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> Same when two pilots give different instructions. That's only true for Airbus (and probably contributed to the loss of Air France 447, https://en.wikipedia.o

> Same when two pilots give different instructions. That's only true for Airbus (and probably contributed to the loss of Air France 447, https://en.wikipedia.org/wiki/Air_France_Flight_447 https://en.wikipedia.org/wiki/Air_France_Flight_447). In Boeing airplanes, the movement of the two yokes is synchronized.

neuronic 8y ago
> In Boeing airplanes, the movement of the two yokes is synchronized. So in case of two equally strong and equally determined pilots you still get averaging of opposing control inputs.
- wikibob 8y ago
  No, the failure mode is not two pilots consciously fighting against each other. The failure mode is two pilots who are UNAWARE they are commanding contradicting inputs. Airbus negligently averages these inputs. This is legacy tech debt because the physical design didn’t leave room to link the two controls. Now they are stuck because they feel they can’t change and have some planes that (dangerously) average the inputs, and some that are physically linked. When controls are physically linked, if one pilot thinks he should nose up, and the other tries to nose down, they can yell “what are you doing” at each other and this create an accurate mental model of what the other is intending. Think of this every time you fly Airbus. It’s very similar to debugging a production technology issue. Imagine you decide to restore the database to a snapshot from 1 hour ago, and at the same time someone else tries to restore to an earlier snapshot from 12 hours ago. Should the system average these inputs and restore from 6.5 hours ago? No, obviously not.
  - SmellyGeekBoy 8y ago
    > Think of this every time you fly Airbus. Why? They're not falling out of the sky so the system obviously works. Stop being a fanboy.
  - foldr 8y ago
    >Now they are stuck because they feel they can’t change and have some planes that (dangerously) average the inputs, and some that are physically linked. This is a really weird way to construe the situation. The accident report doesn't conclude that the handling of dual inputs was a factor, and it's clear from the transcripts that it wasn't. Airbus has no reason to change this. Merely linking sidesticks would be pointless in any case, since sidesticks don't have an identifiable position (but are used with brief movements away from center). It's hardly any easier for a pilot to passively observe the movements of his own sidestick than it is just to look over at the other pilot's stick.
    - neuronic 8y ago
      The commenter appears to have a vested interest in making Airbus look bad, otherwise the comment cannot be logically understood. Is there a case where the averaging of inputs has been proved catastrophic?
      - notfromhere 8y ago
        Air France 447
        foldr 8y ago
        Not according to the official accident report. This is a meme spread by an article in Popular Mechanics that came out long before the official report.
  - deleted 8y ago
    [deleted]
  - benhurmarcel 8y ago
    > Airbus negligently averages these inputs. On an Airbus, in case of dual input the pilots get a voice alarm and a warning lights up right in front of them. Also the stick has a switch to take priority, in case the other pilot continues to give dual input.
    - jandrese 8y ago
      Did AF447 not have this warning? One of the contributing factors to the crash was the copilot continuing to pull back on the stick even as the pilot attempted to push the nose down to get out of the stall.
      - livatlantis 8y ago
        I answered further up but: yes, it did. The DUAL INPUT alarms were audible in the cockpit voice recording. However, unbeknowst to the captain, the co-pilot used priority takeover on his side. (This was always visible on the panel + there was an audible "Priority right" warning around the end) Source: https://www.vanityfair.fr/actualites/articles/vol-af-447-rio-paris-reconstitution-des-minutes-qui-ont-precede-le-crash/23618 https://www.vanityfair.fr/actualites/articles/vol-af-447-rio...
