Japan’s Underwater Aircraft Carriers – conclusion

American naval personnel inspect the hangar of a Japanese submarine aircraft carrier. The hangar tube was sealed by a two-inch-thick rubber gasket, and the hatch could be opened hydraulically from inside

By early 1945, the Japanese Navy had only 20 modern submarines left, including those in the Sen-toku squadron. Problems arose as the two available I-400 subs began test launching their Sieran planes. Each submarine was required to surface and get its three planes unlimbered and aloft within 30 minutes, but actual training showed that it took some 45 minutes.

Because of an increasing sense of urgency, the Japanese further modified their plans. A torpedo attack was ruled out because the pilots had not yet acquired the requisite skills. It was decided that each of the 10 planes designated for the Panama Canal mission would carry one 1,760-pound bomb, the largest in the Navy’s arsenal and similar to the one…