The aim of the article was to develop a tool to support the process of planning and managing aircraft (ac) maintenance. Aircraft maintenance management has been presented for scheduled technical inspections resulting from manufacturers’ technical documentation for ac. The authors defined the problem under investigation in the form of a four-phase decisionmaking process taking into account assignment of aircraft to airports and maintenance stations, assignment of crew to maintenance points, setting the schedules, i.e. working days on which aircraft are directed to maintenance facilities. This approach to the planning and management of aircraft maintenance is a new approach, unprecedented in the literature. The authors have developed a mathematical model for aircraft maintenance planning and management in a multi-criteria approach and an optimisation tool based on the operation of a genetic algorithm. To solve the problem, a genetic algorithm was proposed. The individual steps of the algorithm construction were discussed and its effectiveness was verified using real data.

A Method of Parametric Evaluation of The Technical Object Reliability This work presents a practical and effective method to evaluate the reliability status of an object basing on the observation of changes in its functioning (automatics) and its technical condition (diagnostics). It has been observed that changes of the functioning condition potential could serve to determine the symptoms of transient (momentary) damages and the changes in the potential of the technical condition to determine the symptoms of parametric damages (non-total). Such an information, as it turns out, is sufficient to calculate reliability characteristics before dangerous catastrophic damages occur and to calculate reliability characteristics for every single object without having to deal with a numerous set of objects. The presented computer-aided method can be of a substantial practical importance in coordination of adjusting/control functions, diagnostics and reliability actions and thanks to that it can improve the level of organisation of a system operation.

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This paper presents an analysis of nonsynchronous rotor blade vibrations in the last stage of an LP steam turbine at various condenser pressures. The nonlinear least squares Levenberg–Marquardt method is used in a tip-timing analysis to determine nonsynchronous multimode rotor blade vibrations, which is a novelty. This is done with two sensors in the casing and a once-per-revolution sensor. The accuracy of the nonlinear least squares Levenberg–Marquardt multimode method is compared with the one-mode linear method. The algorithm is verified by comparing it with one-mode tip-timing methods for synchronous and nonsynchronous vibrations. The analysis shows that the rotor blades vibrate simultaneously with two modes in non-nominal conditions, which is also a novelty. The rotor frequencies are unchanged, although the blade vibration amplitudes vary, depending on the pressure in the condenser. Flutter does not appear in the last stage for the various condenser pressures and powers that were tested.

The paper presents the basis of a new method for monitoring the technical condition of rotating blades during their operation. Utilizing the measurement of blade tip instantaneous speed under subsequent sensors, enables direct determination of the blade vibration frequency. The method utilizes a diagnostic model in the form of amplitude amplification W2ij and phase shift φij of a diagnostic signal y(t) resulting from the operation of the blade and the signal from its environment, when the blade tip passes under a cascade of blade tip instantaneous speed sensors. The adopted diagnostic model, indirectly takes into account the current surrounding of a blade without the need to measure it [12, 14]. Evaluation of the blade technical condition in real time and static analysis shall be performed on the basis of the vibration process parameter analysis. The suggested method may play an important role in the diagnostics of rotor machine blades during their operation.