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Helicopter


Helicopter
For nearly forty years after its launch aircraft reigned supreme in the air. During this time, the speed and capacity of the winged cars increased many times that of the clumsy plywood "shelving units" have become a powerful jet handsome, embodies the most advanced technological achievements of human thought. However, for all its virtues Any aircraft has one major drawback - to stay in the air, he has continuously and at a sufficiently high speed to move in a horizontal plane, because the lift of its wings depends on the speed of movement. Hence the need for take-off and landing run that command the aircraft to the airfield.

Meanwhile, there is often a need for such an aircraft, which has a lift, not depending on the flight speed can go up vertically and land, and in addition, is able to "hang" in the air. This niche after much searching was busy designing helicopters - helicopter. With all the flight characteristics inherent in the plane, the helicopter is, in addition, a number of outstanding specific properties: it can take off from a place without a running start, still hanging in the air at the correct height, moving steadily in all directions, to make turns in any direction as in during forward motion and hangs; Finally, he can sit on a small area without a subsequent run. Creating a unit, has a set of these qualities, it was extremely difficult because the helicopter is much more complex theory of the plane theory. It took years of hard work of many designers before the helicopter began to feel confident in the air and was able to share with the aircraft taking care of air transport.

First rotorcraft (helicopters and gyroplanes) appeared almost simultaneously with the first plane. In 1907, the French Breguet chetyrehvintovoy helicopter and Richet first time was able to get off the ground and lift over whose person. After that, various designs have been proposed by many helicopters inventors. All of them had mnogovintovuyu complicated scheme in which several screws serve to maintain the device in the air, and a few others - in order to push it in the right direction. Single-rotor scheme (to which presently owns 90% of all helicopters) by anyone at first seriously considered. And if it was real? Raise the unit into the air with a single screw - still all right. But how to tell him the horizontal forward movement? How to manage it? Those inventors are quite well versed in aerodynamics, indicated a further major drawback single-rotor design - the presence of reactive torque. The fact that in the implementation of the drive motor rotor fixedly connected to the nacelle, the latter was not so much to rotate the screw, as (in the opposite direction) cabinet. It seemed that the reaction torque can paralyze only when used in helicopter design several rotors rotating in opposite directions. Moreover, these screws could be located separately from each other (longitudinal and transverse circuits), and on the same axis - one under the other (coaxial scheme). Comes to mind, and other advantages mnogovintovoy scheme. After having several control screws make it easier to guide the car in the right direction. But soon found: the more the helicopter propellers, the greater the problems - calculation of the unit even with one propeller represented the very difficult task; take into account the mutual influence of many screws proved impossible (at least in the first quarter of the XX century, when aerodynamics just did only the first steps, and the theory of the propeller began to take shape).

A significant contribution to overcoming many of these problems made by the Russian inventor Boris Yuriev. The most important his discoveries did back in the days when he was a student of the Moscow Higher Technical School and was an active member of Ballooning Mug famous Russian scientist Zhukovsky. Intrigued single-rotor design, St. George's, first of all, wondered how to tell the helicopter forward movement in the right direction? Most of the inventors at the beginning of the XX century, as already mentioned, was convinced that this is necessary to provide the device not only rotors, and propellers. However, experimenting with a variety of different models, Yuryev found that by tilting the axis of the rotor can get a good horizontal flight speed, without making a special screw-propeller with a horizontal thrust. Translational motion of the helicopter can also make the body forward tilt unit. In this case, the power of the large screw is decomposed into two forces - the lifting and traction, and the machine begins to move progressively. The more the slope of the machine, the greater the airspeed.

The next problem was how to balance the reactive torque acting on the gondola. St. George suggested that the easiest way it can be achieved with a small screw on the tail of the helicopter and driven in rotation by light transmission. Due to the fact that the force generated by the tail rotor, is attached to the long arm (relative to the machine's center of gravity), the effect of its reaction torque compensated without difficulty. Calculations show that it will take 8-15% of the engine power. Yuryev further proposed to make the blades of the propeller with a variable pitch. By increasing or decreasing the angle of these blades to the plane of rotation can be increased or decreased thrust of the propeller. When a large thrust tail rotor had to overcome reluctance torque of the main rotor and nacelle deploy in the right direction.

