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I401 1945  

Ships

Name	No	Yard No	Builder	Laid down	Launched	Comp	Fate
伊400 [I400]			Kure K K	1/1943	18.1.1944	12.1944	surrendered 8.1945, scuttled 4.6.1946
伊401 [I401]			Sasebo K K	4/1943	11.3.1944	1.1945	surrendered 8.1945, scuttled 31.5.1946
伊402 [I402]			Sasebo K K	10/1943	5.9.1944	7.1945	surrendered 8.1945, scuttled 1.4.1946
伊403 [I403]			Kure K K	4.1943	---	---	cancelled 3.1945
伊404 [I404]			Kure K K	11/1943	7.7.1944	---	cancelled 3.1945, sunk 28.7.1945
伊405 [I405]			Kawasaki, Kobe	9/1944	---	---	cancelled 3.1945

Technical data

Displacement standard, t	3530
Displacement normal, t	5223 / 6560
Length, m	116.0 pp 120.1 wl 122.0 oa
Breadth, m	12.0
Draught, m	7.02
No of shafts	2
Machinery	4 MAN diesels / 4 electric motors
Power, h. p.	7700 / 2400
Max speed, kts	18.7 / 6.5
Fuel, t	diesel oil 780
Endurance, nm(kts)	30000(16) / 60(3)
Armament	1 x 1 - 140/40 11-shiki, 3 x 3 - 25/60 96-shiki, 1 x 1 - 25/60 96-shiki, 8 - 533 TT (bow, 20), 1 catapult, 3 seaplanes (M6A1)
Electronic equipment	2-shiki 2-go, 3-shiki 1-go radars, 93-shiki sonar, 93-shiki hydrophone, E27 ECM suite
Complement	144
Diving depth operational, m	100

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Project history

Sen-Toku (Special submarine) type. Unique ships which did not have analogues in other navies. Largest submarines of pre-nuclear era. Their occurence was obliged to a plan of admiral Yamamoto to attack locks of Panama canal by seaplanes. Attack seaplane Aichi M6A Seiran has been created to this role. Being much more largely than existing reconnaissance seaplanes, it can be not carried in the standard hangars, therefore specially for these aircraft there has been begun designing of specialised submarine (Sen-Toku). At designing work experience of creation of Kai-Ko-Taka AM class submarines was used. It was originally supposed to build 4550t submarine, carrying two seaplanes, but subsequently air group have decided to increase to three planes that has led to growth of displacement to 5223t.

Submarine was actually designed around the cylindrical hangar with 34m length and slightly shifted to starboard (CT, as well as the crane for handling aircrafts, to portside). Construction was double-hulled, and pressure hull has been fulfilled from two horizontal cylinders adjoint into the form of horizontally laid "8". Endurance was about 90 days. Torpedo armament repeated accepted on Hei-Gata: 8 TTs took places on four in two compartments separated from each other one over another.

Under the additional programme of 1942 six submarines of "special type" have been ordered. To end of war three were completed, last was completed as a supply tanker-submarine (by another sources, she was completed as seaplane carrier and conversion to tanker was begun but not finished), and she had no aviation. Building of three remaining was suspended in March, 1945, (I404 was in 95% availability). Planned I406-417 were never begun.

Modernizations

None.

Naval service

I402 was damaged 11.8.1945 by US carrier aircraft at Kure, scuttled by Americans 1.4.1946. I401 in early 1945 was damaged on a mine, scuttled by Americans 31.5.1946. I400 was scuttled by Americans 4.6.1946. Unfinished I404 was sunk 28.7.1945 at Kure by US carrier aircraft.