Why Can't the V-22 Autorotate?

[Kanastrous]

Is it the presence of the wing?

[Vehrec]

I think it's more a matter of too much plane and too little rotor. But that's just an uneducated guess, I'm a biologist not an aeronautics engineer.

[Kanastrous]

I did some reading and found that the main problem is apparently the linkages between the engines, and the ability to position the nacelles properly.

[Sea Skimmer]

A prop is not a rotor… a rotor is not a prop… but the USMC was too damn dumb to realize that when it jumped aboard the tilt rotor trainwreck. Since the main requirement was high speed and cruise range, the proprotor chosen for the thing is optimized towards level flight performance and doesn’t work all that great for vertical lift. This conflicting requirement has crippled V-22 performance, and is what cripples the planes ability to autorotate. The proprotors are always being pushed to the limit of there ability to move air, so it doesn’t take much lost rotor velocity in chopper mode before the thing simply loses all lift and falls out of the sky. The wing blocking airflow doesn’t help. Normal helicopters can have the rotor spin down more before this freefall to earth occurs, giving them enough time to get to ground in an autorotation.

Within a limited flight envelope the V-22 does have the theoretically ability to autorotate, but this envelope is so narrow the USMC refused to test it, and simply deleted autorotation from V-22 requirements! The only real hope in the event of both engines failing (or one engine and the cross link, flight with only one rotor powered will result in the plane flipping over and crashing, the pilot most immediately kill power in the remaining engine if damage of that sort occurs) is to get the nacelles into a forward facing position and try to glide in. However the V-22s glide slope under many conditions is steep enough to amount to suicide in its own right…. Thankfully one good feature it does have is crash seats for everyone onboard, though those same seats also make the rear cabin absurdly cramped which creates its own safety problems.

I did some reading and found that the main problem is apparently the linkages between the engines, and the ability to position the nacelles properly.

None of that has anything to do with autorotation capability directly, but the cross link is a major vulnerability issue, and nacelle positioning is key to being able to attempt a suicide glide.