Even before the end of World War II, Soviet aircraft designers began to study the problems of aircraft with turbojet engines. The first real results of these works were obtained already in April 1946, when two of the newest domestic jet fighters took off at once with a difference of several hours. Soon, work began on the creation of the first bomber with a similar power plant. The first Soviet aircraft of this class was the Il-22.
At the beginning of 1946, the design bureau of S. V. Ilyushin studied the issue of creating a promising jet bomber and soon presented a preliminary design of such a machine. In May of the same year, the documentation was transferred to the Ministry of Aviation Industry. It should be noted that, despite the fairly quick implementation of all the necessary work, Soviet engineers had to study a lot of new issues and propose a significant number of technical solutions that were not previously used in domestic projects. Only with the help of the most daring ideas was it possible to form the appearance of the future aircraft, the first in its class.
Experienced IL-22 during testing. Photo Wikimedia Commons
MAP specialists studied the proposed project and considered it suitable for further development. At the beginning of the summer, an order appeared, according to which it was necessary to complete the development of the bomber, and then begin the construction of a prototype. It is curious that when a new project was included in the experimental aircraft construction plan, some of its specific features were noted. So, experts recognized that the future bomber is not advanced and does not have significant advantages over foreign counterparts, but at the same time it turns out to be a breakthrough in the context of the development of the domestic aircraft industry. One of the reasons for this was the use of only Soviet engines.
From a certain point, the project of a promising bomber was called the Il-22. Looking ahead, it should be noted that the project was not brought to mass production, and therefore this designation "was released". At the end of the seventies, the Il-22 air command post went into production. This machine was based on the glider of the Il-18 serial liner and had nothing to do with the post-war bomber. Three decades separating the two projects of the same name avoid possible confusion.
When creating the first domestic jet bomber S. V. Ilyushin and his colleagues had to solve a lot of complex design problems. So, turbojet engines of that time, developing sufficient thrust, were distinguished by increased fuel consumption and therefore the aircraft needed large fuel tanks. Another problem was the optimal placement of four engines at once, for which a new design of the engine nacelle was developed. The relatively high flight speed made it necessary to abandon the developed features of the aerodynamic appearance. Finally, the aircraft was to receive powerful strike and defensive weapons that met the requirements of that time.
The promising Il-22 was supposed to be a cantilever all-metal high-wing aircraft with four engines placed under a straight wing. The tail unit of the traditional design was used. Due to the lack of space in the wing or engine nacelles, a significant number of units, up to the main landing gear, had to be mounted in the fuselage. To solve such problems, several new ideas had to be proposed and implemented. In addition, the project offered original solutions aimed at simplifying construction and operation.
The aircraft received a high aspect ratio fuselage, built on the basis of a metal frame and having a metal skin. The nose of the fuselage had an ogival shape and a significant part of it was given under the glazing of the cockpit. Under the crew's workplaces there was a niche for the nose landing gear. A technological connector was provided directly behind the cab, which was necessary to simplify construction. The central fuselage assembly was distinguished by its great length. Throughout its entire length, it retained a close-to-circular cross-section. A significant part of the central unit was given under the cargo compartment and niches of the main landing gear. The tail section of the fuselage, starting behind the wing and mating with the central one through the second connector, was made tapering. She had converging sides and a rising bottom. The second cockpit was located at the tail end of the fuselage.
Machine diagram. Figure Airwar.ru
Il-22 was equipped with a straight wing with a trailing edge, which has a reverse sweep. The wing tips were made rounded. A profile with a relative thickness of 12% was used. To reduce the likelihood of the manifestation of the so-called. wave crisis and increased lateral stability, certain measures were taken. Thus, the thickest section of the profile was at 40% of its chord. In addition, a low-bearing profile was used at the root of the wing, and a highly-bearing profile at the wing tip. At the same time, the wing shape changed smoothly. More than half of the trailing edge of the wing was occupied by large flaps. Ailerons were located between them and the tips. The left aileron carried a trim tab.
