Mi-26 HALO - Development
Since the early 1960-ies in the USSR the class of rotary-wing heavyweights brilliantly represented by MI-6, which is now, four decades after the beginning of its production, continues to serve in some countries. But by the early 70s. complexity and scale of facing the problems of the helicopter fleet has increased significantly, and existing cars longer deal with them in full, both in the Armed Forces and the national economy.
As a result of the analysis of the trend of increasing large-size cargo transportation needs it was revealed a mass of 15-20 tons at a distance of 500-800 km. Among these 80-90% was accounted for by new and emerging models of arms motorized infantry divisions, and high altitude areas, where was to conduct operations could reach 1000-1500 m above sea level. In the same period, after strong growth there has been a decline in the size of helicopters. As in the USSR, and the US were curtailed program to create super-heavy Mi-12 helicopters and CHF-62 before entering the stage of mass production for reasons more economic and operational nature than due to technological limitations. In these circumstances, Moscow Helicopter Plant (MVZ) name Mil, who led the chief designer MN Tishchenko after the company's founder in 1970 of the death, he began to develop a next-generation heavy-lift helicopters.
Just work organized G.P.Smirnov chief designer and deputy A.G.Samusenko. The lead designer was appointed O.P.Bahov. Creating a new heavy truck with the selection of the machine scheme and determine its basic parameters. First Mil tried to make maximum use of serial components and assemblies used on the Mi-8, Mi-6 and Mi-12, as well as a number of previously developed technical solutions. This was considered several schemes of the future system: single-rotor, twin-screw - transverse and longitudinal. It seemed that the best is a longitudinal diagram stopped and the creators of the CHF-62.
It promise a number of advantages: reduced-diameter rotors and the power transmitted to the main transmission gearbox (at most every 10,000 hp) and, therefore, reducing their weight, size, and complexity of designing and manufacturing. Do not be required to solve the problem of a large tail rotor. However, studies have shown that the overall result would be a helicopter considerably heavier and more difficult, especially due to the presence between the main transmission gearboxes. Significant difficulties could also arise due to the characteristic of the longitudinal scheme vibration problems. Preliminary calculations showed that the desire to use the new machine components and assemblies previously created helicopters, and in general the old design methods, is unlikely to lead to success, regardless of the chosen scheme. Take-off weight of the new helicopters would come close to 70 tons, and was required to radically change its approach to the design in order to reduce this amount by about 20 tons.
Studies carried out in conjunction with cost center TsAGI and CIAM allowed to opt for the classic single-rotor design. Heavy helicopter of the new generation has received the designation Mi-26 ( "product 90"). His preliminary design was approved by the Scientific and Technical Council of the MAP in December 1971, and the following year received a positive opinion Mil specialized institutes of the ministry and the defense ministry. According to the requirements of the customer, the helicopter had to transport loads weighing up to 20 tons at a distance of 400 km, while ensuring static ceiling of 1500 m.
To achieve these characteristics, required a power plant capacity of not less than 20,000 hp For it to be used two turboshaft engine D-136, which only began to develop in the Zaporozhye engine-building Design Bureau "Progress", headed by General Designer V.A.Lotarevym. The work was conducted on the basis of a bypass D-36 under the direct supervision of Chief Designer F.M.Muravchenko. Modular block design engines with a fault detection means and failures at an early stage promised to significantly facilitate their repair and maintenance. An integral part of the power plant had to be a system of automatic maintenance of rotor speed and synchronization of power, designed to ensure failure of one engine to another automatic output "Maximal". In this case, power ehp 11400 one D-136 should be enough to provide helicopter flight to climb and even the ability to hover near the ground, provided that its weight will not exceed 40 tons.
