Ilyushin Il-62

The Ilyushin Il-62 (russian: Илью́шин Ил-62; NATO reporting name: Classic) is a Soviet long-range narrow-body jetliner conceived in 1960 by Ilyushin. As successor to the popular turboprop Il-18 and with capacity for almost 200 passengers and crew, the Il-62 was the world's largest jet airliner when first flown in 1963. One of four pioneering long-range designs (the others being Boeing 707, Douglas DC-8, and Vickers VC10), it was the first such type to be operated by the Soviet Union and a number of allied nations.

The Il-62 entered Aeroflot civilian service on 15 September 1967 with an inaugural passenger flight from Moscow to Montreal, and remained the standard long-range airliner for the Soviet Union (and later, Russia) for several decades. It was the first Soviet pressurised aircraft with non-circular cross-section fuselage and ergonomic passenger doors, and the first Soviet jet with six-abreast seating (the turboprop Tu-114 shared this arrangement) and international-standard position lights.

Over 30 nations operated the Il-62 with over 80 examples exported and others having been leased by Soviet-sphere and several Western airlines. The Il-62M variant became the longest-serving model in its airliner class (average age of examples in service as of 2016 is over 32 years). Special VIP (salon) and other conversions were also developed and used as head-of-state transport by some 14 countries. However, because it is expensive to operate compared to newer generation airliners, the number in service was greatly reduced after the 2008 Great Recession. The Il-62's successors include the wide-bodied Il-86 and Il-96, both of which were made in much smaller numbers and neither of which was widely exported.

Development

The Ilyushin OKB presented a proposal for a four-engined long-range jet airliner in February 1960, receiving the go-ahead from the Soviet Council of Ministers on 18 June 1960, with the Kuznetsov Design Bureau being instructed at the same time to develop the NK-8 turbofan to power the new airliner. The official specification required that the airliner, designated Il-62, must carry 165 economy-class passengers over a distance of 4,500 km (2,800 mi) or 100 first class passengers over 6,700 km (4,200 mi).Dawes 2004, p. 30.

The Il-62 replaced the fast turboprop Tu-114 on long range routes. As the Tu-114 was just entering service when the Il-62 was on the drawing board, Ilyushin had time for an unhurried design, test, and development programme. This was useful, since the Il-62 did call for significant development.

The Il-62 and the British Vickers VC10 are the only commercial airliners with four engines fitted in twinned/paired nacelles by the sides of, and beneath, a "T" shaped empennage ( T-tail). In the case of Ilyushin, the configuration was dictated by TsAGI, the Soviet Union's aerospace agency, since Ilyushin's design bureau lacked the resources to engage in configuration studies. This layout allowed the wing design to be optimised for aerodynamic efficiency, without being cluttered by having to carry engines. In addition, the rear-mounted engines reduced engine noise in the cabin and allowed smaller vertical tail surfaces (as the yawing moment in the event of an engine failure was reduced compared to wing mounted engines). These advantages are balanced by a number of drawbacks. The wing structure, lacking the weight of heavy engines to pull down against the wing bending moment, needed to be heavier, as did the rear fuselage structure, which had to carry the engines. In addition, aerodynamic wash (shadow) from the wing blankets the tail when the nose is pitched up (high angle of attack) leading the aircraft into a condition known as deep stall. This called for complex and (in the 1960s) unreliable automatic stall warning systems such as stick shakers and stick pushers to prevent the aircraft from stalling, although the Il-62's wing was designed to prevent deep stall.Gordon, Komissarov and Komissarov 2004, pp. 252, 254.

Early aircraft (prototypes, pre-production and initial production aircraft) display an evolution from thin or thick kinked leading inboard edges to the ultimate thick and straight 1966 shape. The characteristic " dog-tooth" also moved until fixed before production began. The engine installation also evolved, with the engines' longitudinal axes canted by 3 degrees from the horizontal, addition of thrust reversers to the outer engines, and slimming down of the entire installation as production began.

The prototype was grossly underpowered as its intended NK-8 engines were not ready, and small Lyulka AL-7 turbojet engines had to be installed temporarily. The prototype with AL-7PB engines (registered СССР-06156) first flew on 3 January 1963, but crashed after clipping a perimeter fence during a maximum weight testing flight of the development program. The production Il-62 was powered by the originally intended rear-mounted Kuznetsov NK-8-4 engines. The first Il-62 powered with NK-8 engines (registered СССР-06153) first flew in 1964.

The Il-62M variant (first flight in 1971, introduced in 1973) has more powerful, more efficient, and quieter Soloviev D-30KU engines and a fin fuel tank. Beneath the skin, the Il-62M has simpler and lighter single-slotted flaps and incremental aerodynamic improvements. Most important of these was the addition of spoilerons (spoilers or wing-mounted lift-disruptors which can act in the same capacity as ailerons by differential deployment in cruising flight), or in concert to kill lift on landing, and the ability to use idle reverse thrust in flight during the final approach so as to shorten the landing run. All but one example in service today are Il-62M. In 1978, the Il-62MK was further developed to seat up to 198 passengers and carry some two tonnes (4,400 lb) more payload and/or fuel than the Il-62M.

Other versions were also planned, including a stretched version to seat up to 250 passengers and a shrunk version to suit smaller airfields.

The Il-62 has tricycle landing gear with an additional lightweight gear strut at the rear of the fuselage which extends when the aircraft reaches its parking position. Aircraft with rear-mounted engines are usually tail-heavy when sitting empty on the ground, and to prevent the aircraft from tipping up on its tail, various devices are used for supporting the tail – from simple "pogo stick" fixed struts on small aircraft, to light-weight extendable struts (Il-62). Aircraft like DC-9 or Boeing 727 use an airstair door under their tail which serves the dual purpose of a tail support as well as an extra door for passenger loading.

The Il-62 is the largest airliner ever built with all-manual flight controls, using steel cables, rods, pulleys, aerodynamic and weight balances, and trim tabs. The Il-62 also has a forward-mounted tank serving as a water ballast. This may be used when the aircraft flies empty or lightly loaded. If this is a fact, it would rank the Il-62 alongside other airliners that use ballast, notably the French Caravelle and the Soviet Tu-154. Due to the rear-mounted powerplants, the wings are aerodynamically clean, and takeoff and landing aids are employed without the disturbing effect of engine nacelles, resulting in free airflow over the dorsal wing surface. This allows the aircraft to fly through air turbulence of 16–18 m/s without affecting its stability.Thiel 2001

Another key Il-62 trademark is the "saw tooth" (" dog-tooth") on the wing leading edge. This prominent feature acts as an aerodynamic fence vortex generator

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