Mil V-12
The Soviet Mil Mi -12 (Russian Миль Ми -12, NATO reporting name " Homer" ) is the largest helicopter ever built in the world. The actual name is W-12 ( for Wertoljot, helicopters ), but is often replaced in publications by the abbreviation of the chief designer Mil. Because of this, however, only officially was used when a model was converted from its design office in the series production, but remained a prototype W-12, the designation Mi -12 is incorrect. From Mils employees of the type as " Slon " (elephant ) or as an allusion to the predecessor Mi-6 was referred to as "Double Six ".
The MI 12 is a helicopter with two lateral counter-rotating rotors, which is not the tail rotor is required. There are two turboshaft engines that were just like the rotors of the Mi-6 borrowed, which already counts with only one of these rotors of the largest transport helicopters in the world at the lateral arms. The first flight of the Mi -12 was on 10 July 1968.
History
Back in 1959 we designed at Mil concepts for an "ultra - heavy-duty helicopters " under the project name W-12 or " Isdelije (product ) 65 ( Изделие 65) ". 1961 got the OKB official mandate to construct a helicopter that should be able to lift a weight of 20 to 25 tons. This was later supplemented by the directive of the Council of Ministers, the helicopter should similarly have a loading volume of the Antonov An-22. This cargo volume ( 4.4 m high, 4.4 m wide and 28.15 m long) was also needed, therefore, to deal with nuclear warheads to transport ICBMs of the type 8K67 ( Scarp ). Up to this time (1961 ) the rockets with a total weight of over 20 tons ( without fuel ) were tied to rail transport. This made an enemy air reconnaissance of the deployment locations of Soviet ICBMs relatively simple. Like almost all technical designs from the time the Soviet Union had the W-12 but with some requirements of major construction projects and be used in geological exploration. When utility of such a helicopter, which can carry heavy loads without runway, road or rail for up to 1000 km, shall be recognized as such in Central Europe or North America in the context of undeveloped expanses of Siberia different standards.
By 1965 they worked on the designs and models. A 1:1 model was required to test the engines, steering and rotor dynamics. The construction that resembled a railway car with two engines and helicopter rotors, was built together with a further 1:1 model for the hull and cargo space design. These models were presented to clients in April 1965. Here the cargo space model, the loading and unloading have been tested with 36 Heavy duty military equipment. After a positive inspection and evaluation of the results of the work order was issued in 1966 to construct the first flying prototype. At the same time began the aircraft factory no. 292 in Saratov with the preparation for the series production of the first five machines.
In the summer of 1967 the first prototype was ready and could be used for flight tests. However in the planned first flight of the prototype in Panki on 18 June 1967 in the presence of military personnel to an incident. Shortly after take-off came, controlled by the chief test pilot Vasily Koloschenko helicopter just above the soil in a partially uncontrollable flight condition and struck 23 seconds hard with the left main landing gear on the ground, the two tires burst and the chassis was bawled. As it was discovered later, self-oscillations and resonances in the cockpit and fuselage were the reason that the pilot unintended control movements could not be avoided. However, this problem could be solved by damping measures relatively quickly. On July 10, 1968 Koloschenko was able to perform the first successful flight, the day is now considered the official date of the first flight. The further course of the experiments proved to be very successful, a sign of the good theoretical groundwork of the development team. In December 1968 the first prototype with the registration number CCCP - 21142 was transferred to the Institute for flight tests at Air Force Base Zhukovsky flight testing for.
According to the official version, there were only two prototypes. According to reports, a prototype is to be crashed in 1969, raising the suspicion of the existence of a third machine. A crash has never been officially confirmed in the media of the Soviet Union. Two years later, the W-12 was presented on an extensive 3600 km round trip through several European countries the public. Finally he landed on 26 May 1971, the Paris Le Bourget Airport, where it was issued on the 29th Aérosalon. The designer Mikhail Mil did not live to the successful presentation. Even after the failed first flight in 1967 he could to health, already chipped, lead the revision of the project only with significant restrictions. Mil finally died on 31 January 1970.
