Vehicle bumping into objects

I have a vehicle similar to a helicopter that has banking behaviour. When the vehicle bumps into something it's Y-axis beocomes tilted, like if I manage to land on something with the forward part of the helicopter the heli will tilt backwards and will then maintain this tilt unless given another impulse to straighten it like if I land on a flat surface.

What is the best way to deal with this? The banking behaviour will straighten the vehicle along the X-axis using VEHICLE_VERTICAL_ATTRACTION_EFFICIENCY and VEHICLE_VERTICAL_ATTRACTION_TIMESCALE but the Y-axis will remain tilted. I'm experimenting with a script on a timer that will straighten the vehicle on the Y-axis but there must be some simpler way as this must be a common problem. I'm thinking on forcing the Y-axis rotation to zero, but I fear the vehichle will get stuck in objects that way.

Any ideas?

Make sure you have this line in your code. It tells the script how the vehicle should settle out after a bump or control change
llSetVehicleRotationParam( VEHICLE_REFERENCE_FRAME, <0, 0, 0, 1> );

Thank you a lot, will try that.

The line above worked, but only before havoc 4. Does anyone have any ideas how to solve the problem?

I have an idea to use 'LlRotLookAt' and rotate the vehicle to make it stay level on the y-axis, but there seems to be no way of just rotating it along the y-axis or is there?

Anyone?

Well, you can calculate a rotation that is different only by a rotation about the y-axis (if the vehicle is only pitched up from horizontal). This function keeps the current forward (local x-axis) pointed as much in the same horizontal direction as possible but levels it and the y-axis:

rotation calculateHorizontalRot()
{
   rotation currRot = llGetRot();
   vector currX = llRot2Fwd(currRot);

   vector newX;
   if (1.0-llFabs(currX.z) < 0.01)
   {
      // Straight up/down; "pitch" to horizontal
      if (currX.z > 0.0)
      {
         newX = -llRot2Up(currRot);
      } else
      {
         newX = llRot2Up(currRot);
      }
   } else
   {
      newX = llVecNorm(<currX.x, currX.y, 0.0>);
   }

   vector newY = <-newX.y, newX.x, 0.0>;

   return llAxes2Rot(newX, newY, <0.0, 0.0, 1.0>);
}

Thank you, I will try that. Trickier than they seem these rotations.