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I'm not sure there was a sensor issue here. It appears that the Flight Computer monitoring routine for the Rudder position somehow caused all three computers to

by zymhan 5y ago

I'm not sure there was a sensor issue here. It appears that the Flight Computer monitoring routine for the Rudder position somehow caused all three computers to crash. This was somehow exacerbated by the pilot's rudder inputs, which I don't fully understand > the combination of a high COM/MON channels asynchronism and the pilot pedal inputs resulted in the rudder order difference between the two channels to exceed the monitoring threshold The flight computer failure resulted in the inability to use two braking mechanisms, Thrust Reversers (make air from the engine go forwardsish) and Spoilers (stop the wing from producing lift, putting more weight on the wheels and making the brakes more effective.

salawat 5y ago
The thing that bugs me is "did the pilots engage those systems manually?" And How was their reaction time doing so compared to someone who would be used to doing so via muscle memory on the regular? Automating things is nice and all, but there is something to be said for keeping manual skills sharp.
- avianlyric 5y ago
  Well in this case the entire system failed safe after a pretty catastrophic failure of the automated systems. So on the whole I would say this incident demonstrates that the current safety standards, contingency plans, and pilot train all work as needed. I don’t think there’s anything here to suggest that the pilots manual skills are rusty. And when talking about the specific systems that didn’t active. They didn’t activate because they require a positive indication from the flight computers that’s it’s safe to activate. Something that probably can’t be overridden by the pilots. Which is why the planning process for flights requires pilots to assume they won’t work, and ensure the runway is long enough for the worst possible scenario.
  - scoopertrooper 5y ago
    > So on the whole I would say this incident demonstrates that the current safety standards, contingency plans, and pilot train all work as needed. I don’t think there’s anything here to suggest that the pilots manual skills are rusty According to the article they had 30 feet of runway remaining when they brought the plane to a halt. So, yeah I guess, everything worked out, but I wouldn't say that was indicative of a well oiled machine.
    - avianlyric 5y ago
      Well yes, that’s one of the criticisms in the final report. That the flight plans didn’t provide adequate additional runway length to handle this specific runway in the rain. I think there may have also been criticism of the airport runway maintenance with too much rubber build up on the runway. All of which resulted in this plane having less margin for error than it should have done. But that’s what we have safety factors, to account human error and natural deviation in the environment. In this case that safety factor prevented this incident from being more serious, and post-mortem has identified areas for improvement, which will no doubt be instituted. To me, all of this points to extremely robust safety procedures that have prevented the loss of life in an extreme and unusual scenario, and is capable of analysing the outcome to find ways of further improving safety so it’s capable of surviving even more extreme situations. Expecting any safety system to cope perfectly with every scenario is unrealistic, but one that handles pretty much all of them without any serious injury or loss of life is clearly working very well.
      - scoopertrooper 5y ago
        To put things in perspective, an A330 lands at 140 kts, which translates to 236 ft/sec, which means that if the plane had travelled along the runway at 140 kts for 130 milliseconds longer, then they'd have a runway excursion. Now, they would have decelerated before the malfunction, so maybe a 500 millisecond slower reaction time would have caused the plane to leave the runway. Maybe, 3 second delayed reaction time would have resulted in the plane hitting a building or a wall. That doesn't sound a robust safety factor to me.
        avianlyric 5y ago
        You’re making a lot of assumptions about the braking capability of this plane. Notably you’re assuming that the plane was completely incapable of stopping in a shorter distance, ignoring pilot reaction time. The report mentions that the pilots failed to apply maximum manual breaking till they were a good distance down the runway. A reasonable interpretation of this fact is that the pilots were afraid of locking up the wheels by accident, so they were applying the minimum breaking they though they could get away with. It was only when they were getting towards the end of the runway that the pilots realised they really needed to break a tad harder. In short if the runway had been an extra 300feet long, the pilots would have still stopped the plane within 30ft of the end. It’s perfectly natural and completely rational for people to consume every ounce of available safety factor when your dealing with the unknown. So measuring the consumed safety factor after the fact isn’t inherently useful or indicative of what the actual minimum safety margin needed to be. Additionally a runway excursion is not inherently dangerous, provided you don’t do it at high speed. It never going to be very good for the plane, but leaving the runway doesn’t automatically result in all the passengers dying.

