B. M. Purohit
Airbus A380: The making of the superjumbo Airbus A380 is the largest passenger jet ever built. Everything about this airliner from its size to its stateof-the-art technology is superlative. This in-depth article explains how it was constructed
A question frequently asked by the persons who have seen the super giant passenger airliner Airbus A380 on TV is how Airbus Industrie, a joint venture of four European countries has managed to build it ? This question can be better asked differently: Which special features have the aeronautical engineers of Airbus Industrie infused in this largest airliner that it can takeoff with the overall weight of 560 tonnes in an ordinary course and cruise in the rarefied atmosphere at the altitude of 13,100 metres (43,000 feet) above the sea level? Weighing almost 200 tonnes more than Boeing747 Jumbo Jet the sight of gargantuan Airbus A380 sprinting on the runway and soaring gracefully in the sky is in itself a most amazing feature. Therefore, when it took-off for the first time on April 27, 2005 more than 2,500 spectators unanimously hailed it as the 8 th wonder of the world. The real wonder of A380 lies in its
manufacture because it is the aggregation of hundreds of small and large components the automatic doors manufactured stan Aeronautics Limited, Bangalore.
thousands including by HinduThe technical
description of its metamorphosis from the embryonic blueprints into 73 metres (239.25 feet) long airplane having wing-span of 79.8 metres (261.93 feet) and spread of 846 square metres (9,100 square feet) is very interesting. But some basics of aerodynamics should be kept in mind in order to understand the stimulating technical description. In short, it is essential to know the rudiments of how a countless times heavier than air thing can keep on flying and what the pilot has to do for it. Four types of forces namely weight, lift, thrust and drag continuously affect a flying airplane. The most important force is lift which must always be positive. If it is not then airplane cannot remain afloat in the air. This point is worth amplifying but before doing that it is better to make some aerodynamic acquaintance with the remaining three forces. (Refer the diagram no. 1 on the next page). The weight
or the gravitation is a negative force; therefore, its effect must always remain less than that of the lift. The lift is the product of thrust. If the strong wind blowing Safari July, 2008 25
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from the opposite direction is creating sufficient pressure under the wings then only the airplane can get the necessary lift. This does not mean that the lift is not generated when winds are calm. If the airplane keeps cruising at a certain speed then the indirect airflow creates necessary pressure under the wings. In short, the airplane must continuously move forward in order to remain above the ground and for the continuous forward movement it must have an engine. The engine gives it thrust or the push. Thrust being a positive force keeps the plane flying in the air. The third force that applies to an airplane is drag. As the wings of an airplane slice through the oncoming airflow, the air is bifurcated in two streams--above the wings and below the wings. The direction of both the air currents are somewhat divergent, so when they converge behind the rear edge of the wings the convergence creates turbulence. Such turbulence obstructs oncoming airflow. This results an airplane experience a force that pulls it backwards. In other words airplane experiences drag, the force that is opposite of thrust. There is yet another problem which also increases drag. The airflow that comes in contact with the surface of the wings tries to remain stuck to them. This increases the drag. Therefore, aeronautics experts have devised curved and movable flaps in the leading edge of the wings to reduce the effect of drag. (See diagran no. 2) The gap between the leading edge and the flap can be increased or decreased. The airflow that enters this gap and flows hugging the wing surface makes up a separate current of air, so it flows away at a great speed without coming under the braking effect of the other currents. Result: A bumper discount in drag. Lift is the most important force affecting an airplane because strong lift overcomes the force of weight. Distinct shape of the wings plays the key role in creating lift that is strong enough to take even a 560 tonnes giant Airbus A380 up to an altitude of 43,000 feet. Perusal of crosssection of wing reveals that it is not level as many people believe. (See diagram no. 3). The bottom of the wing is largely level but its upper surface is considerably cambered. The wing having such a shape is known as aerofoil. It is not difficult to understand how the lift is 26 Safari
