Design of the V-12 started in 1965 by a team lead by Mikhail
Leontyevich Mil. The purpose of the type was to fulfill the need for
a heavy VTOL transport able to carry outsized heavy cargo, similar to
that carried by the Antonov An-22. The original specification called
for a tandem rotor system, however Mil claimed that a side-by-side
rotor system offered better stability and received approval to proceed.
To avoid designing a complete new rotor system, Mil chose to use two
Mil Mi-6 rotor and propulsion systems (with the left rotor mirrored)
mounted at the ends of the strutted wing. The fuselage was similar to
that of the An-22, the cargo compartment having the same square cross
section 14 ft 5.2 in by 14 ft 5.2 in (4.4 m by 4.4 m), although 15 ft
11 in (4.85 m) shorter with a length of 92 ft 4.3 in (28.15 m). Rails
in the unobstructed part of the cabin roof carried a crane capable of
lifting loads up to 22,046 lb (10,000 kg).
Pilot, co-pilot and flight-engineer, electrician were seated in pairs
side-by-side in the lower flight deck in the nose of the fuselage,
with the navigator and radio operator seated in tandem in the upper
flight deck. About 50 folding seats were placed along the main
compartment to seat the troops or work crew accompanying the cargo.
The first prototype was ready early 1967 but heavily damaged during
the initial hovering trials, without harm to the crew. The second
prototype flew for the first time on July 10, 1968 and flown by Vasily
P. Koloshchyenko and his crew this helicopter set records for weight
to heights on February 22 and August 6, 1969, ultimately lifting
88,636 lb (40,204.5 kg) to 7,398 ft (2,255 m).
Aeroflot intended to operate the helicopter in remote areas of the
Soviet Union in support of the oil and gas industry and other
geophysical operations. In a marketing and sales campaign the V-12
would attend the Paris Air Show in 1969, however, due to technical
problems the trip was postponed. By 1970 it was clear that the V-12
was not a success, so the trip to Paris in 1971 must be seen as a
public relations stunt and in that it was a success.
The V-12 was and still is the largest helicopter ever built and the
second prototype is preserved at Moscow Monino airport.