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Plastics offer hope for ultra-efficient aircraft of the future
Source: BI-ME and agencies , Author: BI-ME staff
Posted: Sun July 8, 2007 12:00 am

INTERNATIONAL. The revolutionary materials used to build Boeing’s ground-breaking Dreamliner 787 passenger jet look set to transform the civil aviation industry forever, officials said this week.

Speaking to journalists ahead of the 787’s formal roll-out, Boeing officials declared that the composite plastics that make up around 50% of the plane were here to stay. Jeff Hawk, Boeing’s Director of Certification, Government Relations and Environment for the 787 programme, told journalists he was unaware of any drawbacks to using composites.

Twice as strong as conventional materials, lighter than aluminium and offering greater resistance to fire, state-of-the-art carbon fibre will be used in the fuselage of a commercial passenger jet for the first time with the 787, a medium-to-long range plane capable of seating up to 330 people.

The lighter weight of the aircraft’s component materials allow the Dreamliner to make massive savings on fuel – around 20% less than similar-sized planes – according to Boeing. The US company has also been exploring some radical interior concepts using the new materials (pictured).

With the aviation industry responsible for consuming around 4% of the annual global total of fossil fuels, the Dreamliner’s vastly superior fuel-efficiency is likely to prove attractive to airlines. Carriers flying the plane also stand to make significant reductions in operating costs. The aircraft’s reduced weight means airlines will pay less in landing fees, which are calculated by tonnage.

The durability of composites will also lead to lower maintenance costs, officials say. “Composites don’t fatigue,” said Tom Cogan, the 787’s Chief Engineer. “You don’t have the maintenance problem. Aluminum can corrode, composites don’t corrode.”

Although Boeing declined to predict the lifespan of a 787, they said they expected it to outlast existing passenger jets, which typically remain in service for between 20 to 30 years.

Asked about possible weaknesses in the new materials, Boeing said composites had been used in the beams of long-distance 777 for 13 years and were still in immaculate condition.

“The way it held up over time was exceptional,” Cogan said. “The floor beam was pristine after 12 years.”

While Boeing maintains that the use of composites represented the future of commercial aviation, Cogan added it was unlikely that an all-composite airplane would eventually take to the skies. Metal-based components, for example, would still be used for parts such as landing gear, he said.

Blake Emery, Head of Differentiation Strategy for Boeing, said the striking differences of the new plane’s design would be clearly felt by its passengers. “All of a sudden, we’ve been able to do things that we weren’t able to do,” Emery said, noting that carbon fibre would allow the plane to be equipped with windows up to 65% bigger than standard sizes.

The new materials will also allow the cabin to be pressurised at an altitude of 2,000 metres compared to the standard 2,700 metres of other planes.

The fact that composites do not corrode easily will also enable humidity levels of 15% compared to present levels of around zero per cent, a breakthrough that could make traditional air traveller ailments such as itchy eyes and headaches a thing of the past.

Environmental requirements

The drive for weight saving and new 'green' aviation technologies hit the headlines last month, when UK low cost carrier easyJet became the first airline to outline the environmental requirements that must be met by the next generation of its short-haul 'super-clean' aircraft. Like Boeing, Airbus has pledged to expand its efforts in energy efficiency and it has said it will increase R&D spending by 25% to improve aircraft designs and technologies.

Facing mounting public pressure to become more fuel efficient and reduce greenhouse gas emissions, the airlines are seeking to replace older jets in their fleets with lighter-weight, less-polluting planes. Increasingly, that means jets that replace traditional aluminum components with plastic-based composites that can significantly reduce the weight of an aircraft.

Aircraftmakers, eager for orders, are responding with new designs that make more and more use of these composite materials - much as automakers, sporting goods manufacturers and others have profited handsomely from the revolutionary properties of plastics.

Louis Gallois, the CEO of Airbus, pledged last month to increase spending by 25% to improve aircraft designs and technologies so that by 2020, its aircraft will burn less fuel and emit 50% less carbon dioxide.

Even as global demand for air travel matures over time, several step-changes in technology will be needed to reduce the emissions from aviation in 2050 to below 2005 levels. The futuristic 'easyJet ecoJet' has been presented as the first of these step changes and alone could lead to a stabilisation of emissions from short-haul aviation at 2005 levels until 2035 providing massive environmental benefits. Boeing, too, is investing heavily in developing green technologies, working together with airlines and makers of jet engines to improve fuel efficiency and slash greenhouse gas emissions.

Much of this investment will be devoted to finding uses for new, lighter materials to increase the fuel efficiency of the planes. Both Boeing and Airbus are planning to use composites in at least half the structural components of their latest wide-body jets, the 787 Dreamliner and the A350-XWB.

A composite, broadly defined, is a combination of two or more industrial materials designed to exhibit the best properties of each plus additional qualities that the individual materials do not possess alone.

In the aerospace industry, composites are made of non-metallic fibres - carbon, fibreglass or aramid - embedded in a resin of plastic or epoxy that is molded and then cured in autoclaves at very high temperatures. A material like carbon fibre, for example, is stronger and stiffer than aluminum, titanium or even steel, but its relative weight per volume is half that of aluminum and one-fifth the weight of steel.

Airlines looking to slim down

For airlines, the recent advances in composite technology could not come at a better time. "Our carbon footprint is growing, and that is not politically acceptable," Giovanni Bisignani, CEO of the International Air Transport Association, said last month at a meeting of executives representing 260 of the world's airlines. "Climate change will limit our future unless we change our approach."