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produced. The airflow has to cover more distance to flow above the wing because of the bulging upper surface. As the given volume of air spreads out over the greater area its pressure decreases whereas the airflow passing beneath the wing has to cover a shorter distance. Hence, greater volume of air in comparatively smaller area increases the pressure. Greater pressure beneath the wing in comparison with lower pressure above the wing naturally creates lift. About 70% of the lift of an airplane is contributed by its aerofoil wings and the remaining 30% is contributed by its streamlined fuselage. But this ratio is flexible and not rigid. It is possible to get considerable increase in the lift by shifting the aerofoil towards the middle, by increasing the area of wings and by making them more swept back. As the speed of airplane increases the lift also increases automatically and on getting the upward push the airplane climbs higher. In other words if an airplane is cruising at the same altitude (say 35,000 feet) at a constant speed then the force of lift against weight, and thrust against drag
Airbus A380 superjumbo are perfectly balanced. Howeve r, an airplane does not fly at the s ame altitude throughout its journey. Its trip always comprises of four s t a g es — t a ke - of f, cruising , landing approach and landing; so the pilot flying an airplane has to use controls like elevators, rudder, ailerons, flaps of wings and engine throttle at various stages as required. All these controls are incorporated in Airbus A380 also. Hence, let us discuss the flying operations involving all the four stages from aerodynamics’ point of view. It will also reveal how much challenging task of designing and manufacturing A380 must have been for the engineers of Airbus Industrie. e - o f f is the first stage. Pilot evenly extends the T a kke flaps of both the wings—the flaps that can be compared with the feathers on the bird’s wings—to increase the area of wings. (See diagram no. 4). Similarly, the flaps on the leading edges of the wings are also extended outward to increase the area of wings further. Only thereafter does the pilot release the brakes and makes the plane run at full throttle against the wind. As soon as tremendous pressure of air lifts the nose wheel in the air the pilot turns the elevators of the horizontal stabilizers (see diagram below) upwards. Obviously the
upturned elevators obstruct the airflow and in the process pressure on the entire tail section increases. As the nose of the plane lifts off the ground the tail assembly also follows suit and the airplane becomes airborne. Cruising is the second stage of an airplane’s journey involving travelling at a constant altitude after climbing up to the desired level. Flaps of the leading as well as rear edges are pulled in to reduce the area of wings. (See photograph on next page). This manoeuvre does not affect the lift because the speed is quite high. Elevators at the rear too must be horizontal during the level flight. An airplane covers most of the distance between the airports by cruising at a level height. o a c h involves reduction in speed Landing appr appro because it is the stage preparatory to landing at airport. The pilot decreases the speed as well as altitude gradually and simultaneously. At the same time he manoeuvres to increase the wing area in order to maintain necessary lift i.e., maintain adequate pressure beneath the wings as the speed gradually decreases. The flaps of the leading edge extend outwards. But the rear edge or the trailing edge takes on a different shape. The flaps of this edge are not horizontal but are turned downward. (See photograph on next page). The reason behind such manoeuvre is simple. Airplane does not have brakes like a motor car so the pilot brings about controlled reduction in speed by increasing the drag. Downward turned flaps boost the obstructive force of drag. At the same time pilot turns the elevators of horizontal stabilizer near the rudder downward so that increasing pressure raises the Safari July, 2008 27
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Cruising: Area of wing is reduced
Landing approach: Rear edges of wing are bent low Landing: Rear edges bent, spoiler flaps turned upward
tail section and tilts down the nose of airplane. Landing is the final stage of air journey and calls for as much alertness and quickness from the pilot as that required at the time of take-off. When the wheels touch the ground the speed of the airplane is so high that it may provide enough lift for airplane to take-off. To avoid such situation pilot raises upward the flaps known as spoilers (see, photograph above) and randomly raises other flaps to create additional turbulence for extra drag. At this time the air pressure on the spoilers is so much that the passengers can actually feel the airplane being pressed to the runway by the onrush of airflow. After the plane has slowed down considerably, the last task for the pilot is to apply the wheel brakes. The world’s first powered airplane Flyer-1 (only 1/1350 of Airbus A380 in weight including the pilot and fuel) that Wright brothers flew for barely 12 seconds on December 17, 1903 had no such devices for control ling it . To many persons including the prominent physicist Lord Calvin, the idea that a heavier than air flying machine can remain afloat in the air had appeared like a castle in the air at that time. Yet within fifty years of Wright brothers’ achievement the world’s first (British) jet airliner Comet flew from London to Johannesburg with 44 passengers on May 2, 1952. Weighing 47.6 tonnes, Comet was 115 times heavier than Flyer-1. However, Comet pro ject had to be d i s c o n t i n u e d subsequently due to some design problems. Some years late r revolutionary passenger airplane Boeing-707 28 Safari
