The hidden accident and outbreak of war with the United States and Britain: deciphering institutionalized secrecy

The Shibuya Archives consist of more than 4,000 materials on various subjects, including casualties of the atomic bomb;15 however, this chapter discusses only materials directly concerning the Rinkicho accident. Among these, focus is placed on the special examination committee established in January 1938. The purpose of the committee was stated as follows:

Problems were found with the turbines of Asashio-class destroyers. ... It is necessary to work out remedial measures and study the design of the machinery involved and other related matters, so that such studies will help improvements. These research activities must be performed freely without any restrictions imposed by experience and practice in the past. The special examination committee has been established to fulfill this purpose.

(The Minister of the Navy's Secretariat 1938: Military secret No. 266)

Its organization was as follows (Rinkicho Report 1938b: Top secret No. 35):

  • • General members who did not attend sub-committee meetings
  • • Chair: Isoroku Yamamoto, Vice Admiral, Administrative Vice Minister of the Navy'
  • • Members: Rear Admiral Inoue, Director of the Bureau of Naval Affairs, the Ministry of the Navy; and five other members
  • • First sub-committee for dealing with engine design and planning
  • • Leader: Shipbuilding Vice Admiral Fukuma, Director of the Fifth Department (including the turbine group), the Technical Headquarters of the Navy; and nine other members
  • • Second sub-committee for dealing with maximum engine power and suitable load/volume
  • • Leader: Rear Admiral Mikawa, Director of the Second Department, the Naval General Staff; and eleven other members
  • • Third sub-committee for dealing with prior studies/experiments/systems and operations
  • • Leader: Rear Admiral Iwamura, Director of the General Affairs Department, the Technical Headquarters of the Navy; and ten other members

Ignoring duplication of members belonging to different subcommittees and arranging the net members by section, the results in Table 4.5 were obtained.

The accident, as discussed, concerned the breakage of Kanpon type turbine blades. Following the history of marine turbine development in Japan since 1918, when the Navy began to adopt geared turbines, various failures had occurred with main turbines. When we classify these failures during the period from 1918 to October 1944 by location, failures involving turbine blades account for 60 percent of the total (see Table 4.6).16

The Imperial Japanese Navy had thus experienced many previous problems with turbine blades and had accumulated practice in handling them; accordingly, it is not surprising that the special examination committee considered the accident as merely a routine problem from the outset, based upon such history. In fact, the special examination committee drew a two-point conclusion to the problem in line with such accumulated experience: first, the accident was caused by insufficient blade strength; and second, the turbine rotor vibration made the

Table 4.5 Members of the Special Examination Committee by Section



Administrative Vice Minister of the Navy


Bureau of Naval Affairs


Naval General Staff


Technical Headquarters of the Navy


Naval Staff College


Naval Engineering School




Source: Calculated based on Rinkicho Report (1938b) Top secret No. 35, Appended sheets.

Table 4.6 Naval Turbine Failures Classified by Location: 1918-1944





Impulse blade and grommet




Reaction blade and binding strip




Reduction gear and claw coupling




Bearing and thrust bearing








Casing partition and nozzle




Blade wheel and spindle




Steam packing











Source: Based on Seisan Gijutsu Kyokai (1954: 1-2).

Note: Reaction blade means the blade of a traditional Parsons turbine (Cf., Seisan Gijutsu Kyokai 1954: 4).

insufficient strength emerge as a problem (Rinkicho Report 1938b: Top secret No. 35). On the basis of this conclusion, a plan was developed to improve the design of the Kanpon type turbine blades and rotors for all naval vessels, changing the form of the blades to make their stress concentration lower, thereby enhancing their strength (Rinkicho Report 1938a: Top secret No. 1). The improvement of 61 naval vessels’ turbines was indicated as the first step toward resolution, in accordance with the previous 66 committee-meeting reports held over a period of 10 months (Rinkicho Report 1938a: Top secret No. 1).

However, the blade breakage in the accident was significantly different from those that had occurred in the past. In impulse turbines cases, for instance, the blades were most often broken at the base where they were fixed to the turbine rotor; in contrast, one of the unique features of the Rinkicho accident was that the tip of the blade was broken off, a section that amounted to one-third of its total length.17 Figure 4.2 shows a photograph of the locus of the breakage.

Yoshio Kubota, a naval engineering captain who was transferred to the Military Affairs Bureau in November 1938 when the special examination committee reported its conclusion, noticed this key difference in the breakage point, even though it was not considered permissible for a newcomer to the Military Affairs Bureau to object to the latest conclusion of the special committee. In addition, six months before his transfer to the bureau, the Japanese government enacted the Wartime Mobilization Law on April 1, 1938, for the purpose of “controlling and organizing human and material resources most efficiently ... in case of war” (Clause 1). Against the background of wartime mobilization, a naval engine failure caused by small tip fragments of the main standard engine was a delicate matter for anyone to raise, as naval vessels came first in the specification of the law as “resources for wholesale mobilization” (Clause 2).18 Despite these circumstances,

Broken Part of a Blade in the Rinkicho Accident Source

Figure 4.2 Broken Part of a Blade in the Rinkicho Accident Source: Rinkicho Report (1938a) Top secret No. 1.

