Implementation of the strategy of repairing by technical condition requires the development of unique predictive systems, which may define the malfunctioning part of GTU by operational parameters’ changes. This approach makes it possible to reduce the costs and time requirements for repairing processes. One of the possible approaches for creating such systems is a numerical simulation, which allows providing calculations and analysing different defects that influence the overall GTU performance. The study presents the numerical simulation of an axial compressor as the most complex element of the GTU. Some recommendations for numerical model setup were developed. Results of the compressor with an initial defective blade were compared and shown in this article. Different ways of research were shown.