Shape Memory Alloys (SMAs) are metal alloys capable of undergoing large deformations and recovering their original shape upon thermal or mechanical loading. This work is a systematic effort to help researchers and designers in developing SMA torsional actuators with a particular focus on aeronautical applications. The intent is to critically review the fundamental aspects of SMAs involved during torsional actuation, warning about unexpected and unwanted behaviours. Experimental results, phase diagrams and patents are discussed to provide a wide overview on this topic. Furthermore, this thesis reports all the steps toward the preliminary design of such devices, using a state-of-the-art commercially available FEM software.