In the 1970's the fuel-energy and raw-material base of the USSR began to be moved from the European USSR into the regions of Siberia, extreme north and Far East, with their enormous distances, by complex area relief, by severe climatic conditions and by the practically complete absence of roads, airfields and other transport ways. From year to year ever larger role played helicopters in the national economy of the country, since only they made it possible to fix the steady and uninterrupted supply of these regions with industrial equipment and by the loads independent of of the season.
At the same time practice showed that the load capacity Mi-6 and Mi-10K did not always satisfy the needs of the subjugators of depths. The mass of parts and construction equipment sometimes reached 35-40 Tons, and for transportation it was necessary either to divide them into the elements or to seek the aid of traditional transport technology. The large load capacity helicopters required the armed forces of the USSR, by which were required the machines for the transfer of the heavy large-dimension combat technology: tanks, rocket installations, engineering means, and also for the rapid evacuation of the damaged combat vehicles and the like.
In the middle the 1970's by assignment of government Mil together with TsAGI (Central Institute of Aerohydrodynamics im. N Ye Zhukovskiy) conducted analytical studies of the possibility of the transport of loads more than on two helicopters, connected together by rigid frame. This procedure required the special training of the crews of helicopters and it was connected with the need for the solution of numerous technical problems. In 1976 Mil examined the possibility of the transport of those loads by two and three Mi-26 with a general cable suspension, and also, for the first time, two- or three-screw helicopter, which could be created on the base of systems Mi-26. As a result, in December 1976 GKNT of the USSR let out the decision for Mil to prepare proposal about the creation of the helicopter of the increased load capacity. Analogous task was included also in accepted by government "basic trends in development of aviation equipment and armament to the period until 1993."
The new projected superheavy helicopter obtained designation Mi-32. Preliminary analysis showed that the single-rotor design it is complicated to realize on the new transport helicopter because of the difficulties of designing of the main rotor gearbox and carrier system (this it would lead to an increase in time and cost of development and production of machine.) At the same time the firm possessed the unique experience of the creation in short periods of the helicopter of the increased load capacity via the doubling of the finished and finished carrier systems of the single-rotor helicopter (the helicopter V-12). This pushed the design project leader M.N.Tishchenko to the solution to develop the Mi-32 with the use of the carrier systems and power plants from Mi-26. The civil and military customers requirement for a helicopter lifting 55 tons determined the selection of three-screw diagram.
The analysis of the application of heavy helicopters, showed that bulk of large loads, because of the complexity of load, is transported during the external suspension; therefore it is possible to manage without the landing field and to achieve a construction installation without the preliminary landing. As a result the Mil analysts came to the conclusion that it was expedient to accept for Mi-32 the diagram of heavy lift helicopter with the small volume fuselage. Two schematics of the interconnection of the nacelles were examined: "the star", with which the beams from each nacelle converge at one point in the center of triangle, and "triangle", when beams form the sides of equilateral triangle. In spite of more significant losses to the blowing, preference was returned to diagram "triangle", since it ensures the natural vibration frequencies of constructions, which prevent the appearance "air resonance", and the need for the synchronizing reducer is eliminated with it. In order to decrease losses from the harmful reciprocal effect of rotors, they arranged one nacelle from the front and two nacelles - from behind.
The OKB understood very well that with the selection of the design parameters of multirotor helicopters the determining factor are the self-excited fluctuations of the type "air resonance", since in the case of the large diverse masses the natural vibration frequencies of construction are commensurate with the frequency of the rotation of rotor. The selection of structural load-bearing diagram Mi-32 was caused by the need for fulfilling the requirement: the natural vibration frequency of construction must exceed the frequency of the rotation of rotors with the assigned reserve. The minimum natural vibration frequency of construction of the type "air resonance" depends on the extension of the plane of the rotation of rotors. The less the extension of screw relative to the axes of rigidity of beam, that is other conditions being equal higher this boundary.
