Petya-class

The Petya class, designated Project 159 by the Soviet Union and classified as "Storozhevoi Korabl" (Sentry Ship), was a class of light frigates designed during the 1950s. The Soviet Navy issued the technical specification in 1955 and approved the design in 1956 to replace the Riga class. Production took place during the 1960s at the Kaliningrad Yantar and Khabarovsk shipyards.

The class was the first in the Soviet Navy to utilize gas turbine propulsion. The design employed a multiple-shaft arrangement where a diesel engine powered the central shaft for cruising and gas turbines powered the wing shafts for higher speeds. These vessels were optimized for shallow-water anti-submarine warfare and shared design characteristics with the subsequent Mirka class. Gun armament consisted of gun turrets in the forward and aft positions, directed by a single radar system. Anti-submarine equipment included rocket launchers and torpedo tubes. Export variants were sometimes configured with anti-shipping torpedo tubes instead of anti-submarine versions. The sensor suite featured a hull-mounted sonar and a variable depth sonar.

A total of 54 ships were completed. The Soviet Navy decommissioned its vessels between 1989 and 1992. The class was exported to several navies. India operated eleven ships, designating them Arnala-class corvettes; one vessel was lost at sea. Egypt acquired four ships, with one lost in combat in 1973. Ethiopia operated two ships until they were sold for scrap following the independence of Eritrea. The Syrian Arab Navy maintained two ships until their retirement around 2017 or 2018, with one later used as a training target. The Ukrainian Navy briefly operated a single vessel, SKR-112, following its transit from the Black Sea Fleet in 1992. The type remains in active service with Azerbaijan and Vietnam. Vietnam is modernizing its five remaining vessels with rebuilt superstructures and new combat suites.