Ilyushin Il-62
The Ilyushin Il-62 is a Soviet long-range narrow-body jetliner conceived in 1960 by Ilyushin. As a 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. The seventh quad-engined, long-range jet airliner to fly, Avro Jetliner, Boeing 707, Douglas DC-8, Vickers VC10, and experimental Tupolev Tu-110 ), 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 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 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. Special VIP 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 or 100 first-class passengers over 6,700 km.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. 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. These advantages are balanced by a number of drawbacks. The wing structure, lacking the weight of forward engines to pull down against the wing torsional moment, needed to be heavier, as did the rear fuselage structure, which had to carry the engines. In addition, aerodynamic wash from the wing blankets the tail when the nose is pitched up leading the aircraft into a condition known as deep stall. This called for complex and 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.
Early 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 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 first flew in 1964.
The Il-62M variant 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, 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 about 2 tonnes more payload 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. Aircraft like DC-9 or Boeing 727 use an airstair door under their tail, which serves the dual purpose of a tail support and an extra door for passenger loading.
The Il-62 is the only airliner in its class with unpowered, all-manual flight controls, using steel cables, rods, pulleys, aerodynamic and weight balances, and aerodynamic 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.
Another key Il-62 trademark is the "saw tooth" on the wing leading edge. This prominent feature acts as an aerodynamic fence vortex generator, and fixed leading-edge droop/slat/flap. It ensures vice-free behaviour at high angles of attack and assists efficient long-range cruise. The saw tooth removes the need for hydraulic controls, stick shakers, and stick pushers. Later models of the VC10 also adopted this feature, in their case closer to the wing tips.
Early NK-8-4-engined Il-62s suffered from performance problems, including fatigue and overheating issues with the engines, sometimes leading to false fire alarms, which could possibly cause the crew to accidentally shut down paired engines to prevent contiguous engine and fuselage damage. Flying with only two paired engines on the same side would, however, render the aircraft unbalanced and difficult to control. Subsequent modifications to the Il-62 and the VC10 largely rectified this problem. There were two fatal Il-62 losses involving engine failure, both occurring with aircraft owned by LOT Polish Airlines, which had also leased a number of Il-62s from Aeroflot and Tarom. The higher-fatality accident was a fully laden Il-62M Flight 5055 on 9 May 1987, which experienced a rear fuselage fire that possibly went unnoticed by the crew, hence their decision not to land at one of two nearby airports. Control of the plane was eventually lost on the return flight to Warsaw, most likely due to one of the auxiliary fuel tanks fitted to some LOT Il-62s having ignited. The other was an unmodified NK-8-4-powered Il-62 Flight 007, which crashed on 14 March 1980 with 87 fatalities after being fitted with an engine that had previously caused vibration problems when used on two other LOT aircraft.
Powerplant failure of the type that afflicted the LOT aircraft was extremely rare because bearing wear is generally identified by vibration tests during maintenance. At the time, however, LOT did not have equipment to test or fault-diagnose engines of the size used in the Il-62. Unfortunately this meant that any potential problem might not be identified between overhauls. There were other known instances of engine failure, but these did not result in loss of control. The LOT accidents involving different engine types was a fatal crash-rate 30 times higher than the Il-62 average. At least one other LOT Soloviev D-30-equipped aircraft also suffered a similar engine failure around this time. After 1987, LOT introduced turbine vibration-detecting equipment and shortened the time between inspections. It also adopted the dual flight control system used on some other Il-62s and deleted the auxiliary engine-pod fuel tanks. These planes were subsequently sold to Air Ukraine in 1991/1992, which operated them until the airline closed in 2000. In 2010, 30 years after the loss of Flight 007, an investigation of previously unreleased archives at Instytut Pamięci Narodowej revealed that during the industrial unrest of the 1980s LOT had been instructed by the Polska Rzeczpospolita Ludowa authorities to effect operational cost savings by over-exploitation of service life of its jet engines.
Special Il-62 conversions
Several special conversions were made to the basic Il-62, the main ones being the Il-62 and Il-62M salon VIP versions used by heads of state, and the Il-62M airborne command aircraft used by the Russian government. Although the Il-62 had been introduced during Khrushchev's time, it was during the Brezhnev era that Ilyushin was asked to develop the salon versions, which have been used by Russian leaders ever since right up to the Putin years. The VIP examples were fitted with conference rooms and rest areas, rooms for the retinue, and service personnel and bodyguards, while the secure communication equipment enabled contact with Moscow and other cities from any part of the globe. Examples were also delivered to other countries, including Czechoslovakia, Germany, North Korea, Sudan and Ukraine.An airborne command Il-62M was customised for the emergency-response agency EMERCOM to provide evacuation transport for Russian citizens from foreign countries and act as airborne command post for these and other emergency situations. It operates in conjunction with at least one other Il-62M and a fleet of Il-76, Il-76TD waterbombers, An-72 and helicopters, which have operated in some 60 countries, and is credited with having saved 50,000 lives since the agency was created in 1994. Apart from basic interior changes, RA-86570 features hush-kitted engines and Honeywell electronics with global communication ability via satellite, and an Inmarsat system. The aircraft was used as a command post during the combat of forest fires in the Far East, when dealing with the Chechen terrorist attack in Kaspiysk when an apartment building was blown up, and to bring a Russian Deputy Foreign Minister to Sharjah in 1996 and from there, collecting the crew of an Il-76 freighter who had escaped from the Taliban militia in Afghanistan.