Ilyushin Il-62

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Air Koryo's Il-62M jetliner in Beijing Capital International Airport.

The Ilyushin Il-62 is a Soviet long range airliner. Conceived in 1960 by Ilyushin, it first flew in 1963 and entered Aeroflot service in 1967: the inaugural passenger flight was a service from Moscow to Montreal on September 15. The Il-62 was the USSR's first pressurised aeroplane to have a fuselage with a non-circular cross-section (3.8 x 4.1 metres width by height), the first with ergonomically sized passenger doors, the first with six-abreast seating and the first to be designed with international-standard navigational lights. Soviet and Russian sources credit the type with being the USSR's most impressive civil aircraft overall.

[edit] History

The Il-62 replaced the fast turboprop Tu-114 on long range routes. 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 VC10 are the only airliners with four engines fitted in twinned/paired nacelles by the sides of, and beneath, a "T" shaped empennage T-tail, though the Lockheed JetStar business jet shares this configuration. In the case of Ilyushin, the configuration was handed down by TsAGI, the "Soviet NASA," since Ilyushin's his design bureau lacked the resources to engage in configuration studies. Though offering an efficient clean wing, today the aft-engined T-tail configuration is known to have a number of serious drawbacks. It is tail-heavy, requiring a large and heavy empennage because the tail moment arm is short. Worryingly, aerodynamic wash (shadow) from the wing blankets the tail when the nose is pitched up (at "high angles of attack"). This calls for complex and unreliable (in the 1960s) automatic stall recovery systems such as "stick shakers" and "stick pushers." The Il-62's design alleviates these problems with its four-point landing gear and saw-tooth leading edge, as detailed further below.

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; thrust reversers were added to the outer engines, and the entire installation was slimmed down as production began.

The prototype was grossly underpowered. Its intended NK-8 engines were not ready and small Lyul'ka R-7PB turbojet engines had to be installed temporarily. It crashed during the development programme. The production Il-62 was powered by the originally intended rear-mounted Kuznetsov NK-8-4 engines.

The Il-62M variant (first flight in 1971, introduced in 1973) has more powerful and quieter Solovyov 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 airbrakes which act as ailerons by differential deployment in cruising flight) and the ability to use idle reverse thrust in flight during the final approach so as to shorten the landing run. Nearly all examples in service today are Il-62Ms. In 1978, the Il-62M was further developed to seat up to 198 passengers and carry some two tonnes (4400 lb) more payload and/or fuel than the Il-62M.

A version designated Il-62MK was designed as a much modified medium range machine, though it never reached production and was dropped from the programme by 1978. Other versions were also planned, some "stretched" to seat up to 250 passengers and others suited to small airfields. None of those reached the detail design stage. No civil/military or military developments are known.

The key to understanding the Il-62's design is its "four wheeled" landing gear. The trademark tail prop is there because the aeroplane's main landing gear is deliberately sited ahead of the aircraft's centre of gravity, rather than behind it as in conventional designs. This was done in order to lengthen the tail moment arm (the lever arm over which the tailplane [horizontal stabilizer] acts to control the aircraft in pitch). The longer tail moment arm reduces the size and weight of the tailplane (it is two thirds the size of that of the similar Super VC10), improving controlability and cutting drag. It makes the Il-62 suitable for manual control, since the physical effort needed to fly it is within the capabilities of the average pilot. The Il-62 is the largest airliner with manual flight controls, using steel cables and rods, pulleys, aerodynamic and weight balances, and trim tabs. There are also indications that the Il-62 has a forward-mounted tank for 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.

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, 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. Interestingly, later models of the VC10 (for British United Airways and Ghana Airways) also adopted this feature, in their case closer to the wing tips.

Later examples of the Il-62 are still in regular commercial service, mostly with countries of the former Soviet Union and Eastern Bloc, but also with China, Libya and North Korea. The type also sees service as a VIP/head of state transport.

Like certain other airliners, the Il-62 acquired the public reputation of a "jinxed aeroplane." It suffered a run of spectacular crashes, mostly caused by contagious engine failure (where failure in one engine causes its neighbour also to fail, in the process often causing further damage to adjacent areas).

