3. Detectability of damage

Before going into the details of permanent indentation and its physical origin, which will be done in the second part of this paragraph, we'll start by explaining the different damage detection procedures used in aeronautics, and the size of the damage they can detect.

In aeronautics, scheduled inspections are the basis for detecting damage that is not the result of an obvious malfunction. Inspections of aeronautical structures are based on mainly visual methods. Four levels of inspection are defined (figure 19 )