Aichi M6A1 « Seiran »

[Jemiba]

Reading the chapter about the Aichi M6A1 Seiran/I-400 submarine in "Strike From Beneath The Sea" by Terry C. Treadwell,
I wondered, why this aircraft actually were fitted with floats ? In the mentioned book and in other sources, too, it's said,
that they should be catapulted from the submarine and jettison their floats just after take-off. Due to the nature of those
missions, it sounds very plausible to use every available way to increase speed and range. If they would ever return to their
motherships, it seems they weren't actually intended to be taken aboard again, but to be ditched alongside. Understandable,
as hoisting the aircraft, dismantling them and putting them back into their containers probably would take much longer, than
readying and launching them. And this would have to be done facing a warned enemy ! But then, why was volume, weight
and quite probably time for dismantling sacrificed for parts, that seem to have brought only disadvantages ?

 

[TomS]

The floats could be jettisoned or left off entirely for one-way missions (leaving them off sped the launch process dramatically, BTW), but that wasn't the only mission profile. The design allowed for floats to be used for landing and recovery if conditions and mission allowed.

 

[Grey Havoc]

The Japanese also tried other approaches. One of them was inflatable/ retractable stabilizers, such as those on the Kawanishi E15K Shiun, but they weren't a success. Interestingly, the Shiun was directly related to a competitor of the A6M2-N, the N1K Kyofu (the Kyofu inherited a number of features from the Shiun program, such as it's initial Mitsubishi 1,460hp MK4D Kasei 14 engine).

Kawanishi N1K Kyofu (Mighty Wind) [Also known as Navy Fighter Seaplane Kyofu Model 11 - Allied codename Rex]
[IMAGE CREDIT: The-Blueprints.com]​

 

[Grey Havoc]

The Smithsonian's Seiran at the National Air and Space Museum:

[IMAGE CREDIT: Wikimedia Commons]​

 

[Jemiba]

... or left off entirely for one-way missions (leaving them off sped the launch process dramatically, BTW),...

Thanks, that's the clue I couldn't find still yet. Cannot tell which source it was, but I know, that it was claimed, that
the Seiran had to be put with its floats on the catapult trolley, to give ground clearance for the armed aircraft.
But of course,a suitably constructed cradle could well have done the trick.

 

[blackkite]

Enjoy.

http://www.google.co.jp/search?q=%E6%99%B4%E5%B5%90&hl=ja&rlz=1R2TSHD_jaJP353&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=i_URT7C4NaWriAe21OUw&ved=0CFoQsAQ&biw=1366&bih=517

http://www.google.co.jp/search?q=%E6%99%B4%E5%B5%90&hl=ja&rlz=1R2TSHD_jaJP353&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=i_URT7C4NaWriAe21OUw&ved=0CFoQsAQ&biw=1366&bih=517#hl=ja&rlz=1R2TSHD_jaJP353&tbm=isch&sa=1&q=%E7%B4%AB%E9%9B%BB%E6%94%B9&oq=%E7%B4%AB%E9%9B%BB%E6%94%B9&aq=0&aqi=g3g-S7&aql=&gs_sm=c&gs_upl=143903l148412l0l150487l12l12l0l0l0l3l265l2093l1.5.5l11l0&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=61cf57e05a72a245&biw=1366&bih=517

http://www.google.co.jp/search?q=%E6%99%B4%E5%B5%90&hl=ja&rlz=1R2TSHD_jaJP353&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=i_URT7C4NaWriAe21OUw&ved=0CFoQsAQ&biw=1366&bih=517#hl=ja&rlz=1R2TSHD_jaJP353&tbm=isch&sa=1&q=%E5%BD%A9%E9%9B%B2%E5%81%B5%E5%AF%9F%E6%A9%9F&oq=%E5%BD%A9%E9%9B%B2%E5%81%B5%E5%AF%9F%E6%A9%9F&aq=f&aqi=g1&aql=&gs_sm=s&gs_upl=29547l31887l2l34258l11l10l0l0l0l2l265l1965l0.4.6l10l0&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=61cf57e05a72a245&biw=1366&bih=517

 

[Grey Havoc]

Found by Jschmus over on our sister board, whatifmodelers.com, a couple of photos of a nice model of the I-400, showing the Seiran as it would have appeared for the aborted Panama Canal attack:

In the first photo, you can just see a side display of a couple of Seirans in normal markings in different configurations (floats and stowed).

