In the design of a military helicopter, with the aim to operate at low altitude into enemy territory, the damage of critical components, caused by ballistic impact, plays a primary role in assessing the survival of the entire machine. In this work an experimental study is proposed, concerning the capability of a helicopter to carry out a mission of return to the base at reduced power, in the presence of a tail rotor shaft damaged by ballistic impact of 7.62 NATO projectile. In the first part of this study, some specimen representatives of the tail rotor shaft are subjected to experimental ballistic impact tests. Subsequently, static and dynamic torsional tests have been performed on the damaged components in order to asses the residual strength under the loads encountered during the mission. [ABSTRACT FROM AUTHOR]