But the greatest difficulty is the establishment of a sound management system. The pilot had to have at their disposal a device that allowed him to quickly change the orientation of the machine with respect to all of its three axes: that is, turning it in any direction relative to the vertical axis, tilt the body up and down, as well as apply bank to the right and to the left. turning problems are resolved by a small tail rotor. To this end, as already mentioned, it was sufficient to make the blade pivoting mechanism and to connect them to turn the rudders. But how to ensure control relative to the longitudinal and transverse axes? The easiest means of the device would be another two tail rotors made on consoles at some distance from the car's center of gravity and rotate the helicopter in the right side for the pilot.

Here, the screw 1 is used to compensate reactive moment and also acts as a rudder; screw 2 gives banks and is similar in its effect ailerons (skewed planes airplane wing), and the screw 3 is as if the elevator. But this system, moreover, that was overly complex, yet had the disadvantage that made the helicopter is very unstable in flight. Yuriev began to reflect on the question: is it possible to arrange the main rotor so that he himself created two needed to control helicopter moment? The search for him ended in 1911, the invention of one of the most remarkable in the history of the helicopter units - the creation of the swash plate.

The principle of operation of this machine is very simple. Each rotor blade is described by the rotation of the circle. If the rotor blades do movable relative to their longitudinal axes, so that they can change the tilt angle to the plane of rotation, it is possible to easily manage the motion of the helicopter. Indeed, if a part outlines its range of blade held with a large angle installation, and another part - with a smaller, then, obviously, the desire on the one hand there will be more and the other less, and the rotor (and with it, and the whole machine) will rotated in the appropriate direction.

swashplate exactly provide the required setting of the blades. For this purpose, the shaft of the rotor was set on gimbals ring to which via hinges are attached leashes, reaching to the arms, the blade rotates. Ring rotates together with the screw shaft. On both sides it was covered loosely sitting on it stationary ring. This latter ring can be rotated freely with the help of steering drafts and give him any inclination in two planes. In this case the inner ring and leans simultaneously rotating inside stationary ring. It is easy to see that in this case the inner ring will make one revolution for full swing, which in turn will make fluctuate each an associated lobe: they are all in for a turn will change the installation angle of a certain minimum value to the maximum. these angles will depend on the inclination of the seat ring associated with the control levers. If the pilot was required to turn in any direction his car, he had to send to this side of the outer ring of the swash plate. In this mode, the angle of inclination of each blade is changed independently of the other blades. But it was easy to make and so that swash plate, if necessary, could change the installation angle of the blades at once all at once. It has been claimed, for example, in case of breakage of the motor in a mode called autorotation, when under the influence of the air flow incident helicopter propeller started to rotate spontaneously, acting as a parachute. Helicopter at the same time as it had planned (in the nature of this effect can be seen in the falling maple seeds). To do this, it was enough to make the cardan swash, sliding along the shaft of the screw (top to bottom). Raising or lowering the swash plate, the pilot immediately turned all the propeller blades in one direction, thereby increasing or decreasing the installation angle or making it negative (that is, able to rotate in the opposite direction, that is precisely when needed autorotation).

Thus, by 1911, 22-year-old student Bauman Boris Yuriev worked in general the whole scheme of single-rotor helicopter. Patent it, he could not, as he had no money for it. In 1912 by St. George's students Bauman collected flightless layout helicopter in full size. At the international exhibition of aeronautics and motoring, which took place in the same year in Moscow, this model was awarded a small gold medal. However, funds for it to build a functioning car, at school was not found. The outbreak of the First World soon, and then the Civil War, a long time St. George's distracted from his work on the project.

