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Saturday, November 1, 2008

Rotorcraft Report: Tiltrotor, Not a Helicopter

MILITARY

The Army continues to study a tiltrotor able to carry 20 to 30 tons of cargo or troops at speeds greater than 220 kt under its Joint Heavy Lift program. The JHL will proceed, though, only if selected by the Pentagon’s Joint Staff for the U.S. Air Force-run Joint Future Theater Lift program, officials said during the Association of the United States Army’s annual meeting Oct. 6-8 in Washington. The Air Force program is to choose a replacement for the C-130H in 2010.

The only decision made so far is that the JHL won’t be a helicopter.

Bell Helicopter Textron Inc and Boeing Co’s rotorcraft division, makers of the V-22 Osprey tiltrotor for the U.S. Marine Corps and U.S. Air Force, are continuing studies of their Quad TiltRotor. The V-22 derivative would feature two wings and four tilting rotors. Karem Aircraft Inc is offering an Optimum Speed TiltRotor, a single-wing, two-rotor aircraft that Karem also is touting for civilian use. Sikorsky Aircraft Corp is now studying possible tiltrotor or tilt-wing designs for the JHL after the Army last year rejected Sikorsky proposals to meet the requirement with one of two compound helicopter designs incorporating its X2 technology, which relies on coaxial rotors and additional propulsion to achieve 200 kt-plus speeds.

A company official said Sikorsky has a $2.6-million contract with NASA to study a "variable-diameter tiltrotor" whose rotors would telescope-longer for helicopter flight, shorter for airplane flight-to improve their efficiency.

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