The aim of this work is to characterize the vibration parameters of plastic blades installed in a wind tunnel fan by means of a non-contact method, namely BTT (Blade Tip Timing). Chapter 2 is dedicated to the description of basic theory on the vibration of blades and disks. In Chapter 3 are presented the features of BTT system, including the working principle, a few analysis techniques, the instruments usually employed and some of the main sources of uncertainty. Chapter 4 is a complete description of the work done by the author in ITWL and AERMEC labs, focusing on the particular system analysed and on the techniques used.