 

[blackkite]

Hi! I realize that it's a very interesting project. ;D
But it's too costly and too late. I-400 submarine began to operate in February 1945!!
Source : Imperial Japanese Navy Warplane, GREEN ARROW 1996, ISBN4-7663-3161-3 C0076


http://www.google.co.jp/search?q=%E6%99%B4%E5%B5%90&hl=ja&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=iQ9UT-jEIsLPmAXkkqmQCg&sqi=2&ved=0CEcQsAQ&biw=1366&bih=675

 

[blackkite]

Hi!

http://www.pacerfarm.org/i-400/i-400.htm

http://www.google.co.jp/search?q=%E6%99%B4%E5%B5%90&hl=ja&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=iQ9UT-jEIsLPmAXkkqmQCg&sqi=2&ved=0CEcQsAQ&biw=1366&bih=675#hl=ja&tbm=isch&sa=1&q=%E3%82%A4%E5%8F%B7%EF%BC%94%EF%BC%90%EF%BC%90%E6%BD%9C%E6%B0%B4%E8%89%A6&pbx=1&oq=%E3%82%A4%E5%8F%B7%EF%BC%94%EF%BC%90%EF%BC%90%E6%BD%9C%E6%B0%B4%E8%89%A6&aq=f&aqi=g-rJS1&aql=&gs_sm=12&gs_upl=370008l393285l0l395250l40l38l0l0l0l4l186l3854l26.12l38l0&gs_l=img.12..0i4i37i24.370008l393285l0l395250l40l38l0l0l0l4l186l3854l26j12l38l0&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=2caf29dea2db7f08&biw=1366&bih=675

 

[blackkite]

Seiran was planned to lunch by I-400's catapult without floats when she carried torpedo or No.80 bomb(800kg). When she carried N0.25 bomb(250kg), she lunched with floats for safe landing. After the attack, only pilots were recovered. Seiran's maximum speed without floats was 302kt(558km/h).
Maximum speed : 256kt(474km/h), Cruising speed : 160kt(296km/h), Landing speed : 68kt(126km/h), Service ceiling : 9,900m, Range : 642nm(1,189km), Armament : one 13mm gun, 800kg torpedo or 800kg bomb or 500kg bomb or 250kg bomb.

 

[windswords]

Blackkite,

I see the the M6A1 was officially M6A1-11 (model 11). Was there any plans for an upgrade? Like a model 21 or 22 with improvements? Or even an M6A2?

thanks!

 

[blackkite]

Hi! Officially Seiran seaplane type was called M6A1, Seiran land base trainer type was called M6A1-K(Seiran-kai). I believe there were no advanced plan.

 

[Stargazer]

Hi! Officially Seiran seaplane type was called M6A1, Seiran land base trainer type was called M6A1-K(Seiran-kai). I believe there were no advanced plan.

Wasn't the land-based version called the Nanzan??

 

[blackkite]

Perhaps no. Nanzan was the early name of Seiran. 17-shi special attack bomber.

 

[windswords]

Stargazer,

Blackkite may be correct. I have also heard the M6A1-K trainer referred to as the Nanzan. It may be that they once considered making a land based version of the plane for a combat role (like the N1K1-J) but never went through with it. Maybe that was going to be called the Nanzan and it was confused with the trainer version in the West. This is just speculation on my part but it makes some sense. You don't usually call the trainer version of something by a different name, right? I would also speculate that a land based combat plane based off the Seiran would be designated M6A1-J. Blackkite, do you have any thoughts on this?

 

[Stargazer]

You don't usually call the trainer version of something by a different name, right?

Oh yes you do!! Look at the Ki-200 Shūsui and the MXY-8 Akigusa / MXY-9 Shūka trainers...

 

[windswords]

You don't usually call the trainer version of something by a different name, right?

Oh yes you do!! Look at the Ki-200 Shūsui and the MXY-8 Akigusa / MXY-9 Shūka trainers...

Very true - but these were not exact copies of the Ki-200/J8M. IIRC the MXY-8 was an unpowered glider and the MXY-9 had a small thermojet engine (the Tsu-11 that was to power the Ohka model 22). This was a very low power engine in comparison to the rocket in the Ki-200/J8M. By the way the MXY-9 according to Wikipedia was proposed but not built.

 

[blackkite]

Stargazer,

Blackkite may be correct. I have also heard the M6A1-K trainer referred to as the Nanzan. It may be that they once considered making a land based version of the plane for a combat role (like the N1K1-J) but never went through with it. Maybe that was going to be called the Nanzan and it was confused with the trainer version in the West. This is just speculation on my part but it makes some sense. You don't usually call the trainer version of something by a different name, right? I would also speculate that a land based combat plane based off the Seiran would be designated M6A1-J. Blackkite, do you have any thoughts on this?

Sorry I have no idea and I can't find any information about this.

 

[Stargazer]

I have always read and heard about the landplane version of the Seiran as being the Nanzan...

Here is another example, this time a beautiful plan from AviO No.2:

 

[blackkite]

Hi Aichi M6A1 Seiran.
Seiran(晴嵐)is the wind from the mountain blown on the fine day.

