GAO: Questions remain about safety of composite jets, such as Boeing 787

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  1. sobore
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    sobore Gold Member

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    http://blog.seattlepi.com/aerospace...s-remain-about-safety-of-composite-airliners/
    U.S. and European regulators followed procedures in certifying Boeing’s mostly composite 787 Dreamliner aircraft and took steps to address potential safety concerns, but it’s too soon to say whether these steps are enough, Congressional auditors reported Thursday (pdf).

    “It is too early to fully assess the adequacy of FAA and industry efforts to address safety-related concerns and to build sufficient capacity to handle and oversee composite maintenance and repair, given that composite airframe structures in currently in-service airplanes are mostly limited to the secondary structures,” Gerald Dillingham, directors of Physical Infrastructure Issues at the Government Accountability Office, wrote in a report requested by the top Democrats on the U.S. House of Representatives Committee on Science, Space, and Technology, that committee’s Subcommittee on Investigations and Oversight and the Aviation Subcommittee of the Committee on Transportation and Infrastructure.

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  2. jbcarioca
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    jbcarioca Gold Member

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    A trifle odd, this, given that certification of the Beech Starship, all composite, back in 1989. Myriad issues, including the canard configuration, caused issues, and only 53 were ever made. However, the composite experience gained was huge, and no problems ever happened in use. The issues of maintenance and repair are not materially different in primary vs secondary structures, since the secondary ones are also mostly crucial for safe flight. This seems like a bit of CYA to me, just in case something does happen. With a 100% new aircraft there certainly will be some issues, there always are. I would be surprised if any of the issues related to composite structure per se.

    The only major composite issue for the B787 that I know of is that AA will need to start painting the aircraft, breaking a tradition that started with C. R. Smith in the 1930's.
     
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  3. mattsteg
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    mattsteg Gold Member

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    Long-cycle composite behavior isn't as well-understood as short-term behavior (and long-cycle metal fatigue). Also behavior when damaged is very different. It's a big step forward to move to composites on big planes, and one that wouldn't be made absent the belief that the technology is ready, but it still is somewhat of a step into the unknown.
     
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  4. jbcarioca
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    jbcarioca Gold Member

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    Why do you say that when all-composite planes were certified and flown without incident for twenty years and more? The statement clearly is applicable to metal as well given recent events with B757 and earlier ones with B737, for example. I do not argue that there is more to learn, only that there is nothing materially less-known in this case than there is in most others.
     
  5. mattsteg
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    mattsteg Gold Member

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    We've been flying predominantly aluminum planes for 80 years or more, and pressurized aircraft for similar, including large number of airframes with many, many cycles on them, and we still run into unexpected fatigue issues, as you point out. Even at 20 years, composites are much newer, and typically employed on smaller planes that do not see nearly the amount of cycles that a typical commercial airliner will, and are at a different scale. There is an added level of complexity with composities, where you have a matrix and fibers, their individual properties, how they interact with each other, and how the structure as a whole reacts to damage to portions of it.

    The aviation industry is tremendously conservative, and the composites they are using are doubtless years or decades "behind the times" in terms of state of the art materials, and accordingly tested, retested, and tested again many times over. The composites used in i.e. the 787 are probably the most well-characterized composite materials on the planet. Obviously composites are superior to aluminum in many ways, and every practical effort has been made to characterize their limits and how to test them.

    With all of that said, there's still an element of the unknown regarding how these planes will hold up over long-term, high-frequency use, and how well we will be able to maintain them. I do not want to give the impression that these are serious issues - we're moving to a higher-performance, but somewhat less-understood and more difficult to characterize/diagnose material than used previously, and there's always at least a nominal level of uncertainty in doing this.
     
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  6. sobore
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    sobore Gold Member

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    Is there a process in testing these composites that can simulate years of high frequency use?
    Does anyone know what this might be?
     
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  7. milchap
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    milchap Gold Member

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    If there is such a process, I presume that this was used to test the reliability of composites under a variety of uses.
     
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  8. mattsteg
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    mattsteg Gold Member

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    There are such processes and they are used, but until you can compare the results of the tests with the results of years of use, you are never assured that you have accounted for everything. This is normal and completely OK, by the way - there is no certainty in life!
     
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