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weighing 360 times more than Flyer-1 took-off for the first time on January 11, 1959. (About 1,200 Boieng707 were going to be manufactured over the period of time.) Aeronautical engineering experts of USA took another quantum leap on February 6, 1969 when 365 tonnes giant Boeing-747 Jumbo jet having maximum 412 seats took-off. Whether their moth sized contraption, Flyer-1, could even remain airborne was a question about which Wright brothers were not fully confident themselves whereas the weight of Boeing-747 was 880 times more than Flyer1. (A well-known American daily reporting on the maiden flight of Jumbo jet ran the headline above its picture, ‘Look! It flies!’) Jumbo jet’s record in respect of the enormity was broken 13 years later by a 405 tonnes Russian airplane Antonov-124 on December 26, 1982. For 23 years this giant, 975 times heavier than Flyer-1, occupied the pride of place in Guinness Book till it was dethroned on April 27, 2005 when Airbus A380 soared in the sky for the first time to become numero uno as the heaviest airliner. Ever wondered what 560 tonnes mean? India’s main battle tank T-90 weighs 46.5 tonnes and large railway wagon weighs 22.6 tonnes. MIG-21 at the take-off weighs 9.5 tonnes. The weight of ISRO’s PSLV rocket capable of launching a 1,200 kilogram satellite in 817 kilometres high orbit is not more than 295 tonnes. Even the lethal Veer class corvette of the Indian Navy weighs no more than 450 tonnes. In comparison with these mega machines A380 is a real heavyweight that not only flies but is specially meant for long haul trips might seem unbelievable to many. The European engineers o f Airbus
Airbus A380 superjumbo Industrie have infused each of its components with new technologie s special ly developed for this airplane in order to make it a flying machine. A380 has four main sections like other airplanes: Fuselage, wings, engine and landing-gear. Fuselage: Airplane’s long cylinder shaped passenger compartment with the cargo hold beneath is known as fuselage in technical terminology. One might call it torso of the airplane. Hence, it must be very tough. But in order to increase its toughness there should no t be undue increase in weight. One obstinate principle of physics lays down that in order to increase the toughness of a substance if its thickness is doubled then its weight increases by three times. It is no t sensible to overlook this principle because considerable increase in weigh t will necessita te larger (and bringing about further increase in weight) wings which in turn will necessitate more powerful and heavier engine. In order to avoid such vicious circle the engineers had to get special composite substances made for Airbus A380 to make each airplane suf ficiently durable for 19,000 flights involving 1,40,000 f lying hours spread over its life-span of 25 years. One such special composite substance was carbon fibre, another was quartz (crystalline) fibre, third was glass fibre and still another substance specially
FOR YOUR FACT FILE As all the airplanes are not of the same kind, Airbus-380 qualifies for the accolade as the largest among passenger airplanes. Actually, R ussian freighter An tnov-225 Mriya (dream) has already established the world record of 600 tonnes on March 22, 1989. One might call this plane a deluxe variant of Antnov124. R ussia had manufactured only two Antnov-225 to ferry piggyback the Russian space shuttle named ‘Barun’ from the landing strip to the launching pad but she has little use for them now. From the point of view of the internal volume the largest airplane is Airbus-300-600 ST. This plane is a freighter
and has been manufactured mainly for the transportation of the components and sections of Airbus-380. 1,400 cubic metres (49,400 cubic feet) double-decker cargo hold can carry maximum 47 tonnes load.
invented for this airplane after lengthy research and named Glare (Glass Aluminium reinforced). See diagram no. 6. Al l these substances contributed in reducing the weight of Airbus-380 without jeopardising its toughness. The most revolutionary substance was Glare which in the form of a 0.375 millimetre thick layer o f ad hesive s andwiched between aluminium and glass fibre sheets imparted tremendous toughness. Although used liberally in the manufacture of fuselage it comprised only 3% of the airplane’s weight. How much reduction was achieved in weight due to Glare? Only 500 kilograms or ½ tonne. But it obviated the need for enlargement of the wings and heavier engine s, no mean advantage in aviation technology. Fuselage was manufactured in Hamburg, Germany with about 4,500 small and large components. Being a double-decker the
If the giant size of the wings were the criterion for determining the largest overall size, then the largest airplane was ‘Spruce Goose’ manufactured by an American billionaire industrialist-cum-aviator named Howard Hughes in 1947. Specifications: Propellers 8, weight 193 tonnes and wing-span 97.51 metres (319 feet 11 inches). See, diagram. It flew only once and gained the maximum altitude of 70 feet above the sea level before plunging in the shallow sea never to fly again. Safari July, 2008 29
