By the mid-50s of the last century, the front-line bomber aviation (FBA), which was part of the Air Force of the Soviet Army, numbered more than one and a half thousand aircraft with almost four thousand crews. Among them, two divisions of front-line bombers were considered special and were intended to use nuclear weapons. They were better manned and "put together", and the annual flight time of their crews was one and a half times higher than the corresponding figure for the crews from "regular" divisions, which had flown an average of 55 hours in the previous year.
The FBA was armed with the Il-28 bomber, the prototype of which took off for the first time on July 8, 1948. Serial production of the Ilyushin bomber was launched in 1950 at three plants at once, and later four more aviation enterprises joined the production of the machine. The Il-28 turned out to be the most massive front-line jet bomber in the history of world aviation. In combat regiments, the Il-28 won the sympathy of ground and flight crews. Perhaps for the first time in the Soviet Union, the creators of a combat vehicle paid so much attention to the working conditions of aviators. People accustomed to the Spartan cold and noisy cockpits of piston bombers were amazed at the comfortable conditions on board the new aircraft, the convenient layout and the wealth of equipment. The pilots especially noted the significantly simpler piloting technique of the Il-28 than the Tu-2, especially during takeoff and landing, the disproportionately increased speed and climb rate, and good maneuverability. For navigators, the "twenty-eighth" opened the previously inaccessible techniques of air navigation and bombing, especially in difficult weather conditions. The technical staff received a car, which was easy and convenient to maintain: the engines were easily uncapped, the units were interchangeable, and convenient access was provided to places requiring constant monitoring. The aircraft's reliability and structural integrity are legendary. So, those who served in Chernyakhovsk remember well the case when a car from their base after a forced landing at sea remained afloat for more than two hours, was towed to the shore, repaired, and then continued to operate. The crew of the IL-28U of the 408th Frontline Bomber Regiment (FBAP) from Stryi had to experience the behavior of the machine when it got into a thunderstorm and hail. Their twin "stuck" into a black cloud at an altitude of 6000 m, where it was badly battered and thrown to the left bank. The squadron commander Konoplyannikov, who was sitting in the instructor's place, removed the thrust of the engines, and when the car fell out of the clouds at an altitude of 1800 m, he brought them to the nominal mode, leveled the plane and landed it safely at his airfield. On the ground, it turned out that the car had received several holes from lightning strikes and that paint (in some places even soil) had been stripped off by hail from all the leading edges of the wing and tail.
Despite the fact that the Il-28 was a very successful machine, surpassing both the domestic Tu-14 and foreign classmates, its fate cannot be called happy. In the fifties of the last century, the flight data of aircraft was improved so rapidly that in just one five-year period, the assessment of the machine could change to the exact opposite.
In August 1955, the Presidium of the Central Committee of the CPSU instructed the Minister of Defense, Marshal of the Soviet Union G. K. Zhukov and Air Force Commander-in-Chief, Air Chief Marshal P. F. Zhigarev "to consider the feasibility of further production of Il-28 aircraft", as well as aircraft of other types. The motives were simple: supersonic fighters and fighter-interceptors, as well as cruise missiles, began to enter the armament of the air forces of countries - potential enemies of the Soviet Union.
Chief of the General Staff Marshal of the Soviet Union V. D. Sokolovsky in a letter to P. F. Zhigarevu noted: "… In the USA, the F-104A air combat fighter with a maximum speed of 2400 km / h, a practical ceiling of about 20 km has been prepared for adoption, and the F-102 fighter-interceptor with a maximum speed of 1600 km / h is being mass-produced. with a ceiling of about 18 km, armed with Falcon guided missiles with a firing range of 6-8 km … These examples indicate a significant lag of our research and experimental work on aviation technology from the level of a potential enemy …"
It was also noted that in 1955 the American Air Force adopted the Matador operational cruise missile with a launch range of about 1000 km and was completing tests of the strategic "lionfish" Snark and Navajo, which had a speed of 1800 … 2500 km / h … At that time, naturally, no one knew that all these projects would turn out to be unsuccessful. But the enormous speeds and flight ranges of the newest aircraft were frankly mesmerizing. It was not for nothing that the Soviet Union, in response to overseas threats, immediately began to develop S, P-20, D, Tempest and Buran operational and strategic cruise missiles. In those years, it was believed that speed and service ceiling were the main advantages of any aircraft. It is they who will help him escape from air defense systems and win air combat, or avoid it. After analyzing the situation, the leadership of the Air Force considered it necessary to curtail the production of the "obsolete" Il-28 bomber, reducing the order for 1955 by 250 aircraft, and "in 1956 to produce it only for the countries of people's democracies."
