Eurocopter's X3 has wings which support two propellers. At high speeds, those wings contribute 40 per cent of its lift, so the single rotor doesn't have to work so hard.
Like the Sikorsky X2, it has no tail rotor - so the pitch of the left and right propeller blades subtly adjust automatically in flight to maintain stability and to provide steering, says Billig, but the pilot still controls the craft as they would a regular helicopter.
The X3 has so far only flown once, in a 35-minute flight that tested its hovering behaviour and Billig says it performed as designed. It won't be going for any high speed attempts until late 2011, but they are initially aiming to bust 400 km/h.
Sikorsky is already well on the way to achieving its speed aim of over 500 km/h. In a test flight in September, the X2 unofficially broke the previous record of 400 km/h, which was set by the Westland Lynx in 1986. The X2 achieved 463 km/h, but due to its propellers, it is unclear if the craft will be recognised in the same category by the FAI, the world's air sports federation based in Lausanne, Switzerland, that oversees aviation records.
That won't stop Eurocopter, or indeed Sikorsky from trying to push choppers to ever higher speeds. "The physics of the X2 design certainly don't limit it," says Weiner. "By solving other issues it could go to 550 km/h."
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