Type 814A spy ship with NATO reporting name Dadie^[2][3][4][5](大谍, meaning Big Spy) is a type of Chinese spy ship in service (as of 2014) with the People's Liberation Army Navy (PLAN). Originally, a total of four ships were planned, but eventually, only one was completed due to the availability of newer designs.

History
China
Name	Bei-Diao (900)
Builder	Hudong-Zhonghua Shipbuilding
Laid down	22 December 1983
Launched	12 June 1986
Commissioned	29 October 1986
In service	in active service
General characteristics [1]
Class and type	Type 814A spy ship
Displacement	2,198 t (2,163 long tons)
Length	94.33 m (309.5 ft)
Beam	11.6 m (38 ft)
Draft	4.04 m (13.3 ft)
Propulsion	2 x 6E390 medium-speed diesel engines @ 2646 kW (3600 hp) w/ 466 rpm
Speed	20.03 kn (23.05 mph)
Range	4,000 nmi (4,600 mi) @ 18 kn (21 mph)

PLAN originally issued a requirement of four spy ships to meet its urgent need, after the failure of the earlier cancelled Type 812. To speed up the program, PLAN suggested adopting the hull of Type 635C hydrographic survey ship. The 1st Directorate of the 708th Institute of China State Shipbuilding Corporation, which is also more commonly known as China Shipbuilding and Oceanic Engineering Design Academy (中国船舶及海洋工程设计研究) nowadays,^[6] was assigned to design the ship. However, after the design was completed, it was revealed that the design could not meet requirements issued by PLAN during design review. On March 25, 1980, PLAN issued an order to revise the design to 1500 tons, designated as Type 814. On June 30, 1980, the 708th Institute completed the revision. However, due to drastic changes made by PLAN, it was once again revealed during design review that the revised design could not efficiently meet the new requirements issued by PLAN. The designer recommended enlarging the ship by increasing the displacement by twenty percent from 1500 tons to 1800 tons. The recommendation was accepted and in February 1982 the revision was completed, and in August 1982, design was completed. The finalized design is designated as Type 814A. In August 1983, design work for construction was completed and construction began on December 22, 1983. During sea trials, various aircraft and naval warships were deployed in support of trials, including Type 033 submarines, Harbin SH-5, Harbin H-5, submarine chasers, Type 051 destroyers and Type 403 shore based radars. On-board systems such as acoustic, radar, communication, and optical systems proved satisfactory and the ship was accepted into service in the North Sea Fleet. Because the previous design was experienced excessive vibration, particular attention in design was given to reduce vibration. Type 814A is designed to withstand wind scale of 12. The name of the ship is Bei-Diao (北调, meaning North Investigate) 900.