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In civil aviation primary focus is on the quality of fuel filled in the aircraft fuel tanks, as one of the components of flight safety ensuring. The introduction of digital technologies and trends in automation, digitalization of modern civil aviation aircraft provision are becoming the basic tool for civil aviation refueling complexes in terms of ensuring flight safety of civil aviation aircraft. This article considers the processes of airfield control that take place in the stationary operating conditions of refueling complexes of civil aviation airports as Markov processes and studies the approaches to their mathematical modeling. The authors claim that in the case of disruption, there is a transition from Markov to Poisson processes, which mathematical description requires different approaches. The practical application of these statements is obvious in the study of the states probabilities value as a function of time t. For practical purposes, the limiting probabilities of states at t→∞ are of interest. This creates conditions for entering new variables, such as performance and others. Thus, Markov processes allow us to apply the mathematical apparatus of operations research, where the system of states is transformed into the queuing system. To maintain Markov processes, the authors suggest giving due consideration to the objects and technical means of airfield control functioning including: retrofitting of filling points and refueling facilities with closed sampling systems, operational measurement of aviation fuel quality indicators and registration of their results, automated monitoring of filter elements condition while refueling and its blocking in the case of stochastic differential pressure beyond the specified indicators. A special novelty is the view on the measuring process of the aircraft refueling operations as an integral part of airfield control, using block chain technologies as an advanced application of Markov chains.

Currently, special attention is paid to the aircraft fuel quality as a component of safety to ensure trouble-free operation of the fuel system. The existing system of quality control involves periodic sampling of the fuel in the container and their subsequent control by the normalized quality indicators that do not identify possible reasons for the deterioration of these indicators to remove them for trouble-free operation and do not identify the factors of pollution sources. The monitoring system generally ensures the implementation of measures to preserve the quality of aviation fuel and flight safety of serviced civil aviation airlines at current level according to regulatory requirements. The article describes the mathematical model for calculation parameters of indicator filtering partitions based on cascade filtration theoretical studies of mechanical impurities. Pores of indicator filtering partitions calculated by means of mathematical model have been experimentally tested on simulator stand and showed a good convergence of calculated and experimental results. The use of cascade filtration of fuel with different indicator partitions parameters made it possible to develop a device for fuel purity monitoring, allowing continuous (inline) monitoring the level of liquid flow contamination at various points of technological equipment (for example, after the pump, at the inlet and outlet of tanks and units, the output of the filter, etc.) and to carry out functional diagnostics of units condition process equipment by monitoring changes of particle parameters and the wear occurrence.

Progress in the aircraft engine construction is determined by the increase of operation parameters of gas turbine engines, which is inevitably accompanied by an increase of operating temperatures and load for the vital elements of the turbine hot ducts. Furthermore, the requirements for reliability of the engine in general are also increasing. Achievement of these requirements is determined by the performance of the materials turbine blades are made of and is made possible by the application of high-heat Nickel alloys in combination with combined heat-shielding coatings.This article dwells on the problem of assessing the impact of non-stationary thermal effects on the temperature distribution in a multilayer heatproof coating. With the aim of assessing the working capacity of heatproof coatings we propose a method of calculating the temperature field for the blade profile and the coatingdepth, based on the solution of the basic one-dimensional differential equation of heat conduction.This method allows us to assess the performance of heatproof coating and also gives us an opportunity to choose a combination of heatproof coating layers for the specific operating conditions of a gas turbine engine’s blades.In addition, using the proposed method it is possible to evaluate the effect of non-stationary heat flux on the structure of high-temperature alloy of the engine’s turbine blades and, therefore, to evaluate the capacity with the given coating. At temperatures of 1150–1200 °C and higher in heat-resistant Nickel alloys there starts a coagulation process of the main reinforcing coherent particle phase on the basis of the intermetallic compound, long plates with wavy shapes are formed instead of the cuboids, a formation of topologically close-packed phases which are needle-like compositions happens. These processes lead to a significant deterioration of the strength characteristics of heat-resistant alloys. Making calculations according to the proposed method it is possible to predict the performance of turbine blades, having the information about the intensity of phase transformations in the alloy and the temperature transitions in the process of gas turbine engine functioning (using the data of the on-board parameters monitoring and recording systems).

The article considers the choice of the lubricants for using in the bolted joints of the serial gas-turbine engine AL-31. In a modern gas turbine engine complex bolted joints operating in various conditions are used. They are subject to demolition in the repair process, in which they break as the result of burning and thus the increase of the breakaway moment. On the basis of maintenance conditions analysis there were determined the most characteristic defects in bolted joints, as well as the reasons for their occurrence. It was established that the main cause of failure of bolted joints is the increase breakaway moment of bolted joint. To reduce the breakaway moment one should choose such lubricants as to reduce the thermal influence on the bolt and prevent it from being destroyed in the disassembly process. For choosing lubrications the analysis of the requirements for lubricants for bolted joints used at high temperatures was conducted. Lubricants choice was made based on the results of a comparative study of various compositions of lubricant application in the process of field testing. This research work is aimed to improve the efficiency of bolted connections in a wide operating range and to prevent the increase breakaway moments in gas-turbine engine repair. Obtained in the process of field testing results allow to suggest a lubricant that can be used in the bolt connection operating at high temperatures and to reduce the break-away moment compared to the commercially used one.

The article considers the influence of the parameters of protective coating application process on the structure of the Nickel alloy. Experimental data of the conducted research of the microstructure alloy changes depending on the coating application process are presented. Recommendations on the Nickel alloy structure restoration after coating are proposed.

The important role of non-destructive testing methods as a source of information in evaluating the aircraft products quality is exposed. The problems of unreasonable choice of nondestructive testing methods in the evaluation of the aircraft products technical state are denoted and the ways to solve this problem through correct nondestructive testing methods choice in the concrete conditions are identified. A clear classification of NDT methods according to the criteria: applicability in limited conditions, the sensitivity in detecting the most dangerous defect - crack, weld defects and corrosion damages detection are given.