OVERVIEW: The Tp 431 is a lightweight, submarine-launched, wire-guided torpedo developed by Sweden. It entered service in 1988 as an advanced variant within the Tp 41-series and served as Sweden’s primary submarine lightweight torpedo through the mid-1990s.

DETAILS: “Tp” stands for Torped in Swedish naval nomenclature, and “431” designates the specific lightweight variant introduced in 1988 following earlier versions Tp 411 and Tp 412. It retained a 400 mm diameter, an approximate length of 2.6 m, and employed electric propulsion powered by silver‑zinc batteries. The Tp 431 featured wire guidance for mid-course maneuvers and a passive acoustic homing seeker for terminal engagement. It was deployed aboard Swedish submarines from 1988.

TYPE: Lightweight Wire-Guided Anti-Submarine Torpedo

FUNCTION: Launched from 400 mm submarine torpedo tubes, the Tp 431 navigates via wire guidance during the mid-course phase and switches to passive acoustic homing in the terminal phase to engage submerged submarine targets.

NOTE:
IOC: 1988 (Tp 431)
Manufacturer: Sweden (Förenade Fabriksverken / FFV)
Operators: Sweden
Platforms: Swedish submarines (A‑class variants including Näcken‑class)

SOURCE:
Jane’s Naval Weapon Systems (“Torpedoes Sweden Tp 41–46”) – https://www.torp.esrc.unimelb.edu.au/bib/P00002933.htm ; SeWiki “Torped 41/42/43” – https://sewiki.info/Lexikon/Torped_41