PlaneAdmirer From United States of America, joined Jul 2009, 530 posts, RR: 1 Posted (3 years 7 months 1 week 2 days 18 hours ago) and read 15827 times:
As Boeing raced to find a remedy this summer, it discovered another issue with the composite material in the plane's wings, according to internal company documents and a person familiar with the matter. Metal bolts inside the wings of one of the six test airplanes were found to have slightly damaged the surrounding material—causing so-called delamination, or cracking—the documents show.
The damage created by the metal bolts, called freeze plugs, was confined to a relatively small area. However, according to an internal Boeing document from October, it raised red flags among engineers, who decided the plane couldn't fly until the problem was corrected.
A work order written by one of the company's engineers, and reviewed by The Wall Street Journal, says, "Noted conditions are structurally and functionally acceptable to Engineering for GROUND TESTING ONLY," and adds, "NO FLIGHT TEST IS ALLOWED."
The company acknowledged Thursday that delamination occurred in the composite material surrounding bolt holes, but said it won't affect the plane's first flight or require a repair. It said it routinely uses metal freeze plugs, which are installed after being frozen in liquid nitrogen and expand as they thaw.
"The freeze plug process is a standard repair we perform on both metallic and composite structure. We have extensive experience using these techniques. We have not seen any issues with these repairs that are inconsistent with our experience or the capability of these repair techniques," a Boeing official said.
The above is only part of the article and I will be honest, I simply don't understand the problem or how the metal freeze plugs (I get them expanding into a hole to fill space) work or solve a delamination problem.
Thoughts? Please no what if the worst comments from the other thread.
Khobar From United States of America, joined Mar 2006, 2379 posts, RR: 4 Reply 1, posted (3 years 7 months 1 week 2 days 18 hours ago) and read 15796 times:
Quoting PlaneAdmirer (Thread starter): "The freeze plug process is a standard repair we perform on both metallic and composite structure. We have extensive experience using these techniques. We have not seen any issues with these repairs that are inconsistent with our experience or the capability of these repair techniques," a Boeing official said.
While it's good to know they have the experience to know how to repair the damage, one would think if they had the proper experience they'd know how to install these things without causing any damage in the first place.
Barbarian From United Kingdom, joined Aug 2005, 54 posts, RR: 0 Reply 2, posted (3 years 7 months 1 week 2 days 18 hours ago) and read 15736 times:
i think the point is that the freeze fit plugs caused the delamination, not that they are used to repair it. Sounds like the plug expanded too much causing the composite to delaminate.
Not sure what the repair would be for something like this, would think it unlikely to be able to oversize the hole to clear the delamination.... maybe inject some composite adhesive into the area deliminated via the hole, then clamp and allow to cure?
Am sure some composite expert will be along any minute to answer that one!
RedFlyer From United States of America, joined Feb 2005, 4181 posts, RR: 30 Reply 3, posted (3 years 7 months 1 week 2 days 18 hours ago) and read 15707 times:
A couple of things come to my mind about this. First, it's relatively "old" news in the sense that this event occurred one to two months ago and Boeing's been aware of it. So, I'm inclined to think that it might be simply the typical issues that are encountered on a new plane, and there are probably hundreds of those, and are resolved in quick order. This could be "news" only in the sense that this plane has encountered so many problems and has been delayed for so long that any negative event, no matter how minor, is "newsworthy".
In the meantime, Boeing has been pretty confident that the plane will take flight before the end of the year, so it would appear that they have resolved the issue. On the other hand, (and I'm playing Devil's advocate here), they were aware of the wing-stringer problem last June and kept up a confident belief that the plane would fly by the end of June, and we saw how that turned out.
Oly720man From United Kingdom, joined May 2004, 6225 posts, RR: 11 Reply 4, posted (3 years 7 months 1 week 2 days 18 hours ago) and read 15694 times:
Quoting PlaneAdmirer (Thread starter): The above is only part of the article and I will be honest, I simply don't understand the problem or how the metal freeze plugs (I get them expanding into a hole to fill space) work or solve a delamination problem.
The freeze plugs caused the delamination. I presume that they were slightly too big for the holes they were inserted into so when they expanded they pressed against the inner wall of the hole to such an extent that the composite layers couldn't cope and had to break apart. I assume aluminium or other metals could plastically deform to take the bolt expansion whereas composite won't.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 5, posted (3 years 7 months 1 week 2 days 18 hours ago) and read 15598 times:
Honestly, doesn't strike me as something worrisome. It's a materials problem, to be sure, but seems like one that can be corrected via a procedural / process change.
