The Ka-15 became the first helicopter produced by the Kamov Design Bureau in a large series. This rotorcraft was originally developed for the needs of naval aviation, as an anti-submarine helicopter, ship reconnaissance and liaison. It was the Ka-15 that became the first full-time helicopter on the ships of the Soviet Navy.
Today, some aviation enthusiasts sometimes ask themselves the question: "Why did our sailors prefer the unrevealed at that time coaxial rotorcraft scheme to the usual single-rotor helicopter with a tail rotor? Why did they have to take such a high technical risk?" Indeed, even earlier, thanks to the successes of the venerable aircraft designer I. I. Sikorsky in the USA, a helicopter with a tail rotor has already begun to be used in a wide variety of areas of human activity, including in the navy.
It should be noted that the production of tail rotor helicopters began on an unprecedented scale. American helicopter designer A. Young in the first half of the forties in the USA alone counted more than 340 firms engaged in the development and construction of helicopters of this scheme. At the end of the fifties in our country, in the A. S. Yakovleva and M. L. Mile, on a competitive basis, single-rotor helicopters were built, respectively, the Yak-100 and GM-1 (in the series - the Mi-1) with a maximum take-off weight of about 2500 kg. The preference was given to the Mi-1, which was built in large series. However, he did not fit for service in the Russian Navy. Why is that?
The answer is simple enough. In the United States, helicopters in the navy began to be used on aircraft carriers. There were no problems with the placement, provision of takeoffs and landings for helicopters of the classical scheme on large ships. In the USSR, which did not have such ships at that time, the use of helicopters in the Navy was planned to begin on ships of small displacement. These ships could be equipped with small runways, bordered by already existing ship superstructures, which significantly limited approaches to them during flights.
Meanwhile, in the OKB N. I. Kamov already had some experience in creating coaxial helicopters. With the release and fine-tuning of the first ultralight shipborne single-seat coaxial helicopters Ka-10 and Ka-10M, the formation of the young OKB was completed. Military tests of the light Ka-10, carried out on the Black Sea, revealed the need for the Navy to build a helicopter with a more lifting capacity and more independent of weather conditions. The Ka-15 became such a machine - a multi-purpose helicopter designed also according to the coaxial scheme chosen by Kamov.
The new helicopter was a two-seater machine, in the cockpit of which the operator's seat was located to the right of the pilot. Ships of small displacement are known to be subject to significant rolling and pitching. The powerful turbulent air flow, the presence of various superstructures and the rocking of the ship caused our naval sailors to mistrust a helicopter with a tail rotor, sensitive to the speed and direction of the wind.
To finally be convinced of their correctness, they later even conducted comparative tests of the coaxial Ka-15 and the single-rotor Mi-1 on the Mikhail Kutuzov artillery cruiser. Due to its minimal size and higher maneuverability, the coaxial Ka-15 successfully took off from a small runway and landed on it even with a six-point sea state. Under these conditions, the Mi-1 with a long tail boom and a tail rotor, which significantly limited the possibilities of its operation, could not be operated when there was a high turbulence of the air flow and the rocking of the carrier ship. Thus, the coaxial helicopter scheme in the USSR was in demand by the Navy.
It must be said that the coaxial design of rotary-wing aircraft attracted attention with its obvious advantages not only of domestic sailors, but also of designers from all over the world. Almost all the power of the power plant is used here to create the thrust of the rotors. In addition, the reactive moments created by the propellers are mutually balanced in the main gearbox and are not transmitted to the aircraft fuselage. All efforts and moments of forces from the helicopter carrier system are closed on the short fuselage compartment located between the two power frames, on which the gearbox and the carrier system are located on top, and the landing gear is attached from below, on both sides. It is almost impossible to create a more compact scheme for a rotorcraft. That is why many well-known foreign aircraft designers, such as L. Breguet, D. Perry, S. Hiller, G. Berliner, A. Ascanio and others, as well as aviation firms, including the domestic design bureau A. S. Yakovlev, tried to master the coaxial helicopter scheme. Among the helicopters built in the second half of the 40s on this principle, one can name "Roteron", "Brantly B-1", "Benlix K", "Dorand G-20", Bell "Molel 49", "Breguet G-11 -E "and" Breguet G-111 ", as well as an experimental helicopter of the Yakovlev Design Bureau.