While the airline industry says it accounts for just 2% of global carbon dioxide emissions, steady economic growth and increasing demand for air travel are expected to raise aviation's contribution to 3% of worldwide CO2 emissions by 2050.

Rising oil prices, meanwhile, are cutting into airline profits, pushing carriers to demand better performance and longer range from the new planes they buy. According to IATA, aircraft fuel efficiency has increased by an average of 2.5% a year since 2003, saving the industry about US$2 billion a year. But the industry expects its fuel bill to rise to US$119 billion this year, up US$8 billion from 2006, representing 26% of operating costs.

"The biggest thing about composites is that it gets fuel costs down," said Howard Wheeldon, an aviation industry strategist at BGC Partners in London, in an interview for International Herald Tribune.

Airbus says its A350, which is slightly larger than the 787 and still in the design phase and not expected to enter service until 2013, will be made of 52% composites and achieve comparable levels of fuel efficiency to Boeing's Dreamliner.

But lighter planes don't just burn less fuel. Since airport landing fees are partly based on the weight of the aircraft, a lighter fleet can represent a significant cost saving to airlines. According to the IATA, airlines and passengers pay at least US$43.5 billion a year in airport landing fees and other taxes, equivalent to 11% of global airline revenue.

Jet manufacturers say composites also resist fatigue and erosion better than metal, which reduces maintenance costs because regular jet inspections do not need to be as frequent or extensive. According to Jeanne Yu, an engineer who heads Boeing's environmental performance group, maintenance intervals for composite-built jets could be as much as twice as long as those for aluminum planes, although regulators are likely to await proof of manufacturers' claims before approving significant changes to current inspection regimes.

Following the November 2001 crash of an American Airlines Airbus A300, in which a composite tail fin broke off, some air safety experts called for stricter standards for inspecting and repairing composite components.

According to the International Civil Aviation Organization, airlines spent US$41.7 billion on maintenance in 2005, the most recent year for which statistics were available, equivalent to 10% of total industry operating costs.

Besides slashing fuel consumption, "savings on maintenance is the main factor that makes composites attractive to airlines," said Scott Hamilton, an analyst based in Issequah, Washington.

For jet manufacturers, meanwhile, composites can simplify the production process because they allow for the creation of larger, more integrated parts. According to Boeing, this could eventually help speed up its assembly lines by as much as 40 percent. And since composite sections are cast into precise molds, they do not, like aluminum, have to be cut and shaped from sheets of bulk material, which eliminates a lot of waste.

And there are some benefits for passenger comfort. Because they are stronger and stiffer than aluminum, composites make it possible for airlines to increase the air pressure in the cabin significantly. Cabin air pressure in aluminum wide-body jets is typically equivalent to what a person would experience at an elevation of 8,000 feet, or 2,400 metres, above sea level, a factor that contributes to the fatigue that travellers experience on long-haul flights. Boeing says air pressure on the 787 will be the equivalent of an elevation of 6,000 feet, while Airbus plans to pressurise the A350 at 5,000 feet.

The technology of building airplanes has taken quantum leaps forward since Orville and Wilbur Wright's first biplane - made of wood, wire and cloth - lifted off at Kitty Hawk, North Carolina, in 1903. In the decades that followed, manufacturers have experimented, with varying levels of success, with everything from plywood to aluminum, titanium and other strong but lightweight metals.

Boeing began experimenting with fibreglass in the 1960s with the 747 programme, using it on certain control surfaces of the plane, as well as on fairings - the joint where the wing meets the fuselage - and trailing edge panels on the wings and tail.

Boeing's use of these ultra-light materials has increased significantly in the past decade, with the 777 wide-body made of about 11% composites, most of it in the tail section.

Airbus, too, has stepped up its use of composites in the wing and tail sections of its single-aisle A320 family as well as in its widebody A330 and A340 jets. Its 555-seat A380 superjumbo, due to enter service at the end of this year, is made of 25% composite and other advanced materials, offering a weight saving of about 15 metric tonnes, almost equivalent to half the entire passenger load.

"The trend is clearly towards more composite," Jeff Turner, the CEO of Spirit Aerosystems, which builds carbon-fibre and other composite components for Boeing and Airbus, told investors at a meeting in March. "Whether it totally eclipses the metal airplane or not, I couldn't say."

Spirit, which was spun off from Boeing in 2003, is building the all-composite nose sections of the 787 in its Wichita, Kansas, factory. The sections are moulded as a single piece, measuring 42 feet long and 21 feet wide. Spirit is reported to be in negotiations with Airbus about taking control of Airbus's composite wing factory in Filton, UK, and is eager to get a major role in production of the A350-XWB. It already makes some wing components out of composites for Airbus's A320 family.

Boeing and Airbus have so far chosen to use composites in different ways on their latest planes. While the fuselage of the 787 is made entirely of interconnecting composite barrels, the A350 uses a series of panels made of composite 'skin' mounted on a more traditional aircraft frame that is made of a mix of aluminum and composites.

Engineers may continue to debate the relative merits of different composite-designed jets for many years to come. But it is clear that aircraft manufacturing has crossed a technological threshold with the 787 and the A350 that will shape the way all future aircraft are built.

"There is no going back," said Wheeldon of BGC Partners. "Plastic has finally made its mark in the big toys."

 

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