Having achieved its target speed of 250 ktas in September, Sikorsky continues to flight-test the X2 demonstrator but at a slower pace. The U.S.-based manufacturer has also announced the first application of the technology will be military. The X2 is a compound helicopter featuring two contra-rotating coaxial main rotors and a pusher propeller.



The scheduled external noise-measuring flights have taken place, with the demonstrator flying a prescribed course above an array of microphones on the ground. Asked about the results, Sikorsky said only that "with the prop not turning, the X2 is quieter than conventional helicopters."



Test flights with the full hub fairings have not been conducted yet. They are expected to show that the full fairings provide a 15- to 20-knot speed gain. So far, the X2 has flown with only two elliptical hub fairings at the top and bottom of the hub. Without any fairing, the drag of the hub is approximately 40 percent of the aircraft's total drag. Sikorsky expects that the full complement of fairings (including the center one) will halve hub drag to 20 percent.



Meanwhile, the company announced late in October that it would build two prototypes, dubbed X2 Raiders, for the U.S. Army to evaluate the benefits of applying the technology to armed reconnaissance helicopters. The first prototype "will be heavily instrumented and will be used primarily for expanding the flight envelope," a Sikorsky spokesperson told AIN. The second aircraft will be targeted more at customer demonstrations and will have less flight-test instrumentation.



Unlike the X2 currently flying, the X2 Raider will have a two-pilot cockpit and space for armament and auxiliary fuel or troops. The first flight is projected in 2014. The proposed helicopter anticipated to stem from the X2 Raider is called the S-97. Last March, Sikorsky submitted an X2 aircraft design to the Army's Armed Aerial Scout program in response to a request for information.