Dear all: Today's news contained the item that Boeing's 787 is delayed again, citing 'structural problems' in the wing box area, and saying that certain sections 'need strengthening'.
The 787 is of course designed in imperial units - why, only the people inside Boeing can answer that one. But it looks like a decision that Boeing may come to regret (if it has not already done so). Some 70+% of the aircraft is subcontracted out to 1st tier subcontractors (who in turn sub-sub-contract various sections to 2nd and 3rd tier subcontractors). Most of these are not in the US, but in the rest of the (metric) world. Boeing earlier cited delays that some of these subcontractors had experienced in getting non-metric fasteners (primarily bolts) - not surprising really, as they are available only in the US. I know from personal contacts that at least one 3rd tier subcontractor is Canada was sending some sub-assemblies as 'boxes of bits' (as they called them) rather than fully assembled, due to problems in obtaining the specified non-metric fasteners. The latest delay must involve some composite materials (fundamental in bringing the weight down to some 15-20% less than an equivalent all-aluminum aircraft). Much of the previous work in composite materials was done by Airbus (and there are questions there to be answered, especially after the recent Air France A330 disaster - the A330 has some large composite sections). Could Boeing have taken Airbus's work (done in SI) and got the conversions wrong, causing the latest delay? Just speculation of course, and there may well be other reasons for the structural problems behind the latest delay. But it seems surprising that Boeing, at this late stage, and with all its past history of designing planes, needs to be essentially admitting it got its structural calculations wrong. Now it may be asked why this is so, since all previous Boeings have been designed in imperial, without the problems that the 787 has experienced. I think there are two main reasons: 1) As noted above, so much of the aircraft has been both designed and manufactured in imperial units by companies and their people who have little or no experience in imperial units. That should have rung some alarm bells in Boeing right from the get-go. 2) While there may have been senior engineers in these and other non-US companies who have had some experience working in imperial units in the past, these now are probably retired. The new generation are metric-only. Even if the company had worked for Boeing previously, it is some 15 years since Boeing's last new plane (the 777) was designed. Does anyone here have an 'inside track' at Boeing? Can what I've said above be verified (or refuted, as the case may be)? If working in imperial units HAS cost Boeing dearly, it would be a wonderful case-study of why the US needs to join the metric world. Regards John F-L
