Design Problems with the 787
String Caps Diagram
A few days ago (this past Tuesday), Boeing had to once again delay the maiden flight of the much-anticipated Boeing 787 Dreamliner. It is no surprise that it has harmed the company’s public image stock price as well as had damaging effects on deals with Qantas and Virgin, for example.
According to the Wall Street Journal:
Despite the steadily increased use of carbon-fiber composite parts in airlines, Boeing Co.’s disclosure Tuesday of design troubles with its 787 Dreamliner highlights the engineering, manufacturing and maintenance issues still associated with such high-tech materials.
By indicating that “a relatively small number” of added internal structural supports are needed on some of the upper portions of both wings, the disclosure underscored a broader problem that the aerospace industry has recognized for a while: shortcomings in computer-design systems’ abilities to precisely predict behavior of certain composite parts as they bend and twist in flight. …
You can read more about Tuesday’s delay announcement here, via The New York Times.
To understand what’s really going on here, we turn to Flight Global’s blog, FlightBlogger, “Understanding the 787 structural reinforcement (Update1)“. It talks about the engineering design and the history of design problems that have hindered the completion of the Dreamliner.
Because of the need to go back into the detailed design phase for this fix, combined with the need to fabricate, install and test at component and at full scale levels, several sources with a direct familiarity to the situation estimate that the fix will take “months not weeks.” …
The issue centers around the wing-to-body join that mates the wing box (Mitsubishi/Section 12) and the center wing box (Fuji/Section 45/11). The center wing box is the combination of two pieces, the center wing tank (Section 11) and main landing gear wheel well (Section 45). The area of concern centers on the 18 points where Sections 11 and 12 meet.
Digging deeper, the 18 points in question on each side of the airplane (36 total) are located on the top panel of the center wing box and run port to starboard inside the structure of the center tank through to the other wing. These 18 ‘stringers’ inside the center wing box are matched by 17 stringers on the wing box, which serve to stiffen the wing skin. The wing box has 17 stringers, but a source indicates they are designated 2-18, hence the reference to the 18 points that need to be reinforced.
(Image from Flight Global.)
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