Commandant Rivière - class frigate The " Commandant Rivière " class was a type of frigates built for the French Navy in the late 1950s and early 1960s . Labeled " " aviso - escorteur " " ( fr : " sloop - escort " ) , they were designed to perform the role of overseas patrol in peacetime and Anti - Submarine escort in wartime . Four similar ships were built for the Portuguese Navy as the " João Belo " - class frigates . Design . The main gun armament of the " Commandant Rivière " class consisted of three of the new French 100 mm ( 3 . 9 in ) guns , with a single turret located forward and two turrets aft . These water - cooled automatic dual - purpose guns could fire a shell at an effective range of against surface targets and against aircraft at a rate of 60 rounds per minute . A quadruple 305 mm anti - submarine mortar was fitted in ' B ' position , aft of the forward gun and in front of the ship ' s superstructure , capable of firing a depth charge to or in the shore bombardment role , a projectile to . Two triple torpedo tube s were fitted for anti - submarine torpedoes , while the ship ' s armament was completed by two 30 mm cannon . The ships had accommodation for an 80 - man commando detachment with two fast landing boats , each capable of landing 25 men . While the previous French frigates of the " Le Corse " and " Le Normand " classes were powered by steam turbines , because a long - range was required for the overseas colonial role of the ships , the class was instead fitted with a two - shaft diesel powerplant , capable of propelling the ship at a speed of , although was reached during trials . Two ships of the class were fitted with modified powerplants . " Commandment Bory " was powered by Free - piston engine s driving gas turbines , although it was refitted with a conventional diesel installation in 1974 – 1975 , while " Balney " was fitted with an experimental CODAG ( Combined diesel and gas ) installation , with a and two diesel engines driving a single shaft . The CODAG arrangement took up less space , allowing 100 t more fuel to be carried and giving a range of at . " Balny " omitted one 100 mm gun turret to accommodate the revised machinery . Operational history . The first of the class , " Victor Schoelcher " entered service in October 1962 , with all but one of the class following in the next 27 months . The exception was the CODAG powered " Balny " , which although launched in 1962 and completed in 1964 , did not commission until 1970 , being employed as a trials ship in the meantime . " Commandant Bourdais " was used for fishery protection in the North Atlantic from 1963 to 1972 , while several of the ships of the class were used as training ships , including " Victor Schoelcher " ( 1961 – 1973 ) and " Commandant Bourdais " . In the 1970s , all except " Balney " had one 100 mm turret replaced by four MM 38 Exocet anti - ship missile launchers , while several of the ships had there 30 mm cannon replaced by Bofors 40 mm guns . In 1984 – 1985 , " Commandant Rivière " was converted to a sonar - trials ship . The ship ' s armament was replaced by a single 40 mm Bofors gun and two 12 . 7 mm machine guns , while the ship ' s stern was rebuilt to accommodate a hoist for a variable depth sonar , which was used to test various active and passive towed array sonar s . All French units were decommissioned in the early - 1990s , save for three frigates that were sold to the Uruguayan Navy . Ships . All French ships were built by Arsenal de Lorient