The type set several international records in its class, mostly exemplifying a range capability far in excess of the conservative Aeroflot calculations applied in Sovet times. Some of these records were set by an all-woman crew of five captained by Iraida ("Inna") Vertiprahova.

A sideline to the Il-62 story concerns industrial espionage. The Il-62 series was developed at about the same time as the British VC10, to which it bears a marked resemblance. Some British sources imply the Soviets stole the VC10 design, occasionally dubbing the Il-62 the "VC10-ski." In fact, the Soviet type is larger, lifts a greater load, covers a longer range, and is suited only to developed airports vis-a-vis the British type's adaptability to "up-country" bases. It is an entirely civil machine, whereas the VC10 was designed to double as an airlifter and/or military freighter. The Il-62 also uses conservative technology whereas the VC10 was a technological wonder.

[edit] Description and Equipment

Conventional all-metal low-wing monoplane of riveted sectional semi-monocoque construction to fail-safe design principles (a structure designed so that failure of one major member does not cause immediate failure of the whole). Life initially set at 30,000 flight hours and subject to extensions and curtailments according to the quality of service procedures, inspection and manufacturer's bulletins.

Pressurised cabin and freight holds. Duplex all-mechanical flight controls, though with twin electric motors for tailplane incidence control. Hydraulic nosewheel steering, landing gear and tail strut actuation, and wheel brakes. The Il-62M has spoilers and lift dumpers which extend automatically upon landing and are hydraulically operated. Control surfaces include a variable-incidence tailplane with dynamically and weight-compensated elevators with trim tabs, triple-section tabbed ailerons (outermost for low speed and innermost for high speed) which are interlinked with a torsion bar, spoilerons (Il-62M), spoilers and lift dumpers, and pneumatically-actuated thrust reversers on the two outboard engines (the reversers are flight-rated on the Il-62M).

27V AC electrics throughout with a TA-6 auxiliary power unit (a turbine generator which supplies electric power and air conditioning on the ground) in the lower tailcone plus backup lead-zinc batteries.

Conventional hot air deicing using engine bleed air. Sea level equivalent to 2,400m/8,000 ft above mean sea level and thereafter reducing to the equivalent of 2,400 m/8,000 ft to cruise altitude. Originally built with no automatic oxygen masks; emergency supply comprises hatrack-housed oxygen bottles and masks for manual distribution to passengers by cabin crew. Since 1997, most aircraft retrospectively fitted with automatic oxygen supply systems with drop-down masks.

Avionics include a Polyot-1 automatic flight control system (a "super autopilot," able to be programmed with a set route which it can fly without human intervention but under constant flight crew monitoring; ICAO Cat. 1 approaches standard, Cat. 2 optional), Doppler navigational radar replaced by triplex INSS (Inertial Navigation System Sets) on Il-62M after 1978 and by GPS (Global Positioning System) navigation sets on many aircraft after 1991, triple VHF and HF flightdeck radios, automatic direction finders, Soviet and Western instrument landing system receivers, vertical omindirectional radio range and radio beacon receivers, duplex radio altimeters, automatic radio transponders, a full ICAO-standard navigation lights fit, cabin tannoy and intercom systems. Soviet/Russian and Warsaw Pact sovereign examples additionally fitted with triplex "Odd Rods" (NATO code name) IFF (identification friend or foe) air defence transponders identifiable by three closely spaced short aerials.

Inflatable life rafts and manually extendable canvas evacuation slides. Most aircraft now retrospectively fitted with emergency floor lighting strips and some aircraft equipped with automatically inflatable evacuation slides. Fire extinguishers sited in engine nacelles, flightdeck compartment, cabin crew rest areas and toilets.

Accommodation for up to 198 passengers in a single-class layout, seated six-abreast at 84 cm/33 inches seat pitch in two cabins separated by a vestibule, galley/pantry and cabin crew rest area. Water closet toilets forward, midships, and aft (3 no). Buffet/bar and a further cabin crew rest area in a vestibule forward. Further optional cabin crew rest area aft. Typical mixed-class accommodation ranges between 128 and 144, seated four or six abreast. First class compartment optionally sited aft of forward entry door or just forward of midships entry door, with an economy compartment further forward in the latter case. "Skycot" fitments in hatracks. Later Il-62Ms (1978 onwards) feature enclosed hatracks. Customer-optionable interior fitments. No in-flight entertainment systems except a tannoy system which may be coupled to an open-reel or audio cassette player. Individual aircraft experimentally fitted with television sets for Soviet-standard videotape entertainment during the 1970s. Some aircraft retrospectively fitted with Western in-flight entertainment (solely audio) systems after 1991.

