Modification
Due to the adoption of newer technologies such as the silver-zinc battery, the performance of Yu-4 torpedo has exceeded the Russian SAET-50 torpedo it is based on, and reached that of SAET-50M: the speed of the Yu-4 torpedo is increased more than 25% to 30 knots (56 km/h), even 1 knot (1.9 km/h) faster than the SAET-50M, and the range is increased 50% to 6 km, equal to that of SAET-50M. For these reasons, the Yu-4 torpedo is considered at least equal or better than Russian SAET-50M torpedo, the successor of SAET-50 torpedo, and even comparable to Russian SAET-60 torpedo in some aspects. However, the 6 km range was considered rather short for modern naval warfare by the Chinese navy, which led to one of the major upgrade resulted in increased range (up to 15 km), and in comparison to Yu-1 torpedo, there were not as many Yu-4 torpedoes entering service like Yu-1 torpedo. Like Yu-1 torpedo, Yu-4 torpedoes in Chinese inventory have been continuously modified, such as incorporating ASW capability, updated electronics and propulsion system, and being converted as part of CAPTOR mine type mine systems.
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