Really two different issues:
- The Osprey (which has been in development for over 20 years
) employs the tilt-rotor concept. The concept itself is simple and has been flow in one way or another since the 50's...that I am aware of.
But, like many aviation concepts, the mechanisms for safe tilt-rotor flight is very difficult to engineer on the scale of the Osprey.
I can go into a whole bunch of aero-speak, but the main problems are 6000lb hydraulics, asymmetric lift between the two rotors, which counter rotate, and the fact that it is built by Bell Helicopter, USA, a complete bunch of idiots. I have spent a lot of time in Texas
- The F-18 is not designed for vertical take off, the new Joint Strike Fighter is. There have been many improvement in the technology that allows a fixed wing aircraft to launch and recover vertically. My sense is that the Marine version of the JSF (there are three: Marine, Navy and Air Force) will be a huge improvement over the Harrier but many of the same penalties associated with fixed wing vertical flight (additional weight and complexity, additional maintenance, pilot training, etc.) will make the vertical JSF less capable than the Navy and AF version.
Edit: The Osprey is on it's first deployment to Iraq. I hope things go well. The Osprey is a famous case in DoD acquisition, and not because they did well.