Abstract: An experimental study on the ballistics limit velocities v 50 for steel spheres penetrating normally through TC4, TA7 titanium alloy plates is carried out,and empirical ballistics limit velocity expressions for TC4,TA7 are established. Experimental results show that v 50 decreases exponentially with the sphere diameter when the plate thickness is kept constant, whereas it increase exponentially with the thickness of plates when the diameter of spheres are kept constant. v 50 for TC4 plates are much higher than that with TA7 plates under the same experimental conditions. These results can be applied in equivalent target studies on aircraft for vulnerability analysis.