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Breaking news: Ethiopian Airlines flight has crashed on way to Nairobi

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  • Originally posted by Evan View Post
    The gyros will tell you your attitude relative the to horizon, but not relative to the relative wind. You need pitot data for that. How are you going to get accurate pitot readings if you don't know your AoA?
    Acknowledging that I don't know exactly how these sensor-less AoA indicators work or how accurate and reliable they are....

    You don't need AoA to get good-enough airspeed data. For many decades the airspeed indicator was just a mechanical differential pressure manometer calibrated in a fancy and fake speed scale (remember that the indicated airspeed is not a speed). And in may planes it still is. Sure, you can use AoA to super-fine-tune the airspeed. But look at the plots of airspeed left and right of the Lion Air crash and see how much (read how little) they differ, when the AoA had a difference of 20 (TWENTY) degrees!!!! +/- 5 or 10 knots of airspeed (out of 150 knots) will not have a big influence in the reverse-engineered AoA computation.

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    --- Defend what you say with arguments, not by imposing your credentials ---

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    • Here is the description of an AoA indicator that doesn't use vanes (but still has a dedicated sensor)

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      --- Defend what you say with arguments, not by imposing your credentials ---

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      • Originally posted by Gabriel View Post
        Acknowledging that I don't know exactly how these sensor-less AoA indicators work or how accurate and reliable they are....

        You don't need AoA to get good-enough airspeed data.
        Perhaps not, but you need some reliable airspeed data. What happens when the pitots become iced and the speeds are lost? You lose the sensorless AoA value? Now what if this happens when one of the AoA vanes is already malfunctioning? You lose MCAS. So now you've lost airspeeds and the stall protection feature needed to overcome the airplane's inherent aerodynamic stability flaw. Sure, it seems unlikely, but it also seems like the kind of swiss cheese scenario engineers never see coming.

        As opposed to keeping things simple by simply adding a third standby AoA vane. Why is that so much to ask for?

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        • Originally posted by Evan View Post
          As opposed to keeping things simple by simply adding a third standby AoA vane.
          Until 2 of them fail. Even if it is for stupidity. Sure, it seems unlikely, but it also seems like the kind of Swiss cheese scenario engineers never see coming.

          --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
          --- Defend what you say with arguments, not by imposing your credentials ---

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          • Originally posted by Gabriel View Post
            Until 2 of them fail. Even if it is for stupidity. Sure, it seems unlikely, but it also seems like the kind of Swiss cheese scenario engineers never see coming.
            Not quite touché. Unlike pitots, AoA sensors do not seem to fail due to common environmental factors. They do not 'ingest' anything. They do occasionally fail, but [unless there is a supply chain problem here**] the chances of two failing in one flight is probably remote enough to be considered "practically impossible".

            Unless, of course, there is spectacular stupidy involved. No airframe should be rated to withstand spectacular stupidity.

            ** Which is something we need to be asking.

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            • Originally posted by Evan View Post
              Not quite touché. Unlike pitots, AoA sensors do not seem to fail due to common environmental factors. They do not 'ingest' anything. They do occasionally fail, but [unless there is a supply chain problem here**] the chances of two failing in one flight is probably remote enough to be considered "practically impossible".

              Unless, of course, there is spectacular stupidy involved. No airframe should be rated to withstand spectacular stupidity.

              ** Which is something we need to be asking.
              The 2 AoA sensors did not fail in flight. They failed in ground. They were already failed when the plane took off (at least both in Lion Air flights, because in Ethiopian we don't know yet, but let's assume that it was the same, then the pilots called advising of problems immediately after take off). Even more, at least Lion AIr's never worked properly. It was replaced before the flight that had the 1st incident that was managed by the crew. The risk of a "good" AoA sensor failing in mid-flight seems to be extremely low. The risk of that happening at the same time that you have a pitot tube problem and where in addition you need MCAS to save the day from a stall seems "practically impossible". You have 3 sensor failures (of 2 different kind and with different failure modes) plus the pilots are about to stall the plane. It's 5 conditions at the same time. Note that with 2 AoA vanes and 2 sensor-less systems (that is, software) tied to each air data system (left and right) you have 4 independent sources of AoA with 2 different principles of operations and failure modes. You need only 2 of them agreeing and if none agree, well, that't tbe time for the pilot to save the day, follow the UAS memory items and don't pull up like crazy so you don;t need the MCAS to help (I am considering that the MCAS will not act if there is no pair of AoAs that agrees).