Much attention was paid to the cost center professionals the choice of optimal parameters of the rotor (HB). After conducted jointly with TsAGI studies of metal and the blades were created, which have provided a significant increase in the efficiency of the screw. Sam screw designers have designed vosmilopastnym diameter of 28 m. In this case, it turned out almost 40% lighter than the five-blade 35-meter HB Mi-6 and provides 30% more free traction. HB for producing first sleeve so large decided to use a titanium alloy, which ensured its high fatigue strength and reduced weight by 15% compared to MI6 sleeve. Equally revolutionary was and tail rotor design, the blades of which have decided to do the whole of fiberglass (from MI-6 were solid wood). In the end, it managed to get a five-blade unit, which at most two times more thrust and a 1.4 m diameter have the same weight with the tail rotor Mi-6.
The main difficulty is the problem of transmission to HB enormous power of two D-136, which has been successfully overcome by the creation of the main gearbox VR-26. This interrupted a long tradition: it was designed and built dvigatelisty not like it was before, but just firm Mile. The design of the heavy gear planetary scheme has been replaced by a fundamentally new 3-speed multi-threaded. This and a number of other innovations have led to the transfer to the rotor in two more times in comparison with the power of Mi-6 and a half times more torque, paying only a small (8.5%) increase in the weight of the gear.
In the struggle for weight design perfection does not lag behind their peers and the developers of the fuselage of the largest single-rotor helicopter in the world. A new approach to the problems of ensuring its rigidity and strength has allowed Mil meet the weight limits of the Mi-6, thus to achieve increase in the permissible loads on the power components and the volume of cargo cabin twice.
In the design of the Mi-26 cost centers experts have tried to take into account operating experience of its predecessors. First of all it should be noted the decision to place before the engine air intakes, dust-only memory (ROM), a fungal type with a purity of 65-70%, utilizing centrifugal effect to trap foreign particles. This allowed further helicopter work with dusty areas with little or no decrease in motor life with a minimum reduction of their power. To dispense with the airfield power sources and compressed air, a helicopter equipped with APU. And in order not to use ground-handling operations to the ladders and the like equipment, folding hoods and panels power plant completed in the form of working platforms, and inside the tail boom and fin arranged passage to the tail rotor.
It was improved and means of mechanization of loading and unloading. Thus, the helicopter is equipped with two electric winch and hoist lifting capacity up to 5 tons. The cargo ramp began to rise and fall with the help of a hydraulic system and to control it became possible not only from the workplace or mechanic of the cargo compartment, but also outside of the fuselage. A ladder can be fixed in a horizontal position, enabling transport dlinnomery inside the fuselage. On the ground, it can be installed and fixed flush with the car body or ground equipment used for loading. The design of the main landing gear allows you to change the clearance of the parking lot, lifting the rear part of the fuselage, which makes it possible to approximate the load to the ladder. In order not to interfere with the approach of art to the rear hatch, tail wheel is tightened to the tail boom. As with other helicopters, Mi-26 provided external suspension system that allows to deliver large loads weighing up to 20 tons.
In addition to equipment and cargo, the Mi-26 was to carry personnel. The cargo compartment of the helicopter can accommodate 82 soldiers or 68 paratroopers with full equipment. Cover and sanitary option for conversion which took several hours. This sets the 60 stretchers for the wounded and were equipped with three seats for accompanying medical staff.
The new helicopter equipped with weather radar, included in the navigation system, designed to fly at any time of the day, in simple and adverse weather conditions. It allows to solve problems in the field of 1900x1900 kilometers with an accuracy of notation 0.02-0.2% of the distance traveled, and requires only 10 minutes to prepare for the flight. Mi-26 is also equipped with three-channel complex aerobatic autopilot systems, trajectory and the guiding control, the newest addition to the time of the magnetic recording system of flight data and voice communications equipment, warning the crew of an emergency in flight.
When creating the Mi-26, great attention was paid to the full-scale experiments to simulate its various components and assemblies. It was built a unique stand the test of the power plant and the carrier system, which has no analogues to date. On the other stand the test of the helicopter carried out an interesting method of "full-scale discard the product." Important results were obtained in a flight on a flying laboratory Mi-6, equipped with a rotor Mi-26.
Construction of the Mi-26 layout began in 1972 and took his state commission within three years. By the time most of the work was completed and the design of the machine. Also in 1975 the new lead designer on Mi-26 became V.V.Shutov.
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