Immediately after the advent of aircraft and submarines during World War I, the combined procedure of these two tools were considered by many nations. But ended up being only the Imperial Japanese Navy that could place it to practical usage. At outbreak for the Pacific War, many large-sized submarines associated with the Imperial Japanese Navy had been loaded with catapult and tiny observation-type aircraft designed to attack harbors also to bomb the U.S. mainland. Acknowledging the success of previous assaults by the Imperial Japanese Navy, it decided to prepare shock assault missions toward Panama canal by unique submarineborne aircraft at the start of 1942. The plane had been the Aichi M6A1 Seiran, created solely with this one exceptional objective. It was in May 1942 when the Aichi Aircraft business received specifications to produce and produce a special assault bomber. In the beginning, the use of the then new Suisei bomber with modifications had been proposed, nevertheless the discussion was found not practical because of the difficulty to possess interchangeability of major assemblies. On November 1943, 1st prototype made its maiden flight. Undergoing several improvements, the Aichi Aircraft Company received an order for restricted manufacturing from Navy in 1944. The engine ended up being a 12-cylinder liquid-cooled Atsuta 32, which was based on the German Daimler-Benz DB603. A 12.7mm, type-2 flex mounted machine weapon ended up being equipped on back, and a torpedo or a 250kg/800kg bomb might be carried. The Seiran would be to be carried by the I-400 course submarine inside hanger pipe of 4.2m in diameter and 30.5m long. The hanger tube was capable of holding three Seirans. These were saved on catapult launching vehicles with armaments for quick ejection after surfacing. To cope with the area limitation, the Seiran was built to save space by folding the wings. The wings had been pivoted regarding the main spar where it joined the fuselage. By rotating the best edge downward, the wing could lie straight back flat contrary to the edges regarding the fuselage. The external portions of each and every stabilizer and elevator hinged on 90cm from the fuselage centerline and folded downward. Vertical approval was acquired by folding the tip associated with fin to your right. 28 Seirans including a Nanzan, its ground-take-off-and-landing equivalent, had been manufactured in total by 1945, and submersible providers for them, the I-400 and I-401, had been finished almost simultaneously. Having the target changed from Panama Canal on U.S. Navy aircraft carriers staged at Ulithi Atoll because of the improvement in priorities the war demanded, the 1st Submarine Flotilla including the I-400 and I-401 with three Seirans each departed Japan on 23 July 1945 for their very first and last mission. On 15 August, the flagship I-401 monitored a radio message from headquarters, informing them of Japan's surrender while the flotilla ended up being purchased to go back to your nearest slot in Japan. Hence the opportunity to show the Seiran's worth had been missed forever.
