SUMMARY
Test of assessing a suitability of the phase trajectory pattern for diagnostics of condition changes of axial piston pumps is undertaken in the presented paper. Accomplishment reasons of investigations together with their laboratory realizations are given. They concerned the experimental comparison of changes in the phase trajectory patterns of the hydraulic pump working with a constant output pressure, in which an element of swash plate was degraded. The performed tests confirmed the suitability of phase trajectories in the recognition of degradation changes in axial piston pumps.The paper signals the usefulness of considering the introduction of phase trajectory patterns of the monitored vibration signals into processes of the diagnostic inspection of the hydraulic pump structural elements.