by zymhan 5y ago

salawat 5y ago

The thing that bugs me is "did the pilots engage those systems manually?" And How was their reaction time doing so compared to someone who would be used to doing so via muscle memory on the regular? Automating things is nice and all, but there is something to be said for keeping manual skills sharp.

avianlyric 5y ago
Well in this case the entire system failed safe after a pretty catastrophic failure of the automated systems. So on the whole I would say this incident demonstrates that the current safety standards, contingency plans, and pilot train all work as needed. I don’t think there’s anything here to suggest that the pilots manual skills are rusty. And when talking about the specific systems that didn’t active. They didn’t activate because they require a positive indication from the flight computers that’s it’s safe to activate. Something that probably can’t be overridden by the pilots. Which is why the planning process for flights requires pilots to assume they won’t work, and ensure the runway is long enough for the worst possible scenario.
- scoopertrooper 5y ago
  > So on the whole I would say this incident demonstrates that the current safety standards, contingency plans, and pilot train all work as needed. I don’t think there’s anything here to suggest that the pilots manual skills are rusty According to the article they had 30 feet of runway remaining when they brought the plane to a halt. So, yeah I guess, everything worked out, but I wouldn't say that was indicative of a well oiled machine.
  - avianlyric 5y ago
    Well yes, that’s one of the criticisms in the final report. That the flight plans didn’t provide adequate additional runway length to handle this specific runway in the rain. I think there may have also been criticism of the airport runway maintenance with too much rubber build up on the runway. All of which resulted in this plane having less margin for error than it should have done. But that’s what we have safety factors, to account human error and natural deviation in the environment. In this case that safety factor prevented this incident from being more serious, and post-mortem has identified areas for improvement, which will no doubt be instituted. To me, all of this points to extremely robust safety procedures that have prevented the loss of life in an extreme and unusual scenario, and is capable of analysing the outcome to find ways of further improving safety so it’s capable of surviving even more extreme situations. Expecting any safety system to cope perfectly with every scenario is unrealistic, but one that handles pretty much all of them without any serious injury or loss of life is clearly working very well.
    - scoopertrooper 5y ago
      To put things in perspective, an A330 lands at 140 kts, which translates to 236 ft/sec, which means that if the plane had travelled along the runway at 140 kts for 130 milliseconds longer, then they'd have a runway excursion. Now, they would have decelerated before the malfunction, so maybe a 500 millisecond slower reaction time would have caused the plane to leave the runway. Maybe, 3 second delayed reaction time would have resulted in the plane hitting a building or a wall. That doesn't sound a robust safety factor to me.
      - avianlyric 5y ago
        You’re making a lot of assumptions about the braking capability of this plane. Notably you’re assuming that the plane was completely incapable of stopping in a shorter distance, ignoring pilot reaction time. The report mentions that the pilots failed to apply maximum manual breaking till they were a good distance down the runway. A reasonable interpretation of this fact is that the pilots were afraid of locking up the wheels by accident, so they were applying the minimum breaking they though they could get away with. It was only when they were getting towards the end of the runway that the pilots realised they really needed to break a tad harder. In short if the runway had been an extra 300feet long, the pilots would have still stopped the plane within 30ft of the end. It’s perfectly natural and completely rational for people to consume every ounce of available safety factor when your dealing with the unknown. So measuring the consumed safety factor after the fact isn’t inherently useful or indicative of what the actual minimum safety margin needed to be. Additionally a runway excursion is not inherently dangerous, provided you don’t do it at high speed. It never going to be very good for the plane, but leaving the runway doesn’t automatically result in all the passengers dying.