Originally Posted by
Asturias56
IIRC it was the size of various jet engines that was the design driver
Which is one disadvantage of the Osprey - from the Air & Space article I linked previously:
On the plus side, the CMV-22 will fly farther with more weight—1,150 nautical miles with a 6,000-pound payload on a tropical day, versus 850 nm for the C-2. It will use a palletized cargo system that sailors can load beforehand, meaning it will spend even less time on deck than the bulk-loaded Greyhound. Vertical takeoff and landing makes for slow approaches to the carrier and ends the need for hair-raising, airframe-stressing arrested landings and catapulted takeoffs. The first CMV‑22 pilots are training to land at night, a task all but mythical for the C-2.
But the Osprey also has a few strikes against it. It has less interior space, and so cannot carry as many people or as much cargo; nor will it fit an assembled F-35 engine inside its protective canister, one of the COD’s primary requirements.