Examine the airplane's schematics until you find a cross section of the wing. This is the airfoil, or the shape created by intersecting the wing with a perpendicular plane. If you do not have access to the schematics, you must look at the airplane's wing straight from the side to get an idea of the shape and curvature of its top and bottom.
Look at the bottom of the airfoil. If it is completely flat, the shape is "flat bottom."
Compare the curve of the top of the airfoil to the curve of the bottom if the airfoil is not flat bottomed. If the top curve mirrors the bottom curve precisely, the airfoil is "symmetrical." If the bottom curves differently than the top, the airfoil is "semi-symmetrical."