        foldr 8y ago
        I'm not sure where you're getting the "unbeknownst" from. In the cockpit voice recorder transcripts attached to the official accident reports, it seems that the pilots were aware of who had control at any given point in time.
        jandrese 8y ago
        I remember right before the impact with the water the captain finally realizing why his controls aren't doing anything and asking the co-pilot to finally let go of his stick. IIRC they never did throttle up however. Ultimately the co-pilot got tunnel vision and thought for some reason they were in an overspeed condition for most of the incident and failed to communicate that effectively with the rest of the crew. He made a couple of comments about it, but nobody else realized that he was attempting to correct for an overspeed condition in the middle of a dead stall, even when the airspeed indicator came back it seemed wrong to him because he thought they were going too fast.
  - cjbprime 8y ago
    Or you could think of this: the A330 has fewer total fatalities than the MAX, despite being in service for over 25 years instead of under 2 years.
- kissickas 8y ago
  It sounds far more intuitive if you have a feedback mechanism in the form of a tangible demonstration of what the force is actually averaging out to.
- philpem 8y ago
  If they're mechanically linked, the captain would at least feel the first officer countering their inputs -- giving a prompt that they need to communicate their intentions more clearly! I'll defer to a pilot to say whether they are mechanically linked -- it sounds like they are on Boeing aircraft but possibly not on Airbus?
  - WalterBright 8y ago
    They're mechanically linked on Boeing aircraft. On the 757, and I believe the rest, the mechanical link has a detent. With enough force, the pilot can move it out of the detent and move the controls independently of the copilot. The reason for this is if one side or the other is jammed, the pilot can still fly it.
  - foldr 8y ago
    No, the captain would not, because only one pilot has their hands on the controls in any given instance (with the possible exception of rotation at takeoff).
    - ceejayoz 8y ago
      Clearly, that’s not always the case, given at least one plane falling out of the sky from dual control inputs. Mistakes happen. Part of aviation safety is preventing that from becoming fatal.
      - foldr 8y ago
        >Clearly, that’s not always the case, given at least one plane falling out of the sky from dual control inputs. That's not what the accident report concludes. There's a clearly audible "dual input" alarm to prevent dual inputs. Dual control inputs only occurred for brief moments during the AF flight.
        ceejayoz 8y ago
        It's quite clear that wasn't sufficient. "Brief moments" during critical points in an emergency can matter enormously. From the recorder transcript: > As the plane approaches 10,000 feet, Robert tries to take back the controls, and pushes forward on the stick, but the plane is in "dual input" mode, and so the system averages his inputs with those of Bonin, who continues to pull back. The nose remains high. 02:13:40 (Robert) Remonte... remonte... remonte... remonte... Climb... climb... climb... climb... 02:13:40 (Bonin) Mais je suis à fond à cabrer depuis tout à l'heure! But I've had the stick back the whole time! 02:13:42 (Captain) Non, non, non... Ne remonte pas... non, non. No, no, no... Don't climb... no, no. 02:13:43 (Robert) Alors descends... Alors, donne-moi les commandes... À moi les commandes! Descend, then... Give me the controls... Give me the controls! > Bonin yields the controls, and Robert finally puts the nose down. The plane begins to regain speed. But it is still descending at a precipitous angle. As they near 2000 feet, the aircraft's sensors detect the fast-approaching surface and trigger a new alarm. There is no time left to build up speed by pushing the plane's nose forward into a dive. At any rate, without warning his colleagues, Bonin once again takes back the controls and pulls his side stick all the way back. The crash occurred less than a minute later.

