The article discusses the manner of controlling the propulsion system in the aircraft Zlin 143LSi, which is equipped with a piston engine driving a variable-pitch propeller. All the operating procedures are carried out manually by the pilot in accordance with the flight manual. The authors attempted at developing the project of a controller based on fuzzy logic, whose main goal was automating the control system of the propulsion unit, thus lowering the level of difficulty of pilotage, and increasing the economics of the operation. The project was made in an interactive environment FuzzyLogic Toolbox of the MATLAB programme. In the analysis, three input parameters were taken into account, exerting an impact on changing the rotational speed of the propeller: the charging pressure of the propulsion unit expressed in inches of mercury, the speed of the aircraft (TAS) in knots and the angle of attack, at which the flight is made, expressed in degrees. On the basis of the above-mentioned input signals, the rotation speed of the propeller was determined, by changing the blade pitch and the recommended angle of attack for the parameters in order to make an optimal use of the data of the flight conditions. The article presents the project of the controller and its optimization. The authors simulated the controller operation in the package MATLAB “Simulink”. The article ends with data analysis and final conclusions.