If Boeing’s Sonic Cruiser was meant to be the Lamborghini of commercial jets, the 7E7 is more like the Honda Civic. Its key selling points are fuel efficiency and low operating costs. For Boeing’s engineers, that means reducing manufacturing and maintenance requirements, as well as fuel use, by whittling weight and deploying technological tricks-such as more adaptable software systems and sensors that automatically and cheaply detect structural problems. The 7E7’s 20 percent fuel efficiency boost will come from a combination of new technologies. Almost half will result from the introduction of next-generation jet engines supplied by players like General Electric, Pratt and Whitney, or Rolls Royce, according to Boeing engineers.
But the other half will come from weight reductions stemming from more widespread use of composite materials, more efficient and lightweight electrical systems that will partially replace bulkier pneumatic ones, and from a tweaked aerodynamic shape that reduces drag.
The last Boeing-designed passenger jet, the 777, used some composites. But Boeing says the 7E7 will be the first commercial aircraft the majority of whose main structure, including its fuselage and wings, will be made of these lightweight, superstrong blends of carbon fibers and epoxy. Composites are about 20 percent lighter than standard aluminum alloys and are more amenable to precise shaping (which reduces the total number of parts and saves manufacturing costs). And though composites generally cost 10 to 100 times more than aluminum to produce, Boeing and its suppliers say they have developed proprietary manufacturing technology that could dramatically narrow that gap. Boeing estimates the increased use of composites will alone account for as much as a 3 percent fuel efficiency boost.
Designers expect to lower operating costs even further through improved automated maintenance systems-in particular, advanced structural-health diagnostics. The disaster that befell an Aloha Airlines Boeing 737 in 1988 is a grisly tale familiar to everyone in the commercial-jet business. Tiny cracks that had formed around aluminum rivets resulted in a chunk of fuselage tearing off at 7,200 meters near the coast of Hawaii, sweeping a flight attendant to her death.
After the tragedy, regular checks of commercial aircraft for signs of structural damage were intensified, increasing safety but adding costly, time-consuming trips to the shop. Inspection methods include pouring colored penetrating fluid over the fuselage to reveal any hairline cracks, and exposing the fuselage to sound waves that send vibrations through its skin (the pattern of reflected vibrations indicates if cracks are present). While effective, such inspections can easily add millions of dollars to maintenance costs over the life of a plane.
To lessen the need for these inspections, Boeing says, the 7E7 will likely be riddled with advanced, networked sensors that automatically and continuously monitor structural health. Already, diagnostic sensors are standard equipment on jet engines (see “If It Ain’t Broke, Fix It,” TR September 2001), where they monitor parameters like temperature, pressure, and emissions. And structural sensors are used in some military jets, where installation cost isn’t as much of an obstacle. But now, “The technology is just starting to come along to the point where we can have monitoring technology on the structure of a commercial jet,” says Jenks, the 7E7 technology integration director.
While Boeing won’t discuss the specific kind of sensors it plans to deploy, recent academic and industry research suggests several possibilities. In one leading approach, a patch of ceramic material affixed to the interior of an aircraft’s skin contracts and expands rapidly, sending out vibrations; a sensor detects the wave pattern that reflects back. New cracks provide new reflection points that show up as changes in this pattern. Whatever type of sensors Boeing chooses, their data will be analyzed by software and warnings of potential problems relayed to pilots and ground crews.
Boeing engineers are also rethinking the entire electrical network of the 7E7, hoping to cut back on the maze of wiring found in commercial aircraft. Onboard computing systems are getting simpler and more integrated, requiring less wiring. And wireless technology will play a role, too, in nonessential electronics like flight attendant call buttons. Whereas the similarly sized 767 has 160 kilometers of wiring, the 7E7 would have only 100 kilometers.
The resulting weight savings is modest-equivalent to about eight adult passengers-but the overall benefits of a new electrical scheme are not. “In addition to saving the weight, it’s that much less you have to design, install, and worry about later on,” reducing costs over the life of the plane, Sinnett says.
Boeing’s engineers also plan to take a high-tech, collaborative approach to the design of the plane. The objective is to manufacture the 7E7’s parts in such precise shapes and with such pristine accuracy that many of them can literally snap together. “We call it our Lego airplane,” jokes Frank Statkus, Boeing’s vice president of technology and processes. The Internet is key to achieving such precision. Boeing teams around the world-potentially at sites in Europe, Japan, Russia, and the U.S.-would co-design the 7E7. Despite their far-flung locations, they would all access the same file on a server. “The design lives in one place, where it used to live in 1,000 places,” says Statkus. Eliminating the need to reconcile many versions of a design means fewer tiny errors when it’s finished. What’s more, the digital file containing the final design will be the same file used by suppliers to fabricate the parts. Previously, a supplier would sometimes “have to digitize our picture to tell his machine how to build it,” Statkus says. “This translation sometimes caused errors.”
Long term, the improved design process means a simpler digital catalogue for managing supply chains, as well as more efficient maintenance procedures for the airlines. And it could considerably simplify the process of designing future versions of the plane. All in all, the savings can be counted in the billions of dollars over the decades-long life of the plane design, for Boeing and the airlines that must maintain the planes, Statkus says.