3 ms·

At first I was thinking this was a component like internet or in-flight entertainment. Then: > This alarming-sounding situation comes about because, for reason

by kodah 5y ago

At first I was thinking this was a component like internet or in-flight entertainment. Then: > This alarming-sounding situation comes about because, for reasons the directive did not go into, the 787's common core system (CCS) stops filtering out stale data from key flight control displays. That stale data-monitoring function going down in turn "could lead to undetected or unannunciated loss of common data network (CDN) message age validation, combined with a CDN switch failure". Excuse me? Clearing the queue is not a "solution" if you have to remind a human to do it.

osenthuortuh 5y ago
Flight software is fabulously expensive to maintain and update, because it is safety critical. Furthermore, avionics programmers have a surprisingly captive audience. You would be surprised to learn how many problems are left to operator-based workarounds. It's actually fairly depressing and is part of the reason I transitioned to consumer software.
- sheepybloke 5y ago
  This! One way to mitigate safety critical issues is to pass it onto humans. This lowers how detailed you have to be when verifying the software, because you don't have to handle some critical aspects.
jsight 5y ago
Why not? These are maintenance heavy machines. Another line item in the maintenance procedure isn't necessarily a show-stopper. We have a tendancy in software to think that the software should do literally everything even with a user actively working against it. A lot of times that is even more harmful.
- kodah 5y ago
  Commercial and industrial software are very different things. Humans are an unreliable gate to safety and reliability, so if the gate to staying in the air is a human doing something that they can't see the results of it will inevitably fail.
  - jsight 5y ago
    > Commercial and industrial software are very different things. Exactly my point. Trust no humans is not a philosophy that applies in aviation software. It shouldn't apply quite as much in some other software either.
  - Veserv 5y ago
    And yet commercial airplanes, which have used this methodology for decades, are one of the most reliable mechanical systems humans have ever made. The mean-time-before-failure (MTBF) for component failures that impacted a 787 flight is ~40,000 hours [1] or about 4.5 flight-years per component failure, not full system failure, component failure. After nearly ~4,000,000 flight-hours there has not been a single full system failure or fatality yet in a 787 and this is only a fraction of the standard in aerospace so far. Between 2000 and 2010 there was ~1 death per 50 billion passenger-miles [2]. At an average speed of ~700 mph that would be 1 death per ~71 million passenger-hours or ~8150 passenger-years or ~125 airframe-years. People who want to design reliable systems and processes look to airplanes for how to do that. That does not mean the same techniques are applicable or cost-effective in a different context, but at the very least the historical processes have been empirically demonstrated to produce extremely high reliability far beyond what nearly every other industry can attain and what many industries, such as commercial software, do not even attempt to achieve and may not even think is possible in their environment. [1] https://www.sciencedirect.com/science/article/pii/S1000936120300546 https://www.sciencedirect.com/science/article/pii/S100093612... [2] https://en.wikipedia.org/wiki/Transportation_safety_in_the_United_States https://en.wikipedia.org/wiki/Transportation_safety_in_the_U...

by kodah 5y ago

osenthuortuh 5y ago

Flight software is fabulously expensive to maintain and update, because it is safety critical. Furthermore, avionics programmers have a surprisingly captive audience. You would be surprised to learn how many problems are left to operator-based workarounds. It's actually fairly depressing and is part of the reason I transitioned to consumer software.

sheepybloke 5y ago
This! One way to mitigate safety critical issues is to pass it onto humans. This lowers how detailed you have to be when verifying the software, because you don't have to handle some critical aspects.

jsight 5y ago

Why not? These are maintenance heavy machines. Another line item in the maintenance procedure isn't necessarily a show-stopper. We have a tendancy in software to think that the software should do literally everything even with a user actively working against it. A lot of times that is even more harmful.

kodah 5y ago
Commercial and industrial software are very different things. Humans are an unreliable gate to safety and reliability, so if the gate to staying in the air is a human doing something that they can't see the results of it will inevitably fail.
- jsight 5y ago
  > Commercial and industrial software are very different things. Exactly my point. Trust no humans is not a philosophy that applies in aviation software. It shouldn't apply quite as much in some other software either.
- Veserv 5y ago
  And yet commercial airplanes, which have used this methodology for decades, are one of the most reliable mechanical systems humans have ever made. The mean-time-before-failure (MTBF) for component failures that impacted a 787 flight is ~40,000 hours [1] or about 4.5 flight-years per component failure, not full system failure, component failure. After nearly ~4,000,000 flight-hours there has not been a single full system failure or fatality yet in a 787 and this is only a fraction of the standard in aerospace so far. Between 2000 and 2010 there was ~1 death per 50 billion passenger-miles [2]. At an average speed of ~700 mph that would be 1 death per ~71 million passenger-hours or ~8150 passenger-years or ~125 airframe-years. People who want to design reliable systems and processes look to airplanes for how to do that. That does not mean the same techniques are applicable or cost-effective in a different context, but at the very least the historical processes have been empirically demonstrated to produce extremely high reliability far beyond what nearly every other industry can attain and what many industries, such as commercial software, do not even attempt to achieve and may not even think is possible in their environment. [1] https://www.sciencedirect.com/science/article/pii/S1000936120300546 https://www.sciencedirect.com/science/article/pii/S100093612... [2] https://en.wikipedia.org/wiki/Transportation_safety_in_the_United_States https://en.wikipedia.org/wiki/Transportation_safety_in_the_U...