29 ft. 10 in.
7 ft. 10 in.
26 ft. 5 in.
The Sikorsky X2 experimental coaxial rotor helicopter was produced to combine the versatility of a helicopter with the speed of a airplane.
The top speed of a conventional helicopter is limited by its single rotor system. When the forward speed of the helicopter exceeds the speed at which the rotor blades are traveling, lift is lost and the helicopter will stop flying.
Sikorsky uses coaxial helicopter main blades turning in opposite directions to delay the loss of lift while higher speeds are achieved. A propeller in the tail of the helicopter provides additional thrust for horizontal flight.
In addition to high speeds, a coaxial rotor system allows the helicopter to react more quickly to control inputs and turn in about one third the distance of a conventional helicopter.
The concept of the Sikorsky X2 has been tried before. Limiting factors have been excessive vibrations due to the rotors flexing, and also from it acting as a lifting body while providing for horizontal propulsion.
The Sikorsky X2 incorporates dynamically balanced vibration dampened non-flexible rotor blades with low drag, high lift design technologies. By carefully managing engine output to achieve maximum efficiency utilizing fly-by-wire controls, the Sikorsky X2 was able to achieve an unofficial rotor craft speed (non-jet powered) record in excess of 300 mph.
Performance evaluation of over 22 hours of Sikorsky X2 test flights are being used to aid in the building of high speed helicopters for the U.S. military.