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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
Helicopter. History of invention and production
Directory / The history of technology, technology, objects around us A helicopter is a rotary-wing aircraft in which the lifting and propulsive (driving) forces at all stages of flight are generated by one or more main rotors driven by one or more engines.
For almost forty years after its appearance, the aircraft reigned supreme in the air. During this time, the speed and carrying capacity of winged vehicles increased many times, which turned from clumsy plywood "whatnots" into powerful jet handsome men, embodying the most advanced technical achievements of human thought. However, for all its merits, any aircraft has one important drawback - in order to stay in the air, it must constantly and at a sufficiently high speed move in a horizontal plane, because the lift of its wings directly depends on the speed of movement. Hence the need for takeoff run and landing run, which chain the aircraft to the airfield. Meanwhile, there is often a need for such an aircraft that has a lifting force that does not depend on the flight speed, can vertically rise and land, and, in addition, is able to "hover" in the air. This niche, after a long design search, was occupied by a rotorcraft - a helicopter. Possessing all the flying qualities inherent in an aircraft, a helicopter has, in addition, a number of remarkable specific properties: it can take off from a place without a preliminary takeoff run, hover motionlessly in the air at the desired height, move progressively in all directions, make turns in any direction as in time of forward movement, and during hovering; finally, he can land on a small platform without a subsequent run. The creation of an apparatus that possessed a complex of these qualities turned out to be an extremely difficult task, since the theory of a helicopter is much more complicated than the theory of an airplane. It took years of hard work of many designers before the helicopter began to feel confident in the air and was able to share air transportation concerns with the aircraft. The first rotorcraft (helicopters and autogyros) appeared almost at the same time as the first aircraft. In 1907, the four-rotor helicopter of the French Breguet and Richet for the first time was able to get off the ground and lift a man above someone. After that, various designs of helicopters were proposed by many inventors. All of them had a complex multi-rotor scheme, in which several screws served to keep the device in the air, and several others to push it in the right direction. The single-rotor scheme (to which 90% of all helicopters belong in our time) was not seriously considered by anyone at first. And was she real? Raise the device into the air with a single screw - still all right. But how to tell him the horizontal translational motion? How to manage it? Those inventors who were quite well versed in aerodynamics pointed out another major drawback of the single-rotor scheme - the presence of a reactive moment. The fact is that when the main rotor was driven from an engine rigidly connected to the gondola, the latter had to rotate not so much the propeller itself as (in the opposite direction) the body of the apparatus. It seemed that it was possible to paralyze the jet moment only when several main rotors rotating in opposite directions were used in the design of the helicopter. Moreover, these screws could be located both separately from each other (longitudinal and transverse schemes), and on the same axis - one under the other (coaxial scheme). Other advantages of the multi-screw scheme also came to mind. After all, having several control screws, it was easier to direct the car in the right direction. But it soon became clear: the more screws a helicopter has, the more problems it has - calculating the device even with one screw was a very difficult task; it turned out to be generally impossible to take into account the mutual influence of many propellers (at least in the first quarter of the XNUMXth century, when aerodynamics was only taking its first steps, and the theory of the propeller was just beginning to take shape). A significant contribution to overcoming many of these problems was made by the Russian inventor Boris Yuryev. He made his most important discoveries at the time when he was a student at the Moscow Higher Technical School and was an active member of the Aeronautical Circle of the famous Russian scientist Zhukovsky. Interested in a single-rotor scheme, Yuryev, first of all, asked himself the question: how to tell the helicopter to move forward in the right direction? Most of the inventors at the beginning of the XNUMXth century, as already mentioned, were sure that for this it was necessary to equip the apparatus not only with rotors, but also with propellers. However, by experimenting with many different models, Yuryev found that by tilting the main rotor axis it was possible to obtain good horizontal flight speed without making a special horizontal thrust propeller. The translational motion of the helicopter can also be achieved by tilting the body of the apparatus forward. In this case, the force of the large screw is decomposed into two forces - lift and thrust, and the apparatus begins to move forward. And the greater the inclination of the apparatus, the greater will be the flight speed. The next problem was how to balance the reactive moment acting on the nacelle. Yuryev suggested that this could be most easily achieved with a small propeller located on the tail of the helicopter and driven by a light gear. Due to the fact that the force created by the tail rotor was applied to the long arm (relative to the center of gravity of the apparatus), its action easily compensated for the reactive moment. Calculations showed that this would take 8-15% of the engine power. Yuryev proposed further to make the blades of this propeller with a variable pitch. By increasing or decreasing the angle of inclination of these blades to the plane of rotation, it was possible to increase or decrease the thrust of this propeller. With high thrust, the tail rotor had to overpower the reactive moment of the main rotor and turn the gondola in the right direction.
