6 ms·

Flight augmentation systems work a different way. Those take into consideration all inputs and average it out. Same when two pilots give different instructions.

piquadrat 8y ago
> 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
  - 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.

piquadrat 8y ago

> 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
- 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.