This report shows the results of experimental work carried out with the aim of improving defect analysis and sizing of both volumetric and planar defects, detected and imaged with the phased array probe technique. The phased array technique produces S-scan type images of defects which
indicate easily the structure of the relevant echo indications. Depending on defect morphology, we can see diffracted echoes from planar defects, and also secondary echoes (improperly considered as diffracted echoes), generated by a complex conversion mode process, from volumetric ones. We
can see also single indications, when defect height is comparable with ultrasonic wavelength or its complex geometry destroys diffracted or secondary indications, and, finally, we can see clustered indications. Thus, we have to recognise such different image structures in order to apply the
most suitable sizing procedure. The obtained results are very satisfactory and allow us to be more confident in the application of the phased array technique.