Meanwhile, in other countries continued to appear mnogovintovyh model helicopters. In 1914 he built his helicopter Englishman, Mumford. It was first performed flight with forward speed. In 1924, the Frenchman Amish first flew his helicopter on a vicious circle. At the same time, St. George, taking the post of Chief of the Experimental Aerodynamics Department of TsAGI tried to realize his single-rotor design. Under his leadership, Alex Cheremuhin built the first Soviet helicopter 1-EA.

This machine had two tail rotor and two engines "Ron" capacity of 120 hp each. She was also the first time an auto-skew. The first test in 1930 gave excellent results. Piloted Cheremuhin helicopter confidently off the ground and easily soared to a height of several hundred meters, freely flying through the air and eight other complex shapes. In 1932, this rose to Cheremuhin helicopter to a height of 605 m, thereby putting an absolute world record. However, the helicopter was still far from perfect. He was unstable. Ball screw is made rigid (blades are not changed flapping), making his work unsatisfactory. Subsequently it was designed and built other models. In 1938, under the leadership of Bratukhina first Soviet twin-screw helicopter 11 EA-lateral scheme was established. But in general, in the 30 years of helicopter in the USSR has not received state support. At this time, the increasing popularity got a theory according to which the aircraft is incomparably more perfect than a helicopter and the speed and carrying capacity, and the helicopter - it's just an expensive toy. Only in 1940 Yuriev with great difficulty managed to get permission to create a special design office, which he headed. Soon loaded large teaching work, he handed the department Ivan Bratukhina. A year later, the war broke out, and the creation of a perfect helicopter again otdvinulos indefinitely.

At this time, a leader in the helicopter was Germany. Talented designer Focke created in the 30s several advanced twin-screw helicopter transverse scheme. In 1937, world records have been set on his helicopter FW-61: height - 2439 m, speed - 123 km / h and range - 109 km flight. In 1939, the new helicopter Focke reached an altitude of 3427 m, and in 1941 his machine FA-223 has been launched in a small series. The war put an end to its development, but the success of "Focke-Wulf" for a long time attracted the attention of designers to the cross pattern.

The fact that the single-rotor design is still established in the helicopter as the dominant, the great merit belongs to the American aircraft designer Igor Sikorsky. (Russian-born in 1919, he emigrated to America, "Sikorsky" founded his company here in 1923). During his lifetime, Sikorsky developed several dozen aircraft models, but worldwide fame it brought the creation of the helicopter. It was the first time he has perfected the classic single-rotor design St. George.

His first helicopter S-46 (VC-300) Sikorsky built in 1939. He immediately gave up the idea to define all the parameters of the device by calculation and decided to create a helicopter, which during flight tests could easily make design changes. His car had stressed primitive form: simple fuselage was assembled in a farm of the steel pipe, the pilot sat open in a small chair in front of the engine. Moving from a small engine 65 hp transmitted through the belts up to the gearbox, which is driven by a simple in design and three-bladed rotor trehsharnirny. Caudal single blade tail rotor mounted on a long box-girder.

Already the first tests revealed numerous design flaws. swashplate worked very badly, as was incorrectly calculated; because of this ill helicopter helm and swinging during lifting. In the end, he fell over and badly broken. Then Sikorski refused to swash and introduced three rudder propeller (thus implementing an earlier scheme St. George, which was mentioned above). In this design, the helicopter showed good handling. In May 1940, Sikorski publicly demonstrated his creation in Bridgeport in front of American pilots. At present his car made a big impression: the helicopter to move freely up and down, sideways and backward, still hung and turn on a dime. The helicopter had only one drawback - he stubbornly did not want to fly forward. It took several months trying to figure out the reason for his "stubbornness". It turned out that the air vortices generated by rotor, has a strong impact on the work of tail rotors, so that at a high speed, they refused to work. When steering the screws were removed from the coverage of the main rotor, maneuverability and control VS-300 significantly improved immediately. In general, VS-300 had to Sikorsky great importance. During the two years of test flights it was tested several control systems, various types of screws and designs worked very form of the helicopter. The number of structural improvements made to the original model, it was so much that by 1942, from the former helicopter leaving only the pilot's seat, the central part of the fuselage, the fuel tank and two-wheel main landing gear. These tests will greatly facilitate the creation of these helicopters.

