The Yu-7 (Project 109, also known as ET52 in its export name) lightweight anti-submarine torpedo is a Chinese reverse-engineered copy of the U.S. Mk-46. The torpedo was jointly developed by Xi’an Precision Machinery Institute (also known as 705 Institute) of the China Shipbuilding Industry Corporation (CSIC) and the Northwest Polytechnic University (NPU). The Yu-7 has been produced in both tube-launched and helicopter-carried versions, and is the standard anti-submarine weapon on all PRC-built destroyers and frigates.
In October 1978, Chinese fishing ships found an unexploded U.S. Mk-46 Mod 1 Block 2 torpedo off the coast of Hainan Island. The torpedo was handed to the Chinese military for examination and was later used to develop a reverse-engineered copy under the Project 109. The first phase of the reverse-engineering was carried out by Xi’an-based 705 Institute between December 1978 and April 1979.
The development of the Chinese copy designated Yu-7 began in 1982. The development task was shared between the 705 Institute in charge of the general design and the development of the shallow-water control system, and the NPU responsible for the development of the deep-water control system. 872 Factory and 874 Factory were responsible for the torpedo production. The programme entered engineering development in 1984.
The design team produced 80,000 blueprints and over 100,000 pages of technical documents. Over 90 research institutes and factories across the country were involved in the production of over 5,000 parts and 4,500 instruments for the torpedo. The first two prototype torpedoes were assembled in 874 Factory in December 1984 and tested in the 750 test range in Kuming in December 1985.
The Yu-7 development encountered enormous technical difficulties. In the late 1980s, the PRC was able to obtain some of the Mk-46 technology from the United States, as the two countries formed a temporary ally against the Soviet Union. Although the technology could not complete due to the arms embargo on the PRC imposed by the United States after 1989, some limited technical documents and few Mk-46 samples were received and used to help the Yu-7 development.
By 1989 the Yu-7 torpedo had undertaken 68 successful launches in four rounds of tests in the sea. The initial batch production of the Yu-7 began in the early 1990s and the torpedo was certified for design finalisation in 1994.
Yu-7 torpedo (Chinese Internet)
Design
The Yu-7 is designed to be launched from surface combatant torpedo tubes to attack enemy submarines. The torpedo utilises a two-speed, reciprocating external combustion powerplant using mono-propellant (Otto) liquid fuel, giving a maximum speed of 43kt. The torpedo is armed with a 45kg warhead, and is guided by active and passive acoustic-homing. The torpedo uses snake or circle search.
When carried by helicopters, the torpedo uses a special device consisting of a parachute stabiliser/retarder and release mechanism to ensure that it makes a smooth entry into the water.
The helicopter-carried version of the Yu-7 torpedo (Chinese Internet)
Launch Tube
The PRC purchased few B.515S triple 324mm torpedo launchers and some 40 A.244S Whitehead anti-submarine torpedoes from Italian defence technology Company Alenia in 1987. The launchers and Whitehead torpedoes were installed on some hulls of the Type 051 Luda class missile destroyer for trial and evaluation. The B.515S was later produced locally and installed on all newly built PRC destroyers and frigates to launch the indigenous Yu-7 torpedo.
The shipboard tube-launched Yu-7 torpedo (Chinese Internet)
