Sikorsky’s futuristic X2 high-speed helicopter technology demonstrator made its first flight today in Horseheads, N.Y., in the hands of chief test pilot Kevin L. Bredenbeck.
The single-engined fly-by-wire aircraft features coaxial rotors and a pusher propeller that Sikorsky believes will revolutionize the helicopter world with cruise speeds of up to 250 kts, some 100 kts faster than current production helicopters.
“This isn’t an airplane we are training to hover. It’s a helicopter that will go very, very fast,” said Sikorsky CEO Jeff Pino. “I think it will get to 260 kts.” (The helicopter world speed record is held by a Westland Lynx at 216.45 kts).
Today’s flight lasted 30 minutes, during which Bredenbeck demonstrated hover, forward flight, and a hover turn.
Current helicopter speeds are limited by rotor aerodynamics. In contrast the X2’s coaxial rotor system is optimized for all regimes of flight by a fly-by-wire control system that will slow the rotors at high forward speeds to prevent their tips going supersonic, while maximizing lift and minimizing drag by adjusting the pitch of the rigid, carbon-fiber blades. The counter-rotating rotors provide equal lift on each side of the aircraft and, unlike a traditional helicopter, are relieved of having to provide all the forward propulsion by a large pusher propeller at the rear of the fuselage.
The rigidity of the blades allows the rotors to be closely spaced only two feet apart, further reducing drag. Sikorsky believes the gap can be reduced even more in the future. The X2 technology demonstrator is powered by a 1,452 shp, FADEC-equipped T800 turboshaft engine that was previously installed in one of the Comanche helicopter prototypes. It drives both the rotor and the pusher propeller through two gearboxes.
So far the aerospace industry’s solution to high speed, vertical flight has been the hugely complex tiltrotor, a hybrid airplane with rotors. The X2 differs markedly in that it is still a helicopter that can go fast, autorotate, hover, and fly nap of the earth. The X2 can match the speed of the Bell/Agusta BA609 tiltrotor with far less complexity, according to Steve Estill, Sikorsky’s vice president for worldwide sales. X2 technology is especially well suited to missions such as flying fast to oil rigs, which would call for development of a light to intermediate X2 twin of the same size as the 12-passenger S-76 or 19-passenger S-92.
The X2 is scalable, with some studies showing that a heavylift version is possible that can carry up to 20 tons internally or 40 tons externally and still cruise at up to 250 kts. Sikorsky has also released illustrations of an armed attack version. The timetable? “It will probably take ten to 12 years,” Estill said.