After 10 days of engineering analysis, Boeing said Wednesday that "all test requirements were successfully met" during last month's extreme wing-bend test performed on the 787 Dreamliner.
On March 28, Boeing bent the wings of a test Dreamliner to "ultimate load," which is set by the Federal Aviation Administration at 150 percent of "the most extreme forces the airplane is ever expected to experience while in service."
During the test, hydraulic actuators flexed the carbon-fiber reinforced plastic wings upward by approximately 25 feet while simultaneously pulling down on the fuselage, which was pressurized to 1 1/2 times its maximum normal operating pressure.
Passing this test — maintaining the airframe's structural integrity up to that extreme load — is a key milestone in certifying that the airplane is safe to fly.
"The airframe performed as designed and retained the required structural integrity," said 787 program chief Scott Fancher. "This is further validation that the 787 performs as expected, even in the most extreme circumstances."
The assembly bay where the test took place was evacuated during the event. About 100 people watched the test from a control room, including FAA personnel monitoring the outcome.
In a video of the test posted at Boeing's Web site, 787 chief structures engineer Jim Ogonowski described the moments when the wing approached ultimate load as "the quietest 90 seconds on earth in the control room."
But once the required load was reached and held, then released, spontaneous applause broke out and the video shows Boeing engineers shaking hands and congratulating one another.
Boeing spokeswoman Lori Gunter acknowledged that the airframe did not reach the ultimate load limit unscathed, nor is it expected to.
"At extreme stress levels, damage can be expected and is anticipated in the design," Gunter wrote in an e-mail.
The formal FAA requirement is that despite any localized damage, the overall airframe structure "must be able to support ultimate loads without failure for at least three seconds."
The regulation anticipates some "deformation" of the airframe under this extreme load. This is acceptable provided the effects of deformation are not significant and the outcome is as predicted in pretest computer modeling and analysis.
Ten days of analysis were necessary to show that the Dreamliner met that standard.
"It held structural integrity, which is the requirement," Gunter said. "It held the load. It didn't break."