5 ms·

Interesting bits: > the majority of evidence from the flight data recorder and both thermal and mechanical damage pointed to an initiating event in a single ce

• vermontdevil 14y ago
  From what I have been reading, it seems non-engineering people have taken over Boeing. I wouldn't be surprised these suits have been pressuring everyone to get the 787 out and the culture goes from there.
  • dmethvin 14y ago
    It really feels a lot like the shuttle disasters, with Boeing playing the part of NASA and delegating work out to contractors who feel they must get something out or risk losing the next big contract. God forbid if this does come down to a disaster it will be even more difficult to unravel, since this time it will cross political and cultural boundaries.
  • wpietri 14y ago
    That reminds me of HP. I grew up using their awesome technical products (RPN represent!) and now I get sad every time I see them in the news. Have any pointers on the switch from engineering-driven to whatever they are now? I'd love to read more.
    • InclinedPlane 14y ago
      I have an hp48 emulator on my phone, I use it all the time these days.
• fusiongyro 14y ago
  I thought this sentence was particularly revealing: "In tests to validate these assessments, Boeing found no evidence of cell-to-cell propagation or fire, both of which occurred in the JAL event."
  • magic_haze 14y ago
    yeah, that was the part that had me confused... how does that square with the 10-million-hour figure? Or is a fire not considered a "smoke emission event"?
    • KMag 14y ago
      You appear to be mis-parsing "In tests to validate these assessments". "These assessments" refers to Boeing's certification assessments, not the NTSB's incident assessment. Long before any incidents, Boeing estimated a smoke event as once in 10 million hours. The measured rate of fire events is much higher than Boeing's pre-certification estimate of the rate of smoke events. There is absolutely no implication that Boeing's definition of smoke event doesn't include fires. Edit: as mentioned below, the real problem seems to be that you're assuming smoke implies fire, when smoke merely suggests fire.
      • magic_haze 14y ago
        No, I understand that. Here's the full context of the two sentences: > During the 787 certification process, Boeing studied possible failures that could occur within the battery. Those assessments included the likelihood of particular types of failures occurring, as well as the effects they could have on the battery. In tests to validate these assessments, Boeing found no evidence of cell-to-cell propagation or fire, both of which occurred in the JAL event. The NTSB learned that as part of the risk assessment Boeing conducted during the certification process, it determined that the likelihood of a smoke emission event from a 787 battery would occur less than once in every 10 million flight hours. So, to summarize, in the certification process, Boeing claimed: a: no evidence of a fire. b: a 10-million-hour estimate for a "smoke event". My original question was merely from a statistical/technical perspective: how is this figure calculated if they have no evidence of the event they are supposed to measure? From my understanding, automobiles undergoing similar certification are tested under abnormally rigorous conditions, and the chances of those conditions happening are taken into account when calculating failure rates. But if Boeing claims it had no evidence of a fire happening at all, what is the reasoning behind the number? Is it just a convenient way to say probability=0?
• smackfu 14y ago
  > it is shocking how badly Boeing got its estimates wrong. Does anyone know exactly how they came up with these numbers? Eh, I don't think that means much. You can't put odds on an unknown failure mode.
  • InclinedPlane 14y ago
    Thermal runaway in Lithium-ion and Lithium-polymer batteries is not an "unknown failure mode", it should be constantly in the front of mind every day for everyone working on such cells.
• InclinedPlane 14y ago
  I think it's unfair to call Musk's opinion a "guess". It is a sound criticism of the fundamental safety margin of those cells, and it was backed up by other experts.
  • zalzane 14y ago
    I disagree. Any statement about a piece of engineering without having seen the schematics, diagrams, and tests involved is at best, speculation.
    • fnordfnordfnord 14y ago
      I might call it an informed opinion.
    • Eliezer 14y ago
      He was right on this occasion. I always wait to criticize other people's methods until an occasion when they're actually wrong.
    • InclinedPlane 14y ago
      If it's a fundamental design aspect such as the size and spacing of cells in a battery I don't think detailed schematics are necessary. If I saw a sketch of a car design which called for the fuel tank to be an open top 5 gallon plastic bucket sitting in the passenger's seat with a hose going into it I wouldn't need any additional or more finely grained details to be able to definitively say that it's an inherently unsafe system. If I saw a sketch of a bridge with a 50 meter gap in the bridge deck I shouldn't think to myself "oh, maybe it's just for hovercars, or maybe they've invented something revolutionary" I should think "that's a fundamentally broken bridge design". Sometimes the finer details of a design matter, and sometimes there's no possible way for them to correct for a fundamental design error. Unless Boeing's subcontractors have made ground breaking advances in the design of lithium-ion cells then these criticisms are enormously well founded. And as we've seen those subcontractors have not, in fact, found a magical escape from the fundamental problems of thermal runaway and chain-reaction in lithium-ion cells.
• fnordfnordfnord 14y ago
  >Seems like Musk was right in his guess after all. Yeah, some luck that guy has...
  • maaku 14y ago
    Either that, or he runs the only other engineering company of similar scale using similar batteries under similar conditions.