The aircraft structures complexity and the inaccessibility of rivets setting areas create the need for manual rivet hammers. Many developments in this area provide a wide range of tools for the assembly work. During the assembly work, the multiple-hitting pneumatic impulse hammers are used. Such kind of tools create noise and vibrations that affect a fitter. Moreover, such equipment can be used only by a highly qualified specialist. The purpose of the study is to determine the pneumatic manual impulse devices (PMID) blow energy required to auto-mate the devices design process, taking into account their design features. The engineering process of the PMID operation is simulated using the ANSYS CFX Software. For the numerical study of the problem, a system of Navier-Stokes equations is used. To determine the optimal configuration of the devices gas tracts, energy losses and stress-stain state of structural elements in their interaction, the finite element method is used. As a result of the study, the simulation with various geometry of computational domain has been carried out. The results of different approaches to reduce the calculation time when using 2D geometry are compared. Using the results of gas-dynamic calculations of the devices energy parameters, the task of designing the PMID with the required blow energy has been solved. The comparison of the simulation results made in the ANSYS CFX software with the theoretical data revealed the insignificant error, the maximum value of which is 12%. It may be caused by using many simplifications during the theoretical calculations.