The path to the supersonic front-line bomber. Part five. The first supersonic and undercover fight A.S. Yakovleva

2024 Author: Matthew Elmers | [email protected]. Last modified: 2023-12-16 21:49

June 10, 1954 chief designer of OKB-115 A. S. Yakovlev received a government decree (needless to say that in those days such resolutions were written "as a blueprint" from the proposals of the OKB itself - the initiator of the development), which ordered the creation of a double supersonic long-range fighter-interceptor Yak-2AM-11 on the basis of the Yak-25 (then there is a "Yak" with two AM-11 engines). It was assumed that in the future, a reconnaissance aircraft would be developed on its basis, and then a front-line bomber. It was also assumed that by the beginning of 1955 OKB-300 A. A. Mikulina will be able to provide Yakovlevites with flight copies of AM-11 engines with a thrust of 4000 kgf at maximum mode and 5000 kgf at afterburner. Mikulin was once again not up to par. The AM-11 engine (later this "loser" would become the world famous R11F-300) was at that time so "raw" and undeveloped that further development of the Yak-2AM-11 had to be abandoned, and in March 1955 a new government decree was issued, in accordance with which all three machines (interceptor, reconnaissance and fighter) should have been created using the RD-9AK engine.

According to the assignment, the future Yak-26 bomber (its designation inside the OKB - "123") was supposed to reach a speed of 1400 km / h, climb to an altitude of 16700 m and have a flight range of 2200 km. The normal bomb load remained the same - 1200 (1300) kg, but the maximum was increased to 3000 kg. The technical requirements stipulated the use of the OPB-11P optical bomb sight and set the forward-downward viewing sector 90`. At the same time, it was not possible to glaze the bow of the Yak-125B model, because this shape did not contribute to the achievement of supersonic speed. Therefore, the nose of the Yak-26 was a pointed metal ogival cone with eight side (three large and one small on each side) windows and a flat window below. The mock-up commission was satisfied with the design of the fuselage nose and wrote down in the minutes: "The view from the navigator's cockpit of the Yak-26 aircraft provides the ability to find a target and perform targeted bombing with an OPB-11P optical sight." The contours of the cockpit canopy have also changed somewhat. But this was not enough to increase the speed to the specified value. It was also necessary to reduce the relative thickness of the wing profile.

For bombing at night and in poor weather conditions, the aircraft was equipped with a panoramic radar sight PSBN-MA, the antenna and part of the blocks of which were located under the cockpit. The equipment also included RSIU-4 and RSB-70M radio stations, an ARK-5 automatic radio compass, an OOP-48 blind landing system with an MRP-48P marker radio, a RV-17 radio altimeter, an AP-40 autopilot and other equipment. However, one should pay attention to the sometimes dismissive attitude of A. S. Yakovlev to the customer's views on the appearance of a combat vehicle of the corresponding purpose. For example, not wanting to get involved with equipping the aircraft with a heavy and complex guided defensive cannon installation, A. S. Yakovlev approved a technical solution providing for the use of a backward-oriented stationary AM-23 cannon with an ammunition reserve of 100 shells. At the same time, no means of its guidance on the attacking enemy fighter was provided!

After short-term factory tests, in which the normal take-off weight of the Yak-26 was 10,080 kg, the aircraft was transferred for joint state tests. This happened a little later than the set date - the report on the first stage was approved on June 25, 1956. At the state tests, Hero of the Soviet Union V. Seregin became the leading pilot on the machine (he died in 1968 while performing a training flight with Yu. A. Gagarin). The takeoff weight of the vehicle with a combat load reached 11,200 kg. Already the first flights of the Yak-26 with RD-9AK engines showed its advantage in speed and ceiling over the IL-28. The flight altitude of the new bomber reached 16000 m (on assignment - 16000-17000 m). According to the requirements, at an altitude of 10,000 m, the aircraft had to develop a maximum speed of 1225-1250 km / h on afterburner and 1100 km / h at maximum engine operation. During the tests, a speed of 1230 km / h at an altitude of 10,600 m was reached - the Yak-26 became the first supersonic front-line bomber in the USSR.

But, in addition to this spoonful of honey, a barrel of tar was awaiting the testers. Out of 110 planned flights, only 27 were completed. At the same time, instability at high angles of attack, unsatisfactory stability and control characteristics, poor visibility from the navigator's cockpit, high efforts due to friction in the control of the aircraft, felling and loss of aileron efficiency at high speeds were revealed. At an altitude of 4000 … 6000 m, when the high-speed pressure reached its maximum, the aircraft reacted inadequately to the deflection of the ailerons - it was lurching in the direction opposite to the desired one. The reverse of the ailerons, the reason for which was the insufficient rigidity of the wing (due to the small relative thickness), began to appear at the very first attempts to accelerate the car to maximum speed. The commission for conducting joint tests of the aircraft was forced from August 28, 1956 to interrupt the tests of the Yak-26 under the program of the second stage and demanded to install a new, more rigid wing. At the end of 1956, the first prototype of the Yak-26 was equipped with a reinforced wing, an adjustable stabilizer and forced RD-9F engines (afterburner thrust 3800 kgf), modified the lantern, navigator's entrance hatch and ejection seats. A protruding "tooth" appeared on the leading edge of the consoles, playing the role of a vortex generator.

