Posted on 07/22/2009 1:10:26 PM PDT by AngelesCrestHighway
The structural flaw that delayed the first flight of the 787 Dreamliner is more complex than originally described by the company, and the plane's inaugural takeoff is likely at least four to six months away, say two engineers with knowledge of Boeing's problem.
"It's got to take at least three to four months just to get something installed on an airplane," said a structures engineer who has been briefed on the issue. "It's definitely a costly fix to go and do this work."
(Excerpt) Read more at seattletimes.nwsource.com ...
This article is unusually well written. I commend the author/editor and publisher.
It appears to me that this is more a problem of an engineering detail that was detected in design phase that fell through the cracks than any major design flaw. It was not expected to EVER result in a catastrophic failure, if the article was written correctly. It was only discovered by virtue of the plane being put through a very high stress test that exercised the wing to 150% of the “maximum” stress an aircraft was expected to encounter. If this failure (delamination) had occurred in flight, it would have been noticed upon refueling, and the plane taken out of service for VERY COSTLY repair (or perhaps even junking). I suspect replacing the wing would have constituted the repair which would have been done.
It certainly is not good for Boeing’s bottom line, but in fact it seems that their testing regimen worked to identify a problem that would possibly have shown up sometime in the future and cost them customer confidence then. As it is, Boeing seems to have done precisely what they ought to do.
This all said, if the minor modification that is described works, and it is the only remaining problem that needs to be addressed, it sounds very good. If that modification doesn’t work... well, I am sure that no one at Boeing wants to even think about this one. It sounds like their modeling caught with the earlier design, and the mod has certainly been run through the wringer by now, so I would wager chances are good that it works.
(It has always been amazing to me how wings “flap” on large aircraft to begin with... a bit scary in a way, but thrilling for the daredevil in me, too!)
When you get held hostage by the IAW, you’ll chew your own leg off to get out.
Four strikes in 20 years. Sorry, but the engineers are union too. It was designed by the engineers in WA.
I didn't say, nor did I infer, anything about Airbus. I was simply pointing out that, bad as this problem is, it's far better to find it now, preproduction, than later.
This is true in terms of cost, in reputation, and most importantly, in lives saved. Praising Boeing doesn't “somehow criticise Airbus.
Perhaps your assumption that I was talking about Airbus says something about Airbus - I don't know. I only know about production processes, I'm not an aircraft industry expert. The sooner you find design problems, the better, no matter what the product.
With airplanes, failure has a few more dire consequences than toasters.”
No Sir When you put up the numbers I was pointing my thought on that subject! Now since airbus is Boeing's competition and again they are the NEW kids on the block and the great master Time has yet to play into this and was just pointing out that it looked kinda one sided!
My understanding is the wings were being produced by another supplier. If my memory is correct, did the fact two different companies were building the fuselage and wings have something to do with not catching this error?
That's extremely misleading
True there was structural failure but the reason for the failure was not Boeing but unapproved repairs performed by the carrier
The official cause of the crash according to the report published by Japan's then Aircraft Accidents Investigation Commission is as follows:
“That’s extremely misleading
True there was structural failure but the reason for the failure was not Boeing but unapproved repairs performed by the carrier
The official cause of the crash according to the report published by Japan’s then Aircraft Accidents Investigation Commission is as follows:
The aircraft was involved in a tailstrike incident at Osaka International Airport on 2 June 1978, which damaged the aircraft’s rear pressure bulkhead.
The subsequent repair of the bulkhead did not conform to Boeing’s approved repair methods. Their procedure calls for one continuous doubler plate with three rows of rivets to reinforce the damaged bulkhead, but the Boeing technicians fixing the aircraft used two separate doubler plates, one with two rows of rivets and one with only one row.[11] This reduced the part’s resistance to metal fatigue by 70%. According to the FAA, the one “doubler plate” which was specified for the job (the FAA calls it a “splice plate” - essentially a patch) was cut into two pieces parallel to the stress crack it was intended to reinforce, “to make it fit”.[12] This negated the effectiveness of two of the rows of rivets. During the investigation Boeing calculated that this incorrect installation would fail after approximately 10,000 pressurizations; the aircraft accomplished 12,319 take-offs between the installation of the new plate and the final accident.
