The Natsushio-class submarines were a pair of submarines constructed and operated by the Japan Maritime Self-Defense Force during the Cold War. They were a development of the Hayashio-class submarines and are sometimes considered the same class. They were small and limited in capability but were thought to be a successful class. They entered service in 1963–1964 and were deleted in 1978.
The Natsushios were a development of the preceding Hayashio class and are sometimes considered the same class.[1][2][3] They shared many of the same characteristics with small design improvements. They were small submarines with limited capability[1] but considered handy and a successful class.[4] They were air-conditioned and had good habitability for the crews. The submarines measured 61 meters (200 ft 2 in) long overall with a beam of 6.5 m (21 ft 4 in) and a draft of 4.1 m (13 ft 5 in). The submarines had a standard displacement of 780 long tons (790 t), with a surfaced displacement of 690 long tons (700 t) and 850 long tons (860 t) submerged.[1][3]
The vessels were powered by a diesel-electric system. Two shafts were powered by two Sulzer-Mitsubishi diesel engines creating 1,350 brake horsepower (1,010 kW) and two electric motors creating 1,700 shaft horsepower (1,300 kW). This gave the submarines a maximum speed of 12 knots (22 km/h; 14 mph) surfaced and 15 knots (28 km/h; 17 mph) submerged.[1][a] The Natsushios were armed with three 533-millimeter (21 in) torpedo tubes in the bow. They had a crew of 43.[1]