Cloak comes off Sikorsky’s sleek X2 test aircraft

HAI Convention News » 2008
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February 24, 2008, 3:58 PM

Sikorsky Aircraft yesterday unveiled its X2 technology demonstrator here at Heli-Expo, with hordes of attendees surrounding the black-shrouded helicopter before it was revealed in a cloud of smoke and lights at the company’s booth (No. 1641). What emerged was a sleek-looking, two-pilot ship with a contra-rotating coaxial main rotor and an “aero propeller” in place of the tail rotor.

Jeffrey Pino, Sikorsky’s president, said the technology demonstrator is “true to the pioneering spirit” of company founder Igor Sikorsky. Reflecting this theme, Sergei Sikorsky, the son of the late helicopter pioneer, spoke briefly before the X2 was revealed to all.

So far, the novel helicopter has logged about 20 hours in ground runs, and it would have likely made its first flight by now had Sikorsky not brought the X2 to the show. Pino said, “The aircraft will fly when it’s ready,” noting that safety comes first and pointing out that the X2 will neither be certified nor produced since it is merely a technology demonstrator. “This could be a ‘game changer’ in the industry,” he told the crowd. “We are diligently pursuing this as a research project. We are testing the limits and pioneering this exciting innovation.”

According to Sikorsky, the X2 is intended to show that a helicopter can indeed break 160 knots in forward speed. In fact, the top speed of the aircraft is expected to

be between 250 and 265 knots in cruise, while still retaining “desirable helicopter attributes, including excellent low-speed handling, efficient hovering and autorotation safety and a seamless and simple transition to high speed.”

The X2 demonstrator incorporates a number of technologies to help achieve this goal, including a fly-by-wire system developed at Sikorsky’s flight research center in West Palm Beach, Fla., hub drag reduction and active vibration control. A 1,450-shp Light Helicopter Turbine Engine Co. T800-LHT-801 engine, developed by Rolls-Royce in partnership with Honeywell, powers the tandem, two-seat ship.

But the key technology to reaching 265 knots is an automatic system that keeps the composite main rotor blades from exceeding the speed of sound, which could cause the blades to shatter from vibrations caused by supersonic airflow. When flying above 210 knots, the X2 will automatically slow down the main rotors and shift power to the aft propeller. By the time the X2 reaches 265 knots, the main rotors will be “80 percent of the original rotor speed, with the retreating blade in 80-percent reverse flow,” Pino said. Meanwhile, the power transferred aft provides 900 shp to the aero propeller, “just as much as a Pilatus PC-12,” he added.

Sikorsky first announced the X2 initiative in June 2005, and the technology demonstrator was built as a rapid prototyping collaborative effort with subsidiary Schweizer Aircraft. The project is solely funded by Sikorsky. Pino would not disclose how much the company has spent to get this far; however, he told HAI Convention News, “The cost is probably one third of what people are thinking,” mainly due to the rapid prototyping and the thriftiness of the Schweizer team.

Just when the X2 will lead to a certifiable product is anyone’s guess, and even Pino isn’t quite sure himself. “We’re going to test the X2 to make sure the technology works, then we’ll start thinking about how to incorporate it into a production model,” he said. But that doesn’t mean Pino isn’t already thinking about what such a production helicopter might be. “I’d like to see it in a Super Puma-sized 15- to 19-seat helicopter,” he told HAI Convention News, adding that the technology is scalable and could be used in a machine weighing as much as 240,000 pounds.

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