Jittery Movement

Hi everyone!

I have a "hover craft" that works almost as desired, except its a bit jittery :( When you go straight and slow down it's okay, but as soon as you turn and slow down the background looks jittery even at 600 fps+...

Here's my code so far.

 var desiredHeight = 1.0; 
 var spring = 100.0; 
 var damp = 10.0; 
 var SpeedMovement = 5.0;
 var turnSpeed = 5.0;
 var movDir : Vector3 = Vector3.zero;
 var rotDir : Vector3 = Vector3.zero;
 var attachedRigidbody : Rigidbody; 
 
 function Update() { 
     if(rigidbody.angularVelocity.magnitude > 2)
         rigidbody.angularVelocity = rigidbody.angularVelocity.normalized * 2;
 }
 //HoverCraft Hovering
 function FixedUpdate() { 
 var cam : Transform = Camera.main.transform;
 var hit : RaycastHit; 
 
 var up = Vector3.up; 
 
 if (Physics.Raycast(transform.position, -up, hit, 100.0)) { 
 // Force required to negate gravity 
 var neutralForce = rigidbody.mass * Physics.gravity * 0.2; 
 
 var yDifference = (hit.point.y + desiredHeight) - transform.position.y; 
 var addForce = yDifference * spring; 
 addForce -= rigidbody.GetPointVelocity(transform.position).y * damp; 
 
 rigidbody.AddForceAtPosition(neutralForce + addForce*up, transform.position); 
 
 rotDir.y = Input.GetAxis("Horizontal") * turnSpeed;
 movDir.z = Input.GetAxis("Vertical") * SpeedMovement;
 // Calculate the x-axis relative to the camera
 
 var cameraRelative : Vector3 = cam.TransformDirection (movDir);
 // Apply a force relative to the camera's axis
 rigidbody.AddForce (cameraRelative);
 rigidbody.AddTorque (rotDir);
 //transform.rotation = Quaternion.Euler(cameraRelativeRight);
 } 
 
 Debug.Log(rigidbody.angularVelocity.magnitude);
 
 }

Thanks,

Theokie