Airbus A380 superjumbo beyond a limit decreases the lift, so the engineers increased their width to have a wing area of 846 square metres (9,100 square feet)—sufficient to mark 10 badminton courts on it. Measuring 45 metres along the leading edge the manufacture of each wing involved acc urate assembling o f 32,000 components including one dozen flaps. One important part of each wing was the fuel tank of 36,500 litres capacity. With 73,000 litres fuel in the wings and 2,42,290 litres in the larger tank in fuselage making in all an abundant fuel storage capacity of 3,15,290 litres the Airbus A380 has an enviable flying range: A380 has the largest wing-span than any other airliner in the world 14,800 kilometres. fuselage was really large measuring 10 metres (32 feet One amazing fact about A380 is that although each 9.5 inches) in height, 8 metres (26 feet 4 inches) in width wing has to bear burden of 280 tonnes including its own and spacious enough to accommodate 550 passenger weight, it is fitted over only 15 centimetres long bracket seats. Combined floor space of both the decks was 35% jutting out from the fuselage and the connection is greater compared with Jumbo jet. Among the movable cemented with adhesive and reinforced with rivets. The components of fuselage 16 doors requiring much strength wing overlaps the bracket by a mere 15 centimetres (5.9 and precision engineering were manufactured by inches) but the joint is so sturdy that during the take-off Hindustan Aeronautics Limited, Bangalore. This company and landing, or in an air pocket (partial vacuum in the had manufactured 300 doors for Airbus-320/321 earlier, air) in the sky even if the tip of the flexible wing bobs so it was successful in securing fresh order for 1,000 doors up and down as much as 9 metres (29.5 feet) the joint @ Rs. 3,80,000/- per door. on that 15 centimetres bracket will not become loose. Wings: The task that turned out to be most difficult Engineers of Airbus Industrie had more confidence in in the manufacture of Airbus-380 was the fabrication of chemical bond of the adhesive than on rivets. Even its wings. Engineers wanted wing-span of 82.5 metres 12,850 kilograms combined weight of both the jet to ensure adequate lift for this giant flying machine. But engines hanging from the wing cannot loosen the joint. an international accord regarding safe distance between After attaching the wings spacious enough to park 38 the wings of the aircraft parked at airports stipulated a motor cars on each one the engineers fitted smaller wings box of not more than 80 x 80 metres per airplane. This known as horizontal stabilizers near the tail. Any guess accord tied the hands of engineers. They were compelled about their size? It may appear unbelievable but the fact to shorten the wing-span to 79.8 metres. To compensate is that even horizontal stabilizers of A380 have greater for the resultant reduction in the wing area and span than the wing-span of large passenger airplanes consequent decrease in lift the wings were given some like Boing-737-400 that fly on the trunk routes connecting more backward sweep. The backward sweep of wings the metropolitan cities. Horizontal stabilizers of A380
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Airbus A380 superjumbo have a span of 30.37 metres against the latter’s wingspan of 28.88 metres. Even the vertical stabilizer having the rudder attached to it is 14.6 metres high and its upper tip’s height is equal to 9 storeys from the ground. Engine: Hurling a 560 tonnes airplane at the speed of 900 kilometres per hour is a herculean task beyond the capability of even Jumbo jet’s engine that can generate the maximum thrust of 58,000 pounds/lbs. Like almost every component of A380’s frame that had to be specially made in view of its mammoth size, especial fabrication of supremely powerful jet engine became indispensable. After 5 years of research Rolls-Royce Company of the UK fabricated a 15 feet long engine named Trent-900 that was able to generate thrust of 70,000 lbs (equivalent to total power generated by 3,500 Toyota Corolla cars). Weight of the engine: 6.43 tonnes. Now a brief two-sentence explanation of the design and working of passenger jet plane’s turbofan engine: A multi-blade turbine in the front of turbofan engine draws oncoming airflow, compresses it and crams it into the combustion chamber where fuel is squirted on the compressed, hot air to burn explosively. (End of the first sentence). The exhaust gases released by combustion forcefully rotate the turbine before ejecting from the back of the engine giving a forward thrust to airplane and in Super power engine for super the meanwhile turbine shaft rotates the multi-blade airplane: Rolls Royce Trent-900 turbine to pump-in more air in the combustion chamber. (End of the second sentence). out a practical experiment. They tied explosives on one Designing and fixing turbine blades of Trent-900 of the blades and ran up the engine to give the maximum engine was a challenging task for the aeronautical 80,000 lbs thrust and then triggered the explosion. engineers of Airbus Industrie. Each blade made of The turbine blade got dislodged but the engine casing titanium alloy was to be fixed to the shaft of the trubine effectively blocked it from flying out. Had it not done so in such a way that none gets dislodged due to then it was certain that 16 airlines including Kingfisher tremendous centrifugal force while shaft is rotating at Airlines of India would have cancelled the orders for many high speed. If, by chance one or two blades dislodge and of the A380 airplanes