The steel-hulled Beidiao 991 adopts a Small-waterplane-area twin hull design, with a 2800 kW Integrated electric propulsion (IEP). It is the first ship with a displacement greater than one thousand tons to adopt an IEP in China.[1][2] Research activities are conducted on the 120 square meter afterdeck and the five onboard labs (two on port, two on starboard, and one at the stern).[1][2] The ship is equipped with a galley, conference room, command center, and various equipment for different scientific research missions, such as hydrographic, oceanographic, geologic and acoustic surveys.[1][2]
Initial service proved unsatisfactory: when operating in high seas. The ship suffered from excessive vibration that generated enough noise to prevent onboard scientific research equipment from working properly.[1][2] Fuel and fresh water reserves were inadequate, causing a need for frequent replenishment.[1][2]
The ship went through a major upgrade to resolve these issues,[1][2] which resulted in a Type 639 oceanographic surveillance ship that is forty percent larger with displacement reaching fifteen hundred tons.
