The Yakovlev Yak-42 is a three-engined jet airliner seating 100-120 passengers, designed for short to medium-range flights. It was the first Russian airliner powered by high-bypass turbofan engines.
The Yakovlev Design Bureau started working on the Yak-42 as a replacement for the Tupolev Tu-134 jet and the Ilyushin Il-18 turboprop. The first design proposals showed a twin-engined jet airliner fitted with Soloviev D-30 turbofans, the same as used for the Tupolev Tu-134. Later the Yakovlev engineers chose a three-engined configuration with a swept wing and high-bypass Lotarev D-36 turbofans.
The Yak-42 made its maiden flight on 7 March 1975. The first prototype had an 11 degrees swept wing, but the second prototype had a wing with a sweep of 23 degrees. The latter was chosen for the production version. Later Yak-42s were fitted with leading edge slats and slotted trailing edge flaps to improve runway performance.
Aeroflot started operating the the Yak-42 on 22 December 1980 on a flight from Moscow to Krasnodar. NATO assigned the name 'Clobber' to the aircraft. After an accident in June 1982, when the tailplane detached during flight, the Yak-42 was grounded. It resumed airline service more than two years later, in October 1984.
Two engines are mounted in pods on either side of the rear fuselage. The middle engine is at the end of an S-duct, embedded inside the rear fuselage, under the T-tail. An auxiliary power unit (APU) is also fitted in the rear fuselage. The aircraft lacks thrust reversers.
The cabin seats up to 120 passengers in a six-abreast layout, like in the Boeing 737 and Airbus A320. The aircraft has two airstairs, including one in the rear fuselage under the T-tail.
The original production version was designated 'Yak-42'. The Yak-42ML has modified avionics for use on international flights and the Yak-42D is a long-range variant with increased fuel capacity, which became the later standard production version. The Yak-142 is a derivative with western AlliedSignal avionics, spoilers to allow faster descent and an enlarged cabin door to accommodate jet bridges.
The Yak-42M was a proposed but never built stretched version with a new wing and to be powered by three Progress D-436 turbofans. This version was further developed into the Yak-242 with two Aviadvigatel PS-90 turbofans in underwing pods. This design evolved into the Irkut MS-21, a 150-seater which is now under full-scale development.
More than 180 Yak-42s have been built. Early in 2015 around 50 are still in airline service.
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