Winner: Carbon Takeoff
With a radical carbon-fiber composite wing, Boeing is pushing the envelope of aviation design in its new 787 jetliner
Sometime next year, the first Boeing 787 Dreamliner will rise into the skies above Seattle. The takeoff will probably be like any other, but the plane sure won't.
Why? One word: composites.
The midsize, wide-body 787--whose overall design Boeing finalized just a few months ago--is the first commercial jet to have fuselage and wings made almost entirely of advanced, plasticlike materials known as composites. Composites are mixtures of resins and high-strength fibers of carbon, boron, graphite, or glass. They are generally lighter, stronger, and more resistant to fatigue and corrosion than the aluminum alloys widely used in planes today. In the 787, Boeing is using mostly carbon-fiber composites, which in smaller quantities are found in items such as high-end bicycle frames and the fenders of expensive sports cars.
The aerospace industry has sought to use more and more composites instead of metal to create more agile and fuel-efficient aircraft. These new materials have been going into military planes for decades, and in recent commercial aircraft they account for 10 to 25 percent of the total weight; they are used in small fuselage components, tails, and select portions of the wings, such as trailing-edge flaps.
Composites make up half the weight of the Boeing 787, shown here in an artist's rendering.
But fully half of Boeing's 250-seat Dreamliner will be composites [see photo, "Bold Bid"]. The company says that thanks to the new materials, an improved aerodynamic design, and better engines and onboard systems, the 787 will burn 20 percent less fuel than comparable jetliners and have maintenance costs 10 percent lower.
For Boeing, still recovering from a 2003 government-contract scandal and the forced departures of two consecutive chief executives following accusations of unethical conduct, the composite strategy is part of a bold bid to regain leadership of the US $50-billion-a-year worldwide market for commercial planes. The Chicago-based company, which in the 1950s introduced the hugely successful 707 passenger jet, reigned supreme in that market for decades. Two years ago, however, its archrival and only real competitor, the European jet maker Airbus SAS, in Blagnac, France, surpassed Boeing to become the world's largest commercial plane maker as measured by total revenue. It was hardly a shock: Airbus's ascendancy came years after it began introducing planes widely considered to be technologically superior to Boeing's offerings.
But more recently, while Airbus focused on size with its gigantic 555-seat, four-engine A380, Boeing instead chose to emphasize efficiency. The two-engine 787 will be able to fly long routes previously possible only for jumbos, a capability that analysts say is proving appealing to today's cost-obsessed airlines.
"Boeing put money into developing the most efficient small long-range plane yet--and it's worked out very well," says Richard L. Aboulafia, an analyst with aerospace consultancy Teal Group Corp., in Fairfax, Va. "I call it arguably the best industrial counterattack in the past 30 years."
More than just another all-new plane, the 787 represents an evolutionary transition for Boeing's commercial unit: from a traditional plane manufacturer to a global systems integrator. The company recruited contractors all over the United States and in Australia, Canada, China, Italy, and Japan, to help not only manufacture but also design the new plane. It's an ambitious project with a number of firsts in commercial aviation. At the top of that list is the design of the 30-meter-long composite wings.
On Boeing's sprawling compound in Everett, outside of Seattle, are two identical four-story white buildings with ample blue-tinted windows. It's here that the 787's composite wings are taking shape. From a windowless office overlooking a labyrinth of cubicles inhabited by a troop of engineers, the wing design team leader, Mark Jenks, directs the work. [See photo, " Winging It."]
"Over the last 10 years or so, design tools for composites have improved significantly," Jenks says. "It's not such a black art anymore." He and his team began the design work using supercomputers in which they ran computational fluid-dynamics software to simulate the effects of wing features and geometries. The goal back then was to determine which designs had the best aerodynamics. The computer simulations were complemented by thousands of hours of tests in a wind tunnel.
Jenks says that now the group is preparing for a series of tests that will help validate the design. One involves building a large section of the wing and attaching to it hydraulic actuators and strain gauges to assess its structural behavior. Another involves measurements to make sure the wing will have adequate conductivity characteristics and resilience against lightning strikes.
Lightning strikes on aircraft are not rare events; one study in the 1980s found that, on average, a commercial airliner is hit by lightning at least once a year. The historic tradeoff with composites, from an aviation standpoint, is their inability to conduct electricity without the addition of metal, which lessens their advantage in weight. Aircraft wings--and, indeed, fuselages, tails, nacelles, and other structures--need to conduct electricity to enable the plane to withstand lightning strikes, which generally flow over a conductive aircraft without doing any damage.
