Sikorsky's X2: Developing a Faster Helicopter
Sikorsky is now ground-testing its X2 Technology Demonstrator, a revolutionary helicopter that uses coaxial, counter-rotating blades and a pusher propeller. Sikorsky hopes the X2 will fly nearly twice as fast as today's helicopters.
Credit: Sikorsky Aircraft

Nearly three years ago, Sikorsky Aircraft announced it would develop technologies ? collectively called "X2 Technology" ? that would significantly change helicopter flight. Every day thousands of people in the United States travel in helicopters, among them politicians, executives, tourists and patients.

The main advantage of helicopters ? categorized as rotary-wing aircraft ? is their ability to take off and land vertically. However, compared with fixed-wing aircraft, they are slow. For example, the 12-passenger S-76 helicopter flies at 178 mph, but an 11-seat Beechcraft KingAir 350 turboprop flies at 350 mph, nearly twice as fast.

However, United Technologies Corp. subsidiary Sikorsky Aircraft, the oldest name in helicopter manufacturing, is working to change that by developing a helicopter that will fly almost as fast as a conventional aircraft ? without using the mechanically complex and expensive tilt-rotor system pioneered by Bell.

Sikorsky plans a faster helicopter

On June 6, 2005, Sikorsky announced that it would build and test a technology demonstrator that would maneuver like a conventional helicopter and cruise at 250 knots (288 mph), which is at least 60 percent faster than conventional helicopters.

X2 Technology helicopters will affect passenger travel due to substantially reduced flight times. For example, flights between Bridgeport, Conn. and JFK Airport in New York City would be decreased from 40 minutes to 25 minutes. Also, X2 Technology medevac helicopters would be able to transport people in critical condition to hospitals in significantly less time, potentially saving lives.

?We initiated X2 Technology convinced that the most productive and flexible helicopter is a helicopter which is capable of a significant increase in speed,? said Stephen Finger, then-president of Sikorsky Aircraft. ?Customers are demanding greater speed but without sacrificing any of the unique capabilities that make helicopters the ideal platform for countless civil and military missions.?

Advanced aerospace technologies

Although the top speed of helicopters has not increased much since the 1960s, improvements in computers, materials, navigation systems, and other aspects of aircraft during the past two generations have been unprecedented.

Sikorsky?s X2 Technology Demonstrator incorporates leading-edge aerospace technologies, including digital fly-by-wire flight controls, counter-rotating rigid rotor blades that spin more slowly as the helicopter reaches higher cruising speeds, active vibration control, an integrated auxiliary propulsion system, and more.

X2 Technology aircraft will take-off and land vertically, hover, maneuver at low speeds, and transition from hover to forward flight like regular helicopters. However, the new Sikorsky aircraft will have one or more aft-mounted ?pusher? propellers, a significant difference in design from helicopters of the past six decades.

Coaxial, counter-rotating blades

Most helicopters have a ?disc? of rotating blades on top of the fuselage and shorter blades mounted on the side of the tail that spin in a plane roughly perpendicular to the main disc. The purpose of the aft blades is to provide a counterforce to the torque effect on the fuselage created by the spinning main disc. The X2 Technology Demonstrator has a coaxial rotor system comprised of two hubs with blades attached. The hubs spin in opposite directions, which eliminates the torque effect.

?The X2 Technology Demonstrator is an integrated suite of technologies intended to advance the state-of-the-art, counter-rotating coaxial rotor helicopter. As we continue to work to prove and mature the technologies that will allow the X2 Technology Demonstrator to become a viable product, we are focused on testing its limits and finding out where this technology will take us," Jeffrey Pino, Sikorsky?s president, said recently.

?This could be a ?game changer? in the industry,? Pino said of the X2 Technology Demonstrator at Heli-Expo 2008, the main U.S. helicopter convention. "We are diligently pursuing this as a research project. We are testing the limits and pioneering this exciting innovation."

Sikorsky built the X2 Technology Demonstrator in collaboration with subsidiary Schweizer Aircraft, and funded the project entirely by itself. The aircraft continues to make progress toward its first flight, said Peter Grant, Sikorsky's senior manager of Advanced Programs.

?Throughout 2007, the aircraft made excellent additional build and subsystem test progress, re-entering vehicle ground testing in November 2007,? said Grant. "Extensive test instrumentation is also being installed as preparation for its first flight."

No first-flight date yet

Ground testing of the X2 Technology Demonstrator is still underway and Sikorsky hasn't yet scheduled a date for the aircraft's first flight, said company spokesman Paul Jackson.

"Experimental aircraft have minds of their own ? sometimes you have to let them proceed at their own pace," said Jackson. "For that reason, we have not targeted any date for the first flight."

Sikorsky Aircraft, has been consulting with helicopter operators to determine how X2 Technology aircraft would benefit their business at a price they can afford. Sikorsky is developing plans to design and build a civilian X2 Technology helicopter that would satisfy operators? requirements and appeal to the traveling public.

"Certainly civilian travel appears to be a promising market. People will be able to fly back and forth from visits, dates, and meetings twice as fast each way as it now takes by helicopter," said Jackson. "Perhaps a helicopter air taxi market will evolve as many aviation experts have predicted for the small-airplane segment."