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Mi-30 Vintoplan

A fixed-wing aircraft (airplane) is maintained airborne by the lift produced by the wing. Sufficient lift to sustain the aircraft, however, can only be achieved over and above a given minimum speed, which, in turn, can only be achieved by accelerating the aircraft on a runway of appropriate length. This obviously also applies to commuter turbo-propeller airplanes. Once airborne, a turbo-propeller airplane is capable of reaching and maintaining a cruising speed of about 500 km/h and a typical altitude of 7500 meters enabling it to fly over most cloud formations and atmospheric disturbance. The continual increase in air traffic, however, will eventually result in small--e.g. 15-30-passenger--aircraft being excluded from long-distance routes, by occupying traffic windows which could be used more profitably by larger aircraft. Fixed-wing aircraft also pose environmental problems, particularly as regards acoustic pollution of residential areas around airports, which are necessarily covered at low altitude.

A helicopter is maintained airborne by the lift provided by the rotor, which is rotated relative to the air by the engines with no need for horizontal speed, so that a helicopter can take off and land vertically on small surfaces not much larger than itself. For a helicopter to acquire horizontal speed, part of its lift must be directed forwards, which is done by slightly tilting the rotor disk. Limitations inherent in the aerodynamics of the rotor, however, limit the maximum speed of a helicopter to just over 300 km/h, with a normal cruising altitude of, at best, 3000-3500 meters and a smaller range than an airplane with the same load and fuel capacity. A fundamental characteristic typical of helicopters is their ability to hover, which accounts for their being used almost exclusively in civil and military search, rescue or surveillance applications calling for direct intervention in unequipped areas.

To combine the speed, range and efficiency of a fixed-wing, turbo-propeller aircraft with the hovering and vertical takeoff and landing ability of a helicopter, convertible aircraft or convertiplanes have been developed. These are characterized by an external structure similar to that of a turbo-propeller airplane, but have two rotors, on the ends of the wing, which can be tilted upwards to sustain the craft in helicopter mode, and forwards for thrust in airplane mode, thus enabling the craft to take off and land in small spaces, in exactly the same way as a helicopter, and to cruise at high speed and altitude like an airplane. The advantages, with respect to a conventional helicopter, of such a combination therefore lie in almost twice the cruising speed (500 as opposed to 300 km/h); substantially twice the range for a given load and fuel capacity, which obviously makes the craft more profitable; and over twice the cruising altitude, so that the craft is unaffected by weather conditions (clouds, turbulence) over most of the flight. The advantages with respect to a conventional airplane, on the other hand, lie in the ability of the craft to take off and land in small spaces, and to hover.

Convertiplanes, however, are highly complex aircraft which are extremely difficult to control. Which, together with the high cost involved, is why they have so far only be used on a small scale, and substantially only for military applications. In the case of a tilt-rotor, each engine-rotor assembly can be rotated with respect to the relative half-wing to direct the thrust of the rotor upwards when taking off, landing or hovering, or forwards for cruising. This type of configuration has several drawbacks.

In particular, the downward load on the wing caused by the wash of the rotors seriously impairs hovering performance. The resisting force (in opposition to the thrust of the rotors) may reach 10-14% of the aircraft's weight, which is a significant percentage when compared with the pay load to total aircraft weight ratio of about 20%. To minimize the phenomenon, the wing is provided with movable surfaces of a much larger area and a much wider range of movement than a conventional fixed-wing aircraft, which greatly increases the mechanical complexity of the wing.

Moreover, during conversion, the flow induced by the rotor on the wing combined with the flying speed causes the wing to operate with a very large angle of attack with respect to relative wind, which in turn causes stalling problems accompanied by vibration, oscillatory loads and high resistance. Stalling also reduces the so-called conversion corridor, i.e. the range of permissible rotor positions and aircraft speeds during conversion from helicopter mode to airplane mode and vice versa. Another problem posed by interaction of the rotors and the fixed wing of tilt-rotor convertiplanes is the difficulty in achieving stable autorotation in helicopter mode.

Soviet helicopter-builders, in actually evaluating the numerous complexities connected with the creation converti-planes, had long been skeptical of such projects. The Mil Design Bureau closely followed the tilt-rotor projects at Bell Helicopters, and the concept that Bell proposed seemed to them convincing. In 1972 Mil designers initiated a similar design, the Mi-30. By the beginning of the 1980's scientists and the designers at Mil worked up number of layouts and possible diagrams and constructions of aggregates Mi-30, were conducted in-depth analytical studies of the problems of aeroelasticity, dynamics of construction, aerodynamics and flight dynamics, characteristic for the converted apparatuses.

According to the terminology existed in the USSR it was first named a helicopter- aircraft, but then the workers at Mil devised a special name - vintoplan. The Mil Mi-30 Vintoplan was a passenger transport convertiplane-type rotorcraft project started in 1972. It was intended to replace the Mi-8/Mi-17 helicopters and carry 19 passengers or 2 tons of cargo. It was expected to use a twin TV3-117 turboshaft engine and a four-bladed propeller rotor on each wing.

In 1972, the designers MVZ Mil in an active manner made project-offer transport and passenger tiltrotor, received the title of E-30. According to the available terms in the Soviet Union he initially was called a helicopter-airplane, but later he came up with Mil its own designation vintoplan. The main objective in the design of the Mi-30 was to ensure the performance of the, first range and speed of flight. Initially, he had to carry up to 2 tons of cargo and 19 people landing.

