Falling plane physics problems

Hey guys, i'm making an island game and in the begining, a guy falls from a plane. The problems are simple (i think), but i'm a newbie. Well, the problem is shown in the below link of a video: http://www.infosecom.net/planefalling.mp4

That is not completed yet, i want to make the helix, and other parts of the plane to detach from the plane hierarchy and add a rigidbody to them when it collides. I'm using these scripts:

The script below deactivates the waypoints script so the plane dont follow the waypoint and starts to fall cuz it has a rigidbody attached to.

function OnCollisionEnter () {

var wayPoint = gameObject.GetComponent("WayPoints");

wayPoint.enabled = false;

audio.Play();

}

The following script detaches the parts of the plane like tail, helix, helm and other parts when these parts collides with the mountain shown in the video above.

function OnCollisionEnter () {

gameObject.AddComponent("Rigidbody"); transform.parent = null;

}

I've tried to use Transform.DetachChildren, but i don't know how to use it.

The hierarchy is that: http://www.infosecom.net/hierarchyscreenshot.png

It's that, any tips or tricks you have to the game, like, you can put this in the plane, that in the mountain and etc. Thanks!