The reported problem is the failure of the middle bearing in an aircraft rotor engine. Tip-timing and tip-clearance and variance analyses are carried out on a compressor rotor blade in the seventh stage above the middle bearing. The experimental analyses concern both an aircraft engine with a middle bearing in good working order and an engine with a damaged middle bearing. A numerical analysis of the seventh stage blade free vibration are conducted to explain the experimental results. This appears to be an effective method of predicting middle bearing failure. The blade vibration variance increases when there is bearing failure.

The article discusses typical, operational systems for monitoring vibrations of jet engines, which constitute the propulsion of combat aircraft of the Armed Forces of the Republic of Poland. After that, the paper presents the stage of installing vibration measuring sensors in the direct area of one of the jet engine bearings, which is a support system for its rotor. The article discusses results of carried out analyses of data gathered during tests of the engine in the conditions a jet engine test bed. Results of detecting damages to the bear-ing, using sensors built in the direct area will be presented.

The paper discloses a non-invasive method of visual inspection based on processing of images taken for blade surfaces in the spectrum of visible light and then analyzed with the use of a computer-aided technology. The method of computer-aided analysis of images for blade surfaces is presented in details along with the obtained outcome, whilst the results from metallographic investigation of the blade superalloy are disclosed as well. The comparison is made between the results obtained from the analysis of images for blade surface and the results from the metallographic investigation of their structures. Finally, the relationship is established between parameters of digital images taken for surfaces of gas turbine blades in the visible spectrum of electromagnetic waves and microstructural parameters of the turbine blade metal. The completed investigations and analyses reveal that troubleshooting of gas turbine blades, which employs digital processing of images taken for its surface, offers new opportunities to determine the condition of blades after a long-term impact of a working agent at high temperature.