After undergoing a planned upgrade to its gearbox that enabled it to operate at full engine power, Eurocopter's X3 hybrid helicopter demonstrator has surpassed its original speed target of 220 knots (407 km/h or 253 mph). In a flight on May 12, the X3 maintained a true airspeed of 232 knots (430 km/h or 267 mph) for several minutes during stable, level flight.

Equipped with two turboshaft engines powering a five-blade main rotor system and two propellers on short-span fixed wings, the X3 demonstrator combines the vertical takeoff and landing (VTOL) and hover capabilities of a helicopter with the fast cruise speeds of a turboprop-powered aircraft.

Flight testing of the X3 demonstrator began in September 2010, with the aircraft achieving its initial true airspeed goal of 180 knots (333 km/h or 207 mph) in November when operating at a reduced level of engine power. After an upgrade that integrated its definitive gearboxes to enable it to operate at full power, the aircraft returned to flight testing last week at the DGA Flight Test Center in Istres, France, and achieved the 232 knot milestone on only its third mission.

"We were impressed by the ease at which this speed objective was attained," said flight test engineer Daniel Semioli and test pilot Hervé Jammayrac, who were aboard the aircraft for the May 12 flight. "The X3 handles extremely well, demonstrating remarkable stability at high speed - even with the autopilot off."

In the latest flight tests conducted at full engine power, Eurocopter says the X3 demonstrated "impressive climb and descent rates, as well as excellent maneuverability, while also confirming the hybrid propulsion system's outstanding capabilities for acceleration and deceleration."

Eurocopter says the flight tests to date have also validated the X3's basic handling characteristics and confirmed the aircraft's low vibration levels and ability to provide flight characteristics comparable to the best traditional design helicopters currently in service - all without the use of passive or active anti-vibration systems and without the need of a stability augmentation system.

The company envisions the X3 being utilized in a wide range of applications, including long-distance search and rescue (SAR) missions, coast guard duties, border patrol missions, passenger transport and inter-city shuttle services. It also says the aircraft could be tailored for military applications such as special forces operations, troop transport, combat SAR and medical evacuation.

Eurocopter's X3 flight test program is set to continue throughout 2011.