Sikorsky’s X2 compound helicopter reached another milestone last month by completing two test flights that included full engagement of the high-speed tail propulsor for the first time. In one hour of testing conducted during the two flights, the aircraft flew at speeds up to 52 knots in one test and 42 knots with the propeller providing forward thrust in the second flight. The demonstrator aircraft is designed to reach 250 knots, about twice as fast as current helicopters. The stability augmentation system operated as designed, and vibration and noise levels were very low. The X2 made its first flight in August last year, though using only its contra-rotating coaxial rotors; the propulsor has been undergoing ground testing since January 23. The aircraft will relocate to the company’s flight-test center in West Palm Beach, Fla., by month’s end for continued test flights leading up to the 250-knot goal.