Saturday, November 21, 2009

Yuushio Class




The 10 boats of the Yuushio class have provided the backbone of the Maritime Self-Defense Force's submarine strength since the 1980s. Essentially an enlarged version of the preceding teardrop Uzushio class, the Yuushios differ primarily in having a deeper diving capability. The Uzushios were decommissioned in the 1990s as the new Harushio class was commissioned.

Of double-hull construction, these boats follow the US Navy nuclear attack submarine practice of having a bow sonar array with the torpedo tubes moved to amidships and angled outwards. The first of the class, Yuushio (SS573), entered service in 1980 with the Mochishio (SS574), Setoshio (SS575), Okishio (SS576), Nadashio (SS577), Hamashio (SS578), Akishio (SS579), Takeshio (SS580), Yukishio (SS581), and Sachishio (SS582) following at yearly intervals.

From the Nadashio onwards the class was fitted to carry and fire the American Sub-Harpoon anti-ship missile, a capability which was retrofitted to all of the earlier boats except for the Yuushio itself. All the boats carry the Type 89 dual-purpose, active-passive torpedoes which have a maximum speed of 55 kts (102km/h; 63 mph) and a maximum reduced speed range of 50 km (31 miles).

The electronics carried are of the latest design, and include the ZQQ-5 bow sonar (a modified American BQS-4) and the ZQR-1 towed array (similar to the American BQR-15). Yuushio was removed from front-line service to become a training boat in 1996.

The last of the Yuushios was commissioned in 1989. By that time, the first three boats of the follow-on Harushio class had been laid down, with the name-ship commissioning at the end of November 1990. Harushio was followed at yearly intervals by Natsushio, Hayashio, Arashio, Wakashio, Fuyushio, and by Asashio in 1997. As each entered service one of the Uzushio-class boats was paid off.

The Harushios follow the same basic design as the Yuushios, but are slightly larger in all dimensions. More attention has been paid to reducing noise internally, and all have anechoic material applied to the outer surfaces. A stronger pressure hull means that operational diving depth has been increased to some 300 m (1 150 ft).

Asashio, the last of the class, was completed to a modified design. Increased systems automation has allowed its crew to be reduced from 74 to 71.

The Last of the Yuushio class boat was retired in 2008.

Entered service 1980
Crew 75 men
Diving depth (operational) 275 m
Dimensions and displacement
Length 76 m
Beam 9.90 m
Draught 7.50 m
Surfaced displacement 2 200 tons
Submerged displacement 2 730 tons
Propulsion and speed
Surfaced speed 12 knots
Submerged speed 20 knots
Diesel engines 2 x 3 400 hp
Armament
Torpedoes 6 x 533-mm torpedo tubes for 18 - 20 torpedoes or anti-ship missiles



Source: Military Today



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