**OVERVIEW:** The PL-641 *Foxtrot* is a Project 641B *Som* class diesel-electric attack submarine (SSK) in service with the Russian Navy.

**DETAILS:**

The Project 641B *Som* class, known to NATO as the "Foxtrot" class, represents a significant evolution of the earlier Project 641 (Foxtrot) design. Development commenced in the late 1960s, driven by the need for a quieter and more capable conventionally powered submarine to counter increasingly sophisticated Western anti-submarine warfare (ASW) assets. The *Som* class retained the basic hull form and three-shaft propulsion arrangement of its predecessor, but incorporated significant improvements in acoustic quieting, sensor performance, and combat systems. These upgrades included the use of improved sound damping materials, advanced sonar systems, and a more sophisticated fire control system. While primarily designed for anti-submarine warfare, the *Som* class also possessed a potent anti-surface warfare (ASuW) capability and could be employed for reconnaissance and mine laying. The *Foxtrot*’s design philosophy emphasized endurance and operational flexibility, allowing it to conduct extended patrols in distant waters, a crucial capability for the Soviet, and later Russian, Navy.

The *Foxtrot*'s primary role is anti-submarine warfare (ASW), though it retains a significant anti-surface warfare (ASuW) capability. It can be deployed for patrol and interdiction operations, targeting both enemy submarines and surface combatants. The installation of the Trout Cheek [MG-10M Feniks-M] sonar provides long-range detection and tracking of underwater contacts. Supplementing this is the Wolf Paw [GAS-372 Hercules-2M] sonar, which likely enhances close-range detection and classification. The Acoustic Intercept [MG-23 Svet-M] system allows the submarine to passively detect and classify targets by analyzing their acoustic signatures. The Snoop Plate [Flag] radar, while primarily intended for surface search and navigation, also provides limited early warning against airborne threats. Its twin 533mm torpedo tubes offer a variety of weapons options, including anti-submarine torpedoes and anti-surface cruise missiles, allowing the *Foxtrot* to engage a wide range of targets effectively. The Quad Loop DF further enhances situational awareness by providing direction finding capability.

The Project 641B *Som* class's sensor suite and armament reflect its intended operational environment. The Pike Jaw [MG-200 Arktika] sonar is likely used for mine detection and avoidance, allowing the submarine to safely navigate through heavily mined areas. The Generic Submarine Periscope and Optical periscope provide visual confirmation of targets and situational awareness when operating at periscope depth. The combination of active and passive sonar systems, along with acoustic intercept capabilities, provides a comprehensive underwater surveillance picture. The reliance on torpedoes as the primary offensive weapon underscores the *Som* class’s focus on stealth and close-range engagements. Despite its age, the *Foxtrot* remains a capable platform for littoral operations and constabulary duties due to its relatively shallow draft and endurance. PL-641, commissioned in 1992, represents a later build of the class, potentially incorporating some minor upgrades over earlier vessels.

**SPECIFICATION:** Length: 91.3 m || Beam: 7.5 m || Draft: 5.1 m || Disp: 1952 t

**SENSORS:** Quad Loop DF || Stop Light B [Nakat] || Trout Cheek [MG-10M Feniks-M] || Snoop Plate [Flag] || Acoustic Intercept [MG-23 Svet-M] || Pike Jaw [MG-200 Arktika] || Wolf Paw [GAS-372 Hercules-2M] || Generic Submarine Periscope || Optical

**ARMAMENT:** 533mm TT || 533mm TT