All and Nothing

After Pearl Harbor, the Japanese planned to strike the United States with aircraft borne by giant submarines.

The Aichi M6A1 Seiran (Clear Sky Storm) (shown here on a beaching dolly) was designed to operate from a submarine. (NASM)
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And so the product of Admiral Yamamoto’s elaborate strategy to bring the war to the U.S. mainland came to an end. Captain Ariizumi took his own life in his command ship’s cabin, observing an ancient tradition when faced with the dishonor of surrender, a concept that is not in the vocabulary of the samurai.

The sen-toku submarines were sailed to Pearl Harbor by a U.S. Navy crew for technical assessment and were subsequently scuttled at sea off Hawaii. The submarines, I-401, I-400, and I-14 followed their aircraft to the deep.

The chaotic aftermath of Japan’s surrender and the hasty collection and shipment to the United States of samples of Japanese warplanes by the Allied Air Technical Intelligence Group revealed no special notice of the heretofore secret aircraft. Fortunately, the shipment included at least one Seiran, which eventually found its way to Washington, D.C., to be preserved as the only remaining example in the world.

The I-400 sen-toku had been the largest submarine in the world ever to sail until the U.S. Navy launched the nuclear submarine USS Triton in 1959. Author E. John Long, in the October 1953 issue of Ships and the Sea, described the first U.S. encounter with the sen-toku: “Twelve days after the Mikado told his people to lay down their arms, one of Japan’s most closely guarded secrets was revealed. The pilot of the U.S. Navy patrol plane could scarcely believe his eyes. The great dark object, half awash, looked like a floating wreck. It seemed too big to be a sub—but it was one, on the lam.”

Recently, the staff at the Paul E. Garber Preservation, Restoration, and Storage Facility in Suitland, Maryland, completed a lengthy restoration of the surviving Seiran (see “Team Seiran, p. 26). While searching records in Japan, staff members met individuals involved in the design of the airplane, and they were able to tell their stories. The restored Seiran will re-tell the story for years to come.


Team Seiran

In terms of the challenges it posed to the staff at the National Air and Space Museum’s Paul E. Garber Preservation, Restoration, and Storage Facility in Suitland, the Aichi Seiran is without peer. Here are the restorers’ recollections of the project:

Bob Weihrauch: When we got our first look at the floats, they looked in good shape from the top, but when we looked at the bottoms, we could see internal damage. It was all aluminum except for steel fittings where it attaches to the airframe. Dust and debris were falling out of holes in the skin.

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