The turn of 60’s and 70’s witnessed the development of the new TV3-117 turboshaft engine, producing a take-off 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, coupled 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).
The Mi-8T was initially produced at the Kazan plant; at a later date it was also simultaneously manufactured at the Ulan-Ude works. Distinctive features, which make the Mi-8 look different from the Mi-8MT, include: visibly shorter engines; tail rotor moved to the port side; the addition of an AI-9 turbo starter. The new engines considerably boosted the design’s hovering performance.
The maximum take-off weight was increased up to 13 tonnes (12 tonnes in the Mi-8) and the hovering ceiling was raised from 850 metres (Mi-8) up to 1,760 m (Mi-8MT). The export versions of the Mi-8MT were branded the ‘Mi-17’ (NATO reporting name ‘Hip-H’). Some 2,500 Mi-17s of various sub-types have been produced to date, destined for both the domestic market and for export.
The first Mi-17s entered service with the Polish Air Force in 1987. A special force commando was the first to use them. After this regiment had been disbanded, they reinforced the Air Cavalry, as well as the combat SAR units. Introduction of the TV3-117VM engines, optimised for high-altitude performance, led to production of the Mi-8 MTV-1 variant. The Polish Navy Air Force acquired Mi-8s in the configuration as a result of an exchange with Lithuania. The MTV-1s received were overhauled and equipped with emergency-ditching air bags before being accepted for service with the Navy.
The Mi-8MT was subjected to further modernisation stemming from experience gained during various local wars and conflicts, notably in Afghanistan. Improving the method for unloading troops became the first priority. The helicopter’s narrow side doors allowed only one soldier at a time to disembark, while the rear cargo bay doors could only be opened from outside. In 1993 a redesigned version entered service; it featured side doors widened to 1,250 mm, an additional 830 mm-wide door on the starboard side, as well as a hydraulically lowered rear ramp.
In order to improve protection for the crew, screens were fitted to shield the cockpit from shrapnel and small-arms fire. The upgraded self-defence systems included ASO chaff/flare dispensers mounted under the tailboom and an ‘Ispanka’ infrared jammer installed at the forward end. Further improvements included the installation of exhaust-gas coolers, night-vision equipment and a GPS system. The upgraded machine was designated ‘Mi-171’.
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