Some of the helicopters created in the 40s - 50s, for example, "Breguet G-111" (France), Bell "Molel 49" (USA) and others, had excellent flight characteristics for that period. However, all foreign companies and the Yakovlev Design Bureau refused to improve and develop this promising scheme due to the large number of problems encountered.
The Kamov Design Bureau, during the development, construction, testing and development work of the Ka-15, also encountered a number of difficulties due to the lack of a scientific and experimental base in the field of aeromechanics of coaxial rotors. Designers and scientists of the OKB successfully coped with many problems. Under the leadership of Nikolai Kamov, a unique school of scientific design and practical design of rotary-wing vehicles of various schemes and, first of all, coaxial schemes was formed. Another problem that designers always face when designing new machines is the correct choice of the size of the aircraft.
Chief Designer Kamov believed that after the Ka-10 with a take-off weight of less than 400 kg, the new Ka-15 helicopter, weighing 1500 kg, would best satisfy a wide range of conflicting interests. Apparently, he was not internally ready for the construction of a helicopter in a heavier weight category. Kamov's associates tried to convince him that the Mi-1 helicopter already exists in this class, which has filled a niche in the interests of the military department and the national economy, and the Ka-15 will have a very narrow naval scope. In 1951, on the instructions of the government, the Mil Design Bureau began developing the Mi-4 helicopter with a takeoff weight of 7000-8000 kg, which in 1952 began to be mass-produced. It was not possible to convince Kamov then. In this regard, his OKB lost the pace and the opportunity to take a leading position in the country in the number of serially produced helicopters with the "Ka" code in the class of rotorcraft up to 10,000 kg.
Defense of the preliminary design of the Ka-15 took place in 1951. In December, a full-scale model of the car was built. The first lift of the helicopter into the air took place in April 1953. Serial production of the helicopter was started at the aircraft plant in Ulan-Ude in 1956.
Let's compare the main data of coaxial and single-rotor helicopters. From the above data, it follows that the coaxial Ka-15, with half the engine power, carries a load of about the same mass in the cargo compartment as the famous single-rotor Mi-1, which set about 30 world records. At the same time, the Ka-15 is 1000 kg lighter, and its length, taking into account the rotating propellers, is almost 1.7 times less than that of the Mi-1. It was these indisputable advantages of the compact Ka-15, combined with the highest maneuverability, that made it possible for the helicopter to successfully fulfill its main mission: to successfully conduct reconnaissance of the surface situation and provide communication between ships and coastal bases in the interests of the Navy.
Even on the Ka-10, the coaxial rotor layout and control system were brought to practical implementation. It included two swash plates, common and differential pitch mechanisms, and a number of other elements. Of course, all this had to be improved in the course of fine-tuning the new helicopter. The joint operation of the engine and rotor rotor was united by the control system, which in the cockpit had a "step-gas" control lever with a rotating handle for correcting the engine operating mode.
By the way, there was no such system on the GM-1 helicopter in Mil, and it was very difficult to control the machine in flight. With the common pitch lever, the pilot changed the angles of the rotor blades, and the engine control lever (throttle) selected the required engine operating mode. Mil introduced this system later, already on the modification of the GM-1 helicopter, which received the designation Mi-1.
One of the most difficult tasks that the designers had to solve was the study of the nature of vibrations on a coaxial helicopter and the development of recommendations and methods for bringing them to an acceptable level. To reduce the effect of external aerodynamic periodic forces, back in 1947, enthusiasts led by Kamov, when building the first coaxial Ka-8 helicopter, developed a method of static and dynamic adjustment of the carrier system. In the course of bench and factory tests of the Ka-15 in collaboration with TsAGI and LII, a number of its design improvements were made, aimed at overcoming self-oscillations of earth resonance and flutter of rotor blades. The combination of some constructive measures made it possible to successfully cope with the problem of resonance on the Ka-15. Another, no less dangerous type of self-oscillation was the flutter of the propeller blades in flight, which the OKB specialists discovered in the Ka-15 in 1953. It was eliminated by mounting the original horn-type counterweights on the blade, which shifted its centering forward by the required amount.