Air Force Commander P. F. Zhigarev pointed out, "The Il-28 aircraft does not fully meet modern requirements in terms of its flight and tactical data and especially in terms of flight speed …" Instead of the Il-28, the FBA planned to adopt a new supersonic bomber.
Aviation design bureaus began to develop a new machine at the end of 1952. The official basis was the release of a number of Resolutions of the USSR Council of Ministers in December 1952, according to which Soviet aircraft designers were instructed to work out the issue of creating a front-line bomber with a speed of at least 1200 km / h.
The engines available and being developed in the USSR were supposed to provide supersonic speeds. And it was the correct choice of the power plant that ultimately determined the winner in the aviation design bureaus competition. By this time, A. M. Cradle was created by the AL-5 (TR-3A) engine. In the early 50s, the AL-5 was one of the most powerful turbojet engines in the world. In 1952, for the first time, this engine achieved a 200-hour resource and a maximum thrust of 5200 kgf at a nominal 4200 kgf. The engine had a seven-stage axial compressor, an annular combustion chamber with 24 vortex burners, a single-stage turbine, and a rigid conical nozzle. The engine is started autonomously by means of a TC type turbo starter. The engine was manufactured in small series for installation on Il-46 and La-190 aircraft, which performed only experimental flights and were not implemented. In parallel with the development of the AL-5, A. M. Cradle was engaged in the problem of creating a supersonic compressor, the rotor blades of which are streamlined with air at a speed exceeding the speed of sound. This makes it possible to increase the compressor capacity, increase the pressure increase, and reduce the weight and dimensions of the engine while maintaining or even increasing thrust.
The AL-7 engine, which has the first supersonic compressor stage, was tested in 1952. Its thrust reached 6500 kgf, and its mass was 2000 kg.
Also, engines suitable for a front-line bomber were developed at the Klimov Design Bureau. The first of them is the VK-5 with a thrust of 3800 kgf and is a further development of the VK-1F mastered in production. VK-5 passed state tests in 1953 and flight tests on an experienced photo reconnaissance aircraft MiG-17R, which, with the afterburner turned on, reached the highest flight altitude at that time - 18,000 m. In addition to VK-5, Klimov's design bureau worked on a promising VK-9 engine with afterburner up to 12,000 kg.
The third developer of the required engines was the A. A. Mikulin. It was here that the AM-5 was created, the first turbojet engine fully developed in the USSR. After certification of the engine in 1953, the Mikulin Design Bureau created an improved version of the engine - AM-9, with a new compressor with a transonic air flow rate and with a maximum thrust of 2600 kgf and 3250 kgf in forced mode. The engine passed state bench tests in 1955. It was intended for installation on the MiG-19 and Yak-25 supersonic fighters.
In addition, in 1953, under the leadership of A. A. Mikulin (later replaced by S. K. Tumansky), the development of the AM-11 turbojet engine, which later received the R11F-300 index, began.
When creating the engine, the basic principles of regulation of twin-shaft turbojet engines with an afterburner were theoretically developed and applied, which ensured optimal high-speed characteristics, simplicity and reliability of operation. Maximum thrust was 4200 kg, afterburner 5100 kg, engine weight 1040 kg. Engines VK-5, VK-9, AL-5 and AM-9 were rejected by aircraft designers. The first was a centrifugal compressor engine and had a large cross section. Such an engine would be good if installed inside the fuselage of a single-engine aircraft. But in this case, the engine thrust was not enough to ensure supersonic speed. VK-9 was “pie in the sky”.
The declared high performance was accompanied by a great technical risk. Aviation designers still well remembered how they miscalculated in the 40s when designing aircraft for promising VK-107 (first formation), M-71 and M-90, which never became serial. The AL-5 engine was rejected due to its low gas-dynamic stability, which they had already experienced on the La-190 and I-350 prototypes.
In addition, A. M. Cradle offered a more powerful AL-7. AM-9, according to aviation designers, had a low thrust even when two engines were installed. Thus, the AL-7 and R11F-300 became favorites, it was with them that prototypes of supersonic front-line bombers were later built, which will be discussed in the following parts.
