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WORLD'S LARGEST HELICOPTER - MIL V-12
By far largest helicopter ever built, this was unusual extrapolation of Mi-6 a decade later to match greater fixed-wing airlift of An-22 and Il-76. To avoid immense task of developing new set of rotors, reduction gears and transmission, decision taken to double up Mi-6 dynamics and use two sets of Mi-6 engines, gearboxes and lifting rotors side-by-side, left rotor being mirror image, with small overlap. Rotor rpm reduced to 112; gearboxes linked by transverse shafting. Axes inclined forward 4°30’. Engine/rotor groups carried on wings of light-alloy stressed-skin construction with 8° dihedral, sharp inverse taper and set at incidence 7° root 14° tip. Braced at root and tip to main landing gears with torque reacted by horizontal bracing to rear fuselage. Inner/outer trailing-edge flaps fixed in up position after flight trials. Fuel in outer wings and two external tanks; optional ferry tanks in cabin. Fixed twin-wheel landing gear with main tires 1750 x 730mm, pneumatic brakes, and steerable nose tires 1200 x 450mm. Large stressed-skin fuselage with crew door each side, three sliding side doors and full-section rear clam shell doors and ramp with left/right twin-wheel ventral bumpers. Aeroplane tail with fin, tabbed rudder, dihedralled tailplane with tabbed elevators, and end plate fins mounted vertically but toed inwards. Flight deck for pilot (left) with engineer behind and co-pilot (right) with elec-syst operator behind. Upper flight deck for nav with radio operator behind. Hydraulic flight control with emergency manual reversion. Autopilot with three-axis autostab; mapping radar under nose. AI-8 turbine APU for ground power and engine start. Main cabin 28.15m long, 4.4m square. Overhead gantry crane with four 1t hoists. Tip-up seats along sides (50 to 120). First hover 1967 terminated by impact with ground causing severe damage; cause coincidence of primary airframe aeroelastic freq with natural freq of control system, causing uncontrollable vertical oscillations. Second (21142, now at Monino) flown by V.P.Koloshchyenko Aug 1969 to 2255m with payload of 40,204.5kg. NII tests completed and demos at Paris, but abandoned because Mi-26 far superior. ASCC name ‘Homer’. The Mil Mi-12, known as V-12 in the Soviet Union, and by the NATO reporting name Homer, is so far the only helicopter produced by the Mil bureau to depart from the single main rotor plus tail rotor formula. It is to date the world's largest helicopter and flew for the first time in 1968, but did not enter production. The second prototype, which was presented in the West at the 1971 Paris Air Show, set seven load-carrying records in 1969: in February, a 31030kg load was lifted to 2951m and the following August, 40204kg was taken to 2255m. The Mi-12 project was started in 1965 with the aim of producing a vertical take-off aircraft capable of carrying missiles or other loads compatible with those of the four-engine An-22. The bureau chose the side-by-side rotor formula in order to use the engine-transmission-rotor assembly of the helicopters of the Mi-6 / Mi-10 series with minimal modifications. Two of these assemblies were in fact mounted at the tips of the two short wings, which had an inverse taper from the root to the wingtips. The engines were 6500shp Soloviev D-25VF turbines giving the helicopter a maximum speed of 260km/h, with a 35400kg load and 500km range. The large cargo hold measuring 28.15m long by 4.4m wide could take various kinds of loads, including very bulky ones, as well as troops or handling crews. The fuselage had a conventional, semi-monocoque structure, with large clam shell loading doors at the rear to facilitate handling of bulky loads. The flight deck was on the upper floor of the cabin and there were six crew members. On the ground, the helicopter was supported by large, fixed tricycle landing gear with two wheels on each unit. A large end-plate fin tail unit was mounted at the rear of the fuselage, with moving vertical and horizontal surfaces. As well as being designed for military use, the Mi-12 was probably intended for service with Aeroflot, especially for deployment in areas of Siberia which are rich in resources but which have very poor communications. Technical problems were almost certainly responsible for development of this aircraft being abandoned in favor of the Mi-26. Although only two examples of the Mil Mi-12 were built, both being V-12 prototypes, this giant machine is worthy of mention as the world's largest helicopter to have flown to date. To economize in effort and development cost, the Mil design team adopted the main rotor, transmission and power plant of the Mi-6, using them in duplicate, one such unit being located at the tip of each of the extensively-braced fixed wings. The use of twin counter-rotating main rotors eliminated the requirement for a tail rotor, the tail unit consisting instead of conventional surfaces, plus endplate fins at the tips of the tailplane. The four Soloviev D-25 VF turboshaft engines had a combined output of 19388kW, enabling the V-12, first flown on 10 July 1968, to establish a series of records in February 1969 which, when submitted for ratification, was the first intimation received in the West of the existence of this giant helicopter, then allocated the NATO reporting name 'Homer'. Later in the year, on 6 August 1969, the V-12 lifted a payload of 40204.5kg to a height of 2255m, establishing a record that remains unbeaten. The first prototype was destroyed in a non-fatal landing accident during 1969, but although the second prototype was used for a large number of demonstration flights, no further development or production ensued. 
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