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Summary

Continuous price increase of new fighters and their engines, spare parts, maintenance and usage, as well as the high prices of kerosene have generated modification of existing maintenance systems as well as the development and the application of new maintenance concepts with application of aircraft and engine diagnostic systems. As known, a major problem in designing, development, establishing or modification of maintenance systems for applying to a high-speed jet fighter and its power plant is sudden change of operating conditions and operating environment, primarily temperature and vibrations levels, especially at low altitude flight. In order to establish effective system of aircraft and engine maintenance, it is necessary to provide sufficient relevant information on their status through application of appropriate diagnostic system. 
The first part of the book is devoted to the theoretical aspects of the aircraft and engine life management, while the second part of the book represents some kind of document about hard work of Air Force technical service in maintenance and life extension of the fighter airplanes and their engines. The applied methodology has become a backbone of similar programs applied to other combat and transport airplanes within the Air Forces as well as in some foreign Air Forces. The crown of the work has culminated with new overhaul technology for MiG-21BIS aircraft and with creation of a new test station for jet engines of 120 kN class.

Based on world known experience and knowledge, author presents theoretical background of aircraft development process and launch of new airplane program; aircraft life cycle; introduction of airplane in operational use; initiation and development of defect and faults in aircraft and engine structure, their causes, ways of cracks spreading, craks discovering and flows prevention process; effects of low and high cycle fatigue; examples of aircraft mishap and their causes; maintenance concepts; monitoring of aircraft and engines health through operational use; definition and implementation of equivalent engine cycle; definition and implementation of total accumulated cycle (TAC); usefulness of spectrochemical oil analysis and nondestructive inspection in health  monitoring; need for diagnostics and prognostics in  aircraft and engine health management, as well as possibilities and ways of aircraft and engine life extension. As part of the appendices of the book the MSG analysis, definition of specific terms and calculation of damage assessment are presented.

The main theme of the book is devoted to experience gained through practical examples in life and TBO extension of combat aircraft (MiG-21 and MiG-29) and jet engines (R25-300 and RD-33), as well as simulation of aircraft life management.

Gained experience showed that spectrochemical oil analysis has very important role in diagnostics of engine condition. Regarding that rotation of compressor rotor is running on oil film in thickness of 10 μm, oil should be of adequate quality, pure, and free of humidity. Experiences have proved that engine oil indicates engine appropriateness, and spectrochemical oil analysis converts the indications into valuable information, which help in making correct decisions on engine operation and maintenance procedures. An insight into the wear intensity of bearings, gears, filters and accessory box in engine oil system may be acquired, i.e. abnormal operation of some parts may be preventively discovered. Spectrochemical analysis has been proven as very effective method in engine condition monitoring, because its results timely indicate when the operating performance of components in lubricating system is degraded, and that appropriate procedures or maintenance procedures should be applied at certain level of metallic debris content.

The most serious problem, when elaborating a maintenance concept and considering the possibilities of monitoring engine condition, is how to provide reliable inspection of flow system – compressor, main combustion chamber, fuel injectors, and turbine, i.e. how to detect cracks, damage, exfoliation of protective coatings, vanes and blades burns, or corrosion traces, their actual sizes and the speed of their propagation on inaccessible components of engine flow system. An alternative to solve this problem is to provide modern remote visual inspection (RVI) equipment (flexible fiberscopes, rigid boroscopes and videoimagescopes with CCD image sensor mounted in the end of the flexible probe and computerized video analyzer with inspection manager software). From CCD image sensor a picture is transferred to special liquid crystal display, or to special display mounted on the head of an inspector (Head Mount LCD), or to PC monitor, and at this, the picture may be zoomed, frozen and kept for subsequent analyses. It is also possible to enter numerical grid of stator vanes and rotor blades, which may be integrated with the picture from CCD "camera" and so measure actual length of detected cracks or damage. In this way, it is possible to establish the condition of engine flow system with high precision and reliability, detect cracks or damage on the bottom limit of detectability, monitor cracks propagation speed, forecast service life residue and timely undertake optimal maintenance procedures. The modern RVI equipment with CCD cameras provided objective inspection of the engine flow system condition, because it was enabled that: a few experts simultaneously watched inspected surfaces on the monitor; the condition of inspected surfaces was documented in a computer video-record format, subsequent thorough analysis of the condition of suspicious cracks or damage was performed, cracks lengths or other types of detected damage were measured.

By introducing the algorithm of engine service life, based on actual TAC instead of hour operation life, the extension of service life maintaining the same safety margin, valid evaluation of effective service life residue, and considerable maintenance cost reducing is enabled. One of significant deficiencies of up-to-date diagnostic system is limited forecasting capability of future condition of engine components, which is presently implemented based on experience rates. For this reason, it is necessary to upgrade existing diagnostic system by intelligent algorithm, which would be capable of recognizing failure modes automatically.

This book is aimed to practical engineers in the area of aircraft and engines logistic support for both civilian and military aviation as well as to upper level undergraduate and graduate students.