Semi-12 millet

The Semi-12 Millet (designation of V-12 origin, Code NATO Homer) of the Russian company Mil is largest Hélicoptère ever built in the world.

Its two rotors contrarotating S are laid out at the end of side beams, which makes it possible to make the saving in a Rotor of tail. Its motorization (twice two turbine engines) was taken again Mil Semi-6, which with only one rotor of this type was already one of the largest helicopters of transport in the world. It had accomplished its first flight on July 10th, 1968.

History

The Mil company had started as of 1959 of the studies relating to a helicopter of ultra-heavy transport under the designation of project “V-12” or “had izdélié 65”. In 1961, the research department (OKB) accepted an official order to produce a prototype which can raise a load from 20 to 25 T. This was supplemented later by a Council Directive of the Ministers of the USSR requiring that this helicopter offer a volume out of compartment comparable with that of the Antonov Year-22. This volume was made necessary by the requirement to transport intercontinental nuclear ballistic missiles of the type 8K67 (Scarp). Until this date (1961), the rockets of a total mass of 20 tons (with vacuum) were to be transported by the rail. That facilitated their location and the detection of the points of parking by the unfavourable air recognition. As almost all the technical realizations of the USSR at that time, V-12 was also to meet the requirements of large building sites and to be able to be implemented for geological exploration. It is necessary well to represent the vastness of the Siberia deprived of any infrastructure to include/understand the strategic interest of an apparatus which can transport important loads on more than 1000 km without requiring of track or roads.

The studies lasted until 1965. A model on the scale size was necessary to test the engines, the orders of flight and the dynamics of the rotors. This model which resembled an way-of-iron coach equipped with rotors and engines was built at the same time as another intended for the representation of the fuselage and the compartment. These models were presented to the client in April 1965. One proceeded to this occasion with tests of loading and unloading in the model of the compartment of 36 heavy military materials. Following the positive tests of the inspection and evaluation, an order had placed in 1966 to construct the first prototype able to fly. At the same time, the factory n° 292 of Saratov began industrialization in order to produce the first five standard appliances.

At the summer 1967, the first prototype was ready and started its tests in vol. During a trial flight, a hard landing on only one wheel took place with Panki on June 27th, 1967 in the presence of representatives of the army and other spectators. The damage was limited to a flat tire and a ruffled rim. This event was assembled out of pin in the Western press and was presented like a crash landing. It appeared later that clean modes and phenomena of resonance on the level of the cockpit had caused inopportune requests induced by the pilot. This problem could however be eliminated relatively quickly thanks to cushioning devices. The continuation of the tests proceeded without encumber.

The first prototype (n° CCCP-21142) was given to the flight test center on the basis of air force of Joukovski (in Russian: Жуко́вский) in December 1968.

Officially there were only two prototypes. Not confirmed reports/ratios however give a report on the crash landing of a prototype in 1969, which lets think that there was a third of it.

The Semione was not produced in series. The program was abandoned in 1974. Work on the Semi-12M helicopter of “super-ultra-heavy” transport equipped with engines even more powerful and two rotors with 6 blades was stopped before the end of the construction of the prototype. From a military point of view, the mission reserved for this helicopter had already become null and void. The construction of the intercontinental missiles out of silos was abandoned. The Soviet armed forces already had since 1969 of the intercontinental ballistic missile much lighter of type R-29 (SS-8, SS-18, SS-23) and at the beginning of year 1975 of fused with average carried of the type RS-16 (SS-17) launched starting from slopes of mobiles (cross-country vehicles), of submarine or surface vessels. Most of the experience gained within the framework of the study of Semi-12 could be applied for the development of the Mil Semi-26 which had started with the beginning of the year 1970.

Technical description

The engines, the gear-box and the blades of the rotor had been taken again Mil Semi-6. Each engine actuated a rotor through its own gear-box. The diameter more important rotor resulted from the lengthening of the foot of blade. It is the only helicopter with two contrarotating principal rotors side ever built by Mil.

The originators wanted at the beginning to lay out the rotors one behind the other on the longitudinal axis of the helicopter (as on the Vertol H-21 of Frank Piasecki). In the event of unfavourable flow of the flow of air, the engines back were however likely to introduce exhaust fumes of the front engines. This would have caused a loss of brutal power on the level of the engines back and constituted consequently a serious danger to the safety of the vol. This approach was thus abandoned for the benefit of a side provision (similar to the Focke-Wulf Fw 61). The site of the engines in side nacelles at the end of the wings ensures an easy access for maintenance. For this purpose, the Semione has a trap door located above the cockpit giving access to the back of the fuselage and the suction face of the wings. There exists even a removable parapet being able to be set up along the zones of walk on the wings. The aircraft tool set also includes the suspended platforms allowing maintenance the level of the engine nacelles.

In spite of already impressive dimensions of the apparatus, the two discs rotor are superimposed (see gearing rotors) on a zone of approximately 3 meters of depth. The two contrarotating rotors are synchronized by means of a common driveshaft central which is also used for the compensation of the efforts. The geometrical break of the wings required the design of an additional intermediate gear-box inside the fuselage. The central driveshaft guarantees the controllability of Semi-12 even in the event of double breakdown of two engines on the same side. The control surfaces and pitch the control of the blades are actuated by three redondés hydraulic systems, each one being composed of a principal system and a back-up system. The Semione also profited from the most modern technological advances of the time: it was equipped with a Radar weather and a Autopilot, thing rare on a helicopter at the time.

Records, flights of demonstration, final parking

The Semione made it possible to beat several records. As of on February 22nd, 1969, the Semione carried a load record of 31.030 kg to 2951 m of altitude and on August 6th, 1969, 44.205 kg with 2.255 Mr. From a theoretical and practical point of view, the Semione was in fact able to transport loads much heavier at low altitude of the simple fact of strongest the Densité of the air. A running take-off on track made it possible moreover to benefit from the bearing pressure created by the wings. Such tests took place obviously. One however knows nothing about the limiting values obtained.

The accomplished flights of demonstration with Copenhagen, Groningue and with the Le Bourget were carried out by the apparatus registered CCCP -21142/H-833 It acted in fact of the first of the two prototypes, exposed today on the ground of the factory Mil)) with Lioubertsy-Panki close to Moscow.

(55°40 ′ 02 ″ NR 37°55 ′ 55 ″ E)

Another Semi-12 is exposed to the central museum of the armed forces of the Fédération of Russia to Monino (approx. 50 km in the east of Moscow). It is probably about the second prototype (see photographs). This apparatus does not carry unfortunately of n° of registration. A table indicates like year of manufacture the year 1967.

Data sheet

Overall length: 37 m
Crew: 6 members
maximum Number of passengers: 196
Height: 12,50 m
Scale: 67 m
diam. rotors: 35 m
Empty weight: 69 100 kg
Mass décollable: 97.000 kg
maximum Mass décollable: 105.000 kg
Payload: 20 000 kg
maximum Payload: 40 000 kg
Motorization: 4 engines Soloviev D-25VF
Power of takeoff: 4 X 4048 kw (= 4 X 5500 CV)
maximum Speed: 260 km/h
Cruising speed: 240 km/h
operational Ceiling: 3500 m
Passable distance: 1000 km

See too

Millet
List of the helicopters

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