Chinese Defence Today - Yu-4 Anti-Ship Torpedo

The Yu-4 is a Chinese copy of the Soviet/Russian SAET-60 electric-propelled, acoustic-homing anti-ship torpedo. Two variants have been developed including the passive acoustic-homing variant Yu-4A and the active/passive acoustic-homing variant Yu-4B. The torpedo entered service in the mid-1980s and is carried by the Type 035G (modified Ming class) and Type 039 (Song class) diesel-electric submarines.

China received the acoustic-homing torpedo technology from the Soviet Union in the late 1950s, and began the reverse-engineering work in 1958. The development of the Type 920 electric powerplant for the torpedo succeeded in the early 1960s. However, the Yu-4 programme was postponed in 1963 as the priority was given to the development of the unguided wet heater Kerosene-air torpedo.

The Yu-4 development programme was resumed in 1966, with the prototype finished in 1971. Unfortunately this design was rejected by the PLA Navy due to its poor performance. Later the PLA navy decided to develop a passive acoustic-homing variant Yu-4A and a joint active and passive acoustic-homing variant Yu-4B. The development work was carried out by Northwest Polytechnic University (NPU) and Dongfeng Factory respectively, with Pingyang Machinery Factory being the primary contractor and manufacturer for both variants.

The passive acoustic-homing Yu-4A succeeded in February 1984, and entered service with the PLA Navy in the same year. The torpedo is carried by the Type 035 (Ming class) and Type 039 (Song class) diesel-electric submarine. The Yu-4B with active/passive acoustic-homing received its design certificate in February 1984, but may have not entered service. The Yu-4B has been promoted to the international market under the name ET31.

The Yu-4 is a submarine-launched, heavyweight, acoustic-homing torpedo designed to engage surface ships. The torpedo is powered by an electric propellant using silver-zinc battery, giving a maximum speed of 30kt. The torpedo has a range of 6km and is armed with a 309kg warhead.

Calibre: 533mm
Length: 7,748mm
Weight: 1,755kg (combat torpedo); 1,628kg (training torpedo)
Warhead: 309kg
Propellant: Electric (silver-zinc)
Speed: 30kt
Range: 6km
Depth of Search/attack: 5~45m
Guidance: Passive acoustic homing (Yu-4A); Active/passive acoustic-homing (Yu-4B)