Flightline: 53/TBD

"user314" (user314) 09/24/2020 at 11:00 • Filed to: flightline, Planelopnik, planelopnik history, ww2, ww2 aircraft

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The sole remaining M6A Seiran at the NASM Udvar Hazy Center after an 11 year restoration

Capitalizing on the successful raid on Pearl Harbor, Admiral !!!error: Indecipherable SUB-paragraph formatting!!! , Commander-in-Chief of the Japanese Combined Fleet, proposed a fleet of large submarine aircraft carriers to attack the continental US.

I-401 underway, date unknown

Work on the !!!error: Indecipherable SUB-paragraph formatting!!! , the largest sub constructed until the ballistic missile submarines of the 1960's. began in 1943, though the planned fleet of 18 was scaled back to nine, then five as the war turned against the Japanese. The leviathan subs had a watertight tube which could hold three airplanes, as well as torpedo tubes and a deck gun. Each plane w ould be rolled out, rigged for flight and launched via a compressed air catapult . In the end, only three were completed, and only the first two, I-400 and I-401 were launched before the war’s end. The US captured all three subs, though I-402 was sunk off Fukue Island to prevent the USSR from also inspecting the sub. I-400 and I-401 were sailed to Hawaii for further study, though they were eventually sunk in 1946, again to keep them out of Soviet hands.

!!!error: Indecipherable SUB-paragraph formatting!!! was tapped to build the new torpedo/dive bomber, which would be launched from the subs, attack the targets, then return to the sub’s position, which would then surface and retrieve the crew before sinking the planes. Initially planning to adapt the !!!error: Indecipherable SUB-paragraph formatting!!! (Judy) dive bombers Aichi was building under license, eventually a clean-sheet design was needed as the modifications would be too extensive.

Orthographic view of the M6A1

The final design was a low-wing monoplane with pontoons.The plane featured a crew of two and was armed with an 850kg torpedo or bomb, as well as 13mm machine gun on a flexible mount for self defense . The plane was powered by a !!!error: Indecipherable SUB-paragraph formatting!!! of the !!!error: Indecipherable SUB-paragraph formatting!!! engine, which provided a cruise speed of 296km/h and a range of 1,188km.

Scan of a model kit instructions showing the extensive folding required to fit the M6A1 into its hangar

Cutaway model of the I-400 submarine showing the folded M6A1s

In order to cut down on prep time, t he aircraft, given the designation M6A and called the Seiran (lit. “storm from the clear sky”) would be launched from a cold start, with oil and water preheated separately and pumped into the engine prior to catapult , an idea borrowed from the Nazis, who developed it for their incom plete aircraft carrier Graf Zeppelin . The first Seiran flew in 1943, and production started in 1944. Two trainers, designated M6A1-K Nanzan (“South Mountain”) were constructed, with hand-cranked landing gear replacing the floats.

One of the two M6A1-K , designated “Jake” by the US.

The M6A1 were organized into the Shinryuu Tokubetsukougeki-tai ( “God-Dragon Special Attack Squad”), and commenced training to attack the locks on the Panama Canal, which would cut American supply lines. The plan was for the I-400 and I-401 to be joined by two smaller subs, the I-13 and I-14 , which would be modified to carry two Seirans each, and attack the Gatun locks on the Atlantic side, as this would maximize the damage. Crews trained on a full-scale wooden mockup of the locks, with training concluded on 20 June 1945. Th e aircraft were painted with false US markings and the subs were set to sail when the Allies captured Okinawa.

The loss of Okinawa resulted in the attack on Panama being canceled, and the sub’ s target was changed to Ulithi atoll, where the US Navy was massing in preparation for attacks on the Home islands. The Seirans would be tasked with making Kamikaze runs on the Allied ships. The I-400 and -401 would then sail for Hong Kong to take on additional aircraft to continue raiding Allied warships. The Emperor ordered surrender before the attacks could commence, and the M6As, without wings or tails, were catapulted into the ocean in accordance with orders to disarm.

The Smithsonian’s Seiran undergoing restoration in 1998

One Seiran was surrendered to US forces by Lt Kazuo Akatsuka of the Imperial Japanese Navy, who ferried it from !!!error: Indecipherable SUB-paragraph formatting!!! to !!!error: Indecipherable SUB-paragraph formatting!!! . After examining the airplane, the Navy placed it in storage, and eventually donated it to the Smithsonian in 1962. Restoration work on the Seiran began in June 1989 and was completed in February 2000, when it was placed on display at the Air & Space Museum. The M6A was moved to the Udvar-Hazy Center, where it remains today.
 

Color orthograph of the M6A1, showing the wings and tail folded

The W!N Center of Hard Truth & Good Humor > user314 09/24/2020 at 11:07

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This was really good. Like, better than a lot of the paid writers on G/O sites!

Serious question, how do I post to Oppo? I've got a really good article and no blog to publish it on. 