But the greatest difficulty was the creation of a reliable control system. The pilot had to have at his disposal devices that allowed him to quickly change the orientation of the machine relative to all its three axes: that is, turn it in any direction relative to the vertical axis, tilt the body up and down, and also roll it to the right and left. The turning problem was solved with a small tail rotor. For this, as already noted, it was enough to make its blades turnable and connect the mechanism for their rotation with the rudders. But how to ensure controllability relative to the longitudinal and transverse axes? The simplest means would be the device of two more tail rotors, placed on the consoles at some distance from the center of gravity of the machine and turning the helicopter in the direction necessary for the pilot. Here, screw 1 serves to compensate for the reactive moment, and also acts as a rudder; propeller 2 rolls and is similar in its action to the ailerons (warping planes of the wings of an aircraft), and propeller 3 serves as a kind of elevator. But this system, in addition to being overly complex, also had the disadvantage that it made the helicopter very unstable in flight. Yuryev began to think about the question: is it possible to arrange the main rotor in such a way that he himself creates the two moments necessary for controlling the helicopter? The search for it ended in 1911 with the invention of one of the most remarkable devices in the history of a helicopter - the creation of a swashplate.
The principle of operation of this machine is very simple. Each propeller blade describes a circle during rotation. If the main rotor blades are made movable relative to their longitudinal axes, so that they can change the angle of inclination to the plane of rotation, then the movement of the helicopter can be very easily controlled. Indeed, if part of the circle outlined by it passes through the blade with a large installation angle, and the other part with a smaller one, then, obviously, the thrust on the one hand will be greater, and on the other less, and the main rotor (and with it the whole machine) will be turn in the appropriate direction. The swashplate just provided the necessary installation of the blades. To do this, a ring was installed on the main rotor shaft on a gimbal suspension, to which, with the help of hinges, leashes were attached to the levers that turn the blades. The ring rotated along with the propeller shaft. From two sides it was covered by a fixed ring freely sitting on it. This last ring could be freely rotated by means of steering rods and given any tilt in two planes. In this case, the inner ring also tilted while simultaneously rotating inside the fixed ring. It is easy to see that in this case the inner ring will make a complete oscillation in one revolution, which in turn will cause each blade associated with it to oscillate: all of them will change the installation angle from some minimum value to a maximum during the revolution. These angles will depend on the inclination of the fixed ring associated with the control levers. If the pilot needed to turn his car in any direction, he had to point the outer ring of the swashplate in that direction. In this mode, the angle of inclination of each blade was changed independently of the other blades. But it was easy to make it so that the swashplate, if necessary, could change the angle of installation at once for all the blades at the same time. This was required, for example, in the event of a motor failure in a mode called autorotation, when, under the influence of an air flow, the propeller of a falling helicopter began to rotate spontaneously, acting like a parachute. At the same time, the helicopter seemed to be planning (in nature, this effect can be observed in falling maple seeds). To do this, it was enough to make the swashplate gimbal sliding along the propeller shaft (from top to bottom). Raising or lowering the swashplate, the pilot immediately turned all the propeller blades in one direction, thereby increasing or decreasing the installation angle or making it negative (that is, capable of rotating in the opposite direction, which was exactly what was required during autorotation). Thus, by 1911, a 22-year-old student of Moscow Higher Technical School Boris Yuryev developed in general terms the entire scheme of a single-rotor helicopter. He could not patent it, because he did not have the money for it. In 1912, according to the project of Yuryev, students of the Moscow Higher Technical School assembled a full-size non-flying model of a helicopter. At the international exhibition of aeronautics and motoring, held in the same year in Moscow, this model was awarded a small gold medal. However, the school did not have the funds to build a working machine. The First World War, which began soon after, and then the Civil War, distracted Yuryev from work on his project for a long time.
