Type 917 rescue ship

Type 917 rescue ship (ARS) is a type of rescue and salvage ship developed by China for its People's Liberation Army Navy (PLAN). A total of two ships have entered service by mid-2014, and more units are planned. Type 917 is the first ship in PLAN to adopt a trimaran hull, and hence received NATO reporting name Dasan class, or 大三 in Chinese, which is short for Da-xing (大型) San-ti-chuan (三体船), meaning Large Trimaran. The advantages of trimaran include stability and high speed in rough seas, and large deck area equivalent to a much larger ship, thus enabling a small ship to carry a helicopter that can only be carried by larger ships in traditional monohull design.