However, decreasing the extension of screws relative to the axes of rigidity of beams, it was necessary to exclude the possibility of the touching of blade tips for the elements of construction. Therefore the "Milevtsy" used beams with the characteristic fracture in the middle of flight. In order to decrease losses to the blowing and to simplify the technology of the production of framework construction, was accepted the solution to perform the fuselage in the form of the pipes with a diameter of 3 m. thus it was born the original and not had analogs structural load-bearing schematic of superheavy helicopter.
In the front nacelle along the project the crew of the helicopter was located: two pilots, flight technician operator. The cab of operator they arranged analogously with suspension cab on Mi-10K and in such a way that with the fulfillment of crane- assembly works would be a possibility of direct visual observation of the load during the external suspension and of the field. After the cockpit as on the helicopter- donor Mi-26, was located the department for those accompanying load. The enormous fuselage of helicopter Mi-32 (40.5 X of 36 X of 4.3 m), besides flight deck, included the center section, made in the form of the triangle, sides of which are three load-bearing elements of tubular section, and in the apexes are established the nacelles with the power plants, to which are attached the landing gear struts and the ropes of external suspension.
The chassis is four-legged with two front supports before the front nacelle and two basic supports. The transportation of loads had to be achieved during the external suspension, which was fastened at three points under each of the nacelles. With this method of fastening external suspension on the beams of fuselage acted the not bending moments, but in essence compressive loads. The unique system of external suspension had to ensure: the possibility of the variation of the length of cargo rope from 5 to 60 m; the harvesting of ropes to the march position; gripping load on the hovering and at rest helicopter on the earth; the emergency discharge of load; remote control of the mass of load, and if necessary the transport of loads by mass is more than 55 tons by bond of two helicopters. The power plant of the Mi-32 consisted of six D-136 engines in pairs located in three nacelles, three modified VR-26 main rotor gearboxes were placed under the main rotor gearbox and connected with it by means of the shaft- spring synchronizing reducers and the shafts of synchronization. In the front nacelle the auxiliary starting power plant of was located. Fuel system consisted of three [zakoltsovannykh] subsystems. It was intended to equip helicopter with control system with the electrical installation from the mechanical mixer to the hydraulic amplifiers. The nourishment of the hydraulic amplifiers of control with the blade pitch of each rotor was achieved one of three independent from each other hydraulic systems. Each hydraulic system had its main and duplicating systems, standardized with the hydraulic systems Mi-26.
Calculated takeoff mass of the Mi-32, depending on the assumed application of a helicopter, were about 136-146 tons, the static ceiling - 1000-1500 m, service ceiling 4000 m, speeds- 200-230 km/h, ranges from 300 to 1200 km.
The apparatuses of such gigantic sizes and load capacity did not know world helicopter construction. The enormous experience of firm Mil was the guarantee of the successful realization of this grand project. Avenue- proposal was released in December 1977. The Research Institutes of aircraft industry gave to it the positive conclusion, in which it was said: ". the selection of three-screw layout on the basis of the use of the carrying modules of helicopter Mi-26 for the heavy lift helicopter is substantiated. and. is expedient to charge MVZ im. L.Milya to continue works on Mi-32 at the stage of technical proposal".
In December 1979, followed the decision by the GKNT of the USSR about the development "of heavy helicopter for the transport of large-dimension and heavy industrial equipment". The leader on the project M.N.Tishchenko appointed as engineer G.A.Sinelshchikova. The development of this unprecedented machine was conducted in OKB with the large enthusiasm. The toward the end following year the deep preliminary design Mi-32 was prepared and presented for consideration of institutes MAP and the customer. Their conclusions were again positive. Then began the thorough study of aggregates and systems of helicopter, the calculation of its aerodynamic, strength and piloting characteristics. Engineers conducted the search for the assembly solutions, which make it possible to descend the mass of construction and to ensure the acceptable levels of vibration. With the aid of TsAGI and MAI were carried out the wind-tunnel investigations for the purpose of the search for the methods of reduction in the parasite drag.
In 1982 specialists at Mil, in accordance with the government task, prepared the project of the decision by the CC CPSU and the Council of Ministers of USSR about the creation Mi-32. According to the estimations of the workers at Mil, toward the end decade the country could obtain this unique transportation means. However, decisions to do so did not follow.
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