Aichi M6A1 Seiran
Japanese World War II Navy Special Attack Bomber

Archive Photos 1

Aichi M6A1 Seiran (Clear Sky Storm), National Air and Space Museum Steven F. Udvar-Hazy Center, Chantilly, Virginia, 02-16-2004, Photos by Jim Hough 1

Overview 2

The Aichi M6A Seiran (Clear Sky Storm) was a submarine-launched attack floatplane designed for the Imperial Japanese Navy. It was intended to be used with the I-400 class submarine, a 4,082 tonne (4,500 ton) submarine aircraft carrier. Two or three of the craft would be stowed aboard in disassembled form, and launched by catapult. The twin floats could be jettisoned, and the aircraft was essentially meant to be ditched at sea upon completion of its mission. The Type AM submarine was also intended to carry two of these aircraft.

An alternate version with landing gear instead of floats was designated M6A1-K and named Nanzan (Southern Mountain). While generally described as a land-based trainer, some sources indicate that it was designed for the attack role, to be launched from the submarine and then landed. Besides the difference in landing gear, the vertical stabilizer’s top portion, which was foldable on the Seiran, was removed.

Operational History 2

The first M6A1 was completed in November 1943, and 28 examples (including M6A1-Ks) were completed by 1945. Admiral Isoroku Yamamoto made plans back in early 1942 to launch a surprise air strike on the Panama Canal using the Seiran. The target was later changed in 1945 to the American aircraft carriers stationed at Ulithi Atoll following Yamamoto’s death and reports of an impending attack on the home islands.

This mission was assigned to the 1st Submarine Flotilla, which comprised two submarines, the I-400 and the flagship I-401, each carrying three Seirans. The flotilla departed Japan on 23 July 1945 and proceeded towards Ulithi. However, on 15 August, the flagship I-401 received a radio message from headquarters, informing them of Japan’s surrender. They were ordered to return to the nearest port in Japan, ending the flotilla’s first and only mission, and preventing the Seiran from ever entering combat. All six Seirans onboard the two submarines were catapulted into the sea with their wings and stabilizers folded to prevent capture by the Americans.

Variants 2

Operators 2

Survivors 2

A single M6A1 has been preserved and resides in the Udvar-Hazy Center of the Smithsonian’s National Air and Space Museum. It is located in the Washington, DC suburb of Chantilly, VA near Dulles International Airport.

Aichi M6A1 Seiran Specifications and Performance Data 3

General Characteristics





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