Wednesday, February 27, 2013

Darpa Takes Another Shot at High-Speed ​​VTOL

Undeterred by past failures, the U.S. Defense Advanced Research Projects Agency (Darpa) is launching another attempt to economic development of a high-speed vertical-takeoff-and-landing (VTOL) aircraft with the capability of a helicopter hover.

The VTOL X-Plane program is a 52-month, $ 130 million attempt to fly an experimental aircraft able of Exceeding 300 kt., Aim with a hover efficiency of 75% or better and a cruise lift-to-drag ratio of 10 or more . By comparison, selon Darpa, today's conventional helicopters are able of 150-170 kt., With a hover efficiency of 60% and a cruise L / D of 4-5.

High-speed compound helicopters Sikorsky's X2 Such as are able of 240-260 kt., While the Bell Boeing V-22 tilt rotor can Exceed 275 kt., Aim with low hover efficiency.

"We have a simple objective: to fly much faster, with Improved efficiency in hover and forward flight, without Sacrificing The ability to do useful work," says Ashish Bagai, Darpa program manager and chief engineer Sikorsky form.

Useful work is Defined as the différence entre empty weight and maximum gross weight, he says. The program is targeting a useful load of at least 40% of gross weight, Which is expected to be 10.000 to 12.000 lbs. for the X-plane demonstrator.

This COMPARED with a useful load of 35-40% of gross weight for a state-of-the-art helicopter, selon Darpa.

Bagai says Darpa is looking for "elegant" designs Combining the attributes of fixed-and rotary-wing aircraft, that 'are "not overly complex and not brute-force Approaches," he says. A broad agency announcement has-been released, and is hoping to attract Darpa Proposals from companies and nontraditional "exotic ideas from smaller companies on technologies, agile and rapid teaming design," he says.

This is not the agency's first attempt to economic development of a high-speed VTOL aircraft. The canard rotor / wing Boeing X-50A Dragonfly was designed to Demonstrate a traffic-control rotor That Could be stopped in flight to act as a fixed wing.

Both subscale unmanned demonstrators crashed before transition Could be Achieved and the program was terminated in 2006.

The Groen Heliplane was a high-speed rotor with a gyroplane design powered by tipjets That was for vertical takeoff and landing and in forward flight autorotated at speeds up to 350 knots. The program Encountered technical challenges with noise from the tipjets and was terminated in 2008.

- This Article Appeared first in Aerospace Daily & Defense Report.

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