Sikorsky helicopter is testing its X2 demonstrator in hopes of combining the flexibility and hover of helicopters with the speed and range of airplanes. Flight tests continued with the first engagement of the rear pusher propeller which, in theory, should enable the hybrid to speeds of 250 knots. The helicopter generates lift with two counter rotating main rotor blades, in addition to the rear pusher. This arrangement makes torque more manageable and needs only to be addressed for the pusher rotor.
Sikorsky’s challenge in attempting a 250 knot helicopter was to counter the loss of lift of the retreating main rotor blades as the airframe travels forward. This is being addressed by using a rigid rotor which uses the Advancing Blade Concept (ABC) with which the retreating blade produces little or no lift. First pioneered with the Sikorsky XH-59A, a turbojet powered experimental helicopter, the ABC allowed it to reach 240 knots in 1973. Then current technologies made it impractical, though. More advanced “fly by wire” flight control systems have allowed greatly improved handling characteristics in the X2 demonstrator.
Recently, Sikorsky announced the X2 TECHNOLOGYTM Light Tactical Helicopter (LTH) in anticipation of flight tests confirming the capabilities of its demonstrator. It is envisioned to compete with other smaller combat helicopters like the Eurocopter AS 550 Fennec and HAL Light Combat Helicopter (LCH).
“These technologies can potentially bring new rotorcraft capabilities that, to date, have been unachievable by the industry,” said Sikorsky President Jeffrey P. Pino. “In addition to doubling the speed of helicopters, this technology can improve hot/high performance, maneuverability and low acoustic signature. Sikorsky’s Light Tactical Helicopter concept demonstrates a way to package these capabilities into an airframe that is tailored to meet a range of military missions.”