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Type 635 Yanlai Class

The Model 635 is a medium-sized hydrographic survey ship built in China. The Yanlai class [also seen as Yenlai] of survey ships was first built in the early 1970s. They were design to undertake the sea channel measurement mission in China's coastal and offshore areas. This type of ship is made of steel, long main deck, double propeller, double rudder ship, with good stability which can withstand 10 winds, and meet the requirements of Class I navigation vessels. With strong stability, it can meet the flooding of a single compartment without sinking.

Also known as "Waterway Survey Vessel". Service vessels dedicated to sea and waterway surveys. It is mainly used to measure water depth and navigation aids, detect seabed substrate and landforms, investigate and collect coastal hydrological data such as currents and tides, install and maintain navigation aids, and perform marine surveys. According to the active sea area, it is divided into long-range sea-channel survey ships, offshore-sea channel survey ships and coastal sea-channel survey ships.

The 635 has two types of ships, one is a civilian ship type simple measuring ship type 635I, which includes 635A, 635B, 635C type. The other is a military Pinghu dual-purpose hydrographic survey ship 635II. 635I is a civilian ship type with an elliptical tail; 635II is a military type, with a square stern.

Alexandre Sheldon-Duplaix's "Chinas Auxiliary Fleet - Supporting a Blue-Water Navy in the Far Seas?" in "Chinas Evolving Surface Fleet" reported "The main classes of survey vessels were built in 197072 (Type 635 and Type 635 I [A] Yanlai class), 1975 (Type 635 II [B] Ganzhu class), 198283 (Type 635 III [C] Yanlai class." A total of 3 Type II and 4 Type III ships were reported in service.

Type 635I Civilian

The 635I civilian ship is built with 4 ships, which can not only host sea surveying missions, talents for mine-laying operations and anti-radiation purification, anti-submarine, sea-going warships in China. 635I type is subdivided into 635A, 635B, 635C models, with these three models produced in 4 ships, respectively 635A of Northern Typing 943 (1970 enter service), 635B East Measuring 227 (1972 to enter service) and 635C East Measuring 226 (1982 enter service), Southern Measure 427 ( 1983 to enter service). In 1976, the Navy once again proposed to build two survey ships, and requested to improve on the basis of 635B, that is, 635C. The design was completed in June 1977, and started in October of the same year at Jiangxi Ruichang Jiangzhou Shipyard. The first ship was completed in February 1982 and the second ship was completed in January 1983.

Main performance: 74.8 meters long, 10 meters wide, 3.5 meters draft, 1216 tons full displacement, 4000 nautical miles, self-sustaining 30 days. It is equipped with double 25mm guns and double 37mm guns. Shanghai Zhonghua Shipyard completed the first ship (635A) in January 1970 and the second ship (635B) in 1972.

In 1979, the Navy's Equipment Technology Department proposed the requirements for the construction of 4 offshore survey vessels for the purpose of tracking and monitoring enemy ships' activities, collecting maritime information, and recommending the modification of the 635C mid-range waterway survey vessel. The program design of Institute 708 was conducted, and after review, it was found that it could not meet the requirements of the army.

Ganzhu Type 635II Military Channel Survey Vessel

Type 635 medium-sized hydrographic survey ship, retired from the South China Sea Fleet. The 635II has the capability of air, sea, anti-submarine, mine-laying and anti radiation pollution. It can not only perform hydrographic survey tasks, but also can be used as a light frigate or submarine hunter to perform combat missions. The maximum speed is more than 17 knots. Minimum speed can be adjusted willfully from zero knots; endurance up to nautical miles at 17 knots; self-sustaining force for 45 days. In addition to the engine room, the 635II ship can flood two cabins without sinking, and has an elliptical tail.

This ship can not only carry out sea lane survey missions, but also has the capabilities of air-to-sea, sea-to-submarine, anti-submarine operations, and anti-radiation pollution. It is basically equivalent to a light frigate and can perform combat missions. The long sloping hull was mainly used to undertake the waterway survey tasks in China and offshore areas.

Alexandre Sheldon-Duplaix classified Nan Ce 420, 426, 428 as Ganzhu 635 II. The ONI "China Peoples Liberation Army Navy (PLA(N)) and Maritime Law Enforcement (MLE) 2015 Recognition and Identification Guide" reports Nan Ce 426, 428 as KANYANG AGS, but other sources report these two units as the much smaller Type 646.

Yanlai Type 635 III

Alexandre Sheldon-Duplaix classified Dong Ce 226, Dong Ce 227, Nan Ce 427, Bei Ce 943 as Yanlai 635 III, a nomenclature that is otherwise poorly attested. The ONI "China Peoples Liberation Army Navy (PLA(N)) and Maritime Law Enforcement (MLE) 2015 Recognition and Identification Guide" also reports Dong Ce 226, 227; Nan Ce 427, and Bei Ce 943 as Yanlai, without sub-type designator.

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Page last modified: 25-12-2019 18:43:12 ZULU