July 21, 2010. Copyright 2010, Graphic News. All rights reserved

Sikorsky X2 chases chopper speed record

LONDON, July 21, Graphic News: Sikorsky X2’s attempt to break the world speed record for helicopters later this year could determine the future path of helicopter development at the Connecticut-based company.

Ever since the first helicopter hoisted pilot Paul Cornu less than a metre into the air in 1907, vertical flight has been a compromise between hover performance and forward speed.

Now, 103 years later, Sikorsky has designed the fastest helicopter to date. The X2 Technology Demonstrator has already achieved a speed of 181 knots (208mph, 335km/h) in a test flight -- faster than the 150-knot best cruising speed achieved by production helicopters and edging closer to the eventual aim of cruising at 250 knots (288mph, 463km/h).

The X2 is a coaxial helicopter, incorporating twin rotors spinning in opposite directions above the body of the aircraft. This eliminates the need for the tail rotor that typically counters the angular twist of a single main rotor. In place of a tail rotor, the X2 has a rear pusher prop that boosts thrust in a similar manner as a fixed wing aircraft.

Featuring a fly-by-wire system which controls rotor aerodynamics, high lift-to-drag rotor blades, low-drag rotor fairings, and Active Vibration Control, the craft delivers more speed without having to compromise hovering ability. The fly-by-wire system also stops the rotor blades from exceeding the speed of sound and shattering in the airflow -- a neccessary precaution for a helicopter travelling faster than 210 knots.

Jim Kagdis, who manages advanced programmes at Sikorsky, says forward speed will increase further by improving aerodynamics -- with fairings around the rotors -- as well as increasing thrust from the tail pusher prop.

“About 50 percent of the drag on the aircraft comes from the coaxial dynamic system,” Kagdis says. “With fairings, we think we can cut that drag in half.”

The X2 can hover, land vertically, manoeuvre at low speeds, and switch seamlessly from hovering to forward flight. In the words of Sikorsky’s president, Jeffrey Pino, it could prove to be a real “game changer” for the industry.

Sikorsky’s potential customers for a production version of the X2 include the military as well as civilian customers such as search and rescue, and air taxis.

The current speed record for a helicopter was set in 1986 when a British-built Westland Lynx achieved 249mph (400km/h). If all goes according to plan, the X2 should crush this record by the end of the year.
/ENDS