When the bulkhead gave way, the resulting explosive decompression ruptured the lines of all four hydraulic systems. With the aircraft’s control surfaces disabled, the aircraft became uncontrollable.”
Yes I remember this it flew for a while before crashing.Thank you for the post.
Define a "handful"?
Alright in comparing them too Boeing a Small child like Handful OK?
By Jon Ostrower on July 21, 2009 6:52 PM
With almost a month since Boeing announced it was forced to ground its 787s for structural reinforcement, the company continues to work to develop, install and test a fix that can get its troubled Dreamliner into the sky after more than two years of delays.
According to a senior program source: "There is good news and bad news. The good news is we know what to fix, and how to fix it. The bad news is the location is a [expletive] to get to."
Boeing says that revised schedules for first flight and delivery remain under review, as they have been since the company's June 23rd news conference.
DIAGNOSIS & DEVELOPMENT
While the fix is being developed and a fully revised schedule finalized for airlines, sources at both Boeing and partner suppliers indicate that the existing production plan has slid roughly one and a half to three months for the delivery of Airplane Ten's components to Everett, even as suppliers continue to prep parts for shipment.
The slip, the sources say, allows Boeing to finalize and test the fix and limit the number of aircraft in final assembly required to undergo the fix in Everett. Boeing previously stated that any fix developed would be able to be installed no matter the location of the parts in the supply chain.
Airplane Eight, ZA101, is expected to begin final assembly operations before the month is out, with parts for Airplane Nine, ZA102, believed to be arriving beginning in early August. The slip, one supplier sources say, could mean that structural components for Airplane Ten, ZA104, may not arrive until October. The customer ZA-designations are non-sequential.
The side-of-body issue was first discovered in late-May during a test that saw lower wing loads than the April 21st test of 120-130% of limit load. The test revealed the weakness in the upper section on the stringer caps of the wing to body join at the side of body of the aircraft.
A corps of Boeing engineers are working 80-hour weeks to design the fix that allows the 787 to fly with a robust flight envelope and achieve FAA certification with 150% of limit load on the wing, sources say.
For the development of the remedial fix, widely believed to be made of titanium, engineers have to design a modification that avoids two potential challenges down the road.
Veteran structural engineers tell FlightBlogger that the key to developing a reinforcement centers around ensuring that the loads that caused the initial problem at the site of the wing stringer caps are not redistributed elsewhere causing a further structural issue.
Second, as the area is stiffened Boeing engineers must take great care to develop a fix that isn't susceptible to long term fatigue issues that come from the normal structural aging of the aircraft.
These challenges aren't unique to structural engineering on the 787, in fact, they are part of the normal checklist that comes with developing the solution that is the 3-dimensional puzzle of designing aircraft. This is not to say, however, that solving the problem is any less complex, difficult or time consuming.
INSTALLATION
Several program sources indicate that August is a crucial month for the wing fix as the development phase moves into the installation phase.
Boeing reiterated that its engineers are "working with urgency", and no internal timeline has been finalized for the testing or duration of the installation of the fix.
Sources say the area that will be reinforced at the side of body is extremely tight and difficult to reach as the installation area of the fix will provide very little room to install the fasteners to secure the reinforcement.
The installation of the fix may begin as early as the middle of August, with installation times around one month for each already assembled airplane, sources estimate.
Boeing has nine 787s at its Everett facility (6 flight test, 1 production, 2 ground test) that have gone through, or continue to undergo, final assembly operations, and structural sections for a 10th (Airplane 8) continue to arrive.
ZA001 is expected to leave the flight line for Paint Hangar 45-03 where the first 787 will undergo installation of the fix.
ZA002 will remain on the Everett flight line and the area around the side of body will be covered with a specially ordered tent to protect the aircraft.
In addition, Boeing has moved the approximately 50-foot long, two-thirds span test wing box, known as the "Dash 18" wing, from the company's Seattle Development Center to Building 40-23 where 787 static testing has been taking place in Everett.
