The Harbin Z-5 (Zhishengji - helicopter) is a Chinese copy of the Soviet Mil Mi-4 piston engined helicopter. It was produced in the city of Harbin, China. The USSR provided China with blueprints in 1958, a few years before the Sino-Soviet split. The first flight was in 1959, but serial production was delayed and did not start until the mid-1960s. China has produced a number of unique variants, and the Z-5 was in use with the PLA, PLAAF and PLANAF in large numbers, although it might still be in reserve. China also exported a number of Z-5 to client states. About 545 were built. A few Z-5 helicopters were modified to carry machine-guns and rocket pods.