The Yak-40 is a small three-engined jet airliner, seating up to 32 passengers. It was the world's first regional jet in large scale service, long before the Embraer ERJ-145 and the Canadair Regional Jet appeared.
The Yakovlev Design Bureau developed the Yak-40 as a replacement for Lisunov Li-2s (Soviet built Douglas DC-3s) and Ilyushin Il-12s and Il-14s, of which thousands were flying in the Soviet Union during the early sixties. A Yak-40 prototype first flew on 21 October 1966. Soviet type certification followed in 1968 and Aeroflot started carrying passengers with the type on 30 September 1968.
The aircraft is powered by three Ivchenko AI-25 turbofans, which were specially developed for the Yak-40. The designers chose for the installation of three engines instead of two for increased redundancy in one engine out situations. Three engines also give the aircraft good short field and hot-and-high performance.
Because the Yak-40 was intended to fly to many small and poorly equipped airports, an APU (Auxiliary Power Unit) and a ventral airstair in the rear fuselage are standard to make sure the aircraft can be handled independently from ground equipment. In a three-abreast layout the cabin seats 24-27 passengers. Four-abreast seating is possible for 32 passengers.
The Yak-40 has a straight (unswept) wing, a T-tail and a retractable tricycle landing gear. Two engines are mounted on short pylons at the left and right side of the fuselage and the middle engine is located in the rear fuselage at the end of an S-shaped duct for air supply.
The Yak-40 is the basic version. The Yak-40K is a freighter with a large forward cargo door and the Yak-40D has additional fuel tanks to increase range. The Yak-40DTS is a version for military duties. A number of Yak-40s is being used as VIP aircraft by companies and governments.
Several more versions were proposed, but not built, including a stretched Yak-40M, a variant with western avionics and turbofans to be built in the USA, and a twin-engined version (Yak-40TL). Some aircraft fulfilled special roles, like calibration, meteorological research, testing radio-electronic equipment and testing jet engines.
The Yak-40 was in production until 1978 and 1,011 have been built, of which 130 for export. In early 2015 around thirty Yak-40s are still in airline service.