[away3d] Aircraft Lateral Axis calculation ?

[Julien]

Hi, i am trying to get the value of my Aircraft Lateral axis (in
degrees) compared with earth horizon, but the values are wrong when i
change the pitch of my aircraft.
You can look at my demo here :
http://www.timelessconcept.com/flashLab/sl/main.html

If i roll when the pitch angle is 0, everything is fine, but when for
example, i go up to 25degrees in the air and roll, some values are
skiped...

This is how i calculate the angle for now :
var aircraftLateralVector:Vector3d =
Matrix3DUtils.getRight( aircraft.transform );
var worldLateralVector:Vector3D =
Matrix3DUtils.getRight( aircraft.transform );
worldLateralVector.y = 0;

aircraftLateralVector.normalize();
worldLateralVector.normalize();

var dotProduct:Number =
aircraftLateralVector.dotProduct( worldLateralVector );

return Math.acos( dotProduct ) / Math.PI * 180;

Do you have any suggestion ?
how would you get the aircraft lateral angle ?

Thanks for any help.