However, the operation of the helicopter in a humid sea climate soon brought an unexpected surprise: the flutter again began to give out signals about itself in flight. It turned out that during operation, the wood of the blade swells and moisture accumulates in the space of the compartments between the upper and lower skins. This led to a displacement of the centering back and caused the appearance of a flutter. Soon it was possible to detect flutter phenomena due to the displacement of the centering of the blade back not from its swelling, but as a result of repairs carried out in the conditions of operating units. To prevent the appearance of self-oscillations of the propeller blades, a standardized margin of centering efficiency was introduced into the technology of their creation. He made it possible to finally take control of the flutter of the rotor blades.
After the launch of the Ka-15 into a series, the scope of work to increase the resource of machines and expand the possibilities of their use has changed significantly. Numerous stands were put into operation at the plant for testing units and the most loaded parts under dynamic stress conditions. Long-term life tests continued. Flight research was carried out to study the "vortex ring" and to develop recommendations for the pilot to prevent the helicopter from getting into this phenomenon and methods of getting out of it. The tests of the Ka-15 were completed in the autorotation mode of the rotor propellers, including landings on the airfield and the water surface (with balloon landing gear) with the engines inoperative.
Sea trials of the ship's helicopter began in 1956, in the Baltic from bases on board the destroyer Svetly. In 1957-1958, the first subdivisions of the ship Ka-15 were created. In 1958, the Svetly destroyer began to equip the runway, and in 1961 the fleet was replenished with eight Project 57 missile ships with runways, storage tanks for aviation fuels and lubricants, cabins for aviators, and special equipment to ensure the operation of rotary-wing aircraft.
In the national economy, the Ka-15 was used as a scout for sea animals on ships of the trawl fleet. In the anti-submarine modification, the Ka-15 could carry two radio-hydroacoustic buoys RSL-N or the SPARU receiver. In this case, a pair of helicopters worked together: one dropped buoys in the working square of the water area, and the other listened to them using an SPARU to detect a submarine, and to destroy it, a Ka-15 was used in a shock version, equipped with an OPB-1R sight and equipped with two depth bombs weighing 50 kg.
The Ka-15M variant had improvements to improve the control kinematics of the carrier system, increase the reliability of the vehicle and the efficiency of its operational manufacturability. The Ka-15M was used in various versions and had the appropriate equipment: spraying and pollination units, aerosol generation devices, special hanging containers for delivering mail and small cargo, rescue boats, removable side gondolas for transporting bedridden patients, and much more.
The training UKa-15 was required for training pilots and training flights. It had dual controls, as well as additional aerobatic equipment and shutters for performing training and instructional instrument flights. The helicopter was built in 1956 at an aircraft plant in Ulan-Ude. In 1957, he successfully passed state tests and then was mass-produced. In total, there were 354 “fifteenths” built in various modifications.
Ka-18 is a further modification of the Ka-15M. It was intended for the transportation of passengers, mail and cargo, for transporting sick and injured people to inpatient medical institutions. Along with the Ka-15M, it was also used in aviation chemical work. The prototype was manufactured in 1956, and in 1957 it successfully passed state tests. The Ka-18 was mass-produced and was in operation for about 20 years. More than 110 vehicles were built.
The civilian Ka-18 differed from the basic Ka-15 in an oversized cabin that could accommodate a pilot, three passengers or one patient on a stretcher and an accompanying physician. For the convenience of loading sanitary stretchers into the helicopter, a hatch was made in the fuselage nose fairing.
Under the leadership of Kamov in 1958-1963, a group of designers, technologists and scientists for the first time in the world created, tested and launched large-scale production of propeller blades of an innovative design made of polymer composites, they increased the aerodynamic quality of the rotor and significantly increased the blade resource. Comparative tests of 11 sets of conventional LD-10M wooden blades and 6 sets of new B-7 fiberglass blades were carried out at the EDO's electric propeller stand under the same conditions. At the same time, for rotor blades with B-7 blades, the polars practically coincided, and for screws with wooden blades, their significant scatter was observed.
The design and manufacturing technology of blades from polymer composites were patented in five foreign countries leading in the field of helicopter construction. They served as the basis for the creation of more advanced rotor blades of a new generation. Test pilot V. Vinitsky in 1958-1959 set two world speed records on the Ka-15M. And in 1958, at the World Exhibition in Brussels, the Ka-18 received a gold medal. Nevertheless, much of the credit for this belongs to the basic Ka-15, on which all the systems were previously developed that made it possible to achieve success on the Ka-18.
It was from the Ka-"fifteenth" that the widespread practical operation of coaxial helicopters began in the Navy and the Civil Air Fleet.
