June 2016

2016 JuneMil Mi-12 [V-12] ‘Homer’
Roll-out: June 1967 First successful flight: July 10, 1968
World’s largest helicopter ever built or flown – gross weight: 213,848 lb (97,000 kg)

The Mil V-12 (NATO name Homer) is, to date, the largest helicopter ever built. The designation "Mi-12" would have been the name for the production version had it gone into production.

The specification for the V-12 listed internal cabin dimensions similar to the Antonov An-22 transport aircraft, allowing the V-12 to also transport combat equipment and inter-continental ballistic missiles as required.

The V-12 has a transverse (side-by-side) rotor system consisting of two Mi-6 transmission systems (two Soloviev D-25VF turbo-shaft engines/side) complete with respective 115 ft (35.1 m) diameter synchronized, counter-rotating, five-bladed rotors mounted at the tips of the approximately 98 ft (30 m) span inverse tapered wings. The use of interconnecting drive shafts ensures proper synchronization of both rotors, which intermesh over the fuselage with 9.83 ft (3 m) of blade overlap. Also with two opposite spinning rotors the need for a tail rotor is eliminated.

The large fuselage, having a 92.4×14.4×14.4 ft (28.2x4.39x4.39 m) cabin, has all six crew members located in the nose area on two different levels. The pilot, co-pilot, flight engineer and electrical engineer are in the lower cockpit area, while the navigator and radio operator are in the upper cockpit area.

Construction of the V-12 first prototype began at Panki in 1965. First hover on June 27, 1967, was terminated by impact with the ground, causing severe damage. The cause was the apparent coincidence of primary airframe aeroelastic frequency with natural frequency of control system, causing uncontrollable vertical oscillations.

Both prototype V-12s outperformed their design specifications, setting numerous world records which still stand today; i.e., the V-12 first prototype held eight world records, four of which are still current, in the FAI E1 General class for rotorcraft powered by turbine engines.

Many prestigious awards such as the Sikorsky Prize from the American Helicopter Society were awarded to the V-12 design team for outstanding achievements in helicopter technology. Also note that the V-12 design was patented in the US, UK and other countries.

Of worthy note, in May–June 1971, the first prototype V-12 SSSR-21142 made a series of flights over Europe culminating in an appearance at the 29th Paris Air Show at Le Bourget wearing exhibit code H-833.

However, the Soviet Air Force refused to accept the helicopter despite all of these achievements, with the major reason being that the V-12's most important mission no longer existed, i.e. the rapid deployment of strategic ballistic missiles. This lack of mission reason caused a stop to all development on the V-12 in 1974.

The first prototype remains at the Mikhail Leontyevich Mil Moscow helicopter plant in Panki-Tomilino, Lyuberetsky District near Moscow. The second prototype can be seen at the Monino Air Force Museum 31 mi (50 km) east of Moscow.

(Photos by blueskyrotor.com; text by Peter Noell)

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