著者

佐藤 達男

出版者

経営史学会

雑誌

経営史学 (ISSN:03869113)

巻号頁・発行日

vol.50, no.3, pp.26-51, 2015 (Released:2018-03-30)

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This study aims to investigate Nakajima Aircraft Company's airframe business and its production efficiency during WW II in comparison with Mitsubishi Heavy Industries.During the Pacific War, Japanese aircraft production was essentially based on job shop system for parts fabrication and sub-assembly. Nakajima Aircraft Company the largest aircraft manufacturer of war-time Japan and Mitsubishi Heavy Industries the second largest utilized both job shop and production line systems for their airframe final assembly lines depending on each plant situations. The United States Strategic Bombing Survey reports evaluated that Nakajima's airframe production system was more developed than that of Mitsubishi, which adhered to original, old-fashioned job shop system. This was substantiated from the fact that Nakajima expanded its production by 1944 to more than eight times of its 1941 production, and Mitsubishi produced only three times for the same period.However, in production efficiency measured by airframe weight produced per month per employee, Mitsubishi was predominant until August to October 1944. A positive correlation was observed between production efficiency and monthly number of airframe production. Mitsubishi's improvement degree of production efficiency agreed well with the estimation by learning curve theory, but Nakajima's improvement of production efficiency far exceeded the estimation. This is considered to be the effect that Nakajima's labor utilization rate, which was approximately half of that of Mitsubishi in September 1943, might have increased rapidly as the monthly airframe production increased. The difference of the final assembly line did not have decisive influence on the production efficiency, but the increase in the number of monthly airframe production was influential.The production efficiency continuously increased as the monthly airframe production increased, and then dropped sharply from the end of 1944 and after due to the rapid decline of monthly production, which was caused by shortages of essential materials and engines, US air raids from November 1944 and after, factory evacuation, and labor shortage.