The turn of 60s and 70s witnessed the development of the new TV3-117 turbostiafl engine, producing a takeoff power of 1,900 hp. These powerplants were initially fitted to the Mi-14 and Mi-24 and were also later adopted for the transport version of the Mi-8. The prototype Mi-8, cou-plod to TV3-117 turboshafts, first flew on 17th August 1975 and was given the military designation 'Mi-18'. In 1977. the new Mi-8 fitted with TV3-117 engines was accepted for series production and, shortly afterwards, the first Mi-18s were delivered to the USSR's armed forces. They were first used for search and rescue operations, as well as for Speznaz operations. Since the construction was in fact, a Mi-8 derivative, it was subsequently re-designated 'Mi-8MT (modified/ transport).