Kubota strongly recommended that confirmation tests should be conducted again for naval vessels of the same type. He argued that if turbine rotor vibration was the true cause of the breakage and resulting accident, then the failure would be repeatable when the engine was run continuously at the same critical speed causing rotor vibration (nearly 6/10 to 10/10 of the full speed).19

The Navy finally decided to initiate continuous run tests equivalent to 10-year runs on April 1, 1939. No failures occurred. This means that the remedial measures thus far taken by the Navy functioned to adhere to erroneous precedents, causing problems to be carried over and reproduced, an element of structural disaster. This also provided the Navy with a practical rationale for canceling the overall remedial measures for all naval vessels, which were expected to require significant money and time to check for potential failures and perform necessary modifications.20

Upon the tests’ conclusions, an order was promptly issued to postpone any modifications to the turbine blades and rotors of the Kanpon type for all naval vessels. At the same time, however, there was an urgent need to consider another possible cause for the breakage, and a study to identify the cause was restarted. The Maizuru Naval Dockyard conducted preliminary on-land tests, followed by a more thorough one at the Hiro Naval Dockyard to confirm the conditions that would recreate the failure. However, the tests were extremely difficult to carry out for two reasons. First, the complete test required the dockyards to construct from scratch a full-scale experimental apparatus for a vibration load test, which was only completed in December 1941, the month during which the war with the United States and Britain broke out. Second, the test was on such a large-scale, eventually extending to more than 35 main items, that it took far more time than expected. As a result, the schedule for identifying the cause, which was originally expected to be completed in November 1940, was extended to mid-1943,21 Thus, it is logical to assume that all of Japan’s naval vessels were operating during this time with imperfect turbines when the country went to war in 1941.

What, then, was the true cause for the accident? Previous efforts to avoid turbine vibration had been confined to one-node vibration at full speed, since multiple-node vibration below full speed had been assumed to be unworthy of attention and it was the standard of turbine design in the pre-war period.22 The final discovery of the true cause of the Rinkicho accident drastically changed these standards. It revealed that marine turbines are susceptible to a serious vibration problem below full speed. In April 1943 the true cause was eventually identified as binodal vibration in the final report of the special examination committee - almost one and a half years after the war broke out.23

Only three months before the submission of the report, a theoretical study made at the Hiro Naval Dockyard supported the conclusion that the true cause was binodal vibration.24 The results of theoretical calculation, on-land confirmation testing, and the characteristics of the actual failure matched this conclusion. The complete mechanism creating binodal vibration itself, however, was still left for further studies; even so, all results from the special examination committee that concluded in 1943 pointed to the same single cause: binodal vibration (Ono

Secrecy throughout war and peace 101

1943).25 Strictly in terms of the technology involved in the accident (that is, without hindsight), all the evidence suggests that the Japanese government went to war in haste in 1941, despite having an unaccounted for, highly intricate, and serious problem with the main engines of all its naval vessels. This fact was undisclosed to outsiders by institutionally legitimate procedures ranging from military secret instructions to top secret reports, as shown in Table 4.7.

Within the military-industrial-university complex, facts surrounding the accident and its cause were undisclosed by legitimately designed institutional procedures to other sectors involved.26 The rarity of naval vessel breakdowns due to

Table 4.7 Brief List of Military Secret Instructions Issued to Deal with the Rinkicho Accident: January 1938-December 1941


Military secret instructions

December 29, 1937

The accident occurred

January 19, 1938 '

The Minister of the Navy’s Secretariat Military Secret No. 266 was issued to establish the special examination committee.

February 3, 1938

The Minister of the Navy’s Secretariat Secret Instruction No. 566 was issued to examine the vibration of the main turbine blades and rotors installed in the naval vessels at the Hiro Naval Dockyard.

August 1938

The Technical Headquarters’ Secret No. 15332 was issued to specify the methods of static and dynamic vibration tests on turbine blades and rotors.

November 2, 1938

April 1, 1939

Report from the Committee (Top Secret No. 35) was issued to summarize the 53 sub-committee meetings and 13 general meetings held until this date.

The Minister of the Navy’s Secretariat Secret Instruction No. 1973 was issued to select a representative naval vessel from existing vessels, and to conduct long-run load tests according to the remedy implementation schedule suggested by the special examination committee’s report.

February 12, 1940

The Minister of the Navy’s Secretariat Secret Instruction No. 1122 was issued to begin turbine rotor load tests at the Engine Experiment Department of the Maizuru Naval Dockyard in April 1940.

May 6, 1940 June 20, 1941

The Minister of the Navy’s Secretariat Secret Instruction No. 3185 was issued to postpone modifications to the main turbines of existing naval vessels.

The Minister of the Navy’s Secretariat Secret Instruction No. 5389 was issued to postpone the completion of turbine rotor load tests to March 1943, postpone modifications to the main turbines of naval vessels, and make the final decision by consulting the results of on-land tests by the end of June 1943.

December 8, 1941

War with the United States and Britain declared.

Source: Murata (n.d.)

turbine troubles during the war is a matter of hindsight; thus, the Rinkicho accident strongly suggests that such practical results alone during wartime (and possibly in peacetime as well) do not prove the essential soundness of the development trajectory of technology, nor that of the science-technology-society interface and national decision-making along the trajectory.

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