The Eurocopter X3 technology demonstrator is an experimental compound helicopter under development by Eurocopter. Eurocopter’s X3 has a re...
The Eurocopter X3 technology demonstrator is an experimental compound helicopter under development by Eurocopter.
Eurocopter’s X3 has a revolutionary design, with a conventional main rotor system flanked by a pair of forward-facing turboprop engines. The X3 demonstrator performed its first demo flight in 6 September 2010, and then in May 2011 it exceeded its original speed target of 220 knots(250 mph;410 kmph) by attaining an incredible 232 knots in level, stable flight.
In flight testing the X3 demonstrator, Eurocopter hopes to show that the concept can offer the high-speed cruise efficiency of a turboprop at a more affordable cost – that means a 50 percent increase in performance with only a 25 percent increase in cost.
Test pilots of Eurocopter's hybrid helicopter demonstrator X3 say the aircraft has more than proved its architectural concept of side-mounted propellers during the flight-test programme over the past two years. He adds that he was fascinated by the rotorcraft's much faster acceleration than conventional helicopters, saying the X3 was the most exciting aircraft he has flown to date.
The EC155 Dauphin-based helicopter has logged about 120 flight hours so far, and took part in a demonstration tour in the USA in July and August. While designers targeted a speed of 220kt (400km/h), the aircraft reached 232kt using only 80% of its power. The distribution of power between the main rotor and propellers changes across the speed range. As the aircraft flies faster, the short wings - on which the propellers are mounted - generate up to 40% of lift and consequently reduce the lift requirement from the main rotor. But at the same time the propellers need more energy to maintain airspeed.
The size of the wings was a key focus area of the test programme, as fixed airfoils can reduce the helicopter's autorotation capability. But Dominique Fournier, experimental flight-test engineer, says the X3 showed the same autorotation characteristics as the standard Dauphin.
In cruise flight, the main rotor can receive as little as 25% of the available power.
As a result of the reduced need for lift, the pitch of the five main rotor blades can be reduced in cruise flight, which in turn significantly cuts vibration. X3 has no tail rotors to counter the torque effect of the main rotor as in conventional copters. The starboard propeller of the X3 has a higher rotational speed than the port to counter the torque effect.
The hybrid configuration creates an advanced transportation system offering the speed of a turboprop-powered aircraft and the full hovering capabilities of a helicopter.
The X3 has a much more conventional helicopter structure than the Bell-Boeing V-22 Osprey with a center main rotor and is consider to be of a less complex design.
Eurocopter has not released its engine specs so far, FlightGlobal reported, it would be powered by two Rolls-Royce Turbomeca RTM322 turboshaft engines of1,693 kW (2,270hp) each.
A wide range of utilizations are envisaged for this hybrid configuration, including long-distance search and rescue (SAR), coast guard duties, border patrol missions, passenger transport, off-shore airlift, along with inter-city shuttle services. It also is well-suited for military missions in special forces operations, troop transport, combat SAR and medical evacuation – benefitting from the combination of higher cruise speeds with excellent vertical takeoff/landing performance.