[edit] Operators

[edit] Civil

The Soviets did not export the Il-62 until initial Aeroflot needs (rapid replacement of Tu-114s on international services) had been met. First exports were in late 1969 to CSA Czechoslovak Airlines. The pattern was similar with the Il-62M, whose first export (to Cubana) was delayed until 1979, six years after Aeroflot service entry. Among Eastern Bloc nations, only Bulgaria and Hungary did not operate the Il-62 series, though the Hungarians briefly leased one pending Boeing 767 services in 1990. This was due, among other reasons, to heavy anti-Ilyushin lobbying by Tupolev in the former country and to commercial considerations in both countries whose airlines preferred to concentrate on short and medium range routes.

Current and past operators include Aeroflot, Air India (lessor), Air Ukraine, Alim Airlines, Alpha Airlines, Aviaenergo, Air Koryo, Centrafricain, CSA Czechoslovak Airlines, Cubana, Dalavia Far East Airways, Domodedovo Airlines, East Line Airlines, Interavia, Interflug, Jetline, KAPO, Air Kokshetau, KrasAir, Libyan Arab Airlines, LOT Polish Airlines, Malév Hungarian Airlines (lessor), EgyptAir, Mavial Magadan Airlines, Mekong Air International, Moscow Airways, New Millennium Air, Quadrotour-Aero, Rossiya Russian Air Transport Company, SAT Airlines, TAAG Air Angola, Tarom, Tretyakovo, VIM Airlines, Uzbekistan Airways, Yana Airlines, and CAAC.

In August 2006 a total of 88 Ilyushin Il-62 aircraft remain in airline service. Major operators include: TAAG Air Angola (4), Air Koryo (4), Interavia Airlines (3), Dalavia Far East Airways (7), Air Kokshetau (3), Domodedovo Airlines (17), Rossiya (8), Uzbekistan Airways (5) and Cubana (11). Some 16 other airlines also operate smaller numbers of the type.^[1]

[edit] Military

The Il-62/Il-62M has no known military applications other than as a personnel or head-of-state transport. However, it is thought to have been used by the air forces of Cuba, East Germany (DDR; the GDR), Gambia, Georgia, Libya, North Korea, Russia and Ukraine. NATO's code name for the aircraft is (NATO reporting name: Classic).

[edit] Specifications (Il-62; Il-62M)

General characteristics

Crew: 5; 3 to 5 (a captain, a first officer, and a flight engineer, plus optionally a navigator and a radio officer on long overwater and/or VIP services to operator specification) plus a four to eight-person cabin crew to operator specifications
Capacity: 150-186 passengers; 150-198 passengers
Length: 53.12 m (174 ft 3 in)
Wingspan: 43.20 m (141 ft 9 in)
Height: 12.35 m (40 ft 6 in)
Wing area: 279.5 m² (282.2 m² with fairings and extended portion of leading edge) (3,009 ft² (3038 ft²))
Empty weight: 67,500 kg (149,000 lb)
Max takeoff weight: 165,000 kg (364,000 lb)
Powerplant: 4× NK-8-4; Soloviev D-30KU turbofans, 103 kN; 108 kN (10,500 kgf/23,152 lbf; 11,000 kgf/24,300 lbf) each

Performance

Maximum speed: 900 km/h claimed (486 kt/560 mph terrain, M0.845 plus confirmed air)
Range: 10,000 km; 11,050 km with full reserves, assuming prevailing winds (6215 mi (3354 nautical miles); 6,868 mi (5964 nautical miles))
Service ceiling: 12,000 m (39,000 ft)
Rate of climb: 5.3 m/s (1,000 ft/min sustained to cruise)
Wing loading: 349 kg/m² (71.4 lb/ft²)
Thrust/weight: 0.259; 0.267