OVERVIEW: Type 80 (G‑11) is a heavyweight, submarine-launched, homing anti‑submarine torpedo introduced in 1980. It features wire guidance combined with active and passive acoustic homing and is designed for deep-water submarine engagements.

DETAILS: Type 80 (“Type” refers to 1980, development code G‑RX1, designated G‑11) is a re-engineered and lengthened variant of the American Mk 37 torpedo, adapted to Japanese specifications. It has a 483 mm diameter, battery-powered propulsion (silver-oxide), and a warhead filled with HBX‑3. It combines wire guidance with active/passive acoustic homing and pattern-running search functionality. Developed from 1965–1975, it entered service in 1980 with production from 1984, and remains in use aboard Japanese submarines. Some technical specifics remain classified.

TYPE: Heavyweight anti‑submarine torpedo

FUNCTION: Deployed from submarines to seek and destroy enemy subs at depth using wire guidance to initial acquisition phases, then switches to active or passive acoustic homing and pattern search if the target maneuvers. The HBX‑3 warhead detonates on contact or proximity.

NOTE: IOC: 1980
Manufacturer: Mitsubishi Heavy Industries (Japan)
Operators: Japan Maritime Self‑Defense Force 

SOURCE: Jane’s Underwater Warfare Systems 2006-2007; Friedman, Norman. The Naval Institute Guide to World Naval Weapon Systems, 1991/92; SDF Equipment Yearbook 2006-2007 — these sources accessed via reliable defense reference repositories