This is a bit off putting to start with...a freeze plug is not a bolt.
Quoting PlaneAdmirer (Thread starter): I simply don't understand the problem or how the metal freeze plugs (I get them expanding into a hole to fill space) work or solve a delamination problem.
Empty holes cause a stress concentration (the stress at the edge of the hole is ~3 times higher than the bulk stress). This causes horrible fatigue properties. The easiest fix is to prestress the hole walls. Hole filling fasteners (like rivets) do this automatically, but if the hole isn't going to be filled with a fastener, you've got to put something in there. I.e. a freeze plug.
Quoting Khobar (Reply 1): While it's good to know they have the experience to know how to repair the damage, one would think if they had the proper experience they'd know how to install these things without causing any damage in the first place.
I'm pretty sure no airplane in the history of modern aviation has been built with no assembly damage. They're just too big, with too many steps, for nothing to go wrong throughout the assembly process.
Quoting Barbarian (Reply 2): Not sure what the repair would be for something like this, would think it unlikely to be able to oversize the hole to clear the delamination
Why couldn't you oversize? Provision for oversize is a normal design requirement.
Cloudyapple From Hong Kong, joined Jul 2005, 2425 posts, RR: 9 Reply 7, posted (3 years 7 months 1 week 2 days 18 hours ago) and read 15558 times:
Quoting Barbarian (Reply 2): Not sure what the repair would be for something like this, would think it unlikely to be able to oversize the hole to clear the delamination.... maybe inject some composite adhesive into the area deliminated via the hole, then clamp and allow to cure?
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9 Reply 8, posted (3 years 7 months 1 week 2 days 16 hours ago) and read 15130 times:
Freeze plugs are installed with an interference fit, the plug is slightly larger than the hole it is being installed into. When the plug have been frozen, the article say in liquid nitrogen we used alcohol and dry ice, the plug shrinks enough to allow it to be installed in the hole. When the plug thaws it fits tightly against the structure restoring much of the original strength. It appears that Boeing may have to adjust the amount of interference between a metal plug and composite structure.
Quoting Tdscanuck (Reply 6): Why couldn't you oversize? Provision for oversize is a normal design requirement.
Freeze plugs are used because because oversized fasteners is not always available. Additionally, unlike an oversize fasteners you do not have to open the hole through all layers of the structure. You can plug only one layer, if only one layer is damaged, and then redrill the plug for installation of a standard diameter fastener.
Stratofortress From United States of America, joined Dec 2005, 178 posts, RR: 1 Reply 9, posted (3 years 7 months 1 week 2 days 16 hours ago) and read 15036 times:
Did anybody else notice that Dec 22nd first flight date was mentioned?
Lightsaber From United States of America, joined Jan 2005, 10890 posts, RR: 100 Reply 10, posted (3 years 7 months 1 week 2 days 15 hours ago) and read 14790 times:
Quoting Stitch (Reply 5): Honestly, doesn't strike me as something worrisome. It's a materials problem, to be sure, but seems like one that can be corrected via a procedural / process change.
This is an oops, but not that big of a deal.
I've been frustrated with the 787, but this type of mistake is part of the learning curve of every new aircraft. Its part of the reason why producing the 101st through 400th costs as much (or less) than the first 100.
Quoting Stratofortress (Reply 9): Did anybody else notice that Dec 22nd first flight date was mentioned?
Missed that! So much for Christmas for the 787 team. Note: My program is already looking at scheduling Thanksgiving and Christmas. That is just an &*^%ing part of flight test, so don't get me started. (I LOVE those holidays, so I hate to miss them.)
Cvervais From United States of America, joined Sep 2003, 602 posts, RR: 3 Reply 11, posted (3 years 7 months 1 week 2 days 15 hours ago) and read 14608 times:
OH man, check out the airliner image they used in this article!
Ikramerica From United States of America, joined May 2005, 21043 posts, RR: 60 Reply 12, posted (3 years 7 months 1 week 2 days 15 hours ago) and read 14559 times:
The title of this thread is misleading.
The issue is with improper application of bolts causing localized damage to ONE aircraft that needs repair. It is not a "787 issue with the composite material in wings."
It would be similar to finding microcracks around a bolt hole in a metal section.
Of all the things to worry about... the Wookie has no pants.
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9 Reply 13, posted (3 years 7 months 1 week 2 days 14 hours ago) and read 14316 times:
Quoting Ikramerica (Reply 12): The issue is with improper application of bolts causing localized damage to ONE aircraft that needs repair.
Not according the the original article.
