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Written by unknown author
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Thursday, 19 April 2007 |
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Page 1 of 2 This article submitted by DEY_THOR_USA...
JAPAN’S SUBMERSIBLE I-400 AIRCRAFT CARRIERS
 In many ways HIJMS I-400 was decades ahead of her time. She was the world’s largest submarine with a length of 400-ft and a surface displacement of 3,530 tons. Above her main deck rose a 115-ft. long, 12-ft diameter, hangar housing three torpedo-bombers. These float planes were rolled out through a massive hydraulic door onto an 85-ft 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-in 50-cal deck gun, a bridge 25mm antiaircraft gun, and three
triple 25 mm A/A mounts atop her hangar. The advent of guided missiles
and atomic bombs transformed her from dinosaur to an overspecialized
undersea menacing strategic threat.
The I-400 was originally designed so that it could travel round-trip to anywhere in the world, and it was specifically intended to destroy the U.S. controlled Panama Canal. A fleet of 18 boats was planned in 1942, and work on the first one was started in 1943 at the Kure, Hiroshima arsenal. Within a year the plan was scaled back to five, and four (I-400, I-401, I-14 and I-13) were completed. The I-400's had aircraft storage and catapult for three M6A1 Seiran (Storm from a
Clear Sky) torpedo-bombers. These specially-designed float planes had a length of 35-ft, a wingspread of 40-ft, a range of 654 miles, and a munitions payload of 1800-lb. Additional fuel and bombs could be carried by jettisoning the floats on one-way missions where the pilots and planes were to be expended.. The sleek Seiran bombers, built by Aichi Kokuki at Nagoya, were stowed in the hangar compartment with floats detached and wings and tails folded. Actually with the stabilizers folded down, and the top of the vertical stabilizer folded over the overall profile of the aircraft was within the diameter of its propellor.
A trained team could rig a floatplane for launch with fuel and armament in as short a time as seven minutes, in fact that trained same trained team could prepare all three planes, and have them in the air in under 45 minutes time. The planes were launched from a 120 foot catapult on the deck of the giant submarine.
Accommodations for a crew of 145 were designed into the capacious twin hulls, but on most occasions was much higher....somewhere in the 200+ range. The reason for the high number was to facilitate speedy submarine and aviation operations at sea. Even though the sub could surface, the trained crew could in fact could break out, assemble, fuel, arm, and catapult all three aircraft..........more men was an “assurance” of that. Also the I-400's had great cruising range which enabled them to launch her three bombers within striking distance of targets as far from Japan as San Francisco, the Panama Canal, Washington, or New York. All of these missions were considered by the Tokyo Naval
Strategists.
Below the hangar in the starboard twin hull was a special compartment equipped to conduct aircraft engine overhaul and test. An adjacent magazine stored four aircraft torpedoes, 15 bombs, and gun ammunition; more shells were stored topside in pressure-proof, ready-use lockers handy to the guns. Each of the two engine rooms housed a pair of 1900-hp diesels linked through Vulcan hydraulic couplings to drive the twin propeller shafts.
A 1200-hp electric motor-generator on each shaft drew electricity form her storage batteries to drive her submerged. With a clean bottom this propulsion plant gave her a top speed of 18.7 knots on the surface and 6.5 knots below snorkel depth.
Meals for her oversize crew were prepared in a galley in the starboard hull, where large steam kettles turned out great quantities of rice. As in all long range submarines, a four month supply of food was stowed in every cranny, including a layer of crates laid out on deck which the crew walked on until they’d eaten their way through. Supernumeraries slept on the deck wherever they could find a nook, being used to a floor and tatami mat.
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