Mike Mecham wrote very nice comprehensive article in Aviation Week detailing the latest design issue on the 787. Of note in the article is why Boeing's predictive models didn't catch the issue earlier and that would mean go over the data and models that Boeing used in the computer aided design system.
Mecham also said that for now Boeing along with Fuji and Mitsubishi may design and interim fix followed by a more permanent fix for the production models which might entail rework of the composite molds used to form the various structures of the aircraft.
I do believe it will be quite sometime before ZA001 is in the air, quite possibly not for another two to three months.
Design Issues Starting To Plague 787
Monday, June 29, 2009
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11 comments:
I am working for Airbus, but, believe me, everyone here wants to see the 787 in the air for many reasons. Most of us are aviation enthusiastic, but also because many lessons learned will com from the 787.
I keep reading that article and keep seeing a reference to one issue. How does that translate to a "plague"?
The author is probably thinking about (but not taling about) the center wing box reinforcement that Boeing and FHI had to do in early 2008.
Uresh,
Do you think that this problem is definable and not just part of a larger design issue.
The impression Scott Francher gave at the Conference Call was that there was could be a solution to this problem thta would result in a simple reinforcing fix.
Or, is it just too early to tell
Hard to say if this is the final issue in terms of the structure. Indeed it's something they should've caught sometime ago and I think this places more emphasis on fatigue testing going forward. This is going to gain importance now.
The fix should be simple. It's just addingreinforcments to redistribute the loads that the side-of-body was experiencing. It's good that they're goping for a permanent fix instead of temporary one too. What would be interesting is if they do a fix where it is incorporated into the composite molds thereby not needing to add the reinforcements later in the assembly process.
Not so simple. Every part of the structure is designed to be as strong as it needs to be and no more, and any change shifts loads to different areas which shifts loads to other different areas, infinitum. The parts that were strained wern't too weak. The loads were higher than expected. It's a helluve piece of data crunching to figure out how any change will affect everything else..
Uresh,
Nomadd22's comment questions the ease of a solution...or implies that there has to be alot of data crunching that must preceed the fix.
Perhaps it is not that simple?
Uresh,
It was not the data that created the problem but the model that was used to compare the data.
Doesn't this mean that the model that was used has to be reevaluated or altered...and does this affect the FAA cerification
It's my understanding the inputs into the model (data) was the issue and not the model itself.
I do not know if we are having a rhetorical problem here, but many comments on various web pages indicate that the "modeling used for testing " did not pick up the behaviour of the wing connection at 130% of stress.
Ther real question is what has to be done here..create more "input" or "revise" the model.
Could you clarify and amplify on your last comment.
Seems to me that the "input" revealed the problem because it did not coincide with what the model would have produced. It was this discrepancy that is at heart .
Now the question is what to do to "repair" the source of the input ...and whether the model is sufficient to pass FAA certifications levels.
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