Another 787 design flaw — but no delays, says Boeing

Boeing said Monday a design flaw will require extensive rework on the rear fuselages of almost all the 787 Dreamliners already built.

But the problem will not delay the Dreamliner flight-test program or the scheduled first delivery later this year, spokeswoman Yvonne Leach said.

Leach said Boeing discovered that repeated heating and cooling of the fuselage tube could loosen the aluminum shear ties that attach circular frames to the rear fuselage skin. Loosening those ties could potentially let the frame pull away from the skin.

The composite frames line the inner fuselage at regular intervals to make the fuselage skin a rigid tube.

"We are replacing portions of 12 shear ties," said Leach, and in addition "there are many other shear ties in the (rear fuselage) section where we have to add parts to strengthen them."

"The good news is the location of the shear ties that need to be fixed is easily accessible," Leach said. "Even if the airplane is fully built, you'd just have to move some insulation."

For airplanes already built, Boeing's retrofit solution will reinforce the shear ties with small parts. Leach said these parts include "a big thick square washer" that fits into the angled corner of the shear tie.

A permanent fix using thicker shear ties will be incorporated from Dreamliner No. 55 on, Leach said.

The retrofit is already being installed on the rear-fuselage sections being built in Charleston, S.C., for airplanes No. 23 and 24.

The same fix will have to be retrofitted on all the airplanes already assembled, except for the first three now in flight testing. Those three will never be delivered to a customer and so don't need the fix.

Leach said the problem, first reported Monday by the Flightblogger website of trade magazine Flight International, is "not a safety-of-flight issue."

That being so, she said all the airplanes already fully assembled in Everett — including flight-test airplanes Nos. 4, 5 and 6 and Dreamliner No. 7, the airplane due to be delivered to All Nippon Airways of Japan by the end of the year — can be fixed after the flight-test program ends and the airplane is certified.

Many minor changes are typically done then.

"Every airplane will be fixed before it is delivered to a customer," Leach said.

She described the problem as "a potential issue," one that could develop over time as a plane is repeatedly subjected to cold air at high altitude and hot temperatures on the ground.

The issue was uncovered in Charleston in December then verified during flight tests. Boeing Everett "has been working on it a couple of months," Leach said.

Program leaders "are not treating it like a big deal because they have a solution and it's not impacting flight test or first delivery," she said. "It's a local reinforcement. And it can be done during the current build process."

The parts of the airplane affected are the rearmost fuselage section, made in Charleston, and the smaller cone-shaped section behind that, which houses the auxiliary power unit. That section is built in South Korea by the manufacturing division of the national airline Korean Air.

The detailed design of those sections was originally done by Vought in Charleston and by Korean Air in South Korea.

Last year, Boeing bought out Vought and took full control of the Charleston plant.

Leach said the issue was not a major contributor to the five-week delay in shipping new sections to Everett, announced in April. That was attributed to supply-chain issues, in part caused by late design changes.

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

This story was originally posted May 17, 2010, and revised the next day. Because of incorrect information supplied by Boeing, the original story said that less than a dozen shear ties would have to be replaced on each airplane. Boeing corrected that misinformation, saying mechanics will replace portions of 12 shear ties and also will have to reinforce many other shear ties in the rear fuselage of each plane.