The Eurocopter X³(X-Cubed) is a retired experimental high-speed compound helicopter developed by Airbus Helicopters (formerly Eurocopter). A technology demonstration platform for "high-speed, long-range hybrid helicopter" or H³ concept,[1] the X³ achieved 255 knots (472 km/h; 293 mph) in level flight on 7 June 2013, setting an unofficial helicopter speed record.[2][3] In June 2014, it was placed in a French air museum in the village of Saint-Victoret.
Design and development
Eurocopter X³
Technology
The X³ demonstrator is based on the Eurocopter AS365 Dauphin[1] helicopter, with the addition of short span wings each fitted with a tractor propeller, having a different pitch to counter the torque effect of the main rotor.[1][4][5] Conventional helicopters use tail rotors to counter the torque effect.[6] The tractor propellers are gear driven from the two main turboshaft engines which also drive the five-bladed main rotor system, taken from a Eurocopter EC155.[1][5]
Test pilots describe the X³ flight as smooth,[5][7] but the X³ does not have passive or active anti-vibration systems and can fly without stability augmentation systems,[1][8] unlike the Sikorsky X2.[9] The helicopter is designed to prove the concept of a high-speed helicopter which depends on slowing the rotor speed[5] (by 15%)[1] to avoid drag from the advancing blade tip, and to avoid retreating blade stall by unloading the rotor while a small wing[10][11][12] provides 40–80% lift instead.[1][5][13][14]
The X³ can hover with a pitch attitude between minus 10 and plus 15 degrees.[15] Its bank range is 40 degrees in hover, and is capable of flying at bank angles of 120 to 140 degrees.[16][17] 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.[18][19]
On 12 May 2011 the X³ demonstrated a speed of 232 knots (267 mph; 430 km/h) while using less than 80 percent of available power.[8][20][21][22][23]
In May 2012, it was announced that the Eurocopter X³ development team had received the American Helicopter Society's Howard Hughes Award for 2012.[24]
Eurocopter demonstrated the X³ in the United States during the summer of 2012, the aircraft logging 55 flight hours, with a number of commercial and military operators being given the opportunity to fly the aircraft.[25]
With an aerodynamic fairing installed on the rotor head,[26] the X³ demonstrated a speed of 255 knots (293 mph; 472 km/h) in level flight and 263 knots (303 mph; 487 km/h) in a shallow dive on 7 June 2013,[27][28] beating the Sikorsky X2's unofficial record set in September 2010, and thus becoming the world's fastest non-jet augmented compound helicopter.
Variants
Eurocopter suggested that a production H³ application could appear as soon as 2020.[25] The company had also previously expressed an interest in offering an H³ technology based solution for the United States' Future Vertical Lift program, with EADS North America submitting bid to build a technology demonstrator under the US Army's Joint Multi Role (JMR) program,[29][30] but later withdrew due to cost[31] and because Eurocopter might have to transfer X³ intellectual property to the US,[32] and Eurocopter chose to focus on the Armed Aerial Scout instead.[33][34] Ultimately the company was not downselected for the JMR effort,[35] and the AAS program was cancelled.[36]
Eurocopter saw the offshore oil market[31] and Search and rescue community as potential customers for X³ technology. An X³-based unpressurised compound helicopter called LifeRCraft is also among the projects planned under the European Union's €4 billion ($5.44 billion) Clean Sky 2 research program as one of two high-speed rotorcraft flight demonstrators.[26][37][38][39] Airbus began development of the hybrid composite helicopter with a 4.6-litre V-8 piston engine[40] in 2014,[41]froze the design in 2016 to start building in 2017,[40] and had plans to fly it in 2019.[42]
The Airbus RACER (Rapid And Cost-Effective Rotorcraft) is a development revealed at the June 2017 Paris air show, final assembly was planned to start in 2019 for a 2020 first flight.
Cruising up to 400 km/h (216 kn), it aims for a 25% cost reduction per distance over a conventional helicopter.
^Video 1, 2(Google You tube) (video), Airbus Helicopters, 26 September 2010, 2 m 50 s, archived from the original on 21 December 2021, retrieved 9 May 2014.
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