Boeing recently completed what is known as the plane's "firm configuration." Reaching this stage means that structural, propulsion, and systems architectures are not changing anymore, and the final shape of the wing has been set. Starting around last September, a group of suppliers began working on a detailed design of the hundreds of parts needed to assemble the wing, from large structural spars to thin covering skins of carbon-fiber composite. To produce that detailed design, Boeing partnered with three "heavies" of Japanese industry--Mitsubishi Heavy Industries, Kawasaki Heavy Industries, and Fuji Heavy Industries.
Jenks says that for past planes, Boeing followed a "build to print" model: the partners would come in only at a later stage and would basically fabricate the parts according to Boeing's specifications. But for the 787, the partners were brought in about four and a half years earlier, which gave them enough time to participate in the early design work and provide input based on their manufacturing expertise. The scheme also let Boeing spread the risk, because the company's partners picked up a sizable portion of the development costs in exchange for a bigger share of the profits that will accrue if the plane is successful.
The Japanese wing design team worked side by side with its U.S. counterparts at Boeing's Everett facility until a few months ago. That was when some of the engineers began returning to Japan to start the work of elaborating in detail the shapes, material composition, and types of joints and attachments of the parts they were responsible for. Boeing engineers, meanwhile, shifted into their role of overseeing the integration of the plane's fuselage, wings, and tail.
The teams are creating their drawings and specifications using a system called Catia, developed by Dassault Systèmes, in Suresnes, France. Catia is widely used in the industry, and engineers in Japan, Italy, Australia, and Everett will share the files though a global network. And, of course, team members will also stay in touch by videoconference. "We've got half a dozen clocks in our conference rooms," Jenks says. "First it was kind of a gimmick, I think, but it got to the point where we really needed them."
A wing is basically a cantilever beam consisting of three main structural parts. The largest one is the main box, the framework spanning from the fuselage to the wingtip that is the core of the wing and supports most of the load. To this main box, structural appendages called the leading and trailing edges are added to the front and back to give the wing its aerodynamic shape.
For a plane maker, the wing is "really the heart of the whole airplane and the reason that you build a new one," says William Mason, an aerospace engineering professor at the Virginia Polytechnic Institute, in Blacksburg. The design of a composite wing, he adds, "is a big change, but it was going to happen."
"The properties of composites that can give them a leg up in terms of design is first of all the reduced weight," says Paul A. Lagacé, a professor of aeronautics and astronautics and codirector of the Technology Laboratory for Advanced Composites at the Massachusetts Institute of Technology, in Cambridge. Other advantages of composites, he says, include their resistance to corrosion and fatigue--the two biggest problems that plague airplanes--and their "wonderful flexibility in design."
In the 787 wing, Jenks and his team took full advantage of this flexibility. A metal wing is a compromise between aerodynamic performance and weight. With composites, the compromise is the same, but designers are free to investigate a much larger envelope of sizes and shapes. Composites, Jenks says, allowed them to tailor features that wouldn't be practical with metals, such as subtle curvature variations all over the wing. They also make it possible for the team to create larger and more complex structures, reducing the total number of parts and making assembly less time-consuming.
Moreover, Jenks's team was able to make the 787 wing thinner than it would be with metal. Under the flight conditions of the 787, thinner wings are aerodynamically better, because they can produce the same or more lift than thicker wings while reducing drag. With metal, however, there is a tradeoff: as you shrink the wing, you need to add stronger--and thus heavier--structures. But with composites, the Boeing engineers were able to add strength only where necessary, and in the end they got a thinner and lighter wing.
Boeing officials decided to go with an all-composite wing for the 787 only after years of experience with composite structures in previous planes, notably the tail of the 777, which has been operational for a decade. Also, the company had done extensive design work on the Sonic Cruiser, the much-hyped jet with large composite wings that would have flown at close to supersonic speeds but which Boeing canceled in late 2002.
Those projects helped Boeing engineers better understand the advantages of composites--and also their drawbacks. Problems vary from moisture absorption that can reduce stiffness to tiny fissures that can go undetected and result in abrupt, larger cracks. And then there's the simple fact that designers have more experience with metals. In fact, Boeing is using aluminum, steel, and titanium in some parts of the 787.
Another issue Boeing needed to address was cost. Until now, only military projects could afford composites. Prices for these materials have steadily dropped but remain much higher than those for metal, on the order of $100 or even $200 dollars per kilogram versus a few dollars per kilogram for metal. Moreover, their fabrication requires new tools and methods, while making aluminum parts is easier and cheaper. Boeing's plan is to benefit from economies of scale and also from reduced part count.
