5 ms·

This is so important… most airlines are inherently stable by design but the 737 Max requires software to be stable

twtw 8y ago
No, it doesn't. The 737 max has software to prevent stalls in situations outside of the profile of normal flight. As does e.g. the A320.
- dmix 8y ago
  Yep Apparently the main problem seems to be the fact there is a single point of failure (a single AoA sensor) and it could be resolved by having multiple sensors. Not that some sort of new automation is occurring than before.
  - ggreer 8y ago
    The 737 max has multiple AoA sensors. Having multiple sensors doesn't always help, as failures are correlated. For example, there was an Airbus A321 that had 2 of its 3 sensors get stuck in the same position due to icing.[1] The computer thought that the one working sensor was malfunctioning and disregarded it. It then engaged stall protection, dipping the nose and causing the plane to dive at 4,000ft per minute. > The captain continued to hold “more than 50%” rearward stick in stable flight for a period, but with help from technicians on the ground, the crew was able to reconfigure the automation into the aircraft’s alternate control law, rather than its normal “direct” law. The action removed the alpha-protection checks and canceled the nose-down input. The aircraft then continued to its destination. These failure modes tend to happen more with Airbus planes because their flight control systems default to overriding human input if the computer deems it unsafe. Boeing's flight computers will give more resistance in the controls, but they mostly won't prevent the pilot from doing what they want to do. The exceptions (such as auto-trim and stall prevention) can be disabled with by flipping a couple of switches. 1. https://aviationweek.com/commercial-aviation/german-investigators-cast-wider-net-frozen-aoa-sensors-pamplona-dive-incident https://aviationweek.com/commercial-aviation/german-investig...
    - dmix 8y ago
      True but 2/3 failing instead of 1/1 is still the better option. I’ve read the Max only used one sensor for the MCAS system. But I’m not an expert on the subject so I’ll defer to the reports and more knowedgable people.
    - ScottBurson 8y ago
      I recall reading somewhere that while the 737Max has two AoA sensors, only one of them is connected to the MCAS.
- youngtaff 8y ago
  "The automatic trim we described last week has a name, MCAS, or Maneuvering Characteristics Automation System. It’s unique to the MAX because the 737 MAX no longer has the docile pitch characteristics of the 737NG at high Angles Of Attack (AOA). This is caused by the larger engine nacelles covering the higher bypass LEAP-1B engines." Boeing only told pilots MCAS existed following the Lion crash, almost 18 months after the plane entered service https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/ https://leehamnews.com/2018/11/14/boeings-automatic-trim-for...
AnabeeKnox 8y ago
absolute nonsense
- dang 8y ago
  Maybe so, but please don't post shallow dismissals to Hacker News (https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html). If you know more, it would be better share some of what you know, so we can learn something. Alternatively, it's always fine to post nothing. When you do post, though, please make it civil and substantive.
vpribish 8y ago
this is not true, where did you get this?

twtw 8y ago

No, it doesn't. The 737 max has software to prevent stalls in situations outside of the profile of normal flight. As does e.g. the A320.

dmix 8y ago
Yep Apparently the main problem seems to be the fact there is a single point of failure (a single AoA sensor) and it could be resolved by having multiple sensors. Not that some sort of new automation is occurring than before.
- ggreer 8y ago
  The 737 max has multiple AoA sensors. Having multiple sensors doesn't always help, as failures are correlated. For example, there was an Airbus A321 that had 2 of its 3 sensors get stuck in the same position due to icing.[1] The computer thought that the one working sensor was malfunctioning and disregarded it. It then engaged stall protection, dipping the nose and causing the plane to dive at 4,000ft per minute. > The captain continued to hold “more than 50%” rearward stick in stable flight for a period, but with help from technicians on the ground, the crew was able to reconfigure the automation into the aircraft’s alternate control law, rather than its normal “direct” law. The action removed the alpha-protection checks and canceled the nose-down input. The aircraft then continued to its destination. These failure modes tend to happen more with Airbus planes because their flight control systems default to overriding human input if the computer deems it unsafe. Boeing's flight computers will give more resistance in the controls, but they mostly won't prevent the pilot from doing what they want to do. The exceptions (such as auto-trim and stall prevention) can be disabled with by flipping a couple of switches. 1. https://aviationweek.com/commercial-aviation/german-investigators-cast-wider-net-frozen-aoa-sensors-pamplona-dive-incident https://aviationweek.com/commercial-aviation/german-investig...
  - dmix 8y ago
    True but 2/3 failing instead of 1/1 is still the better option. I’ve read the Max only used one sensor for the MCAS system. But I’m not an expert on the subject so I’ll defer to the reports and more knowedgable people.
  - ScottBurson 8y ago
    I recall reading somewhere that while the 737Max has two AoA sensors, only one of them is connected to the MCAS.
youngtaff 8y ago
"The automatic trim we described last week has a name, MCAS, or Maneuvering Characteristics Automation System. It’s unique to the MAX because the 737 MAX no longer has the docile pitch characteristics of the 737NG at high Angles Of Attack (AOA). This is caused by the larger engine nacelles covering the higher bypass LEAP-1B engines." Boeing only told pilots MCAS existed following the Lion crash, almost 18 months after the plane entered service https://leehamnews.com/2018/11/14/boeings-automatic-trim-for-the-737-max-was-not-disclosed-to-the-pilots/ https://leehamnews.com/2018/11/14/boeings-automatic-trim-for...

AnabeeKnox 8y ago

absolute nonsense

dang 8y ago
Maybe so, but please don't post shallow dismissals to Hacker News (https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html). If you know more, it would be better share some of what you know, so we can learn something. Alternatively, it's always fine to post nothing. When you do post, though, please make it civil and substantive.

vpribish 8y ago

this is not true, where did you get this?