Iwami-class patrol vessel

The Iwami-class patrol vessel (いわみ型巡視船) is a class of 1,000 ton-class PL type patrol vessels of the Japan Coast Guard (JCG).

Backgrounds
In the 2000s, the JCG was building 1000-ton class PLs with a high speed planing hull, such as Aso-class patrol vessel and Hateruma-class patrol vesseles. Although these ships were excellent in security missions, they were also unsuitable for rescue missions because of their poor low-speed stability and cruising capacity.

Since the mass retirement of the Shiretoko-class patrol vessel was planned in the 2010s, general-purpose ships as replacements were needed. For this purpose, construction of the Kunigami-class patrol vessel was started under the FY2009 supplement budget, but they were too expensive to build in large quantities.

Because their high cost, construction of this class was started under the FY2010 supplement budget as more reasonable but still versatile vessels.

Design
Due to the demand for multi-mission capabilities, displacement hull made of steel was adopted as same as the Kunigami class. The superstructure is made of aluminium alloy. She is designed to assume the towing of a distress ship with a bollard pull of 45 tons, two funnels separated on the left and right ensure backward visibility. Because the aviation capability was not required, the helipad on the stern deck was omitted. Also no fin stabilizer was equipped, but antiroll tanks were retained since low-speed stability was required.

Based on the lesson learned from the operation of humanitarian response to the 2011 Tōhoku earthquake and tsunami, the last four ships strengthened the capacity of the fresh water generator, and additionally equipped with a water supply unit, a fuel supply unit, and a loading crane.

As a main weapon, a Bushmaster II 30 mm chain gun system with an optical director is installed.

In service
The level of stability of this class was good, the automation was also proceeding, and it was a popular boat for the crew. However, this class was considered not to be so suitable for the security missions on the Senkaku Islands, and the Kunigami class began construction again in FY2012. This additional construction reduced costs, therefore construction of Kunigami class is continuing from FY 2013 onwards.