Design and Development
The Yak-25 originated from a need for long-range interceptors to protect the USSR's northern and eastern territory. The specification for a two-seat, twin-engine jet fighter and a related reconnaissance aircraft was issued by Joseph Stalin on 6 August 1951. The aircraft was to use the new Mikulin AM-5 turbojet. The first prototype, the Yak-120, flew on 19 June 1952.
The new design mounted the turbojets in pods in the wings, with bicycle landing gear, leaving the fuselage volume free for the two crewmen and a substantial fuel load, giving an unrefueled range (with external tank) of about 2,560 km (1,600 mi). The large, blunt nose contained the radome for the air-interception radar. Armament was two 37 mm NL-37L cannon with 50 rounds per gun.
Despite some significant problems the type was cleared for production in 1953 and the first were produced in 1954. Early production models, designated Yak-25, were delivered the following year, although they were not yet to operational capacity because of problems with the 'Sokol' radar. As a result early aircraft used a modified version of the RP-1D 'Izumrud' (NATO 'High Fix') ranging radar instead. When the 'Sokol' (RP-6) was finally available, the newly equipped aircraft were designated Yak-25M, with deliveries starting in January 1955. The Yak-25M received a number of other improvements, including recoil dampers for the cannon, upgraded AM-5A engines (with the same thrust), and a slight increase in fuel capacity. In 1955 and 1956 several Yak-25Ms were refitted as testbeds for air-to-air missile armament.
A reconnaissance derivative of the Yak-25, the Yak-25RV (Razvedchick Vysotnyj, "high-altitude reconnaissance"), was developed in 1959 (NATO codename 'Mandrake'). It had a completely new, long-span straight wing of 23.4 meters (more than twice that of the Yak-25M interceptor) with a total area of 55 square meters. Camera and sensor packs were added in the fuselage. Some versions may have retained one cannon.
Despite its low wing loading, the 'Mandrake's' altitude performance was marginal at best, with considerable engine problems at high altitudes, excessive vibration, and primitive equipment that imposed high workloads for the crews. The Soviet Air Force nevertheless kept the Yak-25RV in service until 1974. A few were used in the late 1970s for monitoring of radioactive contamination, with specialized sensors; these were designated Yak-25RRV. Efforts in 1971 to develop the 'Mandrake' as a high-altitude interceptor (Yak-25PA) proved unsuccessful.
The derivative Yak-26 was developed as a bomber, but only nine were built.
In 1961 a series of lightened 'Mandrakes' were produced as high-altitude target drones. The Yak-25RV-I was used as a manned target for unarmed (no live fire) interception practice, the Yak-25RV-II as a remote-piloted drone.
483 were built at Saratov plant, including 406 in Yak-25M variant, and 10 in Yak-25R reconnaissance variant. Additionally, 155 Yak-25RV reconnaissance high-altitude planes were built.
Read more about this topic: Yakovlev Yak-25
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