It is difficult to use an accelerometer to calculate angle changes though in dynamic situations since the many of the accelerations registered by the accelerometer will be caused by vibrations and bumps and not just from the tilt of the sensor.
It is not just the vibrations, bumps and sensor errors which are the problem. The actual change of direction of the vehicle ( whether it is a turning car or a turning airplane ) causes an actual acceleration which cannot be distinguished from gravity, and will lead your program to the wrong conclusion. That is unless you have some independent means of determining the actual orientation of the moving vehicle.