In 1957, OKB-115 built a second experimental vehicle with similar modifications, equipped with RD-9F engines and a radio range-finding station "Lotos", which was mated with the OPB-11 sight. On this plane, the Air Force Research Institute investigated the reverse of the ailerons. On October 3, 1957, the first prototype aircraft began testing bomber weapons with bomb drops at subsonic and supersonic speeds. By the end of 1957, factory tests of prototypes were completed, during which the main design characteristics of the Yak-26 were confirmed. The maximum speed has reached the specified level of 1400 km / h, the ceiling is 16800 m, the maximum range is 2400 km. However, flights on the Yak-26 were constantly accompanied by accidents associated with design and production defects that were not eliminated.

The third prototype Yak-26, which was released for testing, also underwent significant improvements. The aircraft was equipped with a stabilizer adjustable in flight and a modified wing without aerodynamic ridges, which had a nose protruding forward bent downward, serving to prevent end stall and reduce drag at high angles of attack, as well as to improve the characteristics of the aircraft when flying on the ceiling and at cruising modes. A periscope was installed on the cockpit canopy. In 1956, OKB-115 and LII conducted joint tests of the Yak-26-3 to determine the maximum speeds and flight range. They showed that the measures taken improved the flight qualities of the aircraft, but it was not possible to get rid of the shortcomings completely. Work on the bomber continued, as they considered it promising. The first prototype also underwent modernization.installed a modified stabilizer, aft cannon, periscope and tried to improve the view from the navigator's cockpit by solid glazing of the nose cone (except for the upper part). The aircraft, together with an experienced Yak-121 interceptor, took part in the 1956 air parade in Tushino. As a result, A. S. Yakovlev managed to achieve a solution that made it possible to manufacture a small series of 10 Yak-26 bombers at the Moscow aircraft plant number 30.

Now let's remember that G. K. Zhukov arrived at the Il-54 bridegroom, described in the second part of the article, in June 1956. As it turned out later, that trip was preceded by a meeting at the Ministry of Defense, at which A. S. Yakovlev reported on the characteristics of an experienced front-line bomber Yak-26. One of the posters had an expressive picture: the silhouettes of two Il-54 and Yak-26 aircraft were shown, as well as a plate from which it followed that the Yak-26, at a smaller size, performs most of the combat missions assigned to the Il-54 aircraft.

As a result of all the efforts of A. S. Yakovlev, by the end of 1956, all ordered Yak-26s were completed at the plant number 30. But the military, dissatisfied with the test results, stubbornly refused to accept the aircraft, despite repeated attempts by director P. A. Voronin to hand them over. Meanwhile, 1957 has come. In January, the Air Force was again headed by Air Marshal K. A. Vershinin, who replaced the Chief Marshal of Aviation P. F. Zhigareva. Not bound by any obligations and preliminary behind-the-scenes "agreements", Konstantin Andreevich began to strictly demand the fulfillment of all the conditions specified in the TTT for the development of aircraft, and the elimination of defects revealed during the tests. OKB-115 was not ready for this turn of events. Perhaps for the first time in the history of the OKB, his "products" were so resolutely rejected! All this took place against the background of the well-known cooling of the country's political leadership in the person of N. S. Khrushchev to manned aircraft. But this time too, Yakovlev showed miracles of diplomacy and reached an agreement with the Air Force: the acceptance was formalized, and the OKB took over the issue of further use of aircraft. As a result, three cars remained at the company (formally - for finishing work according to the remarks of the state commission), two were transferred to the LII, one to the MAI. It was not possible to find out the fate of the remaining bombers.

According to the memoirs of E. G. Adler, at that time the chief designer of OKB-115 came to the conclusion that it was inexpedient to continue work aimed "at the development of the Yak-26." Archival documents show that this is not entirely true. The fact is that the Air Force, for the time being reconciled with the lack of replacement for the Il-28 bombers, did not want to endure the shortage of operational-tactical reconnaissance aircraft. Of all the three Yak aircraft with RD-9F engines, the Yak-27R turned out to be the most in demand, which “with a creak,” but nevertheless, was brought to a state that made it possible to start relatively large-scale production. And since the machines of all three purposes were structurally similar, this made it possible to continuously improve the appearance of even "frozen" projects and propose new options based on serially built ones. And just as the Yak-25 fighter-interceptor served as a kind of "pretext" for the creation of the Yak-26 front-line bomber, the Yak-27R reconnaissance aircraft subsequently led to the appearance of a new front-line bomber.