>>299308The osprey functions like a helicopter AND a fixed wing aircraft, so its flight envelope (speeds, altitudes, and manuvers it can safely operate at) is twice as complex as a normal craft might be.
If I recall the big crash that got this project in hot water was caused by an osprey converting from flight to hover while flying (forward) too slow and falling (downward) too fast. Somehow stalling the blades when she was also unable to manuver with control surfaces.