carrying a warhead. It would have been the largest aerial torpedo in the Imperial Japanese Navy Air Force, but the operating concept became outdated and the project was never completed. However, the Type91 aerial torpedo project members did not regard it as a part of the Type91 series. Type 91 history Chronological Table 1931Type 91 aerial torpedo is put into service, production begins. 1936Revision 1. Self-detachable wooden plates are introduced. 1937Launch-tests at with wooden damper. 1939Revision 2 starts production. Not running true after water entry is identified as a major problem. 1941Revision 2 clears the shallow water launching test due to the introduction of an anti-rolling controller. Battle of Pearl Harbor, sinking of HMS Prince of Wales and HMS Repulse. 1941Revision 3 starts production. 1942 Indian Ocean raid, Battle of the Coral Sea, Battle of Midway, Battle of the Santa Cruz Islands. 2 August: Type 91 torpedo technology reaches Nazi Germany via IJN sub I-30 1943Revision 5 starts production. 1944Battle of the Philippine Sea, Aerial Battle of Taiwan-Okinawa. Initial development Rear Admiral Seiji Naruse led the team in charge of the initial development of the Type91 aerial torpedo at the Yokosuka Naval Arsenal. The team was known as the Ninety One Association and included Lt Cmdr Haruo Hirota, Lt Cmdr Makoto Kodaira (Matsunawa), Naval Assistant Manager Iyeta, Naval Engineer Noma, Naval Engineer Moritoshi Maeda, Lieutenant Hidehiko Ichikawa, and Teruyuki Kawada, a university student who was a naval apprentice. Captain Fumio Aiko was in charge of further development of the torpedo from 1931. Captain Aiko managed the team as it developed an effective aerial torpedo and anti-rolling controller. He considered the Type91 aerial torpedo to be his great achievement. Delayed development At the beginning of 1934, Kan-Pon or the Imperial Japanese Navy Technical Department, an operating division of the Ministry of the Navy of the Imperial Japanese government, which had the primary responsibility for naval weapon systems, had their own plan for a Japanese aerial torpedo. In their concept, a big flying boat was to carry a variant of the heavy Type93 oxygen torpedoes to launch at long range, and then turn back towards safety. This eventually proved to be an unrealistic desk plan. Kan-Pon confidentially developed their own Type94 torpedo and even ordered a halt to production of the Type 91. This significantly delayed the development schedule of the Type91 and frustrated the project members. Wooden tail stabilizers added The