Series production of the Mi- 12 is no longer took place then but. The program was discontinued in 1974. Work on the Mi- 12M as a "super - ultra- heavy lift helicopters " with more powerful engines and two times six rotor blades were completed before the construction of the actual prototype. From a military perspective, the main purpose of the helicopter had become obsolete. The expansion of silogestützten ICBMs was not further pursued. The Soviet forces possessed since 1969 on much lighter ICBMs from the types of R -29 ( SS -8, SS -18, SS -23) and with the beginning of the year 1975 on medium-range missiles of the type RS -16 (SS- 17) of mobile launchers ( all-terrain trucks ), ships or submarines could be fired. However, many of the won in the construction of the Mi -12 Mil Mi -26 findings were incorporated in the development of heavy transport helicopter that has already begun in the early 1970s. The Mi -26 is now the largest production helicopter in the world and is still being manufactured.
Technology
The two engines per rotor, transmission and rotor blades for the Mil Mi -12 were taken from the production of the Mi-6. Thus, significant costs could be saved. Own gear for driving the rotor head was used per engine. The larger diameter rotor was achieved by the use of longer rotor head legs ( Shanks ). It is the only dual-rotor configuration, the Mil has ever built.
The designers wanted the two rotors originally arranged one behind the other, as it was then and still being practiced in a number of U.S. transport helicopters is (tandem configuration). In this arrangement, however, saw the risk to suck the hot exhaust gases of the front double engine under adverse conditions. This would have led to a sudden loss of power to the rear double engine, thereby jeopardizing the ability to fly. Therefore, finally, the lateral arrangement was implemented. The Mi -12 is the date the last helicopter, which was built with this configuration.
The lateral assembly of the rotors and turbines in freely suspended gondolas, at the ends of the wings, there is easy accessibility of the engine components was ensured during maintenance. For this purpose, there is on the top of the Mi- 12 is a " roof hatch ", the maintenance personnel may reach the top of the machine and on the wings. The equipment on board the helicopter also includes a plug- railing and the necessary suspension platforms for maintenance on the engine nacelles. Their covers can be opened quickly by a folding mechanism.
The connecting surfaces of the engine nacelles were performed as wings with ailerons, so they helped in faster forward flight to lift and improved the maneuverability of the Mi -12 about the roll axis.
Despite the large dimensions of the rotor circuits in the center had an overlapping area of about three meters. To prevent contact of the counter-rotating rotors, and to synchronize the transmission and also for equalizing power transmission, both rotors are connected to a central shaft. Due to the " kink" in the wing design a shaft joint was required to in the form of another gear inside the hull. Due to the central shaft and the use of double engines, the Mi -12 was also in case of failure of both engines airworthy on one side.
Steering gear and the rotor blade pitch took over three independent hydraulic systems, which, in turn, each consisted of a main and spare component. The Mi -12 was also equipped with the latest electronic developments of the era, including a weather radar and - unusually for a helicopter - also an autopilot.
Records and whereabouts
The Mi -12 various records were set. Among other things, the Mi -12 was pointed out on 22 February 1969, record weight of 31,030 kg at 2951 m and on August 6, 1969, payload of 44,205 kg to a height of 2,255 m. Theoretically and practically could be transported with the Mi -12 at a lower level ( higher air density) even heavier loads. The buoyancy to achieve this result was " Roll on " the helicopter on the runway used even under the wings. However, nothing has been known about these " heavy-duty experiments " moving payloads.
The public screenings of the Mi- 12, as well as in 1971 in Copenhagen, Groningen and Le Bourget flew a plane with registration number CCCP-21142/H-833. This was around the first of the two prototypes of today on the grounds of Mikhail Leontyevich -Mil helicopter plant in Panki - Ljuberzy located near Moscow ( 55 ° 40 'N, 37 ° 56' O55.66733333333337.932027777778 ).
Can be seen in the Central Museum of the Air Forces of the Russian Federation in Monino (about 50 km east of Moscow) Another still preserved Mi -12. This is probably the second prototype. Most of the images in this article come from this machine, which carries no more registration number; a display board indicates year of manufacture as also in 1967.