to gradually work their way to 180 knots by December.

Eurocopter's X3 without the main rotor

After a three month upgrade over the winter, the X3 will resume testing in March 2011 and the company says it expects the helicopter to reach cruise speeds of 220 knots.

Unlike the slim, two seat Sikorsky X2 that resembles an attack helicopter, the X3 does have a much larger cabin with room for cargo or several passengers. Both companies say the technology can be used on different size airframes for a variety of military and civilian applications.

Sikorsky X2 during its record setting 250 knot flight

With more than two years of flight testing already complete, Sikorsky appears to have a head start in the race to develop a new class of fast helicopters. But with dramatically different approaches on how to design a speedy helo, it looks like the race to the finish line is far from over.

Photos: Eurocopter, Sikorsky

Authors: Jason Paur

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