The Eurocopter X³(X-Cubed) is an experimental high-speed compound helicopter developed by Airbus Helicopters. A technology demonstration platform for "high-speed, long-range hybrid helicopter" or H³ concept, the X³ achieved 255 knots (472 km/h; 293 mph) in level flight on 7 June 2013, setting an unofficial helicopter speed record.
The X³ demonstrator is based on theEurocopter AS365 Dauphin helicopter, with the addition of short span wings each fitted with a tractor propeller, having different pitch to counter the torque effect of the main rotor. Conventional helicopters use tail rotors to counter the torque effect. The tractor propellers are gear driven from the two main turboshaft engines which also drive the five-bladed main rotor system, taken from an Eurocopter EC155.