The Yak-40 was the first jet powered airliner in its class in service in large numbers anywhere in the world, preceding the ERJ-135 and 328JET by three decades.
Design of the Yak-40 resulted from a mid 1960s Aeroflot requirement for a replacement for the thousands of Lisunov Li-2s (Soviet built DC-3s), Ilyushin Il-12s and Il-14s (described separately) then in service. Aeroflot attached great significance to the Yak-40 program, as the aircraft was intended to operate regional services that accounted for 50% of Aeroflot's passenger traffic.
A S Yakovlev (after whom the design bureau is named) led the Yak-40 design team, and the program's existence was revealed on October 21 1966, when the first prototype made its maiden flight. The type went into production in 1967 and entered service with Aeroflot in September 1968. Production continued until 1978, with 1011 built by the Saratov aircraft factory, of which 125 aircraft were exported to 18 countries.
The Yak-40's most noticeable design feature is its trijet configuration, with three specially developed Ivchenko AI-25 two shaft turbofans. The three jet engine layout was chosen for increased redundancy (and hence better one engine out performance, allowing good short field performance). The unswept, high aspect ratio wing is also designed for good field performance. An APU and a ventral airstair in the rear fuselage allow autonomous operation at remote airfields. A high power-to-weight ratio allows the Yak-40 a good hot-and-high performance - operating economics was a lesser priority.
The Yak-40 remained basically unchanged during its production life, but a number of developments were proposed, including the Yak-40M, a 40 seat stretched development. For a time a US company, ICX Aviation, planned to build the type in the USA with western avionics and three Garrett TFE731 turbofans. The Yak-40TL twin engine conversion was also proposed. The main difference would have been the replacement of the Yak-40's three engines with two Lycoming LF 507s.
The Yak-40K is a cargo-passenger version with a port-side forward cargo door with a maximum payload of 3200kg (7055lb) in all freight configuration.
The Yak-40D has two additional fuel tanks to increase the total fuel capacity to 6000kg (13,200lb). The Yak-40DTS is a troop carrier and paramedic configuration. Other versions are equipped for calibration, meteorological research, testing and inspecting of radio-electronic equipment, and for use as an engine testbed.
Apart from airliner use, a number are in service as corporate or government transports with a VIP interior.
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