|ALL-WEATHER FIGHTER||Virtual Aircraft Museum / USSR / Russia / Yakovlev|
In 1955, the Yakovlev OKB flew the prototype of a light tactical bomber, the Yak-26, which, evolved from the Yak-25, embodied aerodynamic refinement and was powered by two Tumansky RD-9AK turbojets each rated at 3250kg with afterburning. During test, the Yak-26 achieved 1235km/h at 3000m, or Mach = 1.05, but suffered from serious instability at high attack angles, development consequently being discontinued in favour of a tandem two-seat all-weather fighter, the Yak-27, as a potential successor to the Yak-25. Similarly powered to the Yak-26 and flown in 1956, the Yak-27 featured extended wing root leading edges increasing sweepback inboard of the engine nacelles to 62°, and a sharply pointed nose radome to reduce drag and lessen rain erosion. Armament remained paired 37mm N-37L cannon, but provision was made to supplement this with two RS-2U beam-riding AAMs. Parallel development was undertaken of a tactical reconnaissance aircraft, the Yak-27R, which accommodated the navigator in a pointed, glazed nose. Recurrence of the instability problems that had afflicted the Yak-26 led to major redesign of the wing, broader-chord outer panels being introduced and the tips were extended beyond the outriggers which were enclosed by streamlined under-wing blisters.
Series production of the Yak-27 fighter was not undertaken - although 180 examples of the Yak-27R were built - but a single-seat mixed-power development, the Yak-27V, underwent extensive evaluation. Intended as a high-altitude interceptor and first flown in May 1957, the Yak-27V was powered by two RD-9Ye turbojets with an afterburning thrust of 3800kg each and a tail-mounted Dushkin S-155 bi-fuel rocket motor of 1300kg. Basic armament remained two 37mm cannon. The Yak-27V attained zoom altitudes of up to 25000m during a test programme that continued for two years, but the disbandment of the Dushkin OKB and a loss of interest in rocket propulsion resulted in termination of the programme.