> 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). In Boeing airplanes, the movement of the two yokes is synchronized.
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.
>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.
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.
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)
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.
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.
The copilot actually suggested to use the airbrakes at one point.
Neither Bonin nor Robert, nor the third crew member (Marc
Dubois, the captain) who entered the cockpit 90 seconds
into the episode, recognized that the aircraft had stalled
despite multiple cues. In the confusion, