V-22... Times Two

If you like the twin-engine, twin-rotor Bell-Boeing V-22 Osprey... you'll love what just came out of the wind tunnel.

Testing has just been wrapped up on the Quad TiltRotor -- a four-engine tilt-rotor about the size of a Lockheed C-130 Hercules. The aircraft would take off like a helicopter, lifted by four huge rotors... two forward and two aft.

"It is a more complex aircraft, but it is what we consider a very logical extension of the V-22," said Alan Ewing, manager of advanced concept development for Bell, to the Dallas Morning News.

A one-fifth scale model has been undergoing tests at the NASA Langley Research Center Transonic Dynamics Tunnel, as part of the Army's Joint Heavy Lift project.

If the research conducted at Langley pans out, Bell-Boeing hopes to build a proof-of-concept demonstrator as early as 2008.

Still to be determined is which manufacturer will provide the four engines needed to power the aircraft -- engines that need to provide enough ooomph to keep the Quad TiltRotor in the air, even if two are inoperable.

One of the biggest issues facing designers on the Osprey was creating a driveshaft to keep its two rotors in sync, and allow one engine to power both rotors. That problem -- since resolved on the Osprey -- is compounded by the additional complexity of the Quad TiltRotor.

Besides the Bell-Boeing team, three other teams are also competing for the Joint Heavy Lift Project. Sikorsky has two entries in the competition, each with two counter-rotating main rotors, one placed on top of the other. One also includes conventional pusher-propellers for forward flight.

Boeing's Phantom Works is also working on an advanced tandem-rotor helicopter, a modern version of the venerable CH-47 Chinook. Another company, Karem International, is working on what it calls an "optimum-speed" tilt-rotor.

FMI: www.globalsecurity.org/military/systems/aircraft/qtr.htm