Yakovlev Yak-120

Yakovlev Yak-120
Type:	Interceptor aircraft
Design country:	Soviet Union
Manufacturer:	OKB Yakovlev
First flight:	June 19, 1952
Commissioning:	only prototype
Number of pieces:	2 prototypes 1 break cell

The Jakowlew Jak-120 ( Russian Яковлев Як-120 ) was an aircraft from the Jakowlew design office . It was a test fighter and after minor changes went into series production as the Jak-25 .

development

At the end of the 1940s, the need arose in the Soviet Union for heavy, two-seat interceptors with a long range for the air defense of large areas, such as the northern and eastern borders of the USSR with their thin infrastructure. The first test samples such as the Mikoyan-Gurevich I-320 , the Sukhoi Su-15 and Lavochkin La-200 could not meet the requirements, especially regarding the range. The Luftwaffe leadership was happy that A. S. Jakowlew took the initiative to develop such a model, which was honored in August 1950 with an official development contract to OKB Jakowlew for a two-seater interceptor and reconnaissance aircraft, while OKB Tupolev had one in parallel twin-engine escort fighter should develop. Both projects were to use the new, compact Mikulin AM-5 axial thruster. According to the plan, the construction of Jakowlew's interceptor Jak-120 and reconnaissance aircraft Jak-125 should be completed by the end of 1952. The first prototype flew on June 19, 1952, still with a dummy of the intended Sokol radar device, which at that time was not yet ready for use, in the bow. The factory trials were completed in November. All in all, apart from the range, which was just below the requirements, all the requirements were met, but the lack of radar did not yet allow the state testing to begin. As a result, attempts were made to accelerate the testing of the Sokol radar. a. the La-200B was also shut down, while the Jak-120 was provisionally equipped with the Isumrud radar that had already been tested in the Mikoyan-Gurevich SP-5. In this configuration, the state trials were successfully completed between May and June 1953. Minor problems were reflected in further changes, with which the model then went into production as Jak-25 in 1954.

After the positive impression of the Jak-120, it was requested to equip the aircraft with the new afterburner engines AM-9A and the heavy rocket ARS-57, for which the new radar device Sokol-M had to be installed. Delays in the completion of the Sokol-M also delayed the completion of the aircraft, which was the second prototype of the Jak-120, which had been converted before completion. In December 1954, a standard Sokol radar was finally installed. The machine differed from its predecessor in that it was longer and thicker engine nacelles as well as larger and outward-facing boundary layer fences. In the underside of the fuselage were two recesses for the missiles, which is why the internal arrangement of the fuselage tanks had to be changed. By installing small caliber cannons, weight could be saved. The flight tests of the Jak-120M took place in January 1955 and ended in the same month. The Sokol-M was still not finished (and work on it was finally stopped a short time later), and the afterburners of the AM-9A could not be activated below 5,000 m, which significantly worsened the possible operational characteristics of the interceptor. Since the designers were already working on a new successor to the Jak-27 , the project was finally abandoned and the machine was used as the Jak-120MF as a test vehicle for the RD-9F engines.

technical description

Yakovlev's solution was an unusual combination of a tandem landing gear and engine nacelles under the wings. This design made it possible to carry large amounts of fuel in the fuselage, to get space for the large cabin and the radar device and to keep the wings aerodynamically clean thanks to the compact engines. A novelty for fighter aircraft was a de-icing system for the wing leading edges and engine intakes, but this was absolutely necessary for the planned patrol flights under polar conditions. Although large amounts of radio electronic equipment were built into the sample, new technical design and construction solutions made it possible to make the cell almost a quarter lighter than comparable twin-beam samples.

Technical specifications

Parameter	Yak-120	Yak-120M
span	10.96 m	10.96 m
length	15.67 m	15.67 m
Wing area	28.95 m²	28.95 m²
Takeoff mass	8,530 kg	-
Wing loading	295.00 kp / m²	-
Engines	two turbine air jet engines Mikulin AM-5A , each 2,000kp	two turbine air jet engines Mikulin AM-9A , each 2,650kp without and each 3,250kp with afterburner
Top speed	1,075 km / h in 10,000 m, 1,140 km / h in 4,000 m	1,122 km / h at 5,000 m
Climbing time to 10,000 m	4 min 18 s	-
practical summit height	14,500 m	16,300 m
Range	2,800 km	-
Takeoff route	735 m	-
Landing route	800 m	-
Armament	2 cannons 37mm ( N-37L ) with 50 shells each	2 cannons 23mm, 2 guided missiles air-to-air
crew	2	2

Individual evidence

1. ↑ Joachim Barschin: Jakowlews Zweistrahler in War and Peace. In: Flieger Revue Extra No. 8. Möller, 2005, ISSN  0941-889X . P. 96.