Yak-120

August 10, 1951 the Resolution of the Council of Ministers #2929-1379, which OKB-January 15 ordered to create and submit to the test in August 1952 Double or twin-loitering interceptor Yak-120. At its base it was required to create a tactical reconnaissance of the Yak-125, which should submit to the test in October 1952. In order to meet the government's job design team worked with great dedication and in the autumn of 1951 have been basically completed all design work for both options, and built their layouts. December 12 signing of the protocol finalized mock-up committee. It is possible to start production of working drawings and start building the prototype interceptor. Lead engineer on the aircraft assigned M.I.Leonova.

Yak-120 was significantly different from other interceptor OKB. Achieving a significant increase in the duration of the flight, yakovlevtsy engines placed under the wing panels, which allowed release of the volume of the fuel under the fuselage. By Arrangement reasons decided to use a bicycle scheme chassis (front and rear main bearings and two auxiliary on wingtips). Under the fuselage between the main landing gear bays provided for the suspension of additional fuel tank. Radar "Falcon" were placed in the bow of the fuselage under a lot of fairing. The pilot's seat in a pressurized cabin installed in tandem under a common cover slides back lantern. The wing was a constant chord sweep of 45 °. The stabilizer was raised and fixed at half swing keel.

The armament consisted of two 37-mm guns H-37L with ammunition 50 rounds on the barrel, which were installed at the bottom of the fuselage. It provides for the suspension under the wing of two large-aircraft rockets ARS-212. A distinctive feature of the Yak-120 was the presence of air-thermal anti-icing system protects the front edge of the wing, tail and shell intakes. Flight-navigation and radar systems allowed to intercept targets in all weather conditions and in a wide range of heights. The whole construction of the interceptor has been well thought out, and it is possible in the future to create a number of modifications thereof.

During the construction of the prototype of its geometric characteristics practically have not changed, only the area of the vertical stabilizer was increased from 5.1 sq.m. to 5,329 sq.m. With equipment situation was more complicated. Since finishing the radar "Falcon" was delayed, then on the first prototype of the Yak-120 had set its equivalent weight. Also, instead of the radio altimeter RV-H-2 CM set. Despite the difficult and very heavy equipment, the machine was relatively easy for the twin-engine fighter. This was due not only to the use of cycling gear, but also for the new design-time power circuit with an internal wing strut. Strict compliance with weight limits allowed to lower the relative weight of the glider up to 29%.

June 19, 1952 the first flight of the Yak-120. Factory tests conducted by test pilot V.M.Volkov, and they ended in November. Normal take-off weight of the machine is 8530 kg. The plane was smaller and lighter than the interceptor "200B" Lavochkin. With the new small-sized engine and good aerodynamics of the Yak-120 was able to get higher performance characteristics. At flight weight of 7650 kg the maximum speed at an altitude of 4000 m was 1140 km / h, and at 10,000 m - 1075 km / h (M = 0.997). This altitude interceptor experienced gained in 4.3 minutes.

Almost all the basic parameters of the terms of reference (TOR) have been exceeded. However, the flight range of the aircraft several "nedotyagivaet" at an altitude of 12,000 meters, the figure was 2,800 km and 3,250 km with overhead tank, and the flight was 3 hours 45 minutes and 4415 minutes, respectively. Nevertheless, these data allow us to carry on combat duty in the air at a considerable distance from the airport. The plane had good handling and is capable of performing complex aerobatics figures. However, the lack of regular radar hampered his presentation on the state tests. Therefore, in early December 1952 in the MAL decided to immediately equip the Yak-120 with the RP-1 "Emerald" radar (which satisfactorily passed state tests on the interceptor OKB Mikoyan SP-5 and recommended for serial construction) and in this way to convey it to the test in the Civil Code NII VVS. In this plane, "200B" ordered to transfer to the NII-17 for use as a flying laboratory for testing and debugging in the air station "Falcon".

State tests of the Yak-120 took place in GK NII VVS and took more than a year. From March to June 1953 were evaluated primarily LTH aircraft. There were obtained the following maximum values: speed - 1090 km / h (at an altitude of 5000 m), the practical ceiling - 14500 m, range - 2,700 kilometers (outboard tank at takeoff weight of 9450 kg at an altitude of 12,000 meters). The height of 10,000 m machine gained 5.5 minutes. Although the number of observations of the state commission, it was decided to launch the aircraft after a series of improvements under the designation Yak-25. At the end of the year received tactical flight characteristics have been approved for production aircraft of the USSR Council of Ministers Decree #2359-965.

In the process of testing and preparation for serial production of the interceptor in the prototype introduced some structural improvement, in particular, have established a second crest on the detachable parts of the wing. After the elimination of defects take-off weight of the Yak-120 is increased to 8700 kg. From 1 to October 26, 1953 Wolves held the factory control tests to finalize the car, and then in November, its state tests continued. They confirmed the good flight characteristics of the aircraft, which allowed him to deploy production in full. Since the radar "Falcon" was still nedovedennoy, the production of Yak-25 began with radiopritselom RP-1, modified for the new interceptor and received the designation RP-1D. The first production aircraft left the shop at Saratov aircraft factory in September 1954

Lapping radar "Falcon" flying laboratory "200B" continued during the 1953 tests have shown that compared with RP-1, it has a greater range, can detect low-altitude targets (300 meters) and has a number of other advantages. In November 1953 there was an order to terminate the test MAL and install it on the Yak-120. In April 1954 completed state tests interceptor Yak-120 radar "Falcon" and the station launched into production under the designation RP-6. According to the results of state tests of the Yak-120 with the standard station on May 13 issued a decree of the USSR Council of Ministers #899-385, which "demanded to release" [ie, produce] 30 serial Yak-25 RP-6 in 1954.