neuronic 8y ago

> In Boeing airplanes, the movement of the two yokes is synchronized. So in case of two equally strong and equally determined pilots you still get averaging of opposing control inputs.

wikibob 8y ago
No, the failure mode is not two pilots consciously fighting against each other. The failure mode is two pilots who are UNAWARE they are commanding contradicting inputs. Airbus negligently averages these inputs. This is legacy tech debt because the physical design didn’t leave room to link the two controls. Now they are stuck because they feel they can’t change and have some planes that (dangerously) average the inputs, and some that are physically linked. When controls are physically linked, if one pilot thinks he should nose up, and the other tries to nose down, they can yell “what are you doing” at each other and this create an accurate mental model of what the other is intending. Think of this every time you fly Airbus. It’s very similar to debugging a production technology issue. Imagine you decide to restore the database to a snapshot from 1 hour ago, and at the same time someone else tries to restore to an earlier snapshot from 12 hours ago. Should the system average these inputs and restore from 6.5 hours ago? No, obviously not.
- SmellyGeekBoy 8y ago
  > Think of this every time you fly Airbus. Why? They're not falling out of the sky so the system obviously works. Stop being a fanboy.
- foldr 8y ago
  >Now they are stuck because they feel they can’t change and have some planes that (dangerously) average the inputs, and some that are physically linked. This is a really weird way to construe the situation. The accident report doesn't conclude that the handling of dual inputs was a factor, and it's clear from the transcripts that it wasn't. Airbus has no reason to change this. Merely linking sidesticks would be pointless in any case, since sidesticks don't have an identifiable position (but are used with brief movements away from center). It's hardly any easier for a pilot to passively observe the movements of his own sidestick than it is just to look over at the other pilot's stick.
  - neuronic 8y ago
    The commenter appears to have a vested interest in making Airbus look bad, otherwise the comment cannot be logically understood. Is there a case where the averaging of inputs has been proved catastrophic?
    - notfromhere 8y ago
      Air France 447
      - foldr 8y ago
        Not according to the official accident report. This is a meme spread by an article in Popular Mechanics that came out long before the official report.
- deleted 8y ago
  [deleted]
- benhurmarcel 8y ago
  > Airbus negligently averages these inputs. On an Airbus, in case of dual input the pilots get a voice alarm and a warning lights up right in front of them. Also the stick has a switch to take priority, in case the other pilot continues to give dual input.
  - jandrese 8y ago
    Did AF447 not have this warning? One of the contributing factors to the crash was the copilot continuing to pull back on the stick even as the pilot attempted to push the nose down to get out of the stall.
    - livatlantis 8y ago
      I answered further up but: yes, it did. The DUAL INPUT alarms were audible in the cockpit voice recording. However, unbeknowst to the captain, the co-pilot used priority takeover on his side. (This was always visible on the panel + there was an audible "Priority right" warning around the end) Source: https://www.vanityfair.fr/actualites/articles/vol-af-447-rio-paris-reconstitution-des-minutes-qui-ont-precede-le-crash/23618 https://www.vanityfair.fr/actualites/articles/vol-af-447-rio...
      - foldr 8y ago
        I'm not sure where you're getting the "unbeknownst" from. In the cockpit voice recorder transcripts attached to the official accident reports, it seems that the pilots were aware of who had control at any given point in time.
        jandrese 8y ago
        I remember right before the impact with the water the captain finally realizing why his controls aren't doing anything and asking the co-pilot to finally let go of his stick. IIRC they never did throttle up however. Ultimately the co-pilot got tunnel vision and thought for some reason they were in an overspeed condition for most of the incident and failed to communicate that effectively with the rest of the crew. He made a couple of comments about it, but nobody else realized that he was attempting to correct for an overspeed condition in the middle of a dead stall, even when the airspeed indicator came back it seemed wrong to him because he thought they were going too fast.
- cjbprime 8y ago
  Or you could think of this: the A330 has fewer total fatalities than the MAX, despite being in service for over 25 years instead of under 2 years.
kissickas 8y ago
It sounds far more intuitive if you have a feedback mechanism in the form of a tangible demonstration of what the force is actually averaging out to.
philpem 8y ago
If they're mechanically linked, the captain would at least feel the first officer countering their inputs -- giving a prompt that they need to communicate their intentions more clearly! I'll defer to a pilot to say whether they are mechanically linked -- it sounds like they are on Boeing aircraft but possibly not on Airbus?
- WalterBright 8y ago
  They're mechanically linked on Boeing aircraft. On the 757, and I believe the rest, the mechanical link has a detent. With enough force, the pilot can move it out of the detent and move the controls independently of the copilot. The reason for this is if one side or the other is jammed, the pilot can still fly it.
- foldr 8y ago
  No, the captain would not, because only one pilot has their hands on the controls in any given instance (with the possible exception of rotation at takeoff).
  - ceejayoz 8y ago
    Clearly, that’s not always the case, given at least one plane falling out of the sky from dual control inputs. Mistakes happen. Part of aviation safety is preventing that from becoming fatal.
    - foldr 8y ago
      >Clearly, that’s not always the case, given at least one plane falling out of the sky from dual control inputs. That's not what the accident report concludes. There's a clearly audible "dual input" alarm to prevent dual inputs. Dual control inputs only occurred for brief moments during the AF flight.
      - ceejayoz 8y ago
        It's quite clear that wasn't sufficient. "Brief moments" during critical points in an emergency can matter enormously. From the recorder transcript: > As the plane approaches 10,000 feet, Robert tries to take back the controls, and pushes forward on the stick, but the plane is in "dual input" mode, and so the system averages his inputs with those of Bonin, who continues to pull back. The nose remains high. 02:13:40 (Robert) Remonte... remonte... remonte... remonte... Climb... climb... climb... climb... 02:13:40 (Bonin) Mais je suis à fond à cabrer depuis tout à l'heure! But I've had the stick back the whole time! 02:13:42 (Captain) Non, non, non... Ne remonte pas... non, non. No, no, no... Don't climb... no, no. 02:13:43 (Robert) Alors descends... Alors, donne-moi les commandes... À moi les commandes! Descend, then... Give me the controls... Give me the controls! > Bonin yields the controls, and Robert finally puts the nose down. The plane begins to regain speed. But it is still descending at a precipitous angle. As they near 2000 feet, the aircraft's sensors detect the fast-approaching surface and trigger a new alarm. There is no time left to build up speed by pushing the plane's nose forward into a dive. At any rate, without warning his colleagues, Bonin once again takes back the controls and pulls his side stick all the way back. The crash occurred less than a minute later.