It was proposed to equip the bomber with a tail unit of a traditional design, modified in accordance with new requirements. On the rear of the fuselage was a keel with a small sweep of the leading edge and a rounded tip. Its entire rear part was used to install a large rudder. There was a small triangular gargrot in front of the keel. Above the latter, on the keel, there were stabilizers with a small sweep of the leading edge and a straight trailing edge. They carried rectangular elevators. Taking into account the high flight speeds, the empennage used a profile with a thickness of only 9%.
In the course of research into the problems of jet aircraft, it was found that insufficient precision in the manufacture of a wing can lead to the most unpleasant consequences, up to a stall in flight. To get rid of such problems, it was proposed to change the technology for assembling the fuselage, wing and empennage. The technological base for the assembly was now the skin surface. Previously, a frame was used as its capacity, which led to certain errors.
By the mid-forties, Soviet and foreign aircraft designers had not yet managed to find the most convenient and effective options for the layout of the power plant, which is why various new ideas were regularly proposed and tested. Another variant of the placement of engines, which later proved itself well and became widespread, was first proposed in the Il-22 project.
Four turbojet engines were proposed to be placed in separate engine nacelles, one in each. The gondolas themselves were to be located under the wing on pylon racks. Studies have shown that a nacelle located on a pylon and extended forward relative to the wing has a reduced drag, facilitates engine maintenance, and also eliminates the possibility of fire spreading from one emergency engine to another. Thus, the engines had to be housed in streamlined nacelles with frontal air intakes. More than half of the total length of the gondola was carried out in front of the wing, and its tail section was mounted on a small underwing pylon.
Side view. Photo by PJSC "Il" / Ilyushin.org
The aircraft was equipped with four TR-1 turbojet engines developed under the leadership of A. M. Cradle. This product had an axial eight-stage compressor and an annular combustion chamber. The temperature of the gases behind the combustion chamber did not exceed 1050 ° K (no more than 780 ° C), which made it possible to dispense with the means of cooling the turbine parts. The engine was supposed to show thrust up to 1600 kgf at an estimated fuel consumption of 1.2 kg / kgf ∙ h.
In the central part of the fuselage there was a relatively large cargo compartment for carrying payloads in the form of bombs of various types. The normal combat load was 2 tons. With a certain preparation, the Il-22 could take on board bombs with a total mass of up to 3000 kg.
When creating a new bomber S. V. Ilyushin and his colleagues took into account the main trends in the development of fighter aircraft. The high flight speed could no longer protect the strike vehicle from the attack of the interceptors, which is why it needed powerful defensive weapons. To obtain sufficient firepower capable of being a good response to existing and prospective threats, the IL-22 project used an advanced cannon armament system.
It was proposed to attack targets in the front hemisphere with the help of a fixed directional automatic cannon NS-23 of 23 mm caliber, located on the starboard side and having an ammunition load of 150 shells. This gun was controlled by the commander, in whose place there was a simple ring sight. On the upper surface of the fuselage, between the planes, a remotely controlled installation with two pairs of 20-mm B-20E cannons was placed. They could fire in any direction horizontally and had a total of 800 rounds of ammunition. An Il-KU-3 installation with an NS-23 cannon and a box for 225 shells should have been mounted in the tail fairing. The installation provided horizontal guidance within a sector with a width of 140 °. The elevation angles varied from -30 ° to + 35 °.
Two shooters were supposed to control the aft and turret installation, in whose workplaces the corresponding consoles were placed. The fodder installation had electric and hydraulic drives, with the help of which the gun was moved. It was controlled by a radio operator who was in the aft cabin. The turret was controlled only by electrical systems connected to the consoles in the front cockpit. At the disposal of the shooters were relatively simple sights, the automation of the two control stations tracked the movement of the sight and accordingly directed the guns, taking into account the parallax. There was an automatic blocking system that did not allow the tower installation to shoot at the tail.