Meanwhile, models of multi-rotor helicopters continued to appear in other countries. In 1914, the Englishman Mumford built his helicopter. It was the first to fly with translational speed. In 1924, the Frenchman Emishen flew his helicopter for the first time in a closed circle. At the same time, Yuryev, having taken the post of head of the TsAGI Experimental Aerodynamic Department, tried to implement his single-rotor scheme. Under his leadership, Alexei Cheremukhin built the first Soviet helicopter 1-EA.
This machine had two tail screws and two Ron motors with a power of 120 hp each. each. It was also equipped with a swashplate for the first time. The very first tests in 1930 gave a brilliant result. The helicopter piloted by Cheremukhin confidently lifted off the ground and easily soared to a height of several hundred meters, freely described eights and other complex figures in the air. In 1932, Cheremukhin flew this helicopter to a height of 605 m, thus setting an absolute world record. However, this helicopter was still very far from perfect. He was unstable. The main rotor was made rigid (the blades did not change the flywheel), which made its work unsatisfactory. Subsequently, other models were developed and built. In 1938, under the leadership of Bratukhin, the first Soviet twin-rotor helicopter 11-EA of the transverse scheme was created. But in general, in the 30s, the helicopter industry did not receive state support in the USSR. At that time, the theory became very popular, according to which an airplane is incomparably more perfect than a helicopter both in speed and in terms of carrying capacity, and a helicopter is just an expensive toy. Only in 1940, Yuryev, with great difficulty, managed to obtain permission to create a special design bureau, which he headed. Soon loaded with a lot of teaching work, he handed over the leadership of the department to Ivan Bratukhin. A year later, the war began, and the creation of a perfect helicopter was again postponed indefinitely. At that time, Germany was the leader in the helicopter industry. The talented designer Fokke created in the 30s several perfect twin-rotor transverse helicopters. In 1937, world records were set on his FW-61 helicopter: altitude - 2439 m, speed - 123 km / h and range - 109 km of flight. In 1939, the new Fokke helicopter reached an altitude of 3427 m, and in 1941 his FA-223 machine was launched in a small series. The war put an end to its development, but the success of the Focke-Wulfs for a long time riveted the attention of designers to the transverse scheme.
The fact that the single-rotor scheme nevertheless established itself as the dominant one in the helicopter industry, a huge merit belongs to the American aircraft designer Igor Sikorsky. (A Russian by origin, he emigrated to America in 1919, and in 1923 he founded his company Sikorsky here.) During his life, Sikorsky developed several dozen models of aircraft, but the creation of a helicopter brought world fame to him. It was he who first brought to perfection the classic single-screw Yuryev scheme. Sikorsky built his first S-46 (VC-300) helicopter in 1939. He immediately abandoned the idea of determining all the parameters of the apparatus by calculations and decided to create a helicopter in which design changes could be easily made during flight tests. His car had a markedly primitive appearance: a simple fuselage was assembled in the form of a truss of steel pipes, the pilot sat openly in a small chair in front of the engine. Propulsion from a small 65 hp engine. It was transmitted by means of belts up to the gearbox, from which a three-bladed and three-hinged main rotor was driven, which was simple in design. The tail single-bladed tail rotor was mounted on a long box-shaped beam.
