Eight B787 pulled from service over structural issues
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Eight B787 pulled from service over structural issues
According to this article , Boeing identified manufacturing defects in eight B787 and asked the companies to stop using them.
Any better source?
Any better source?
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From what I remember weren't the early production section 48 assemblies made in Italy. Boeing pulled the contract due to 'tolerance' issues.
I think that particular problem related to the stab cut out area. Shimming was the answer to that problem too I think.
I think that particular problem related to the stab cut out area. Shimming was the answer to that problem too I think.
I bet they were all built in Charleston.....
edit. The first article I read about this issue did not specify where the assembly was built but I now see in the article embedded in the link in the first post specifies that the offending structures were indeed built in Charleston. This is what happens when Boeing execs decide union busting is more important than production quality. Yet another example of a once proud company renown for engineering and production excellence driven into the ground by MBA bean counters who know the price of everything and the value of nothing......
edit. The first article I read about this issue did not specify where the assembly was built but I now see in the article embedded in the link in the first post specifies that the offending structures were indeed built in Charleston. This is what happens when Boeing execs decide union busting is more important than production quality. Yet another example of a once proud company renown for engineering and production excellence driven into the ground by MBA bean counters who know the price of everything and the value of nothing......
Last edited by Big Pistons Forever; 28th Aug 2020 at 18:28.
FAA ?
...
So Boeing have 'acted' on the double assembly error problem - making a combo of shims and roughness unsafe, sufficient to justify immediate grounding of a small number of 787s.
Who's to decide whether one or other of these issues alone, can be safely discounted ?
I mean, its not as if the backend is going to fall off, or is it ?
Are we waiting for an FAA AD ?
...
So Boeing have 'acted' on the double assembly error problem - making a combo of shims and roughness unsafe, sufficient to justify immediate grounding of a small number of 787s.
Who's to decide whether one or other of these issues alone, can be safely discounted ?
I mean, its not as if the backend is going to fall off, or is it ?
Are we waiting for an FAA AD ?
...
Lordflasheart
Apparently it can adversely affect the fatigue life - so it needs to be fixed to avoid longer term issues.
Boeing technically doesn't have enforceable authority to ground those aircraft - so this is really just a recommendation. I'm sure an FAA AD will be coming shortly - which does have enforceable authority.
Apparently it can adversely affect the fatigue life - so it needs to be fixed to avoid longer term issues.
Boeing technically doesn't have enforceable authority to ground those aircraft - so this is really just a recommendation. I'm sure an FAA AD will be coming shortly - which does have enforceable authority.
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According to the article, it's not a fatigue issue - it's an inability to withstand limit loads issue (so yes, at least a theoretical back end falling off issue). Due to improper shim thicknesses installed during joining of the sections, installation of the fasteners for the joint causes localized pull-up loads and stress to be introduced in the composite material at the highly stressed areas of the joint. The surface discontinuities then apparently add stress concentrations. The joint strength with these conditions is apparently insufficient to withstand one or more of the applicable design limit loads. I don't know what flight conditions set the most critical limit loads for the section 47/48 joint, but gust loads, engine failure on takeoff, and hard landing touchdown are likely candidates.
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Originally Posted by Rodak
I'd be curious to learn how the defects were discovered and isolated to eight aircraft. Did Boeing look at all manufacturing inspection data for this joint for all aircraft?
Assuming (always risky on a forum where speculation is frowned upon . . . ) that the two issues were uncovered by review of inspection data, hmmm, what is the nominal time lag between generating of the data sufficient to review for such issues, and these inspections? Is that time lag (if it exists) subject to particular engineering discipline standards (prompted by "tolerance" issue re: Italian production earlier)? Were any of the certification Special Conditions - some were pertinent to this first very extensive use of composite materials in the airframe, weren't they? - pertinent to time lags between completion of inspection data sets and review of this data?
I'm not going to say anything specific about No Highway in the Sky.
Last edited by WillowRun 6-3; 29th Aug 2020 at 13:51.
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Originally Posted by 70 Mustang
What has happened to what used to be the best aircraft manufacturer?
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Originally Posted by Dave Therhino
According to the article, it's not a fatigue issue - it's an inability to withstand limit loads issue
I think what is going on is that there are two issues, bad shimming (cut too small leaving gaps) and ridges on the internal surface of the composite.
The bad shimming on it's own might cause fatigue issues - gaps mean more movement thus more potential for fatigue. It isn't clear that they know that this is definitely a problem, yet, and if it is it may just reduce the fatigue life - more frequent inspections may be the only remedial action.
On the other hand if you have both the bad shimming and the rough internal surface it seems there is an immediate problem that the structure might not handle limit loads. This might be because of poor load transfer - ridge pushes shim away from composite and all the localised load goes through the ridge - or maybe the ridge means that any gap is guaranteed to be between composite and shim giving the composite space to delaminate and fail, or something else.
My guess on how this has been found is that they have found the poor shimming (and maybe some earlier-than-expected fatigue) in routine inspections and that the second issue with the rough composite may be theoretical. Since, apparently, they cut the shims custom for each airframe from scans they may well have kept the scanning data which would make identifying the affected airframes straightforward. Suspect the shimming issue is more widespread, I can't see them ending up with eight airframes affected by both issues if it was just one bad batch of shims.
From Boeing patent.
https://patents.justia.com/patent/20200271016
Aerodynamic, also known as “wetted”, exterior surfaces of aircraft can experience significant manufacturing tolerance variations during component fit-up. If gaps at faying edges (i.e. fastening joints) are fixed and/or locked in place with contoured fillers or shims, resulting variations can create turbulent air flows which may create erosion of aft joint surfaces. When the components are formed of composite materials, the erosion may actually produce delamination. As a result, special care must be taken in the manufacture of faying edges of wetted aircraft components at risk for erosion damage.
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A relevant aviationweek article.
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Shims
I have not found a clear explanation of the shims. Are the two imperfect mating surfaces scanned and then individual shims made for each mechanical fastener, leaving possible gaps between the fasteners?
Or is one continuous annular shim made in order to mate the two surfaces perfectly?
Or is one continuous annular shim made in order to mate the two surfaces perfectly?
