The engineering legacy of Ya. M. Gakkel: unknown pages of biography, new sources and interpretations

The subject of the research is the biography and scientific-engineering activities of Yakov Modestovich Gakkel, an outstanding Russian engineer, inventor, and educator. The authors examine such aspects of the topic as Gakkel's contribution to the development of aviation, locomotive building, and instrumentation, as well as his role in training a new generation of engineers at institutions such as Leningrad Electrotechnical University and Leningrad Institute of Railway Engineers. Special attention is given to little-known and previously unstudied pages of his life, including his early years, the formation of professional interests, and the influence of personal circumstances on scientific decisions. The analysis focuses on unique archival documents, among which the personal handwritten diary of the scientist is published for the first time, along with his autobiographical materials and sources from the funds of the Central Museum of Railway Transport and the Russian State Historical Archive. The research methodology is based on a comprehensive approach, including the analysis of manuscript and printed sources, archival documents, autobiographies, and memoirs, as well as the application of historical-biographical, source studies, and comparative-historical methods. The novelty of this research lies in the introduction of previously unknown materials into scientific circulation, including Gakkel's handwritten diary, which is stored in the Central Museum of Railway Transport and allows for the reconstruction of the engineer's personal views and scientific priorities. A significant contribution of the authors is the systematic consideration of Gakkel's biography not only through the prism of his contribution to aviation but also in the broader context of the development of locomotive building, instrumentation, and the pedagogical activities of the scientist. The main conclusions of the conducted research are the identification of the multifaceted nature of the scientist's engineering legacy, the significance of his innovative ideas for domestic science and technology, and the clarification of his role in forming scientific schools that contributed to the industrialization and modernization of transport in the 20th century.