Shortly Command US Air Force Sikorsky made an order to develop a military helicopter, which could be used to adjust the fire and for communication. A new sample was VS-316 name (S-47). Numerous setbacks with the first car designer convinced that the swash plate is absolutely necessary for the single-rotor design. At this time, the machine was designed with great care, and that sealed the success of the model. In January 1942, it began flight tests of the finished helicopter. In April, the car has already been demonstrated to the military. Sitting at the wheel of test pilot Charles Maurice was able to show great opportunities rotorcraft. He hung over the heads of astonished spectators, took off again and sat down on the old place - right in the recesses of the wheels, moving forward, backward, sideways, turn on a dime. Then he raised a special tube with a string bag eggs and moved to another place and dropped without breaking any. It was demonstrated, and other tricks, such as the descent and ascent of the passenger on a rope ladder in a helicopter hovering above the ground. Now this, of course, is not surprising, but at the time it was a novelty, and deeply impressed seasoned generals. One of the high-ranking chiefs were present said, "This thing can do everything that makes a horse!" A famous British test pilot Bree admitted: "We were present at the miracle." In the end, Maurice showed a cruising speed - 130 km / h, rose above the ground at 1500 meters, and then carried out a landing with the engine off autorotation.

In May 1942, the VS-316 was passed by the US Army under the designation XR-4 and put into production. In total 130 of these helicopters were built. In 1944, they were first tested in combat conditions in Burma. The war here was in the jungle, and the helicopter was the only means of transport suitable for the supply of troops. Japanese fighters launched a real hunt for low-speed "decks", but could not knock down any - at the slightest danger helicopter was pressed to the ground, hiding among the trees and thus easily avoided combat.

In 1943, the company released a new helicopter Sikorsky XR-5, have a much greater speed and carrying capacity. For the first time he had developed a special helicopter engine. In total 65 of these machines were built, as of the end of the war, the defense ministry canceled their orders. Meanwhile, in 1944 at the Sikorsky I was ready a new model - S-49 (a total of 229 pieces were produced).

After the war, helicopters began to spread rapidly throughout the world. Sikorski long retained a monopoly on their production, because only in the United States 300 companies have begun to develop their own models of helicopters. However, Sikorski had before them important advantages - well established structure and established production. Despite the competition, his company not only flourished, but expand production. In 1946, he developed the S-51 model (just released 554 machines), which has found wide application both in the military and in economic spheres. The helicopter was equipped with an autopilot for the first time, which will greatly facilitate the management. However, the greatest success fell to the S-55 helicopters "Chickasaw" (1949) and S-58 "Sibet" (1954). Only at the plant were collected in 1828 Sikorsky helicopter units of the first model, and in 2261 - the second. Furthermore, many companies in different countries has acquired the license to manufacture them. In 1952, two S-55's for the first time made a flight across the Atlantic Ocean (with a stopover on the deck of an aircraft carrier) from America to Europe. S-58 has been recognized as the best helicopter of the first generation. He also became the "swan song" of the Sikorsky. In 1957, 68-year-old designer has departed from the management of the company.

During these years, in full swing to develop helicopters in the USSR. After the war, St. George has managed to achieve the organization of two new CB: Mikhail Mil, who undertook to develop a single-rotor helicopter and Nikolai Kamov, which elected coaxial scheme. The work on the design of the helicopter was involved and Yakovlev Design Bureau. He continued his work on the helicopters lateral Bratukhin scheme. In 1946 it appeared his helicopter F-3. In 1947 he released his first helicopter Kamov Ka-8. But when at the end of the 40s was a competition for the best Soviet model, he won a helicopter Mil Mi-1, created by the St. George's single-rotor scheme. In 1951, he was put into production.

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