Yak-120 interceptor prototype by A.S.Yakovlev

67k b/w Yak-120 from Yak-25 page at 'Russkaja Sila'

In 1949- 1951 new class of combat aircraft started to take shape - heavy two-seat interceptor, capable to engage enemy aircraft in any weather and day/night conditions. Introduction of radar/weapon operator dramatically increased aircraft combat efficiency, but pioneering in this filed A.I.Mikoyan/M.I.Gurevich I-320 and S.A.Lavochkin La-200 failed to fulfill all requirement.

Lack of long range interceptor made Northern and Eastern borders of the USSR poorly protected, and Soviet leadership was very pleased when A.S.Yakovlev came up with initiative to start development of new long-range fighters. On 6 August 1951 on a meeting with I.V.Stalin following orders were issued:

• 2-engine escort fighter - to OKB-155 (A.I.Mikoyan);
• 2-seat 2-engine interceptor and it's tactical ('front line') reconnaissater version - to OKB-115 (A.S.Yakovlev);

Both projects had to use new compact AM-5 turbojets by A.A.Mikulin. Yakovlev's Yak-120 interceptor and Yak-125 reconnaissater had to be presented fro trials correspondingly in August and September 1952. On December 12 mock-up commission approved the projects, and assembly started under supervision of leading engineer M.I.Leonov.

A.S.Yakovlev solution was an unusual combination of bicycle landing gear and under-wing engines. Such a choice allowed to place substantial amount of fuel into fuselage, easily accommodate the second crew member and keep wing clean (thanks to new slim engines). Nose section contained radar station. De-icing system for wing leading edge and engine intake edges was a novelty for fighters, but a necessity for patrol interceptor flying long missions in Polar conditions. Despite heavy radio-electronic was added, new technical solutions allowed to lower weight of airframe by 29% compared with similar 2-engine fighters, and allowed to use Yak-120 platform during many years for development of new aircraft.

50k b/w Yak-120 drawing from Yak-25 page at 'Russkaja Sila'

First prototype was flown 19 June 1952 (test-pilot V.M.Volkov on controls) with 'weight equivalent' instead of the Sokol radar station (was not ready in time) and older version of radioaltimeter. Factory trials were finished in November. Yak-120 was much smaller and lighter than 200B by S.A.Lavochkin. Except the range (which was slightly shorter than demanded) all demands were faced, but missing radar was a serious obstacle on the way of State Acceptance trials.

As a result, Lavochkin's interceptor was send to NII-17 for Sokol radar evaluations, while the Yak-120 was urgently fitted with Izumrud aiming radar, successfully tested on Mikoyan/Gurevich SP-5 aircraft. State trials in May-June 1953 revealed some secondary shortcomings, but overall conclusion was positive. Yak-120 was cleared for production under designation Yak-25.

Airframe of the second prototype was used for new fighter with new engines and conformal installation of heavy unguided rockets. But this is already Yak-120M story.