This from Wikipedia:
The aircraft is incapable of autorotation in the case of engine failure, fact that led a director of the Pentagon's testing office in 2005 to say that if the Osprey loses power while flying like a helicopter below 1,600 feet (490 m) emergency landings "are not likely to be survivable." But Captain Justin (Moon) McKinney, a V-22 pilot, says that this will not be a problem, "We can turn it into a plane and glide it down, just like a C-130".
Hopefully they have enough altitude to do that since it takes 12-15 seconds to transition the nacelles...