As the power plant for the newest vehicles would be used 2 engine TV3-117, located above the cargo cabin, engines had to drive a box with two inconsequential pulling the screw with a diameter of 11 meters each. The screws were placed at the ends of the wings. The estimated speed of the Mi-30 was estimated at 500-600 km / h, and the range was to be 800 km. Take-off weight of the aircraft was 10.6 tons in the framework of the research programs from Mil. Soon jointly started construction of an aerodynamic shield for testing models of the screw. At the same time, the designers have made Mil pilot flying radio-controlled model vintoplana, so that in-flight study transients, maneuverability and stability of the machine.

During the development the customer desired to increase the capacity of Mi-30 to 3.5 tonnes and passenger capacity to bring up to 32 people. As a result, the project vintoplana was redesigned for the introduction of 3-boosted engines TV3-117F. With all this the diameter of the rotors increased up to 12.5 meters, and the take-off weight of Mi-30 to 15.5 tons

The work progressed slowly as an internal venture by Mil until 1981, when the Soviet government issued a requirement for a tilt-rotor transport aircraft for military and civilian use. The commission of the presidium of the Council of Ministers of USSR for questions of armament [VPK] published in August 1981 a decision about the development of helicopter with the converted carrier system ([vintoplana]) Mi-30. The corresponding technical proposal was presented for consideration of institutes at MAP and the customer.

At the beginning of the 1980s, scientists and engineers from a cost center managed to work out a number of possible schemes, layouts and designs machines machines, conducted thorough analyzes of the structure behavior problems, aeroelasticity, flight dynamics and aerodynamics, suitable for converted vehicles. Given the depth study of the project, the factory had long-standing experience in solving difficult problems, the Commission of the Presidium of the USSR Council of Ministers on weapons in August 1981 issued a decree on the development of the Mi-30 with the transformed rotor system (vintoplana). A technical proposal was submitted to the customer and institutions MAP. Military approved the creation of the machine, but claimed to put on vintoplan more massive engines 2 Engine D-136, the calculated mass of tiltrotor increased to 30 tons. For the Soviet military, the potential advantages of a tilt-rotor were self-evident, in the light on the ongoing war in Afghanistan, where the problems of insufficient speed and range were magnified by the requirement to operate helicopters over high-altitude mountainous terrain in hot weather. The civil aviation value of a tilt-rotor helicopter appeared greater in the Soviet Union then it was in the United States.

The new Mi-30 was superior in speed and range to the Mi-8 but its specifications changed constantly over the years at the militarys behest. Its payload of 2 tons and 19 troops rose to 3.5 tons and 32 troops, with an accompanying increase in flight speed to 500-600 km/h over a range of 800 km. This increased both engine power and the size of the rotor blades and pushed up the aircrafts overall weight from 10 to 30 tons.

The military approved development, but they required equiping the vintoplan with more powerful power plant with two engines D-136. The calculated mass of this apparatus increased to 30 tons. During the subsequent years the type of power plant repeatedly changed. Versions were examined with two and three TV7-117 engines and with two D-27. The takeoff mass of vintoplanov was respectively equal to 11, 20 and 30 tons.

In the initial step, carried out fundamental theoretical research in the field of aerodynamics and dynamics, areas of strength, including the calculation of certain types of instability, natural vibration system, balancing features, such as self-oscillation "air resonance" mode vertical autorotation "flatter pods", "chordal flutter "etc. Determined vintoplana transport efficiency, the mass of the support system were selected characteristics of the propeller, tail and wings, propeller efficiency, the characteristics of the propeller blades and the tension in it. Developed a variety of design options screws, boxes, wing and other units.

In the end, the creation of the Mi-30 was included in the state program of armaments for 1986-1995. Unfortunately, due to the collapse of the Soviet Union and the economic difficulties emerged, vintoplan Mi-30 and did not climb out of the stage of the analytical and engineering research. In the last year of the Soviet Union experts at OKB designed 3 different vintoplana Mi-30C, Mi-30D and Mi-30L who had the capacity of 3.2, 2.5 and 0.95 tons, respectively, and a passenger capacity of 21, 11 and 7 people. First 2 tiltrotor had the highest take-off weight of 13 tons planned to equip the power plants of 2 engines TV7-117, and the third Mi-30L (weighing 3.75 tons) power plant of 2-AL- 34. They eere working on the creation and combat options.

By 1991, Mil projected three versions of the aircraft: Mi-30S, Mi-30D, and Mi-30L, with a load capacity 3.2, 2.5 0.95[t] and by passenger capacity 21, 11 and 7 people respectively. First two with the maximum takeoff mass of 13[t] were intended to equip with power plants of two engines [TV]7-117, and the third (with mass of 3.75[t]) - of two AL -34. Combat versions of the vintoplan were also examined.

The Mi-30 project was included in the 1989-1995 Soviet Five Year Plan, with the vehicle was to enter service in 1996. The only flyable version ever built was a small-scale RC version for testing its flight characteristics. And the collapse of the Soviet Union made such plans impossible to realize.

  V-22 Osprey

Mi-30 (draft)

Maximum take-off weight 27.4 tons 30 tons
Airspeed
(in airplane mode)
463 km/h 500-600 km/h
Airspeed
(helicopter mode)
185 km/h -
Load capacity 24 people or
5 tons of cargo
32 people or
5 tons of cargo




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