Meanwhile, the Japanese partners, which will be charged with actually manufacturing the wings, are getting ready for production at their plants near Nagoya, one of Japan's main industrial centers. Mitsubishi is working on the main wing box, Kawasaki is doing part of the trailing edge, and Fuji is making the so-called center wing box, which is a heavily reinforced structure inside the fuselage that secures the wings and holds the landing gear. (Spirit AeroSystems Inc., in Tulsa, Okla., is making the leading edge, and Hawker de Havilland Ltd., in Bankstown, Australia, is making the rest of the trailing edge.)
The Japanese expertise with composites comes from a variety of projects, among them the F-2 attack fighter, for which Mitsubishi designed and built composite wings. Japan has also chalked up experience in building space vehicles, helicopters, trains, and other transportation systems. But even for the three Japanese companies, making the 787's wings is a big step in terms of scale and complexity. All three are expanding their plants, with Mitsubishi alone spending $768 million, half in R&D and half to build a new facility capable of fabricating the 787's parts.
The fabrication of a composite part begins at a large automated stacking machine that lays sheets of composite material on top of a mold known as a layup mandrel, which gives the part its shape. Next, the piled sheets go into an immense autoclave, which is essentially a pressurized oven that cures the sheets together. After the part undergoes some trimming, polishing, and painting, it is ready for use.
Boeing is also enmeshed in the tests required to make sure it will get the wing it needs. Later this year, a group of engineers plan to perform a series of lightning experiments in a laboratory to assess the 787's ability to withstand direct strikes.
A lightning strike can damage the composite material and also produce a voltage surge that, in theory at least, can interfere with electronic equipment, such as flight-control computers. But the most serious problem would be a spark inside the fuel tanks, which are usually located inside the wings. In 1963, the left wing of a commercial airliner exploded over Maryland, resulting in the deaths of all 81 onboard. An investigation ruled that lightning was the cause of the explosion.
"The idea with lightning protection is you really want to get the current spread out over large areas," says Edward Rupke, a senior engineer at Lightning Technologies Inc., in Pittsfield, Mass. With a metal fuselage and wings, he says, the electricity will do just that, dispersing without much problem. But composites do not conduct as well as metal, and some don't conduct at all.
Rupke says the usual solution is to add aluminum or copper sheets or meshes to the surface of the plane. These metallic laminates provide a conductive path for the electrical current, which for a potent strike can reach 200 000 amperes.
Boeing says that even though no one has ever built such a large composite wing, lightning protection solutions already available will work for the 787. The company declines to give any details other than to say it will embed a metal mesh throughout the entire surface of the wings.
In their tests, the Boeing engineers will use special high-voltage equipment to produce lightning and hit a large piece of the composite wing. They will then measure the electric current levels around the wing's surface and analyze the extent of damage to the material, using nondestructive inspection techniques that involve ultrasound, X-rays, and thermography.
"We'll actually get some very serious current put through it," Jenks says. "We want to validate that there's no way for that current to get into the wing itself."
If things continue on track for Boeing, the first 787 jets will be certified and enter service in 2008. The company says parts will come in from all over the world to its facilities in Everett, where the final assembly of a 787 will take only three days.
The development of any large new plane is risky. Estimates for the development costs of the 787 range from $8 billion to $10 billion. Boeing is expected to spend $5.8 billion, with its partners kicking in the rest. The project seems on target so far, but Boeing's previous projects have often suffered from delays and cost overruns. And a few observers worry that Boeing has outsourced so much of the 787 that someday it may find itself competing against a Japanese company--Mitsubishi, for instance--in the market for commercial airliners.
And, of course, Airbus isn't standing idly by. Not long after Boeing announced the 787, the European jet maker said it was going to develop the two-engine A350, which will have large composite wings. Airbus has ample experience with composites and other advanced materials, such as Glare, a laminate of aluminum, fiberglass, and epoxy. But because the A380 is keeping Airbus quite busy, the A350 won't take flight before mid-2010. At press time, Boeing had 293 firm orders and commitments for its 787, versus 143 for the A350.
When the first 787 takes off for its inaugural flight, the wing design teams in Everett and Nagoya will savor the moment with a mixture of contentment and relief.
"If you look at what they're doing, there's an awful lot of risk there," says Teal consultant Aboulafia. "If it works out, though, this would be one of the most successful industrial programs we've seen in years."
Boeing 787 Composite Wing
Goal: Design a wing made primarily of composites instead of aluminum for the new 787 jetliner.
Why It's a Winner: The new wing is lighter and more resistant to fatigue and corrosion than aluminum wings. It will help save fuel and lower maintenance costs.
Organizations: Boeing, Mitsubishi Heavy Industries, Kawasaki Heavy Industries, and Fuji Heavy Industries.
Centers of Activity: Everett, Wash., and Nagoya, Japan.
Number of People on the Project: Confidential.
Budget: Confidential (estimates for the whole plane range from US $8 billion to $10 billion).