As a transmission component, gears take on a great significance for the Electromechanical system of aviation equipment and has long aroused the widespread attention of researchers. Fault diagnosis and remaining useful life (RUL) prediction during the gear operation is critical to prognostics and health management (PHM) of gear transmission systems. In this paper, the focus is placed on gear PHM methods. This paper attempts to review the existing methods and summarize them into four types (including physical model-based, knowledge model-based, data-driven model-based, as well as hybrid model-based methods). Based on a wide variety of methods, the principle and the application situation are indicated. In particular, the data-driven model-based methods consist of stochastic algorithms, statistical algorithms, as well as the artificial intelligence (AI) method. The fault diagnosis, performance degradation and RUL prediction of various methods are primarily summarized. Furthermore, the advantages and disadvantages of various methods are assessed, and the prospect of the Digital Twin (DT) is forecasted to boost the applications of PHM.

The cross-generational development of aviation products, promoting carbon fiber reinforced composite materials to be gradually upgraded from the secondary bearing structure to the primary bearing functional structure. Assembly as the final manufacturing link, determines the final service performance of CFRP structures. The complexity of aviation products and the anisotropy of materials require high-performance mechanical connections in assembly. This article focuses on the technical connotation of high-performance mechanical connection of aviation CFRP structure, summarizing the academic development trend and the existing problems on the aspects of connection accuracy and damage. In terms of accuracy analysis and control, combined with aircraft product characteristics and assembly process, theories and methods related to its modeling, transmission and control were summarized. In terms of damage analysis and damage control, combined with the characteristics of CFRP and the process of hole-making and connection, the related theories and methods of damage initiation, transmission and control were summarized. On this basis, the development trend of high-performance connection of aviation CFRP structure was analyzed and the development trend of the critical technology of high-performance mechanical connection of aviation CFRP structure was summarized.