Reply #4: There were two issues that caused the crashes and they have [View All]

been fixed as far as I know. I was an electronics sales rep calling on Bell in Ft Worth for many years and worked with the engineers on this project.

Problem one was that because of the much higher rotor speeds vibration wore through hydraulic lines causing a loss of control. It was fixed by re-routing those lines such that visual inspection was possible.

Problem two was a fly-by-wire problem. The flight control computer was instructed to maintain rotor speed during hover. To do that it would increase and decrease rotor pitch. If one engine fell below specified RPM the pitch was pulled out and that side lost lift, allowing the other side to rotate the aircraft into an inverted position. Not a good thing close to the ground.

There is a civilian version of the craft that hasn't been released due to the publicity of the Osprey. It hasn't suffered the problems of the military version because it doesn't carry as much payload and the operating environment is much more benign,