According to ASTM E1316-17a and NET.net, a flaw is defined as ‘‘an imperfection or discontinuity that may be detectable by nondestructive testing and is not necessarily rejectable.” A flaw is also something that can occur in various sizes, shapes, orientations, locations, and can even only be isolated to a tiny portion of the material properties within a material volume. Flaws can be also be naturally occurring or can be introduced by material processing or finishing. So, with this wide range of definition and generation possibilities, there is also a lot to take into consideration when understanding NDT capabilities for detecting flaws.

NDT Level IIIs are always faced with deciding which nondestructive testing method is the most appropriate for detecting a specific flaw type. Is the area of interest internal or external? Is the material metallic, ferrous or nonferrous, composite, single layer, multilayer, dual material? Is there proper access to the areas of interest to allow for detectability? Are the standard NDT methods appropriate or does an advanced method need to be investigated and deployed? All of these things need to be considered to ensure that the flaw can be detected.