Design flaws discovered in Dreamliner rear fuselage shear ties

Design flaw may cause rear fuselage shear ties to separate from fuselage skin. Completed planes will get retrofit fix.

The Seattle Times and other news organizations reported last week that The Boeing Co. (Seattle, Wash., USA) has discovered a design flaw in the rear fuselage shear ties of the 787 Dreamliner that will require rework on already-built aircraft. The problem won't delay test flights or the schedule for first delivery, says The Seattle Times report.

According to the report, Boeing discovered that repeated heating and cooling of the fuselage could loosen the aluminum shear ties that attach the air frame to the rear composite fuselage skin. Loosening the ties could potentially cause the frame to pull away from the skin. The report says the parts of the craft affected are sections 48 and 48 aft (tail cone), made at Boeing's Charleston, S.C., facility. The tail cone section is built in South Korea by the manufacturing division of the national airline Korean Air. The report says design of those sections was originally done by Vought (which owned the Charleston facility before Boeing bought it) and by Korean Air in South Korea.

"We are replacing portions of 12 shear ties," Yvonne Leach, Boeing spokesperson, told the newspaper. In addition, she told the paper, "there are many other shear ties in the (rear fuselage) section where we have to add parts to strengthen them."

The report says that for airplanes already built, the retrofit will reinforce the shear ties with a 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 told the newspaper.

The report says the problem was discovered the Charleston facility in December 2009 and then verified during flight tests.

Information: Click here for The Seattle Times report. Click here for a Flightblogger report on this matter.