JAPAN'S SUBMERSIBLE AIRCRAFT CARRIERS


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In many ways H.I.J.M.S. 
I-400 was decades ahead of her time.  She was the world's largest submarine, with a length of 400 feet and a surfaced displacement of 3,530 tons.  Above her main deck rose a 115 foot long, 12 foot diameter, hangar housing three torpedo-bombers.  These floatplanes were rolled out through a massive hydraulic door onto an 85 foot pneumatic catapult, where they were rigged for flight, fueled, armed, launched, and, after landing alongside, lifted back aboard with a powerful hydraulic crane.  The I-400 was equipped with a snorkel, radar, radar detectors, and capacious fuel tanks that gave her a range of 37,500 miles: one and a half times around the world.  She was armed with eight torpedo tubes, a 5.5 inch 50 caliber deck gun, a bridge 25mm antiaircraft gun, and three triple 25mm A/A mounts atop her hangar.  The advent of guided missiles and atomic bombs transformed her from an overspecialized undersea dinosaur to a menacing strategic threat.  Like Germany's Type XXI U-boat she was too late to influence World War II. From: TOM PAINE'S JOURNAL



I-400's aircraft storage and catapult for her three M6A1 Seiran (Storm from a Clear Sky) torpedo-bombers.



I-400 beside submarine tender USS Proteus after the war

From link: http://www.amazing-planet.net/I-400.html

TRANSPACIFIC VOYAGE OF THE I-400

After she was taken over from the Japanese on her way home from patrol you can imagine that the I-400 required a massive clean-up from stem to stern.  The field day started with all hands moving aboard the U.S.S. Proteus, after which cylinders of fumigating gas were opened in every compartment and the boat sealed.  Next morning bushel after bushel of dead rats and cockroaches were swept up.  I'd noted with some revulsion on the Ha-boats the occasional rat leaping through a hatch from compartment to compartment, and hordes of scurrying roaches when a light was switched on, but I'd no idea that these boats carried so many verminous shipmates on patrol.  If the I-400 had been rigged for dive when the rats and roaches were thrown overboard the Diving Officer would have had to order: Flood two hundred pounds to Auxiliary Tank from sea. 

My friend Admiral Joe Vasey, who was "Junior" McCain's (i.e. Senator John McCain's father) Exec on the U.S.S. Gunnel, sent me this description of the condition of the I-400 when the U.S. Navy took over.

While you were at Sasebo I was in Yokosuka with the Proteus group.  When the I-400 entered Yokosuka I was detailed, along with a few marines, to accompany the squadron doctor for a medical inspection of the boat.  This was quite an experience - as you so eloquently described in your report.  The sub was incredibly filthy, with a layer of grease and left-over food on the decks and rats running freely in every compartment.  The stench was almost unbearable, particularly near the heads where one of our party lost his breakfast as he was hovering over the sanitary tank opening.

Despite the unhygienic conditions we witnessed, the physical appearance of the crew was remarkably good.  Everyone seemed to be lean and alert.  I think that in the closing weeks of the war, the Japanese submarine crews realized the collapse of the Empire was imminent and morale dropped sharply.  Incidentally, when we questioned the ship's officers as to the total complement, the reply was 187.  By our count it was 213, I believe.

The next morning, the crew was ordered on deck and the fumigation commenced.  If my memory is correct it was conducted under Joe McDowell's supervision and resulted in about a dozen gunny sacks full of dead rats.

Sailing across the Pacific to Pearl Harbor (or through space to the moon) requires a sound plan for fitting out, manning and supplying your ship.  The I-400 had no blueprints or Machinery History describing her equipment, no crew's Watch, Quarter & Station Bill, and no Standard Allowance Lists of tools, spares and supplies.  It was clear that we'd have to improvise, so we were given wide latitude by the powers that be in readying and supplying our unusual boat for her transpacific voyage.  The Euryale's workshops and stores were put at our disposal, and we were authorized to salvage any Japanese spare parts and supplies we needed from the warehouses and caves I'd explored around the Sasebo Navy Yard. 

Experienced submariners can imagine the results of opening a trove of untended Japanese stores to the crew of a homeward bound submarine equipped with a cavernous hangar and 12 ton crane.  Yes, the I-400 quickly became history's first Undersea Interisland Trader.  Overnight our hangar became an armory suitable for a major gun running operation, with stacks of rifles and bayonets from a relatively dry cave I'd spotted.  From Japanese uniform buttons and rating badges to rubber stamps and a sampan, down our capacious hatches they went to stock our Submarine War Surplus Store. 

The prize crew which had brought the I-400 from Yokosuka had maintained her well, and it didn't take long to put her in shipshape seagoing condition, with vital machinery inspected, overhauled and tested by a responsible crew member.  Since we had no plans to dive the boat before a complete overhaul at Pearl Harbor we didn't worry about her malfunctioning snorkel, stiff diving gear or minor defects like leaky hatch gaskets or an inoperative automatic trim system.  To conserve the Euryale's supplies we loaded provisions for only 14 days to carry us through the first leg of our passage to Guam, where we'd reprovision for the rest of the voyage to Hawaii.  By the end of November we were able to report the I-400 "in all respects ready for sea."

From: TOM PAINE'S JOURNAL: JULY 1945 TO JANUARY 1946 http://www.pacerfarm.org/i-400/

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