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AICHI M6A1 SEIRAN
Soon after the advent of aircraft and submarines during World War I, the
combined operation of those two weapons were considered by many countries.
However, it was only the Imperial Japanese Navy that could put it to practical
use. At the outbreak of the Pacific War, many large-sized submarines of the
Imperial Japanese Navy were equipped with catapult and small observation-type
aircraft desiged to attack harbors and to bomb the U.S. mainland. Acknowledging
the success of former attacks by the Imperial Japanese Navy, it decided to plan
surprise attack missions to the Panama canal by special submarineborne aircraft
at the beginning of 1942. The plane was the Aichi M6A1 Seiran, designed
exclusively fot this one exceptional mission. It was in May 1942 when the Aichi
Aircraft Company received specifications to develop and produce a special attack
bomber. At first, the use of the then new Suisei bomber with some modifications
was proposed, but the conversion was found impractical because of the difficulty
to have interchangeability of major assemblies. On November 1943, the first
prototype made its maiden flight. Undergoing several improvements, the Aichi
Aircraft Company received an order for limited production from the Navy in May
1944. The engine was a 12-cylinder liquid-cooled Atsuta 32, which was based on
the German Daimler-Benz DB603. A 12.7mm, type-2 flex mounted machine gun was
equipped at the rear, and torpedo or a 250kg/800kg bomb could be carried. The
Seiran was to be carried by the I-400 class submarine in the hanger tube of 4.2m
in diameter and 30.5m in length. The hanger tube was capable of holding three
Seirans. They were stored on catapult launching cars with armaments for quick
ejection after surfacing. To cope with the space limitation, the Seiran was
designed to conserve space by folding the wings. The wings were pivoted on the
main spar where it joined the fuselage. By rotating the leading edge downward,
the wing could lie back flat against the sides of the fuselage. The outer
portions of each stabilizer and elevator hinged at 90cm from the fuselage
centerline and folded downward. Vertical clearance was obtained by folding the
tip of the fin to the right. 28 Seirans including a Nanzan, its
ground-take-off-and-landing equivalent, were produced in total by 1945, and
submersible carriers for them, the I-400 and I-401, were completed almost
simultaneously. Having the target changed from the Panama canal to the U.S. Navy
air craft carriers staged at Ulithi Atoll due to the change 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 first and last
mission. On 15 August, the flagship I-401 monitored a radio message from
headquarters, informing them of Japan's surrender and the flotilla was ordered
to return to the nearest port in Japan. Thus the chance to prove the Seiran's
worth was missed forever.  |
