Hi Wenderson,
You have few options:
first the most friendly on cpu usage:
if your model to test is huge and holds lots of geometry
you can do this using either normalmaps or heightmaps
both generators are in Prefab
normalmaps would even allow banking readings since you can extract the
normal vector from the color values
you can also use combo elevation+reader
http://away3d.com/tutorials/tutorial-surface-tracking-elevationreader
or make simple hit test, but probably more expensive that above solution
you can use the Ray class found in away3d.materials.utils.data for this.
Fabrice