Chinese subs for Thailand, Yu-4 ‘fire and forget’ torpedoes on board

BANGKOK, ($1=32.97 Thai Bahts) — Two decommissioned Chinese submarines were offered to Thailand through the Thai military attache in Beijing. The submarines are Type 039, NATO name Song-class, diesel-electric submarines manufactured at the end of the last century.

Chinese subs for Thailand, Yu-4 ‘fire and forget’ torpedoes on board
Photo credit: Pinterest

The offer was announced by the Thai online portal Tai PBS. Tai PBS says the offered submarines will need repairs before they can be reopened. It remains unclear whether China will want to sell or donate the two submarines to Thailand. The Thai PBS thinks Beijing will donate the submarines, asking only for a fee, as a “gesture of friendship.” According to sources in Thailand, this fee will be the cost of arming both submarines with Yu-4 torpedoes.

This is not the first such deal between the two Asian countries. Years ago, Thailand received two Ming submarines from China, donated. However, Thailand wants more details about the Song class submarines offered today. Tai PBS reports that Admiral Somprasong Nilsamai, commander-in-chief of the Clara Fleet of Taiwan, has already notified the Taiwanese army command of the Chinese offer.

Chinese subs for Thailand, Yu-4 'fire and forget' torpedoes on board
Photo credit: Twitter

Type 039 / Song-class submarines

Type 039 is a diesel-electric submarine made in China. Over the years, two Chinese companies have manufactured and serviced this class of submarines – Wuhan Shipbuilding and Jiangnan Shipyard. China has planned and built 13 submarines of this class.

Type 039 is the first all-Chinese submarine. It is equipped with a modern teardrop hull shape. It is 75 meters long and 8.4 meters wide. Develops 22 knots maximum speed [41 km]. It is equipped with 6 × 533 mm torpedo tubes and is armed with 18 torpedoes [or 36 naval mines].

The torpedoes in service are Yu-4 acoustic homing. They are a Chinese copy of the Russian SAET-50 ASuW passive acoustic homing torpedo. They are electrically powered by a silver-zinc battery, the range of damage is between 6 and 15 km, depending on the version of the torpedo. It runs at a maximum speed between 30 and 40 knots, again depending on the version.

This type of torpedo can be aimed passively or actively and is known as ‘fire and forget’. Passive acoustic torpedoes home in on emissions from a target. Active acoustic torpedoes home in on the reflection of a signal, or “ping”, from the torpedo or its parent vehicle; this has the disadvantage of giving away the presence of the torpedo. In semi-active mode, a torpedo can be fired to the last known position or calculated position of a target, which is then acoustically illuminated [pinged] once the torpedo is within attack range.


Follow us everywhere and at any time. has responsive design and you can open the page from any computer, mobile devices or web browsers. For more up-to-date news, follow our Google News, YouTube, Reddit, LinkedIn, Twitter and Facebook pages. Subscribe to our Newsletter and read our stories in News360App in AppStore or GooglePlay or in FeedlyApp in AppStore or GooglePlay. Our standards: Manifesto & ethical princliples.