JAPANESE AIRCRAFT MATERIALS
At the conclusion of the Pacific War various agencies of the Allies were directed towards technical intelligence gathering work in Japan. Wartime groups charged with collecting and analysing captured aircraft on the battlefield such as the Air Technical Intelligence Group (ATIG) became subsumed, in the case of the British Commonwealth nations, within the British Intelligence Objectives Sub Committee (BIOS). BIOS published reports, both secret and public, on the various topics of these investigations. BIOS, in turn, was absorbed into the postwar technical intelligence gathering arm of M16.
In the immediate postwar period, under the Allied Occupation of Japan, an official policy of demilitarizing Japanese society and industry saw the destruction of Japanese aircraft, production capacity and technical information. Original Japanese aircraft plans, wartime material standards and other technical information is therefore scarce today. Surprisingly, the most concise and intact literature on the topic can be found today in BIOS reports and the studies made by various Allied agencies and manufacturers investigating Japanese aircraft designs and industry.
The restoration of Japanese aircraft today can be described as an evolving art, hampered by lack of original technical information, barriers of language, archaic Japanese dialect forms and a lack of information on Japanese materials of construction. Within this topic is the wartime Japanese effort to create substitute materials in response to an increasing lack of critical alloys such as nickel. All nations struggled during the war to source critical materials, and it is poignant that in Japan antique temple bells were melted down for their copper. In navigating through modern substitutions for old Japanese materials, it is worth knowing the context of scarcity to understand an appropriate material choice today. A unique and perplexing Japanese wartime alloy might only have been striving to substitute an easily obtainable material today. Often, in particular with engines, Japanese constructors were lavish in the use of scarce and conventional materials, so shortages may not be evident in critical components. It is also worth knowing that the products of Japanese industry, as the BIOS reports struggle to suppress, were often excellent, and go a long way to explain the terrifying possession of the sky Japanese aircraft held in the first part of the Pacific War.
BIOS Report on Japanese Metallurgical Specifications is a basic primer on a range of Japanese wartime metals and their application. It is the author’s understanding that both Navy and Army designs shared common materials and material specifications, despite those agencies renowned antagonism to working cooperatively. BIOS JAP/PR/89 ‘Structural Requirements and Techniques Used in Design of Japanese Aircraft’, of which the “British AP970 Design Requirements for Aircraft of the RAF” might be considered an equivalent, states that the “Japanese Army uses Japanese Navy Strength Requirements in the Design Specifications for Airframes” in support of this hypothesis.
Japanese Aeronautical materials are described using an alpha numeric designation, typically one letter followed by three numbers, eg C222. In the BIOS Report on Japanese Metallurgical Specifications, additional Naval shipbuilding material standards are described, with Type and Mark number.
JAPANESE_METALLURGICAL_SPECIFICATIONS
A rich vein of material was found in Australia in the form of analyses of Japanese aeronautical materials conducted in 1946 by the Department of Aircraft Production. These documented materials used for specific aircraft designs and within Tachikawa Aircraft. Within the report, the Tachikawa concern is described as part of the Kawasaki industrial combine, which in the chaos of wartime Japan it may have been. Tachikawa Aircraft built primarily Army aircraft but also the Zero under licence so the DAP analysis provides a remarkable insight into wartime materials in both the early and later war periods.
Introduction to Japanese Aircraft Materials DAP 1946
Standard_Materials_used_by_a_Japanese_Aircraft_Factory_Ki_74_and_1941_Lists.pdf
Most importantly, the DAP analysed these materials and generated tables on equivalent Allied contemporary materials, which can now be considered a remarkable and authoritative English language reference for guidance in the selection of substitute materials today.
DAP Analysis of 1941 Standard Materials
DAP Analysis of Standard Materials used on KI74
DAP Comparison of Japanese Materials to US & UK materials
The DAP also analysed a late war Tachikawa interceptor design, the Ki94, and standard datasheets on Aircraft Design and Forging, which offer a unique insight to wartime practices and capabilities.
BIOS Metallurgical analyses of Japanese radial engines used in Navy aircraft provide detailed insight into materials of construction and Allied equivalent materials.
Metallurgical Examination of a Japanese Kasei 21
Metallurgical Examination of a Japanese Sakae 12
Metallurgical Examination of a Japanese Sakae 21
Where you have copies of any old Japanese aircraft Standards or technical information please use the Contact button to arrange scanning and sharing.