booked by them. Landing-gear: Can you figure out how hit the fuselage the many wheels are required to bear 560 tonnes safely of the plane weight of A380 ? Answer: 22. and the passengers These wheels are parcelled among five clusters on board would be making up the landing-gear or undercarriage. jeopardised. In order Two large clusters of 6 wheels each are under to ensure that the the fuselage and two more with four wheels each damage is minimal support the wings. The most important (and also in case o f such a the one used for steering) landing-gear having mishap the casing of only two wheels is in the front beneath the the jet engine must cockpit. Since there is hardly anything about A380 be sufficiently stout. that is not superlative hence, its landing-gear Good enough to with the clusters of heavy wheels and stout shock prevent the uprooted After fitting all the 24 blades in Trent-900 engine the absorbers does not have a match in the world of blade from f lying diameter of its fan became 3 metres aviation. Each six-wheel landing-gear weighs 6.5 out. The engineers tonnes. (The air pressure in each pneumatic nose wheel did not want to take any risk about the safety of 550 is maintained at 350 bar i.e., about 350 times more than passengers and dozens of cabin crew. So they carried Safari July, 2008 31
Airbus A380 superjumbo atmospheric pressure at the sea level). After the takeapprehension pertains to a mishap in the air. Designed off all the clusters of landing-gear are retracted in their to carry 550 passengers to start with and the maximum respective holds in the fuselage and wings. In view of of 800 passengers later on, if A380 meets with an the size and weight of the landing-gear of A380 its accident the probable loss of life that can result boggles operating by hydraulic the mind, whereas sys tem becomes mere though t of indispensable like other collision between two airplanes. Therefore, A380 is simply spinesuperior hydraulic system chilling. The second employing 5,000 lbs per apprehension pertains square inch pressure is to mini- cyclone like installed instead of 3,000 conditions created by l bs per square inch. A380 as it takes-off in Operation of flaps and the air. As this airplane spoilers of the wings, ascends the sky ailerons or horizontal thous ands of cubic stabilizer and rudder on metres air is compelled the vertical stabilizer are to move aside. But after made possible by the airplane has passed hydraulic system only. on the gusts of wind High-tech h ydraulic rush in from all around Clusters of A380’s landing-gear wherein each wheel has diameter of 23 inches sys tem multiplies by to fill the void and the many times little physical efforts made by the pilot when turmoil they create is no mean thing. flying an airplane. During the test as the A380 took-off after racing down Airbus A380 is 36% larger than Jumbo jet. However, the runway a mini tornado following in its wake tore-up only two pilots (commander and co-pilot) are adequate a garden parasol in the compound of a house outside to control its reins. State-of-the-art computer system the airport and flung it 65 feet away. This was caused by powered by the aeroplane’s 150 kVA generator set keeps the mass of air at the ground level that had rushed a watchful eye and provides feedback on the performance upward to fill the void. Another obvious problem is that of nearly 25,000 moving components on eight 15” x 20“ a smaller airplane cannot take-off till the turbulence LED screens in the cockpit. During long distance journeys created by A380 subsides. Yet another question is: How there are periods when the commander and co-pilot do many airports in the world can handle A380? The not have to attend any work pertaining to flying the plane infrastructure like 2.9 kilometres long runway is available because A380 is equipped with fly-by-wire control at the international airports only. Similarly, the task of system. Once necessary data in respect of altitude, speed managing 550 passengers and their luggage in a short and course are furnished in the flight computer of A380 time is difficult indeed. the computer takes-over the charge of flying operations Be that as it may, didn’t such questions arise when and continuously monitors them. If the feedback received Boeing-747 Jumbo jet was brought into service in 1970? indicates any deviations from the pre-set parameters In spite of many problems and objections posed at that then the computer system activates appropriate time, most of the airlines and airports world over have corrections. In short, the flight computer constantly got used to it. Not only that but having been surpassed compares the feedback on the by Airbus A380 by a margin Air turbulence left behind by the passing giant passenger airliner actual performance of the of 185 tonnes calling it components or systems with the Jumbo is also a misnomer. parameters and instructions given In the meanwhile Airbus by the pilot. Industrie are upbeat about After such in-depth description of the future of A380 and the superlative aspects of A380 does main tain that many anything more remain to be said? airlines and airports will There are some apprehensions to become accustomed to this which the engineers of Airbus superjumbo within two or Industrie might not agree. The first three years. 32 Safari
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