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It's important to note that this is just Airbus's best guess as to the cause, as there's no smoking gun: they simply exhausted their troubleshooting and were le
by RankingMember 10mo ago
It's important to note that this is just Airbus's best guess as to the cause, as there's no smoking gun: they simply exhausted their troubleshooting and were left scratching their heads so this was the "least unlikely" cause they could come up with given the circumstances.
- serial_dev 10mo ago…but if I respond with this to a user’s bug report, I’m “not taking this seriously”…
- RealityVoid 10mo agoI thought the same, but in a deeper dive into the postmortem, I think it's not a cop out from their side. The report is actually really well done ( I personally was impressed). The reasons it probably was a bit flip is that the CPU did not have edac on it in this instance so bit flips are expected. The consensus mechanism failed in this case and that is what they are updating, because even though the module gave wrong data because of presumably bit flips, the consensus should have prevented the dive.
- N19PEDL2 10mo agoDo you happen to have a link to that report?
- RealityVoid 10mo agoSure. https://www.atsb.gov.au/sites/default/files/media/3532398/ao2008070.pdf#%5B%7B%22num%22%3A837%2C%22gen%22%3A0%7D%2C%7B%22name%22%3A%22FitH%22%7D%2C207%5D https://www.atsb.gov.au/sites/default/files/media/3532398/ao... My reaction was initially that it was a cop out, but looking a bit in the report and thinking things through, I think that, yes, it's most likely a bit flip.
- meatmanek 10mo agoThis is for a similar incident that happened in 2008, not the Jetblue incident from October of this year.
- RealityVoid 10mo agoOh my god, you are correct. I read the technical details and did not bother to check it's the same issue. I am mortified. Apologies.
- RachelF 10mo agoI would argue that designing avionics without EDAC is negligent design by Airbus. Most modern servers at least implement ECC on their RAM. I would expect flight electronics to be designed to a higher standard.
- 15155 10mo agoMulti-module consensus is a form of EDAC - it's exceptionally unlikely that multiple units will fail identically simultaneously.
- skylurk 10mo agoSure, until management sells a version with reduced redundancy to Ethiopia and Indonesia. Swiss cheese model and all that.
- ahartmetz 10mo ago>version with reduced redundancy Not going to happen. The potentially huge cost to their reputation alone makes it not worth it, the modification would cost money and make logistics more difficult, and the plane couldn't be used (or sold) worldwide anymore.
- skylurk 10mo agoI think you are being sarcastic, but just in case: https://www.nytimes.com/2019/05/05/business/boeing-737-max-warning-light.html https://www.nytimes.com/2019/05/05/business/boeing-737-max-w... https://www.boeing.com/737-max-updates/mcas/ https://www.boeing.com/737-max-updates/mcas/
- serial_dev 10mo agoThe links are Boeing and this article and thread are about Airbus. Two different companies. Boeing had tons of failures recently, flight search services started adding filters for the airplane because people didn’t want to fly with them. Airbus is doing better for now, hopefully it will stay that way.
- thegrim33 10mo agoIsn't a major feature of consensus algorithms for them to be tolerant to failures? Even basic algorithms take error handling into account and shouldn't be taken out by a bit flip in any one component.
- RealityVoid 10mo agoYes. To clarify, my understanding of _this_ particular incident was wrong because it was based on reading the report of a previous incident. But for the 2008 incident I read and linked the report, that was what happened. The ADIRU unit did probably get a SEU event and that should have been mitigated by the design of the ELAC unit. The ELAC unit failed to mitigate it so that's the part that they probaby fixed.
- DecentShoes 10mo agoJust like that Mario 64 speedrunner! People say it's like it's gospel, but it's really just a bunch of peoples best guess. No proof.