Graham Warwick/MONTREAL
Bell Boeing is studying a four-proprotor tiltrotor aircraft as a potential replacement for both heavylift helicopters and tactical transports.
The initial concept for the Quad TiltRotor (QTR) is to use the wing, nacelles, engines and proprotors from the Bell Boeing V-22, mating them to a modified Lockheed Martin C-130-30 fuselage to produce an aircraft that could be developed "within a few years".
The resulting tandem-wing aircraft would have a vertical take-off gross weight of over 45,500kg (100,000lb) - twice that of the V-22 - and a maximum take-off weight of more than 63,500kg. Compared with a V-22, payload could be more than doubled, to 36,000-40,000kg.
Using existing components would reduce development and production costs. One set of V-22 wing/nacelle sections would be attached to the top of the forward fuselage. Another would be attached to a stub wing mounted over the rear fuselage, extending span. Using a stretched Hercules fuselage would allow the resulting aircraft to carry C-130-compatible payloads. Talks have been held with Lockheed Martin, but no agreement is in place, sources say.
The QTR is in conceptual design, with watertunnel testing under way to visualise the complex flow around the two wings and four proprotors.
As four propellers are not required in the cruise, a more advanced concept would fold the blades of the rear pair of rotors back along the nacelles after the transition from vertical to forward flight.
Bell is considering modifying its Eagle Eye tiltrotor unmanned air vehicle to flight test the folding-proprotor concept. In this case, the blades would be folded flat along the nacelles and jet thrust used for forward flight, to produce a high-speed convertible tiltrotor.
Work on the QTR is company-funded, but sources claim there is considerable interest in the concept from potential customers. These could include the US Marine Corps, which is in the early stages of looking for an advanced rotorcraft to replace both its KC-130 tankers and Sikorsky CH-53E heavylift helicopters. US Special Forces also have a long-standing requirement for an "ultra-short take-off and landing" advanced tactical transport.
Source: Flight International
