The tremendous achievement of the 747

Last updated 11:16 17/04/2012

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In many surveys, the Boeing 747 is named humanity's greatest engineering achievement. Imagine life without it.

The rest of the world would be a long sea voyage away and tourist numbers would be a mere trickle if it weren't for the ability to transport hundreds of people and tonnes of freight in a single aircraft anywhere in the world within 24 hours.

Consider for a moment what an impressive piece of engineering a Boeing 747 is. Anyone who has sat in the departure lounge with 400 other passengers cannot help but wonder how all these people, baggage and fuel can possibly fly. A fully laden 747 weighs 397 tonnes, has a range of 13,500 kilometres and cruises at a speed of 910 kilometres per hour. Someone from the 19th century, suddenly dropped into 2012, would be awestruck by these facts.

Modern airliners are incredibly safe: you are three times more likely to win Powerball than to be killed in a plane crash. Perhaps the greatest marvel is the 747's four jet engines. This huge aircraft is perfectly capable of flying on two engines. Not only that, but these days aero engine companies such as Rolls- Royce monitor the performance of each of their engines "live".

As you are reading your airline magazine, an engineer sitting in the Rolls-Royce control room in Britain is able to monitor all the operating parameters of the engines on your aircraft in real time. The control room is like a scene from Star Trek, festooned with television screens through which each of the 3000 operational Rolls-Royce aero engines is monitored. Further reassurance for the nervous flyer lies in the fact that aircraft are designed to eliminate "common- cause failures" - for example, separate fuel lines, separate pumps and separate electrical and instrumentation cables are run to each of the engines, so that if a single fuel leak or fire occurred, the fuel and utilities are not lost to more than one engine.

Very occasionally, birds are sucked into jet engines. A well- known test is required before any jet engine can be certified and that is the turbine blades and engine must be able to withstand the impact of a chicken - dead, of course - shot from a large- diameter compressed air cannon pointing directly at the engine inlet. Modern jet turbine blades are (surprisingly) hollow but made of an extremely strong and flexible titanium composite material. Despite the insult of ingesting a chicken, the engine must continue operating; if not, the engine isn't certified.

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Of course all this technology comes at a price, both financial and environmental. A new 747-800 costs about NZ$400 million. It consumes about 12 litres of fuel per kilometre and from Auckland to London its engines will discharge about 560 tonnes of carbon dioxide. Aircraft carbon emissions account for only 3 per cent of that from all fossil fuel emissions; however, the number of air passengers per year is increasing by about 5 per cent.

The head of the International Air Traffic Association has committed to halving the 2005 emissions by 2050. This means there is huge pressure on jet engine manufacturers to make ever more efficient and less polluting engines.

As of January 2012, the European Union included aviation in its emissions trading scheme. This requires airlines operating in the EU and using EU airports to purchase "credits" if they exceed strict carbon emission limits.

China has refused to agree to the EU conditions. However, the EU is hesitant about banning the fastest-growing market in the world from landing at EU airports.

The legacy of the Boeing 747 has been passed on and revised in the form of its successors, both twin- engined, the Boeing 777 and the new Boeing 787.

In the Boeing 787 huge weight savings have been made with the use of advanced composite materials. The 787 is 20 per cent more fuel efficient than its predecessor. Because the airframe of the 787 is not metal, the humidity of the cabin air can be increased to more comfortable levels. High humidity in the cabin air isn't desirable in other aircraft since it promotes rusting of the metal air frame.

The Boeing 787 and its rivals are set to continue this proud and impressive engineering endeavour. The challenge now is to ensure they become more efficient and cleaner.

- © Fairfax NZ News

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