This paper deals with electrical propulsion system for light aviation. Parameters and construction of the specially designed permanent magnet synchronous motor, is presented. In the article, influence of 3 aspects on the efficiency of the particular components, i.e on efficiency of the motor and frequency converter separately, as well as on efficiency of the whole drive (motor + converter) were investigated. In first phase manufacturing technology of the electric motor were examined - investigation of annealing (a heat treatment that alters the microstructure of a material causing changes in permeability and losses of an iron core of the motor). In second phase, switching frequency of the converter were tested adjusting of the switching frequency changes switching losses in the converter and the additional losses in the motor. Third phase of the research was an investigation of influence 3 different propellers (I fixed, 2 adjustable) on the efficiency of the entire system.