Staff members examine the helicopter carried by marine patrol ship "Haixun 31" before it sails out of the port of Sanya, south China's Hainan Province, Feb. 28, 2013. A formation of three marine patrol ships "Haixun 21", "Haixun 31" and "Haixun 166" started their coast guard mission in South China Sea on Thursday, a second one by the national Maritime Safety Administration at this water area in 2013. The first mission was conducted from Jan. 15, 2013 to Jan. 17, 2013. (Xinhua/Hou Jiansen)