[nradov]

Tilt rotor aircraft have interconnected gearboxes so that they can fly on a single engine. In case of a dual engine failure in vertical lift mode the autorotation capability is very limited due to low rotor inertia; chance of survival is low from any significant altitude. In case of a dual engine failure in airplane mode it can glide like a regular airplane, but the glide ratio is low and stall speed is high so although in ideal circumstances the pilot might be able to put it down safely the most likely outcome is everyone dies.