OVERVIEW:  The L5 Mod 3 is a heavyweight French submarine-launched torpedo designed for both anti-surface and anti-submarine roles. It operates electrically with active/passive sonar homing and serves primarily as a defensive and counter-attack weapon.

DETAILS:  L stands for Lourde (heavyweight) and Mod 3 designates the submarine-launched variant of the ECAN/DTCN L5 torpedo. It is 4.40 m long, 533 mm in diameter, and weighs approximately 1 300 kg. The warhead contains 150 kg of high-explosive, and propulsion is provided by a silver‑zinc battery-powered electric motor enabling speeds up to 35 kn and a range of approximately 9.25–9.5 km. Guidance is achieved through a Thomson‑CSF active/passive sonar head with both direct attack and programmed search modes. Introduced in the early 1970s, the Mod 3 remained in service through the Cold War aboard French submarines and was later succeeded by the F17 series.

TYPE: Heavyweight submarine-launched acoustic homing torpedo

FUNCTION:  After launch from a 533 mm tube, the torpedo uses gyroscopic steering initially then transitions to active or passive sonar homing to detect and pursue surface ships or submarines within its range. Once the target is acquired, it maneuvers to detonate its warhead upon impact or in close proximity.

NOTE:
IOC: Circa early 1970s (exact year for Mod 3 variant unconfirmed)
Manufacturer: Direction Technique des Constructions Navales (DTCN), France
Operators: France
Platforms: French Rubis‑class (Améthyste) and Agosta‑class submarines
Conflict used in: No confirmed combat deployment

SOURCE: U.S. Naval Technology: SSN Rubis/Amethyste class armament; NavWeaps: Torpedoes of France variant info; Wikipedia (French DTCN L5 technical data); Naval‑Encyclopedia and GlobalSecurity data on L5 performance