Yakovlev Yak-140

Yakovlev Yak-140

Company type	Experimental aircraft project
Industry	Aerospace
Founded	1954
Defunct	1956
Fate	Project cancelled
Products	Lightweight supersonic fighter aircraft (prototype)

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The Yakovlev Yak-140 represented a Soviet experimental lightweight supersonic fighter concept from the 1950s. Although the prototype was finalized in 1954, it never received clearance for flight testing and the initiative was ultimately discontinued in 1956.

Development

Designed around the Tumansky R-11 turbojet—specifically the Mikulin AM-11 engine delivering 40 kilonewtons (9,000 lb_f) of thrust without afterburner and 50 kilonewtons (11,000 lb_f) with afterburner—the Yak-140 was created to fulfill a 1953 requirement for a supersonic fighter capable of reaching speeds between 1,650–1,750 kilometres per hour (1,030–1,090 mph) and having a range of 1,800 kilometres (1,100 mi). Its armament was planned to include three 30 millimetres (1.2 in) cannons with an ammunition capacity of 75 rounds each, along with the capability to deploy air-to-ground rockets and carry up to 200 kilograms (440 lb) of bombs. The fully loaded mass was estimated at 4,850 kilograms (10,690 lb), with expectations to present the aircraft for State acceptance trials by March 1955.

The airframe featured a circular-section semi-monocoque fuselage with an air intake positioned at the nose. A radar system limited to range detection was integrated within the conical inlet cone of this intake. The wings were swept back at an angle of 55° measured at quarter-chord, each equipped with two upper-surface wing fences. The horizontal stabilizer was mounted halfway down the rear fuselage, and dual air brakes were installed on its underside. The cockpit canopy blended smoothly into a dorsal spine extending along the fuselage's top. Landing gear consisted of a tandem configuration: a single-wheel front unit and a dual-wheel main unit, with outrigger struts retracting rearward into fairings located at the wingtips.

Delays in securing a flight-ready AM-11 engine postponed State acceptance trials until early 1956. Consequently, the design was modified to accommodate the less powerful Mikulin AM-9D engine, which produced only 26 kilonewtons (5,800 lb_f) dry thrust. To compensate for this downgrade, armament was reduced to two 23 millimetres (0.91 in) Nudelman-Rikhter NR-23 guns, each supplied with 75 rounds; however, this adjustment resulted in an approximate 400 kilometres per hour (250 mph) reduction in top speed. Despite this decrease, the performance remained sufficient to initiate flight testing.

Completion of the prototype occurred in December 1954, and it successfully passed all ground evaluations by 10 February 1955, clearing it for flight trials. Nevertheless, authorization from the Template:Lang-ru (Ministry of Aviation Industry) to commence these tests was withheld, as preference was given to rival designs from Sukhoi and Mikoyan. Ultimately, a directive from the Soviet Government Council dated 28 March 1956 mandated termination of the project, followed by an official MAP order on 6 April to discontinue development.