              --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
              --- Defend what you say with arguments, not by imposing your credentials ---

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              • Originally posted by Gabriel View Post
                The 2 AoA sensors did not fail in flight. They failed in ground. They were already failed when the plane took off (at least both in Lion Air flights, because in Ethiopian we don't know yet, but let's assume that it was the same, then the pilots called advising of problems immediately after take off). Even more, at least Lion AIr's never worked properly. It was replaced before the flight that had the 1st incident that was managed by the crew. The risk of a "good" AoA sensor failing in mid-flight seems to be extremely low. The risk of that happening at the same time that you have a pitot tube problem and where in addition you need MCAS to save the day from a stall seems "practically impossible". You have 3 sensor failures (of 2 different kind and with different failure modes) plus the pilots are about to stall the plane. It's 5 conditions at the same time. Note that with 2 AoA vanes and 2 sensor-less systems (that is, software) tied to each air data system (left and right) you have 4 independent sources of AoA with 2 different principles of operations and failure modes. You need only 2 of them agreeing and if none agree, well, that't tbe time for the pilot to save the day, follow the UAS memory items and don't pull up like crazy so you don;t need the MCAS to help (I am considering that the MCAS will not act if there is no pair of AoAs that agrees).
                I suspect either the replacement sensor was incorrectly installed/miscalibrated or there are some bad sensors coming down the supply chain. These should be identical to the NG, but maybe Boeing had to find another supplier to meet their hurried schedule, or their part supplier had to find another component supplier, etc, etc. The New York TImes quoted an engineer who had worked on the -MAX testifying to receiving 'sloppy' wiring plans that could result in failures. We are just beginning to hear the story of how the -MAX was rushed through production. This is not your traditional made-with-care-in-Everett Boeing. It was designed and constructed under great time-pressure and those traditional corners appear to have been cut. I'm not looking forward to flying on it.

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                • 20% discount on Brilliant!👉 https://brilliant.org/mentourpilot/ If MCAS would activate on The Boeing 737MAX, what is the procedure that the pilots are suppo...

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                  • Originally posted by Evan View Post
                    Actually, the entire 737-MAX feels like a fool's errand to me. Why not do things right in the first place?
                    $$$$$$$$$$$$$$$$$$$$$$$$$$$$$

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                    • Originally posted by birdguts
                      just wondering if the complex flight automation could be played with by malice on the ground. The same type of people that stab Londoners, fly drones over the airports, hack elections..
                      Trump's view on air travel is correct - go back to basics.
                      Yes, it could. Some expert in the proprietary units controlling the MCAS can replace the code with one that was tampered with (it's not like it would work with HTML or Python). Or someone can install a parallel connection to the trim motor with a switch that is operated by remote control from the ground. Or the terrorists can have taken a young person, brainwashed since he was a kid, have them pretend be a good citizen and train as a regular pilot, but always had this suicide mission waiting to be executed and he just killed the other pilot and manually applied full nose-down trim. Or perhaps a micro-meteor impacted the plane and created a short that actuated the trim.

                      I mean, the moment that you ask "could", anything that is not impossible is possible.

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                      • Originally posted by Gabriel View Post
                        Yes, it could. Some expert in the proprietary units controlling the MCAS can replace the code with one that was tampered with (it's not like it would work with HTML or Python). Or someone can install a parallel connection to the trim motor with a switch that is operated by remote control from the ground. Or the terrorists can have taken a young person, brainwashed since he was a kid, have them pretend be a good citizen and train as a regular pilot, but always had this suicide mission waiting to be executed and he just killed the other pilot and manually applied full nose-down trim. Or perhaps a micro-meteor impacted the plane and created a short that actuated the trim.
                        Or mind-control. Don't forget about the Russian mind-control ray.

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                        • Originally posted by birdguts
                          Trump's view on air travel is correct - go back to basics.
                          Trump's view on air travel is like that of a man in a cave, with no light to speak of.

                          These two crashes will turn out to be the result of not moving forward enough. Boeing has tried to patch an old airframe with new technology. Boeing should have designed an entirely new plane with new technology. Like they did with the 787.

                          Can you count on one hand how many 787 crashes have occurred since its introduction over seven years ago?

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                          • Originally posted by birdguts
                            There were three crashes in the last 6 months + some reported near misses from other airlines.
                            3 crashes involving 737 max 8 in the last 6 months? wasnt that 2 crashes only?

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                            • Originally posted by birdguts
                              3 Boeings. By narrowing to one model, you are implying stuff. Keep it objective
                              ok.

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                              • Originally posted by birdguts
                                3 Boeings. By narrowing to one model, you are implying stuff. Keep it objective
                                Weren't you implying that we should 'go back to basics'? The third one was a 767, which is relatively 'basic' and has a spectacular safety record.

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