The company is considering using the test wing box, which was formally broken in November 2008 above 150% of limit load, to test installation methods as a dress rehearsal before modifying the static test airframe and ZA001.
PERMANENCE & PRODUCTION
Even with the remedial fix in the works, a key discussion centers on the future of 787 production and when the permanent fix is designed into the wing to body join.
Sources say a revision of the upper part of the wing to body join is almost certainly necessary to create a permanent long-term solution and eliminate the time consuming installation of the remedial fix.
Boeing says there are about 40 787s in process throughout the global supply chain and a question yet to be answered is the timing of incorporation for the permanent fix.
Boeing has already planned a series of blockpoint changes to incorporate weight reduction and performance improvements into the design of the aircraft. The first major blockpoint was for ZA100, the first production 787 (Airplane 7), with the next expected to follow around Airplane 20.
Airbus faced a similar challenge when the A380 wing ruptured below the 150% mark in 2006 forcing the European airframer to modify aircraft already in final assembly. Airbus eventually incorporated its own remedial fix into A380 production before the wings were delivered to Toulouse, however the company has had to redesign the effected area as a long-term solution.
5000+ aircraft isn’t a handful.
Really compared to who? Not Boeing!
“Ok but Boeing has had a lot of planes up for many years so the law of probability says there would be a hell of a lot more mishaps with Boeing than the handfull Airbus has flying around.”
Excuses excuses.
I was reading an article over at Leeham, and the talk there is that the 787 isn’t living up to it’s range expectations.
Knowing how Boeing operates, they’re probably using the excuse of “structural flaw” to buy enough time to cook their figures again.
Yeah I am trying to find all the war planes they built also. new kids on the block using technology lifted from the real guys.
“new kids on the block using technology lifted from the real guys.”
Oh really?
And what technology is that?
And what technology is that?
Gee adhesive metal bonding and testing ,fasteners, Panel assembly techniques, Fly by wire.When were they setup 1970??
It doesn’t seem to be the case that the wings being produced by another entity would have anything to do with this. The root cause is that the composites have no “flex” as metals previously used for large wing skins, such as aluminum and steel. The internal struts MUST flex as the wing flaps. The dissimilar characteristics of the two adjoining materials is the cause. The problem apparently showed up as a “hot spot” (Certainly graphed in red) in their CAD modeling and virtual testing to very high stress levels. In many ways, it is amazing to me that it did show up there. For some reason (shrug) that discovery wasn’t followed up the way the company now wishes it had been. I have an impression (with some of my mechanical and materials engineering training) that this “fix” has been used in the past, though I didn’t see that claim anywhere. It is a logical change to a strut, in any event. It could well be that since it was a well known mod (in their business) that everyone who noticed the hot spot knew that someone else would specify that change to the struts, and no one followed through. I can see that happening easily, in a super-sized project like this where everyone is looking at so many detailed bits of data.
A dozen years ago, the types of modeling that caught this weren’t even close to being able to be done, to say nothing about the materials that are being used. Such a “hot spot” wouldn’t have shown up in the design process and would only have been located by “stress to failure” testing or some such process. I call to mind the way the F-111’s wings started failing due to needing a different heat treatment for the pivots. For quite a while, that plane’s losses were entirely blamed on the Terrain Following Radar, though cracking wing pivots were certainly cause of some of those crashes. No one even considered those to be the problem, and that project was much less difficult than the current technology. I’m not sure that the model testing now done would have caught that “mass metal” flaw in the F-111, though it might have at least reported a similar hot spot. Crashed airplanes may still have been what finally revealed the flaw.
To me this isn’t any real fundamental flaw with the science, the engineering, the design process, or the management. It is simply part of the reason we build prototypes and test them, and a consequence of our being human. Despite all the computer modeling, such testing still often reveals things that have to be modified. This particular item simply is more costly than most mods due to it being so difficult to do on an existing prototype.
I'm sure Boeing wishes the delay never happened, but it sounds like a good fix.
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