Quoting PlaneAdmirer (Thread starter): The company acknowledged Thursday that delamination occurred in the composite material surrounding bolt holes, but said it won't affect the plane's first flight or require a repair.
Keesje From , joined Dec 1969, posts, RR: Reply 14, posted (3 years 7 months 1 week 2 days 12 hours ago) and read 13956 times:
To be honest I am a little bit worried. I have been alert on the composite inspection and repair methods for years. I shows again how critical composites can be if loaded in wrong directions. Even Boeing itself has problems doing it right. Let alone some young mechanic under time pressure in a far away country on a dark & cold platform..
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 15, posted (3 years 7 months 1 week 2 days 11 hours ago) and read 13303 times:
Quoting Keesje (Reply 14): To be honest I am a little bit worried. I have been alert on the composite inspection and repair methods for years. I shows again how critical composites can be if loaded in wrong directions. Even Boeing itself has problems doing it right. Let alone some young mechanic under time pressure in a far away country on a dark & cold platform..
But that wouldn't be specific only to composites on the 787...
Ikramerica From United States of America, joined May 2005, 21043 posts, RR: 60 Reply 16, posted (3 years 7 months 1 week 2 days 10 hours ago) and read 12815 times:
Quoting 474218 (Reply 13): Not according the the original article.
What article are you reading that contradicts me? The damage happened around certain bolts in ONE aircraft. Your quote confirms that.
Sounds very similar to the problems that happened elsewhere where the wrong sized bolts were used.
It doesn't mention which of the six test birds this damage happened on, but doesn't sound like LN1 or LN2 from other news of the two racing toward first flight. Maybe #4, which I believe is the aircraft rumored to fly late/out of order?
Of all the things to worry about... the Wookie has no pants.
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9 Reply 17, posted (3 years 7 months 1 week 2 days 10 hours ago) and read 12550 times:
Quoting Ikramerica (Reply 16): What article are you reading that contradicts me? The damage happened around certain bolts in ONE aircraft. Your quote confirms that.
You stated that the ONE aircraft needs REPAIR, see below:
Quoting Ikramerica (Reply 12): The issue is with improper application of bolts causing localized damage to ONE aircraft that needs repair. It is not a "787 issue with the composite material in wings."
The artical states Boeing said no REPAIR is required, see below:
Quoting PlaneAdmirer (Thread starter): The company acknowledged Thursday that delamination occurred in the composite material surrounding bolt holes, but said it won't affect the plane's first flight or require a repair.
Rheinbote From Germany, joined May 2006, 1956 posts, RR: 52 Reply 18, posted (3 years 7 months 1 week 2 days 10 hours ago) and read 12484 times:
Quoting Ikramerica (Reply 16): What article are you reading that contradicts me? The damage happened around certain bolts in ONE aircraft. Your quote confirms that.
Well, only ONE aircraft was subject to in-flight loads. How could the others have been damaged?
Quoting Ikramerica (Reply 16): Sounds very similar to the problems that happened elsewhere where the wrong sized bolts were used.
How do you infer from the article that wrong bolts were used?
Quoting Ikramerica (Reply 16): It doesn't mention which of the six test birds this damage happened on
The static test airframe, ZY997. The article said the damage was discovered while the delaminated stringers were inspected.
Manfredj From United States of America, joined Mar 2007, 1132 posts, RR: 0 Reply 20, posted (3 years 7 months 1 week 2 days 10 hours ago) and read 12279 times:
Quoting Rheinbote (Reply 18): The static test airframe, ZY997. The article said the damage was discovered while the delaminated stringers were inspected.
Wait a sec, the aircraft in question isn't even an aircraft?
This is the problem when only a portion of the article is posted. I do not seem to have access to the rest of it.
I find it hard to believe that people who have inside information that the wing join fix was not working are nowhere to be found when good news or new information is posted. I'm puzzled. Can we have a little more direction with this thread?
Rheinbote From Germany, joined May 2006, 1956 posts, RR: 52 Reply 21, posted (3 years 7 months 1 week 2 days 10 hours ago) and read 12199 times:
Quoting Manfredj (Reply 20): Wait a sec, the aircraft in question isn't even an aircraft?
Quoting PlaneAdmirer (Thread starter):
GROUND TESTING ONLY," and adds, "NO FLIGHT TEST IS ALLOWED."
Is this a provision put on a static test frame?
Don't be silly. The results of the static test determine the airworthiness of the flight test aircraft. The engineer who wrote "NO FLIGHT TEST ALLOWED" inferred that the issue is affecting all aircraft.
