This thesis aims to investigate the power transmission from the engines of a helicopter to the tail rotor. The tail rotor is an essential component for the proper control of a helicopter. Even though different methods for the control of such vehicles have been developed, the tail rotor remains the principal solution for most helicopter types. In general, the power transmission requires two gearboxes which allow translation in the direction of power coming from the main gearbox to the tail rotor, which is at a ninety-degree angle and possibly at a higher level with respect to driveshaft coming from the engines, as well as a speed reduction.