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Yakovlev Yak-40
The Yakovlev Yak-40 (NATO reporting name:
Codling) is a small, three-engined airliner. It is the world's
first commuter trijet. Maiden flight was made in 1966, and
production took place from 1967 to 1981. Introduced in September
1968, the Yak-40 was exported since 1970.
By the early 1960s, the Soviet state airline
Aeroflot's international and internal trunk routes were flown by
jet or turboprop powered airliners but their local services, many
of which operated from grass airfields, were operated by obsolete
piston engined aircraft such as the Ilyushin Il-12, Il-14 and
Lisunov Li-2. Aeroflot wanted to replace these elderly airliners
with a turbine-powered aircraft, with the Yakovlev design bureau
being assigned to design the new airliner. High speed was not
required, but it would have to operate safely and reliably out of
poorly equipped airports with short (less than 700 m, (2,300 ft))
unpaved runways in poor weather.
Yakovlev studied both turboprop and jet-powered
designs to meet the requirement, including Vertical Take-Off and
Landing (VTOL) designs with lift jets in the fuselage or in
wing-mounted pods, but eventually they settled on a straight-winged
tri-jet carrying 20 to 25 passengers. Engines were to be the new
AI-25 turbofan being developed by Ivchenko at Zaporozhye in
Ukraine.
The Yak-40 is a low-winged cantilever monoplane
with unswept wings, a large T-tail and a retractable tricycle
landing gear. The passenger cabin is ahead of the wing, with the
short rear fuselage carrying the three turbofan engines, with two
engines mounted on short pylons on the side of the fuselage and a
third engine in the rear fuselage, with air fed from a dorsal
air-intake by an "S-duct", as is an auxiliary power unit, fitted to
allow engine start-up without ground support on primitive
airfields. The three AI-25 engines are two-shaft engines rated at
14.7 kN (3,300 lbf). The engines have no jetpipes, and initially no
thrust reversers.
The pressurized fuselage has a diameter of 2.4
metres (94 in). Pilot and co-pilot sit side-by-side in the
aircraft's flight deck, while the passenger cabin has a standard
layout seating 24 to 27 passengers three-abreast, although 32
passengers can be carried by switching to four-abreast seating.
Passengers enter the aircraft via a set of ventral airstairs in the
rear fuselage.
The wing is fitted with large trailing-edge
slotted flaps, but has no other high-lift devices, relying on the
aircraft's low wing loading to give the required short-field
take-off and landing performance. The wings join at the aircraft
centerline, with the main spar running from wingtip to wingtip The
wings house integral fuel tanks with a capacity of 3,800 litres
(1,000 US gal; 840 imp gal). The aircraft has a large fin, which is
swept back at an angle of 50 degrees to move the tailplane
rearwards to compensate for the short rear fuselage. The horizontal
tailplane itself is unswept.
The first of five prototypes made its maiden
flight on 21 October 1966, with production being launched at the
Saratov Aviation Plant in 1967 and Soviet type certification
granted in 1968. The type carried out its first passenger service
for Aeroflot on 30 September 1968.[9] In the 1972 version, a
tailspin was removed. In 1974, new version was introduced, with
non-stop flight distance increased. Also, the forward door on the
right side of the fuselage changed its place – it was located
together with the sixth window.
By the time production ended in November 1981,
the factory at Saratov had produced 1,011 or 1,013 aircraft. By
1993 Yak-40s operated by Aeroflot had carried 354 million
passengers. As well as being the backbone of Aeroflot's local
operations, flying to 276 domestic destinations in 1980, the Yak-40
was also an export success. More than this, Yak-40 became the first
Russian/Soviet aircraft getting flying certificates of Italy and
West Germany. It was demonstrated in 75 countries of the world,
including the USA, where orders on Yak-40 were made.
A total of 130 were exported to Afghanistan,
Angola, Bulgaria, Cambodia, Cuba, Czechoslovakia, Equatorial
Guinea, Ethiopia, Germany, Guatemala, Honduras, Hungary, Italy,
Laos, Madagascar, Philippines, Poland, Syria, Vietnam, Yugoslavia
and Zambia.
Variants:
Yak-40 – The first production model.
Yak-40-25 Military conversion with the nose of a MiG-25R and SRS-4A
Elint installation.
Yak-40 Akva (Aqua) – Military conversion with nose probe,
pylon-mounted sensors, a fuselage dispenser and underwing active
jammer pods.
Yak-40D (Dal'niy – long-distance) – with non-stop
flight distance enlarged.
Yak-40EC – Export version.
Yak-40 Fobos (Phobos) – Military conversion with two dorsal
viewing domes and a removable window on each side.
Yak-40K – cargo / convertible / combi version with a large
freight door. Produced in 1975–81.
Yak-40 Kalibrovshchik – Military Elint conversion with a
"farm" of blade, dipole and planar antennas.
Yak-40L – Proposed version with two Lycoming LF507-1N
turbofans, a joint program between Skorost and Textron (now
Allied-Signal) Lycoming. The original design would have had a
slightly swept wing.
Yak-40 Liros – Military conversion with nose probe carrying
air-data sensors.
Yak-40M – Proposed 40-seat stretched passenger version.
Yak-40 M-602 – Flying testbed with a Czechoslovak M 602
turboprop installed in the nose.
Yak-40 Meteo – Military conversion with multipole dipole
antennas and fuselage dispenser.
Yak-40P – Yak-40L with large nacelles projecting ahead of the
wings.
Yak-40REO – Military conversion with large ventral canoe for
IR linescan. Lateral observation blister on right side.
Yak-40 Shtorm – Military conversion with multiple probes and
sensors on the forward sidewalls.
Yak-40TL – Proposed upgraded version, to be powered by three
Lycoming LF 507 turbofan engines.
Yak-40V – Export version powered by three AI-25T turbofan
engines.
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