InFierority Complex > The W!N Center of Hard Truth & Good Humor 09/24/2020 at 11:14

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https://oppositelock.kinja.com/i-a-glutton-for-punishment-want-you-to-be-on-opposit-1844164784

Add a comment there asking for authorship and you should get it once a mod sees it.

ttyymmnn > user314 09/24/2020 at 11:15

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I’ve seen that aircraft before, and always thought it was an attractive plane. Very nice lines and proportion, even with the floats. But then I got to thinking about the fact that it has an inverted V-12, a very German sort of thing. And that got me thinking about how many other Japanese warplanes used inline engines rather than radials. And that led me to the Kawasaki Ki-61 , which Wiki says was “ the only only mass-produced Japanese fighter of the war to use a liquid-cooled inline V engine.” More than 3,000 Ki-61s were built, which is certainly a definition of “mass production,” while less than 30 Seirans were built. 

PowderHound > user314 09/24/2020 at 11:24

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That’s such a wild design idea. I remember reading about this quite a while back and never realized that the pontoons came off as well for storage.

Bit of a side note, the pontoons reminded me, but we had two fire bosses flying laps around the other day for a near-by fire. A friend got some video of them scooping up water in the reservoir.

ClassicDatsunDebate > ttyymmnn 09/24/2020 at 11:38

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The HA-40 engine was a licence built DB-601. They built just over 3000 Ki-61, mainly -1 and -1a. The y also fitted them with MG-151's which makes it very German.

Funny thing, when they abandoned using the inverted V and equipped the last 250 or so with Ha-112 radials, it became the Ki-100, which was the best Japanese fighter of the war.

Chariotoflove > The W!N Center of Hard Truth & Good Humor 09/24/2020 at 11:41

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Also, you do have a personal blog to post to, by virtue of your Kinja account. However, you won’t get the comments and interaction you want if you do, so you will want to make sure that you post what you write to Oppo instead of your personal page when you do.

Chariotoflove > user314 09/24/2020 at 11:43

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I’d never heard of this before. I can’t imagine it would have worked out to be very effective in influencing the course of the war, but it’s very impressive that they thought of this and made it work with 40s tech.

user314 > Chariotoflove 09/24/2020 at 12:32

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Yeah, the attack on the locks would have been a blow, but probably not as crippling as they thought. Even the attack on Ulithi would have only slowed things a little.

The IJN was really in love with the submarine aircraft carrier idea, with the I-400s joining the A1 , A2 , and B1 classes, all of which could carry 1 or two scout planes, and the AM class, derived from the A2, being modified to carry two Seirans.

Chariotoflove > user314 09/24/2020 at 12:39

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It’s a cool idea, but when you look at how all the strategic bombing we did on Germany, I think the hit they took on war production from each individual target was only temporary.

What ever damage the Japanese could have done to the canal with a handful of war planes I’m guessing could probably have been bypassed by the Army Corps of Engineers is pretty good time. And also, wasn’t the Pacific fleet fully constituted on the west side by that time anyway?

KingT- 60% of the time, it works every time > user314 09/24/2020 at 12:44

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Very interesting stuff, thanks for sharing

user314 > Chariotoflove 09/24/2020 at 12:50

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AFAIR, yeah. Even if the Navy was moving  ships from ‘Lant fleet over I think going around the Horn would have been easier. 

Chariotoflove > user314 09/24/2020 at 13:33

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And for supplies, I suspect that  our cross country transportation systems were up to the task, even before the Interstate highway system.

415s30 W123TSXWaggoIIIIIIo ( •_•))°) > user314 09/24/2020 at 13:59

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They have a D4Y1 at the Yshkan, I thought it was the same plane just with floats but it is different . It’s in a room you can’t take pictures in but people have. We were being closely watched by a guard so I didn’t....

gmporschenut also a fan of hondas > Chariotoflove 09/24/2020 at 21:51

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a giant misconception of the effectiveness of allied bombing on production is from albert speer. after he was captured he said it only hindered war production something like 6%. This number is highly misleading because that is only the percent of time war plants were out of action due to damage.

After the war this number ws thrown around by all sorts of groups pushing for certain agendas.

It leaves out how manufacturing had to be decentralized and added greater time and labor costs. Damage to rail lines that now screw up timetables and make transport slower. Now the plant isn’t damaged, but held up waiting for parts. knocking out refineries that put greater stress on the rail lines, and hinder tank, ship, and plane movement.

And then there are hundreds of thousansds of troops with thousands of flak guns that it tied up. Not to mention a sizeable chunk of the luftwaffe that was then tied up.

Chariotoflove > gmporschenut also a fan of hondas 09/24/2020 at 22:22

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Interesting.

gmporschenut also a fan of hondas > Chariotoflove 09/24/2020 at 22:44

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I think it was Military History V isualized. Its easy to tally how much was destroyed, it is more difficult to account how much wasn’t built, ( or how much was built and sat unused. .)