12/09/2026
Aichi M6A "Seiran" & I-400-class submarine - video
Last week, one of the AI slop videos we uploaded showcased the launch procedure of an Aichi M6A "Seiran" floatplane from an I-400-class submarine. It was entirely incorrect and unappealing, but I found a brief video on UTube that displays the procedure far more precisely. Here's a link to the source video. https://www.youtube.com/watch?v=Ge-h6OaBJRY
The channel is very highly recommended, regardless of any cutesy elements that may not appeal to you.
https://www.youtube.com/
Acording to Wikipedia:
The hangar of the I-400s was originally designed to hold two aircraft. In 1943, however, Commander Yasuo Fujimori, Submarine Staff Officer of the Naval General Staff, requested it be enlarged. This was deemed feasible and, as remodelled, I-400s could stow up to three Aichi M6A Seiran floatplanes.
The Seiran was specifically designed for use aboard the submarines and could carry an 800 kg (1,800 lb) bomb, with a range of 1,000 km (620 mi) at 475 km/h (295 mph). To fit inside the narrow confines of the hangar, the floats were removed and stowed, the wings rotated 90 degrees and folded backward hydraulically against the fuselage, the horizontal stabilizers folded down and the top of the vertical stabilizer folded over so the overall forward profile of the aircraft was within the diameter of its propeller. When deployed for flight, the aircraft had a wingspan of 12 m (39 ft) and a length of 11.6 m (38 ft). A crew of four could prepare and launch all three in 30 minutes (or 15 minutes if the planes' pontoons were not first attached, which would make recovery impossible). As the Seiran would normally be launched at night, parts and areas of the plane were coated with luminescent paint to ease assembly in the dark.
The Seirans were launched from a 26 m (85 ft) Type 4 No. 2 Model 10 compressed-air catapult on the forward deck of the submarine. Underneath the catapult track were four high-pressure air flasks connected in parallel to a piston. The aircraft, mounted atop collapsible carriages via catapult attachment points along their fuselages, would be slung 70–75 feet along the track, though the piston itself only moved between eight and ten feet during operation.
Two sets of pontoons for the Seirans were stored in special watertight compartments located just below the main deck on either side of the catapult track. From there they could be quickly slid forward on ramps and attached to the plane's wings. A third set of pontoons and additional spares were kept inside the hangar.
The aircraft were to be launched by catapult, and fly their missions. The launching submarine was to submerge and stay in place to allow the aircraft to navigate back to the area by dead reckoning, where it would land on the water with its floats, and be hoisted back aboard by crane. Overall the system was the same as used by Japanese Navy cruisers and light cruisers when launching their reconnaissance floatplanes (like the Aichi E13A), only with aircraft specially designed for use with the I-400 class submarine, and with the added complexity of having to locate a submerged and hidden vessel on return from the mission.
Although this was the typical mode of operation, in cases where fast launching and recovery was essential for escape, the floatplanes could be launched without their floats, and ditched upon landing, saving the time spent recovering and re-hangaring the aircraft, which was a complex and lengthy procedure. This had the added benefit of eliminating the weight and considerable drag of the large and bulky floats, which in turn increased the speed and range of the aircraft, but made any recovery of the aircraft after completing the mission impossible. (For a similar defensive measure involving catapult-launched disposable aircraft used by Allied convoy groups in the Battle of the Atlantic, see CAM ship.) In extreme circumstances, the aircraft could theoretically be launched and abandoned altogether while the submarine retreated, leaving the crews to fly their missions with no hope of return, perhaps as kamikazes.
