Considering the inspecting requirement of widespread cracks in aircraft metallic structures

a flexible rectangle eddy current array sensor is introduced

and response characteristics of cracks is analyzed by finite element model

and a crack inspecting system which can simulate different cracks is established. The crack inspecting capability is researched and optimize crack inspecting frequency. Research show that amplitude of output signal of sensor will increase greatly as crack propagating into the inspecting region of sensing coil. If the point where the amplitude begin to increase greatly is regard as the characteristic quantity

the sensor is able to inspect cracks quantificationally; and when the normalized exciting frequency is 0. 3

the sensor will have the maximum crack inspecting capability.