Pilot cockpit, door open. Photo Aviadejavu.ru
Interestingly, in the early stages of design, it was proposed to use the tail section of the fuselage with a reduced cross-section. For this, the gunner-radio operator had to be located in his cockpit lying down. However, it was soon found that this would lead to an unacceptable decrease in visibility from his workplace. The tail fairing was enlarged and received a normal cockpit with advanced glazing. The shooter was positioned on a chair of adjustable height. Subsequently, a similar gunner's cockpit was repeatedly used on new IL aircraft.
The crew of the Il-22 bomber consisted of five people. Two pilots, navigator-bombardier and gunner-radio operator were in the forward pressurized cockpit. The tail cockpit was single and was intended for the shooter who controlled the stern installation. Both cabins had advanced glazing. Access was provided by doors and hatches. In an emergency, the crew was asked to leave the plane on their own through standard hatches. Bailouts were not used.
The aircraft was equipped with a three-point landing gear with a nose support. The front pillar was placed directly under the cockpit and retracted into the fuselage by simply turning back. Small diameter wheels were installed on this rack. The two main struts received larger diameter wheels, designed for use on unpaved airfields. The limited dimensions of the engine nacelles did not leave room for the chassis compartments. In this regard, it was proposed to remove the main supports in the fuselage niches located behind the cargo compartment. To further increase the track gauge, the main struts in the working position were at an angle to each other.
The landing gear struts were comparatively lightweight, which led to some specific consequences. Small and medium caliber bombs could be loaded onto aircraft without much difficulty. However, before the suspension of large ammunition weighing 2500-3000 kg, the main landing gear had to be lifted on special jacks. Without the use of the latter, the bombs on the bogies literally did not pass under the bottom of the fuselage.
A promising bomber was of medium size. Its total length was 21.1 m, the wingspan was 23.1 m. The wing area was 74.5 sq. M. An empty plane weighed a little less than 14.6 tons. The normal takeoff weight was set at 24 tons, the maximum - 27.3 tons. Imperfect engines were forced to take on board up to 9300 kg of fuel.
The starboard side of the nose of the aircraft. A forward-facing gun is visible. Photo Aviadejavu.ru
The development of all the necessary documentation for the Il-22 bomber continued until early 1947. Soon after the completion of the design work, the construction of the first prototype began. In the summer of the same year, the prototype was taken out for testing. After short ground checks, the testers began flying. The experienced Il-22 first took to the air on July 24, 1947 under the control of the crew of the commander V. K. Kokkinaki. Quickly enough, the test pilots managed to establish the pros and cons of the new machine.
Despite all the efforts of the engine builders, the refinement of the TR-1 engine was not completed by the beginning of the tests of the prototype IL-22. The maximum thrust of these products did not exceed 1300-1350 kg, which was noticeably less than the calculated one. In addition, the actual fuel consumption significantly exceeded the planned one. Insufficient engine performance has led to certain limitations. So, the plane was planned to be lifted into the air with a total weight of no more than 20 tons. The flight speed and range were also noticeably reduced. At the same time, the takeoff run increased. In practice, it significantly exceeded the calculated one and amounted to 1144 m.
Due to imperfect engines, the aircraft could reach a maximum speed of up to 656 km / h at the ground and up to 718 km / h at altitude. Cruising was 560 km / h. The fuel supply was only enough for an hour and a half of the flight and for 865 kilometers. The service ceiling has reached 11.1 km. The actual characteristics were less than the calculated ones, but still confirmed the correctness of the main technical solutions and showed the possibility of their further development. In other words, with more powerful engines, the IL-22 could show the desired parameters.
Despite inadequate flight data, the bomber was easy to control and rudder responded well. Disabling one of the extreme engines did not create significant moments and was countered without much effort by the pilot. The large size of the fuselage could lead to some difficulties when landing with a crosswind, but in this case piloting was not difficult. There were also some problems due to insufficient engine thrust. In this case, however, the plane could taxi on the ground or fly on two engines. The takeoff was simple, albeit delayed. The plane could go in a straight line with abandoned controls, and the controlled flight did not tire the pilots.
