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MiG I-75

The I-75 became, in practice, the first project of OKB-155 designed to destroy air targets using only guided missiles. In this project, two K-8 missiles (weight 275 kg, range 12 km) were sent to the target along the radar beam. With the suspension tanks, the tactical radius of the new interceptor was 720 km, the maximum speed at the altitude of 18,000 m was 2360 km / h, the dynamic ceiling was up to 24,200 m, and the static ceiling with the missiles was 20,100 m.

The interceptors were calculated for various variants of the power plant (for the upgraded AL-7F engines with the afterburn thrust of up to 10 tons and for the new OKB-300 engine of SK Tumansky P15-300 with the afterburner thrust of up to 11 tons) and missile armament. In particular, under the Lyulkovo turbojet engine I-75 was designed (which could well mean the I-7 5th version) with a swept wing, and for the Tumen engine E-150 with a triangular one. Both fighters were distinguished by a nose air intake of increased diameter with a large central body-cone. Suhovtsi concentrated their work on one project of the heavy interceptor T-37, suggesting to achieve the best result with a more powerful engine P15-300 (the take-off weight of the aircraft, increased due to the installation of more heavy equipment, perhaps, did not allow to rely on another) and triangular wing, successfully worked out on the experimental fighter T-3.

The I-75 was built in two copies. The first prototype had to install the existing AL-7F engine (the design of the aircraft was designed specifically for this type of turbojet engine). The second prototype, which received the designation I-75F, was already designed for the installation of the AL-7F-1 engine (also with a design thrust of up to 10 tons). In connection with the complete failure of the I-7U tests to reduce the construction of the I-75F, the latter decided to build by altering the "seven".

From the foregoing it follows that in the variant I-75F the rate was made for a modified AL-7F-1 engine with a 50% increased rate of forcing. This modification of the turbojet engine was calculated for flight at altitudes up to 20-22 km and speeds N = 2.1-2.2. Set by the decision of the Council of Ministers of the USSR in August 1956, with a deadline for testing at the end of the same year, the new version of the engine was still unsatisfied by the end of 1957. Its reliability was low. So, the thrust on the maximum mode reached 6240 kg, on afterburner - 9200-9215 kg (later, in the course of batch production, it was possible to increase to 9600 kg). The thrust increase was provided by a new afterburner of increased diameter.

The chief designer of OKB-51 P. 0. Sukhoi made the first bid for the Lyulkovo engine. At the developed TRD AL-7 suhovtsy drew attention in 1953, stopping on it their choice and installing it in 1955 on prototypes of the front-line fighter S-1 and interceptor T-3. Due to the small number of produced engines, the timing of the transfer of aircraft prototypes to some extent depended on who was the first to get the prototypes of Lyulkovo engines.

Tests of the first prototype I-75 without radar began on April 28, 1958. In the air, the machine was picked up by GK Mosolov. A maximum speed of 2050 km / h was achieved at an altitude of 11,400 m without K-8 missile suspension, with rockets - 1670 km / h at an altitude of 12,400 m. The aircraft's ceiling was 16,000 m with shells, 18,700 m without shells.

In December, the station was installed "Uragan-5B" and the tests continued until mid-May 1959. The flying weight of the fully equipped interceptor with the suspension of missiles and wing tanks was 11 470 kg. In general, the tests of the complex were successful and the interceptor received a positive evaluation.

However, competing aircraft OKB P. 0. Sukhoi proved to be more successful. The Sukhovtsy managed earlier to conduct state tests of their cars (and, in addition, very successfully), after which the government in 1958 decided to build both types of aircraft under the Su-7 and Su-9 serial.