Boeing 787's wing fix passes crucial test, sources say

Boeing's new 787 Dreamliner on Monday successfully completed the wing test the jet failed last May, and now looks set to fly before Christmas, according to two sources familiar with the test outcome.

Engineers are still analyzing data from the repeat test and haven't yet given the official thumbs-up, but the composite fibers in the wing did not delaminate when it was bent to the same point as in the previous test, the sources said.

An initial look at the data suggests the structure performed as anticipated after a complex fix Boeing has worked on since postponing the scheduled first flight in June.

Boeing's current target date for first flight is Dec. 22, according to people familiar with the plan. That hinges on a successful outcome of the wing test.

The company issued a statement confirming the completion of the test late Monday, adding that it will take 10 days to do a full analysis of the results.

During the test, engineers bent the wings on a ground-test airplane upward until they passed "limit load," the maximum load the wing is expected to bear in service.

Sometime next year, the wings will be bent further, beyond "ultimate load," which is 50 percent higher than limit load. That's the level required before the Federal Aviation Administration will certify the plane to fly passengers.

In the previous test in May, at a point just above limit load, the wings had delamination at the ends of each of 17 long stiffening rods, called stringers, on the upper skin of the wing boxes. The fibers ruptured and the stringers came away from the skin.

The damage occurred on the upper skin of the exterior wing at the point where it joins the fuselage. Corresponding damage occurred on the other side of the join on an inner structure called the "center wing box."

Boeing attributed the failure to a design flaw.

Discovery of the damage led company executives in June to cancel a maiden flight planned for the week after the Paris Air Show.

The last-minute cancellation — marking the fifth delay to the plane's first flight — caused consternation among industry observers, and in August Boeing Commercial Airplanes CEO Scott Carson stepped aside, replaced by Jim Albaugh.

Responding to the failure, Boeing engineers first designed a fix that involved cutting a U-shaped piece out of each stringer end to shift the load, then reinforcing each of the stringer/skin joins with fasteners.

They tested it on computer models, then methodically began installing the fix on the airplanes already built.

Installation of the fix on Dreamliner No. 1, the first plane to fly, was completed Nov. 11. The installations were completed on the ground-test airplane and on Dreamliner No. 2 a few days later.

But No. 1 couldn't fly until the bending of the wings of the ground-test airplane was successfully completed.

With that done, Boeing must roll out Dreamliner No. 1 again and repeat some of the systems tests done last summer.

Monday, that jet was moved outside to the fuel dock on Paine Field, where the wings will be filled with jet fuel for initial engine runs and system tests.

After that, the Dreamliner will proceed to taxi tests. Then, barring another mishap, it should be in the air by Christmas.

Dominic Gates: 206-464-2963 or dgates@seattletimes.com