Amid reports of hairline cracks in the wings of its A380 superjumbo, Airbus has delayed making long-term repairs to the passenger jet until 2013. Earlier this year several airlines, including Qantas and Lufthansa, found the cracks in the plane's wings, although Airbus has stated that they don't pose safety risks.
It turns out that the cracks occurred because of a combination of materials and assembly issues, as well as problems with the design process in adapting new materials into an existing design. They were caused by the interface between metal and carbon-fiber composite components inside the double-decker airliner's wings.
"We thought we understood the properties of the materials and the interface between carbon fiber and metal and found out the wrong way we didn't know everything," said the company's chief executive officer Tom Enders at a briefing in Toulouse, France. Airbus also didn't have the right design controls in place to anticipate possible problems, he said.
The Airbus A380 demonstrator prepares to take place in the 2012 FIDAE (Feria Internacional del Aire y del Espacio) International Air and Space Show near Santiago, Chile. (Source: Airbus)
The reason for the cracks has been traced to a not-flexible-enough aluminum alloy used to make the wing brackets, as well as the method for inserting fasteners through holes. The cracks were found in the aluminum L-shaped brackets, called rib feet, that connect the wing's aluminum skin to its structural ribs, which are made from a combination of metal and composites. Each wing contains 2,000 brackets. Airbus will start building replacement wings for the in-service A380s next year using a new type of aluminum, said Enders.
A short-term fix to replace the brackets that takes around five days has been applied to about a third of the A380s currently in service, and will be extended to more in operation. Longer-term repairs to each jet will require the plane to be grounded for eight weeks if the work is done in one sitting. Those repairs can either be done before delivery, or after delivery during "heavy check" maintenance visits after two and four years.
The new, permanent wingset redesign must be approved by the European Aviation Safety Agency before it can be incorporated into future planes. Since it won't be included in new planes until 2013, those planes won't come off the final assembly line until 2014. Meanwhile, Airbus's parent company, European Aeronautic, Defence & Space Co., said that Airbus will assume the costs of repairing wingsets of the A380, which entered service in 2007. The company is negotiating with airlines to schedule the repairs.
Delaying wing replacements until 2013 means that Airbus can't deliver as many A380s during 2012 as it had expected. The company is also slowing delivery of its single-aisle A320.
It's interesting that the cracks were found in the aluminum and not the composites. Earlier this year, Boeing had composite delamination problems in the fuselage of its 787 Dreamliner due to incorrect shim placements. But Boeing said those repairs would require only 10 to 14 days per plane and would not affect future deliveries. If Boeing's problem can be resolved with better shims, and if composites can go to Jupiter, the design issues are more likely to be at fault than are inherent drawbacks in the materials. That also applies to Airbus's problems.
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.
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.
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"
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?
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.
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...
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.
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