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By far largest helicopter ever built, this was unusual extrapolation ofMi-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 tyres 1750 x 730mm, pneumatic brakes, and steerable nose tyres 1200 x 450mm. Large stressed-skin fuselage with crew door each side, three sliding side doors and full-section rear clamshell doors and ramp with left/right twin-wheel ventral bumpers. Aeroplane tail with fin, tabbed rudder, dihedralled tailplane with tabbed elevators, and endplate 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’.
Bill Gunston "The Osprey's Encyclopedia of Russian Aircraft", 2000
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 clamshell 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 crewmembers. 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 favour of the Mi-26.
G.Apostolo "The Illustrated Encyclopedia of Helicopters", 1984
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 economise in effort and development cost, the Mil design team adopted the main rotor, transmission and powerplant 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.
D.Donald "The Complete Encyclopedia of World Aircraft", 1997
The V-12 had a fuselage and tail unit more akin to a fixed wing trans-port and was lifted by two Mi-6 rotors mounted at the ends of outrigger wings. A pair of D-25VF turbines was fitted at the tip of each wing to power the rotors. With the crew perched in a cockpit above the nose the V-12 had an unobstructed cabin capable of carrying 120 passengers. Unfortunately, testing of the V-12 started with a disastrous heavy landing and the Mil team experienced major stability difficulties with the two remaining prototypes. The performance of the V-12 never matched that of Mil's other large trans-port helicopters and it was eventually abandoned.
R.Simpson "Airlife's Helicopter and Rotorcraft", 1998
The Mil V-12 (Mi-12), which was allotted the NATO reporting name Homer, is currently the world's largest helicopter, but does not appear to have progressed past the development phase. This is presumably because of technical problems rather than performance deficiencies, for the V-12 holds many world records for payload and payload- to-altitude.
The origins of the V-12 lie with a 1965 Soviet air force requirement for a heavy-lift helicopter able to carry major missile components. These would be brought into remote missile site areas by fixed-wing aircraft, notably the Antonov An-22, and then lifted from the airfield to the launch site by the new helicopter.
There also existed a civil requirement for such a machine, principally for use in developing Siberia which is resources-rich but communications-poor. The military specification, calling for a tandem-rotor configuration using dynamic system components from existing helicopters, was paramount, however, as evidenced by the fact that the V-12 has the same basic hold dimensions as the An-22: 4.4m by 4.4m, with length only 4.85m less than that of the An-22 at 28.15m.
Although the requirement called for a tandem-rotor layout, Mil received early permission to concentrate instead on a twin side-by-side rotor configuration, which the design bureau claimed as having better reliability, fatigue life and stability. Thus the V-12, which first flew in the second half of 1968, appeared with a fuselage resembling that of a fixed-wing aircraft, from whose top spring two inversely tapered wings carrying the twin dynamic systems at their tips. Each of these dynamic systems is very closely related to that of the Mi-6 helicopter: it comprises two 6500shp Soloviev D- 25VF turboshafts, uprated from the 5500shp of the Mi-6's Soloviev D-25V by the addition of a zero stage to the compressor and by an increase of operating temperature.
The two engines are located side-by-side with twin intakes, and drive five-bladed metal rotors. The left rotor rotates anti-clockwise and the right unit clockwise; the two units are connected by transverse shafting to ensure synchronization and the continued rotation of both units in the event of engine failure at either wingtip. The lower part of each cowling can be dropped to form a working platform for mechanics. Fuel is housed in two cylindrical tanks mounted externally on the lower fuselage sides. The main units of the fixed tricycle undercarriage are supported by a plethora of struts bracing the wings and running from the lower fuselage, wings and engines.
Although the V-12 could accommodate large numbers of passengers, tip-up seats are provided for only 50; the reason for this is that the type is intended mainly for heavy-lift work, with accommodation only for drilling crews, missile crews etc. The main freight hold has overhead rails for a moving crane which has four loading points, each rated at 2500kg, or can alternatively lift a single item of up to 10000kg. The bottom of the rear fuselage comprises an inbuilt loading ramp, with large clamshell doors forming the rear fuselage aft of this point.
The first prototype crashed, apparently as a result of engine failure, during 1969, but the second prototype established seven world records the same year. On February 22, the V-12 lifted a payload of 31,030kg to 2951m, breaking the records for maximum payload carried to 2000m. On August 6, a load of 40,204.5kg was lifted to an altitude of 2255m, which constituted a new payload record for 2000m, and payload-to-height records for 35,000kg and 40,000kg.
Despite these impressive performances, little has recently been heard of the V-12, and technical problems have presumably led to its abandonment.
Bill Gunston "The Illustrated Encyclopedia of Commercial Aircraft", 1980
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Introduced in 1983 and still in production, the Mi-26 is powered by two Lotarev D-136 turboshafts with a combined output of... 22,480 shp or 16,760 kW and has a maximum takeoff weight of 56,000 kilograms (123,500 lb). It can transport payloads of up to 20,000 kg (44,000 lb) for distances of up to 800 kilometers or 497 miles.
If you fail to assess the Mi-26’s humongous size and capacity, you should know that such a helicopter was used by the Americans to rescue one MH-47E Chinook.
The Mi-26 has a standard crew of four, including pilot, copilot, navigator, and flight engineer. The cockpit side windows are bulged to improve visibility. Three TV cameras are fitted to allow observation of loads. The cockpit is pressurized, though the cargo bay is not.
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