Already the first tests revealed numerous design flaws. The swashplate worked very poorly, as it was incorrectly timed; because of this, the helicopter did not obey the steering wheel well and swayed when lifting. In the end, it capsized and broke badly. Then Sikorsky abandoned the swashplate and introduced three tail screws (thus implementing Yuryev's early scheme, which was mentioned above). In this design, the helicopter showed good handling. In May 1940, Sikorsky publicly demonstrated his offspring in Bridgeport in front of American pilots. His car made a great impression on those present: the helicopter moved freely up and down, sideways and back, hovered motionless and turned around in place. The helicopter had only one drawback - it stubbornly did not want to fly forward. It took several months to find out the reason for his "stubbornness". It turned out that the air vortices created by the main rotor had a strong effect on the operation of the tail rotors, so that at high speed they refused to work. With the tail rotors moved out of range of the main rotor, the maneuverability and control of the VS-300 immediately improved dramatically. In general, the VS-300 was of great importance to Sikorsky. During the two-year test flights, several control systems, various types of propellers and structures were tested on it, and the shape of the helicopter itself was worked out. The number of structural improvements made to the original model was so significant that by 1942 only the pilot's seat, the central part of the fuselage, the fuel tank and two wheels of the main landing gear remained from the previous helicopter. Thanks to these tests, the creation of the following helicopters was much easier. Soon, the US Air Force command ordered Sikorsky to develop a military helicopter that could be used for fire control and communication. The new sample was named VS-316 (S-47). Numerous failures with the first machine convinced the designer that the swashplate was absolutely necessary for a single-screw circuit. This time the machine was designed with great care, which predetermined the success of the model. In January 1942, flight tests of the finished helicopter began. In April, the car was already demonstrated to the military. Test pilot Charles Maurice, who was sitting at the helm, was able to demonstrate the enormous capabilities of the rotary-wing aircraft. It hovered over the heads of the astonished spectators, took off and landed again in the old place - right into the recesses from the wheels, moved forward, backward, sideways, turned around in place. Then he lifted the string bag with eggs with a special tube, carried it to another place and lowered it without breaking a single one. Other stunts were also demonstrated, for example, the descent and ascent of a passenger on a rope ladder into a helicopter hovering above the ground. Now this, of course, is not surprising, but at that time it was a curiosity and amazed the worldly generals to the core. One of the senior officials present exclaimed, "This thing can do everything a horse can do!" And the famous English test pilot Bree admitted: "We were present at the miracle." In the end, Maurice demonstrated cruising speed - about 130 km / h, rose above the ground by 1500 m, and then landed with the engine turned off in autorotation. In May 1942, the VS-316 was adopted by the US Army under the name XR-4 and put into mass production. A total of 130 such 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 vehicle suitable for supplying troops. Japanese fighters launched a real hunt for low-speed "turntables", but could not shoot down a single one - at the slightest danger, the helicopter pressed against the ground, hid between the trees and thus easily evaded the battle. In 1943, the Sikorsky company released a new XR-5 helicopter, which was distinguished by much greater speed and payload. For the first time, a special helicopter engine was developed for it. A total of 65 of these machines were built, as the Ministry of Defense canceled its orders due to the end of the war. Meanwhile, in 1944, Sikorsky already had a new model ready - the S-49 (a total of 229 were produced). After the war, helicopters began to spread rapidly throughout the world. Sikorsky did not long maintain a monopoly on their production, since only in the USA 300 firms began to develop their own models of rotorcraft. However, Sikorsky had important advantages over them - a well-established design and well-established production. Despite the competition, his company not only prospered, but also expanded production. In 1946, he developed the S-51 model (a total of 554 vehicles were produced), which found the widest application both in the military and in the economic spheres. This helicopter was the first to be equipped with an autopilot, which greatly facilitated control. However, the biggest success came with the S-55 Chickasaw (1949) and S-58 Seabat (1954) helicopters.
Only at the Sikorsky plant, 1828 pieces of helicopters of the first model and 2261 of the second were assembled. In addition, many firms in different countries have acquired a license for their production. In 1952, two S-55s made the first flight across the Atlantic Ocean (with one refueling on the deck of an aircraft carrier) from America to Europe. S-58 was recognized as the best helicopter of the first generation. It also became the "swan song" of Sikorsky himself. In 1957, the 68-year-old designer stepped down from the leadership of the company. During these years, the development of helicopters in the USSR was in full swing. After the war, Yuriev managed to organize two new design bureaus: Mikhail Mil, who undertook to develop a single-rotor helicopter, and Nikolai Kamov, who chose a coaxial scheme. The Yakovlev design bureau also joined the work on the design of the helicopter. Bratukhin continued his work on transverse helicopters. In 1946, his G-3 helicopter appeared. In 1947 he produced his first Ka-8 Kamov helicopter. But when a competition for the best Soviet model was announced at the end of the 40s, it was won by the Mil Mi-1 helicopter, created according to Yuryev's single-rotor scheme. In 1951 it was put into production. Author: Ryzhov K.V.
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