Mil Mi-12 / V-12
The origins of the V-12 / Mi-12 (NATO reporting name Homer) 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, and 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.
To avoid the 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.
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.
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 two 6500shp Soloviev D- 25VF turboshafts are 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. Rotor rpm reduced to 112; gearboxes linked by transverse shafting. Axes inclined forward 4deg 30min. Engine/rotor groups carried on wings of light-alloy stressed-skin construction with 8deg dihedral, sharp inverse taper and set at incidence 7deg root 14deg 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).
Two V12 prototypes were built. Both prototypes had the same registration! This registration CCCP-21142 is in Cyrillic and means SSSR-75499. The first prototype was damaged in a heavy landing, but was repaired.
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.
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. When submitted for ratification, was the first intimation received in the West of the existence of this giant helicopter. 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.
The first prototype was destroyed in a non-fatal landing accident during 1969, caused by engine failure.
The second prototype (21142, now at Monino), which was presented in the West at the 1971 Paris Air Show, and had set seven load-carrying records in 1969. On 22 February, a 31030kg load was lifted to 2951m and on August 6 1969, a load of 40,204.5kg was lifted to 2255m flown by Vasily Kolochenko. This was a new payload record for 2000m, and payload-to-height records for 35,000kg and 40,000kg.
No further development or production ensued.
The rebuilt first prototype Mil V-12 is located today next to the Mil Helicopter factory in Lyubertsi-Panki. The second prototype Mil V-12 CCCP-21142 is at the Central Museum of the Air Forces at Monino, located approximately 38 km from Moscow, Russia.
Mil Mi-12 (V-12)
Rotor dia: 114 ft 10 in (35 m)
Overall rotors span: 67m
Length: 121 ft 4.5 in (37 m)
Height: 41 ft 0 in (12.5 m)
Fuselage width: 4.4 m
Engines: 4 x Soloviev D-25VF turboshaft, 6500 shp / 4780kW
Empty weight: 60000kg
Max TO wt: 231,500 lb (105,000 kg)
Max level speed: 161 mph (260 kph).
Cruising speed: 240km/h
Service ceiling: 3500m