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Feature Story

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BOEING/Bernard Choi

A 787 Dreamliner is strapped inside a test rig in Everett, Wash.. The structural airframe will be poked and prodded over the next three years.

Strapped in, 787 Dreamliner undergoes fatigue testing

By Bernard Choi

As he gazed at a 787 Dreamliner mounted in a metal cage and attached to hundreds of mechanical devices, Peter Brownlow recalled his childhood.

Rectangular pads

Boeing/Bernard Choi

Rectangular pads allow engineers to distribute loads evenly onto the leading edge of the 787's wing. More than 100 mechanical devices are connected to the plane's exterior to simulate the pounding the airframe will face during its lifetime.

"Every kid's dream is to build something and then try to break it, right?," asked Brownlow, the fatigue testing conductor for the 787 program. "In essence, that's what we're doing. We take an airplane and we try to put it through its paces and try to break it at the end."

Brownlow and a team of engineers recently began an extensive program of twisting and tugging a 787 structural airframe. The ongoing punishment will simulate more than 100,000 flights.

Unlike static tests, which push the airplane to extreme loads to see how well it handles in once-in-a-lifetime emergencies, fatigue tests show how the structural integrity stands up to the day-in, day-out stresses that build up over thousands of flights spread out over decades.

"We're demonstrating the durability of the airplane," said Ray Clark, the 787 static and fatigue test director. "We're checking our structural maintenance procedures so we do them first on this airplane before an airline has to. And we validate that we do have inspection techniques where we can find any cyclical damage well before the fleet will experience it."

The process continues seven days a week for three years as engineers push and pull on the control surfaces over and over again.

To simulate multiple flights, Boeing engineers direct mechanical devices to apply pressure to selected spots on the airframe's surface, from the leading edge of the wing to the tail fin to the fuselage.

"The devices impose loads typical of backing off the gate, taxiing out, taking off, climbing, cruise, experiencing a storm, descending, landing, taxiing back to the gate," said Clark. "So we mimic the ground-to-air-to-ground cycle of an airplane in service."

Boeing engineers monitor

Boeing/Bernard Choi

Boeing engineers monitor the loads being applied to the 787 structural airframe from a nearby control room.

Since airlines will use the 787 on very different routes, stress analysts designed several flight profiles to recreate the range of conditions the airplane is likely to face over its lifetime.

The process continues seven days a week for three years as engineers push and pull on the control surfaces over and over again. When all is said and done, the airplane will have "flown" about three times the number of flight cycles a 787 is likely to face in its lifetime. It's part of the exhaustive program to certify the Dreamliner.

"It's certainly a long campaign," said Brownlow. "There's a lot of pride involved to be part of a program like this and to help usher it into the public and see people flying it safely." .