Design News for Mechanical and Design Engineers

Boeing in a statement Thursday acknowledged design changes are being made to the wing box, which is made by Mitsubishi Heavy Industries in Japan. Boeing spokeswoman Yvonne Leach confirmed the problem, first reported in the flightblogger blog, related to thickness shaved from structural spars made from composite as a weight-saving measure. Boeing has said all along reducing the plane’s weight is a key goal.

The interim fix for planes 1-6, which are being assembled in Boeing’s sprawling Everett plant now includes “aluminum stiffeners” alongside the spars, Leach said. Beginning with plane 7, a permanent fix, presumably thicker spars, will be incorporated. 

“They shaved off too much weight so we did not have the strength,” she said. The problem was found in testing, but Leach said she was not familiar with details of the testing. On Wednesday, Boeing said the horizontal stabilizers passed key tests.

Leach said Boeing is sticking to the power-on/first flight schedule announced on January 16. Critical first power on is slated for the second quarter and first flight by the end of the second quarter with commercial deliveries delayed from May to early next year. However, Boeing also said in January it would perform a further schedule assessment that is due right around now.

More delays in the 787 schedule may well come out of that assessment and be announced in the next 787 quarterly update to the media and analysts. Leach said a date has not been set for the next update, but if more delays are in order they would be announced during that call.

A detailed explanation of the problem and customer reaction can be found in the James Wallace on Aerospace blog at the Seattle Post Intelligencer. Stories there and in this morning’s Wall Street Journal say a further six-month delay is likely. However, Leach said the wing box issue was not a “pacing” item, meaning it would not delay the plane’s schedule.

Boeing’s wing box statement is below:

Boeing Statement on 787 Center Wing Box

EVERETT, Wash., March 20, 2008 -- It is a normal part of the development of a new airplane to discover need for improvements, and that is what we are experiencing on the 787. The robust test process in place on the 787 program has confirmed the majority of our designs but we have found the need for some improvements.

The center wing box issue has been addressed. The fix is being installed on Airplanes 1-6 in the Everett factory. Installations have begun on the four airplanes currently in Final Assembly. All airplanes after Airplane 7 will have the solution incorporated from the beginning.

The fundamental technologies being used on the 787 are proving to be reliable and effective. The material choices and manufacturing techniques for the airplane are sound.

Boeing is working its normal processes for developing a new airplane. The test process is working when issues are discovered and we are reacting appropriately by implementing normal design validation and fixes when we find issues.

	The first 787 Dreamliner demonstration wing box. Courtesy Boeing Photo