Stitch From United States of America, joined Jul 2005, 26961 posts, RR: 83 Reply 22, posted (3 years 7 months 1 week 2 days 9 hours ago) and read 11609 times:
Quoting Keesje (Reply 19): But these are non line replaceable & you can't get a C-scan on the platform.
Well I can think of another plane that uses CFRP panels in it's wings, so I guess it's at risk of damage, as well.
Pygmalion From United States of America, joined Jun 2006, 932 posts, RR: 38 Reply 23, posted (3 years 7 months 1 week 2 days 8 hours ago) and read 11025 times:
Quoting Rheinbote (Reply 21): Don't be silly. The results of the static test determine the airworthiness of the flight test aircraft. The engineer who wrote "NO FLIGHT TEST ALLOWED" inferred that the issue is affecting all aircraft.
As one of those folks who writes this kind of paper for a living... this is common wording for any possible issue that can affect units on the flight line. "Can" not "Does" affect.... The FAA takes a very dim view of not putting holds on airplanes that may have defects that could affect safety prior to that defect being understood and dispositioned. Its just that simple.
After you make the safety determination, you pull off that note. (depending on the outcome)
Dynamicsguy From Australia, joined Jul 2008, 778 posts, RR: 8 Reply 24, posted (3 years 7 months 1 week 2 days 7 hours ago) and read 10872 times:
Quoting Rheinbote (Reply 18): Quoting Ikramerica (Reply 16):
It doesn't mention which of the six test birds this damage happened on
The static test airframe, ZY997. The article said the damage was discovered while the delaminated stringers were inspected.
Nothing in the article says it was the static test airframe. That its says "one of six" and not "one of eight" suggests that it was one of the flight test airframes. That is says "NO FLIGHT TEST IS ALLOWED" also says that it is not the static test airframe since it is not going to be flight tested.
Quoting Rheinbote (Reply 18): Well, only ONE aircraft was subject to in-flight loads. How could the others have been damaged?
None of them have been subject to flight loads. Plenty of damage can be done and repaired or bought off during production, as happens to any airliner.
Quoting Rheinbote (Reply 21): The engineer who wrote "NO FLIGHT TEST ALLOWED" inferred that the issue is affecting all aircraft.
How can you say that without knowing anything more about the document quoted? As I read the quoted sections of the article it seems to refer to damage to a specific airplane.
25 Amicus: You need an interference fit of 0.004 inches. any more and you can get into trouble with surrounding structure. For past thirty years, solid carbon di
26 Dynamicsguy: I'm familiar with the idea of freeze plugs, but not with the detail of their use. Why does it matter whether they use liquid nitrogen or dry ice to c
27 Amicus: Hi Dynamics Guy, Re your questions, I hope that I have coherent answers. !. Amount of interference is governed directly by initial fit temperature and
28 Dynamicsguy: Thanks. I realised that the different temperatures mean that the difference in size between cooled and room temp plugs is greater for liquid nitrogen
29 Aircellist: (layman's opinion) It reminds me of the Gimli glider, when the metric system was not yet widely used... And the wrong conversions happening between ol
30 Rheinbote: Read the article a second and third time. Indeed. the article does NOT say it is the static frame and suggests it is one of the flight test airframes
31 LN-KGL: Any thoughts about the change in brittleness of titanium alloy plugs "freezed" with liquide nitrogen compared with dry ice?
32 Tdscanuck: If they found the problem and wrote a tag against it, it sounds like it *didn't* pass QA. In-service fleets find flight critical issues fairly freque
33 TISTPAA727: For anyone who has not read the entire article, there is a little trick to non WSJ subscribers. Copy the headline and paste it into Google. From there
34 TISTPAA727: What I find interesting is the article paints the 787 as the first composite aircraft (not airliner) and that there are many unknowns with composites
35 Pygmalion: As one who has called out freeze plugs for a long time... We never use a flat .004" interference. We always size the interference relative to the hole
36 Nomadd22: Pygmalion can be very annoying, the way he wrecks perfectly good argument with boring facts. He'd make a terrible WSJ writer. I would have thought the
38 Amicus: Thank you, Pygmalion, but why the crushing and delamination around freeze plugs if Boeing had everything sized? Ah, there's the rub.
39 Pygmalion: You are making an assumption that ALL the plugs had some issue. It is not completely uncommon for the mechs to not quite get the plug in all the way b
40 Rheinbote: Exactly my understanding, I just failed to put it that clearly. Thanks.
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This is an oops, but not that big of a deal. 
Note: My program is already looking at scheduling Thanksgiving and Christmas. 
That is just an &*^%ing part of flight test, so don't get me started. (I LOVE those holidays, so I hate to miss them.) 
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