Sikorsky's ambitious X2 prototype, designed to conquer the 170kt (315km/h) speed barrier for conventional helicopters, passed its first test by getting airborne for 30min on 27 August.
The first flight, at Sikorsky's Schweizer Aircraft rapid prototyping facility in Horseheads, New York, tested hover performance and forward speed up to 20kt. Test pilot Kevin Bredenbeck says vibration levels were less than for a production aircraft.
The X2 now enters a 16-month, four-phase flight-test period to demonstrate a 250kt top speed using a coaxial main rotor, aft pusher propeller and fly-by-wire controls.
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The long-awaited milestone for the compound helicopter comes almost two years late, but well ahead of the company's previous forecast that first flight may be delayed until 2009.
The X2's progress was slowed mainly by the company's need to divert resources to an unanticipated spike in demand for its military and civil helicopters, says Jim Kagdis, Sikorsky's business development director. The aircraft's unique design also led to delays with developing and installing the instrumentation package, he adds.
Kagdis emphasises that no delays were caused by the engine, structure or flight controls for the vehicle, which are the key elements of the X2's high-speed technology.
The first phase of flight tests will evaluate the aircraft's forward speed up to 40kt. The aft pusher propeller is installed, but it is not being engaged because it has not been fully built.
For phase 2, Sikorsky will install a completed aft propeller and move the flight-test programme to the company's West Palm Beach, Florida facility, where the rest of the flight-test programme will be completed.
Sikorsky wants to prove the aircraft is feasible for civil market production within five years. A military application for the aircraft is also expected, but the timeline to deliver a product ready for that market is at least a decade away.
Kagdis identified three mission areas for a military version of the X2: armed escort for the Bell Boeing MV-22, carrier-based anti-submarine warfare and urban combat support for special operations forces.
The X2 demonstrator is powered by the LHTEC T800 engine, which was developed to support the cancelled Sikorsky/Boeing RAH-66 Comanche.
Sikorsky launched the X2 as a modern reprisal of the 1970s-era XH-59A advancing blade concept. The X2, however, features fly-by-wire controls and avionics that are hoped to counter the high vibration levels that doomed the XH-59.
Source: Flight International