 

[blackkite]

Seiran's mother sub I-400 and Seiran.

 

[blackkite]

Hi I-400 submersible carrier!

https://www.youtube.com/watch?v=7QVMAtcrM08

 

[blackkite]

Hi!
https://www.youtube.com/watch?v=1zxVbyuxIJY

https://www.youtube.com/watch?v=R1yuu4C5xJU

https://www.youtube.com/watch?v=0PgTwwI7pyQ

 

[blackkite]

Hi Aichi M6A1-K Nanzan. Two Nanzan were made.
The reason the upper part of the vertical tail stabilizer of the Nanzan attack plane was removed was recovering the balance lost by removed float.
Nanzan is a name of the colliculus of the China Liaoning province.
It was a grueling battlefield of the Russo-Japanese War.

 

[blackkite]

Hi! Some more Seiran images.

 

[Stargazer]

Ah... The Seiran/Nanzan... One of my all-time favorite aircraft!!! So many great pics, hard to find something to add... Hope I'm not duplicating any of your images here, blackkite!

 

[Stargazer]

Plans...

 

[Stargazer]

Photos...

 

[blackkite]

It is wonderful.
To put it bluntly, it is my defeat.

 

[Stargazer]

More photos...

 

[Stargazer]

Scale models of the Seiran...

 

[Stargazer]

Scale models of the Nanzan...

 

[Stargazer]

The Seiran today, wonderfully restored for museum display:

 

[Stargazer]

It is wonderful.
To put it bluntly, it is my defeat.

Ha ha! I have little merit here... Not only do I save nearly every picture I find onto my HD, but Aichi, and especially the Seiran/Nanzan, is one of my prefered manufacturers... Glad you enjoy the pics, anyway!

 

[blackkite]

Although the navy in not only Japan but the world tended to make it put in practical use the concept of it not being discovered by the enemy, but trespassing upon strategy ocean space, and sending in airman power, only the IJN was successful.
Since around Showa 17(1942) after the Pacific War inrush, although the submarine which can be carried one set appeared the small aquatic reconnaissance plane, by the performance of the loading machine, at most, reconnaissance is main and the attack for a warship, etc. had not been completed.
This concept was expanded and developed and the naval high official who advocated construction of the "submersible aircraft carrier" which can attack the Panama Canal which is a vital part for the United States was.
He was that famous Isoroku Yamamoto.
Although the naval fleet has been built even in Seattle or San Francisco, the centers of U.S. industry were the Great Lakes and an eastern part industrial area.
If the Panama Canal is devastated, it will become impossible for a vessel to convey these goods.
Yamamoto was put into action immediately after opening a submersible aircraft carrier plan just because it knew the scale of U.S. industrial power.
The capability for a loading machine to be also able to carry an at least 500-kg bomb since Panama Canal blasting is naturally the purpose is needed.
Although the navy examined the converted type of the next high-speed carrier dive bomber "Kugisho D4Y1 Suisei" , the conclusion of it having been new and having developed the special-purpose aircraft which is easy to employ by submarine as it is advantageous was reached, and the development command was given to the Aichi airplane which was a distinguished family of carrier bomber development as a "17-shi special attack plane."

Seiran/Nanzan resembles Suisei.
Seiran's maximum speed was 560km/h after drop float.

 

[blackkite]

Hi!
http://www.youtube.com/watch?v=yUilM21VZhU

 

[Jemiba]

An interesting aircraft and an interesting concept, too, that could have had
quite a diversionary effect, probably more, than achieving actual damage.

One question remains to me, triggered partly by the picture of the Seiran with
deceptive markings : Were those floats for training purposes only ? What I read
still yet, for the actual attack, the floats would have been jettisoned and the
aircraft ditched, when coming back. But why then take-off with them at all ? And
for training I can imagine, that the floats would have quite an effect on handling
characteristics. On board of the subs, they occupied space and weight. Or doubled
they as a kind of jettisonable fuel tank ?

 

[Stargazer]

Great images! Now that's quite a rare bird... I don't have ANY more pictures to offer on this one. You win!! ;D

 

[Justo Miranda]

Suicide variant here ...

 

[blackkite]

An interesting aircraft and an interesting concept, too, that could have had
quite a diversionary effect, probably more, than achieving actual damage.

One question remains to me, triggered partly by the picture of the Seiran with
deceptive markings : Were those floats for training purposes only ? What I read
still yet, for the actual attack, the floats would have been jettisoned and the
aircraft ditched, when coming back. But why then take-off with them at all ? And
for training I can imagine, that the floats would have quite an effect on handling
characteristics. On board of the subs, they occupied space and weight. Or doubled
they as a kind of jettisonable fuel tank ?

I will try to answer your good question. Give me time.