I started working on this in my Level 6 Games Design class at MIT, we were learning how to handle terrains in XNA and collsions with terrain. After getting a terrain imported and working in XNA.
The helicopter was pretty easy, at first it was just a model which could move forward/backward, up/down and rotate left/right. Added the particle system from the creators club example to add effects like a rocket fireing or a helicopter exploding.
Recently i’ve begun working on it again. I started following Riemers tutorial on Advance terrain, which is a really excelenttutorial.