The advent of the Mi-6 gave the Soviet Union the very useful ability to move and place large, bulky or heavy loads with precision. Limitations of the Mi-6 in the flying crane role included a weight to payload ratio and the inability of the crew to easily see the load and its intended final position. A Council of Ministers directive of 20 February 1958 tasked OKB-329 (OKB Mil) with the development of a dedicated flying crane helicopter for carrying bulky loads unable to be carried in the hold of a Mi-6. The Mil OKB's response drew heavily on the Mi-6, utilising the dynamic components and 4,100 kW (5,500 hp) Soloviev D-25V turboshaft engines, on a slim fuselage sitting on four tall strut braced undercarriage legs, with a wide track allowing the helicopter to taxi over loads, or for mobile loads to be moved underneath. The fuselage can carry 28 passengers inside the cabin as well as 3 t (6,600 lb) of cargo loaded through a side door in the aft fuselage, by an integral boom and winch. Underslung loads can be attached directly to the fuselage by hydraulically operated clamps, or carried on a 8.5 m × 3.6 m (28 ft × 12 ft) pallet lifted by the winch and braced by cables and/or struts to the undercarriage legs. The external sling system of the Mi-6, with a capacity of 8 t (18,000 lb) could also be fitted under the centre fuselage. The first prototype V-10 emerged with canted main undercarriage legs with single wheels on all four legs, as well as a retractable emergency escape chute extending below the cockpit and external auxiliary fuel tanks either side of the centre fuselage. As development progressed the main undercarriage legs were replaced with vertical units carrying twin wheels, twin nose undercarriage wheels after a period retaining the single wheels, an Auxiliary power unit (APU) installed behind the cockpit on the starboard side and emergency escape slide cables for use when the pallet is carried. The limitations of the Mi-10 in the slung load mission soon became obvious, chiefly, the loss of payload due to the heavy and complicated undercarriage, and more importantly the almost complete lack of oversight of the slung load, despite the inclusion of a CCTV (closed circuit television) system intended for observation of slung loads. Foregoing the requirement to carry palleted or podded cargoes, Mil redesigned the Mi-10 with a much shorter, fixed, four-leg undercarriage and replaced the extendible escape chute with a gondola fitted with flying controls for a pilot to fly the aircraft during slung load operations. The remainder of the aircraft is essentially identical with the long-legged version. Seventeen of the new flying crane were produced as the Mi-10K, including two conversions from Mi-10s from 23 March 1974 to 1977. For details of the world records held between the 10 variants of the Mi-10, click here. Short legged Mi-10K