Just a few weeks after the first flight, on August 3, 1947, an experienced Il-22 was shown at the air parade in Tushino. The plane was at the head of the formation of the latest Soviet jet aircraft. A bomber of a new type and several fighters built by that time, clearly showed the successes of the Soviet aircraft industry in the field of jet engines and aircraft with similar power plants.
Large caliber bomb suspension. Jacks are installed under the main landing gear. Photo Aviadejavu.ru
For several months, the crew of V. K. Kokkinaki managed to study well a new experimental car, which during this time managed to develop the resource of the engines. Soon the Il-22 received new engines of the same type. Simultaneously with their installation, a minor modernization of several on-board systems was carried out. After that, the prototype was taken to the second stage of flight tests.
The purpose of the new stage of inspections was the next development of the power plant and other systems. At the same time, the onset of winter made it possible to study the operation of engines at low temperatures. In addition, this time, special attention was paid to defensive weapons. It was found that the hydraulics and electric drives are working properly and facilitate the protection of the aircraft. There were no noticeable problems with the tower installation, while the stern was too sensitive and required training. At the same time, the shooter could quickly get used to the peculiarities of the installation and learn how to use it effectively.
On February 7, 1948, an experienced Il-22 took off for the first time using solid-propellant boosters. Under the fuselage, at the level of the trailing edge of the wing, two SR-2 products with a thrust of 1530 kgf were installed. These experiments were continued and carried out at different take-off weights of the aircraft. As a result, it was determined that a pair of accelerators can reduce the takeoff run by 38%, and the takeoff distance by 28%.
By the beginning of the spring of 1948, two stages of factory flight tests were carried out, according to the results of which the further fate of the Il-22 project was to be determined. Despite all the efforts of the engine building, the characteristics of the power plant were still insufficient. The lack of thrust relative to the calculated one did not allow obtaining the desired flight and technical characteristics. Specialists from the design bureau and the Ministry of the Aviation Industry began to doubt the need to continue work and submit the aircraft for state tests.
The unresolved problems of the TR-1 engines had a negative impact on the fate of several aircraft at once, among which was the Il-22. The commission responsible for conducting the inspections considered it inappropriate to transfer the bomber to state tests. He really had rather high characteristics, but was no longer of any interest from the point of view of the development of the Air Force with a reserve for the future. The project was closed. It was now up to other aircraft to update the jet bomber aircraft.
Modern reconstruction of the appearance of the bomber. Figure Airwar.ru
According to reports, only one flight prototype of the Il-22 bomber was built. After completing the tests, he was sent to the showroom of the Bureau of New Technology. There, specialists of the domestic aviation industry could get acquainted with the most interesting machine. It is quite possible that representatives of various design bureaus, studying a bomber designed by S. V. Ilyushin, spied on certain technical solutions and later used them in their new projects.
There is also information about the construction of a second glider, apparently intended for static tests. Due to its specific purpose, this product had to pass the most rigorous tests, and then go for recycling.
A few years later, a similar fate befell the only flight Il-22. Having worked for several years as an exhibition model, this car went for disassembly. Unlike a number of later domestically developed jet bombers, the Il-22 has not survived, and therefore now it can only be seen in photographs from tests.
In the Il-22 project, for the first time in domestic and world practice, some original technical solutions were applied, which made it possible to ensure compliance with sufficiently high requirements. At the same time, the unresolved drawbacks of the TR-1 turbojet engines did not allow to realize the full potential of the aircraft, and then led to its abandonment. The first domestic jet bomber retained only this honorary title. Another aircraft became the first production aircraft of this class.
Nevertheless, the work on the Il-22 was not lost. Even before the completion of work on this aircraft, the design of several other bombers with turbojet engines began. So, soon an experienced Il-28 bomber came out for testing. This machine, created using developments on a closed project, later went into series and became a milestone for the domestic air force. Thus, the Il-22 could not go to the troops, but provided invaluable assistance to the further development of bomber aviation.
