Eurocopter X3

X³
Eurocopter X³ in flight
Role	Experimental compound helicopter
Manufacturer	Eurocopter
First flight	6 September 2010
Status	In museum
Number built	1
Developed from	Eurocopter EC155

The Eurocopter X³ (X-Cubed) is an experimental high-speed compound helicopter developed by Eurocopter (now Airbus Helicopters). A technology demonstration platform for Eurocopter "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 the Eurocopter 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.

Guest pilots describe the X³ flight as smooth, but the X³ does not have passive or active anti-vibration systems and can fly without stability augmentation systems, unlike the Sikorsky X2. The helicopter is designed to prove the concept of a high-speed helicopter which depends on slowing the rotor speed (by 15%) to avoid drag from the advancing blade tip, and to avoid retreating blade stall by unloading the rotor while a small wing provides 40–80% lift instead. The X³ can hover with a pitch attitude between minus 10 and plus 15 degrees. Its bank range is 40 degrees in hover, and is capable of flying at bank angles of 120 to 140 degrees. During testing the aircraft demonstrated a rate of climb of 5,500 feet per minute and high-G turn rates of 2Gs at 210 knots.

The X³ first flew on 6 September 2010 from French Direction générale de l'armement facility at Istres-Le Tubé Air Base.

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Wikipedia