OVERVIEW: The TEST‑71M (NATO designation TEST‑83) is a Soviet heavyweight, wire-guided torpedo introduced in 1982, designed for submarine-launched, anti-submarine warfare. It is an enhanced version of the SET‑65M torpedo fitted with guidance wire for improved mid-course control.

DETAILS: “TEST” comes from the Russian designation “ТЕСТ‑71M”. The TEST‑71M evolved from the SET‑65M, adding a wire guidance system (using the KTU‑81 telecontrol system) while retaining the SET‑65M’s Sapfir (later Keramika) acoustic homing sensor and a 205 kg warhead. It is powered by an electric motor driven by silver‑zinc batteries and can operate at two speeds: approximately 40 kn for short-range (15 km) engagement and 25 kn for extended range (up to 25 km). The torpedo supports a wire guidance length of approximately 20 km (15 km on torpedo, 5 km on submarine) and a maximum depth of 400 m. It was specifically tested on Foxtrot (Project 641), Tango (Project 641B), and Kilo (Project 877) class submarines.

TYPE: Heavyweight Wire-Guided Anti‑Submarine Torpedo

FUNCTION: Launched from 533 mm submarine tubes, the TEST‑71M travels under wire guidance during the initial and mid-course phases, allowing real-time steering adjustments. In the terminal phase, it switches to active/passive acoustic homing to seek and engage enemy submarines with high precision.

NOTE:
IOC: 1982 (TEST‑71M)
Manufacturer: Soviet Union (Gidropribor / Dvigatel)
Operators: Soviet Union, Russia, China, other Kilo-using navies 
Platforms: Project 641B (“Tango”) class, Project 877 (“Kilo”) class, Project 671 (“Victor”) class submarines

SOURCE:
WeaponsSystems.net: TEST‑71 overview; Wikipedia “Type 53 torpedo” and “TEST‑71”; Russian post‑WWII torpedo data – https://www.weaponsystems.net/system/1443-TEST-71 ; old.weaponsystems.net – https://old.weaponsystems.net/weaponsystem/HH14-Type%2053.html