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Ann R. Thryft
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Blogger
Re: Airplane wings. Who needs them?
Ann R. Thryft   7/27/2012 1:01:39 PM
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warren, I agree: not enough design controls to anticipate potential problems, not enough "what if" scenarios in both design and testing. I find it interesting that the Airbus CEO came right out and said that the company didn't understand the materials and interfaces as well as they thought they did. That's quite an admission. It's also scary: not knowing what you do and don't know. Of course, I wonder if there weren't some engineers who did know, but weren't listened to, as several commenters have suggested.

warren@fourward.com
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Platinum
Re: Airplane wings. Who needs them?
warren@fourward.com   7/26/2012 2:49:28 PM
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I think this strengthens my point.  Not enough attention was paid to the changes composites would make to old processes.  I remember reading your article and thinking how would an old timer used to aluminum and plastics think to modify his old way of doing things for something so space edgy and different.  I think the answer is, "He won't."  Now maybe he will after this high profile failure.

Too bad.  I like the idea of new technologies coming on line.  I just like to see them properly thought out before putting my life on the line...

 

Ann R. Thryft
User Rank
Blogger
Re: Airplane wings. Who needs them?
Ann R. Thryft   7/26/2012 2:32:25 PM
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warren, what I'm hearing is that part of the problem that's occurred with composites in aircraft was not completely redesigning components to take fully advantage of this different material, instead of what did happen, which is trying to make the new composite materials fit old processes designed for metals. John Moore of Hexcel explains why this complete redesign did not happen in my aircraft materials feature here: http://www.designnews.com/author.asp?section_id=1392&itc=dn_analysis_element&doc_id=246025&page_number=2 This is not an unusual situation in manufacturing, especially of large, complex systems like aircraft: there's no such thing as a drop-in replacement in materials. OTOH, one would hope there would have been a lot more testing of those metal/composite interfaces, which seems to have be the culprit in the Airbus case.

warren@fourward.com
User Rank
Platinum
Airplane wings. Who needs them?
warren@fourward.com   7/26/2012 9:27:51 AM
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So, the airplane built by committee is falling apart?  I know this is an exaggeration, but I could see it coming a mile away.  I like Boeing and the fact that a private (publicly owned private company) has every control in-house.  The European governments spread everything over politically correct avenues.  I never like when governments get involved in anything other than what governments were designed to do.  And that isn't making airplanes!

As far as the cracks are concerned, mixing materials is a relatively new science and has yet to play itself out.  My confidence level is not high, and as a very frequent flyer, I want it nailed down tight before I risk my very precious hiney at 5 miles in the air going 600 MPH!  I want the wings, at least, to hold together.  The food can be lousy or nonexistent, the service crummy and grumpy, and we can circle while the President gets a haircut, but I want the wings to be just peachy.

Perhaps "we" have rushed into this composite thing too fast.  Maybe it is time to step back a generation and take another look at the long-term stresses and the conditions the wings will operate under.  Takeoffs and landings, radical changes in temperature and pressure, extreme wind forces, birds and other objects, and expansion and contraction and other phenomena affect the boundaries between the different materials that seem to be separating.  Do we need to rush into this thing?

KingDWS
User Rank
Gold
Re: Its fair shair of problems
KingDWS   7/23/2012 5:19:35 PM
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I wouldn't worry about this unless they ground the fleet then AVOID. A year in the life of a airliner is a long time. And during that period it will be monitored normally and I would bet money in a quite paranoid fashion about these cracks. If the customers loose confidence in a design and won't fly it that design can soon be in trouble, witness the MD vs Loughheed. Both looked about the same ie 3 engines but only the MD was seeing issues with floors and controls yet people wouldn't book a flight on either. And other than flying boxes for Fedex there aren't any around in the air.

For the 380 this is just another problem its had. It may turn out to be nothing. For the most part Airbus designs are typically pushed a bit further than what Boeing will do. In the case of the 380 they set goals for performance and weight that forced them to use some semi exotic materials such as the alli alloy. That saves about 20% in weight but as a few guys have mentioned is a "slight" pain to work with. And the company that pioneered its use and has the most experience was bought out by a company called Boing so Airbus was unlikely to get much help in designing a competitor. And this may just require a retraining of the workforce. We had headaches from the floor guys banging stuff together in the same ole usual way which usually meant they ignored what we designed cuz they knew better. We even tried putting written instructions that they comply with all specifications and to contact engineering if there were any questions and hence was born MIL-TDP-41 which we stamped on every drawing for about a month. And of course no one asked about it until a aqap inspector saw it and asked as he was not familiar with it. So we had to explain to him that it meant "Make It Like The Damn Plans For Once"

Ann R. Thryft
User Rank
Blogger
Re: Its fair shair of problems
Ann R. Thryft   6/28/2012 1:00:16 PM
NO RATINGS
Thanks for clarifying. Your experience with AlLi sure sounds like the problems identified in the unnamed aluminum alloy. And that link gives a wealth of detail about the A380 materials.

ScotCan
User Rank
Platinum
Re: Its fair shair of problems
ScotCan   6/27/2012 2:43:30 PM
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It wasn't intended to imply that the A 380 problem was related to AlLi, rather experience with the material has shown that it is a tricky material to work with and doesn't like preload. 7449 is the Aluminum Alloy in the A 380 ribs which are cracking and it is susceptible to Stress Corrosion Cracking and it also doesn't like preload.

http://www.keytometals.com/page.aspx?ID=CheckArticle&site=ktn&NM=227 has a good write up on the materials development for the A 380 FYI

 

Ann R. Thryft
User Rank
Blogger
Re: Its fair shair of problems
Ann R. Thryft   6/27/2012 1:12:55 PM
NO RATINGS
ScotCan, thanks for all the detailed feedback. The cracks were stated to be in an aluminum alloy, although it was unnamed. You seem to be implying that the alloy is AlLi--is this true? If so, can you tell us how you know that for a fact?

ScotCan
User Rank
Platinum
Re: Its fair shair of problems
ScotCan   6/26/2012 5:17:38 PM
NO RATINGS
Hi Beth, the cracks will be monitored for growth vs flight hours and an update would be issued regarding the seriousness or otherwise of the condition. The communication problems with the Europeans reminds me of a helicopter program they once ran where the Germans and the French were partners and since very few Germans spoke French and few French spoke German they settled as English as a common language! So, there were 3 sets of paperwork kicking around to make everything legal one in German, one in French and one in English!

ScotCan
User Rank
Platinum
Re: Wrong testing procedures...
ScotCan   6/26/2012 5:06:35 PM
NO RATINGS
You're very welcome!!! 40 years in aerospace Design/Liaison gives a pretty major oversight of what goes on in these human endeavours...methinks the experienced hands should be using this technology (digital communication) to get the word out and keep things from going astray.

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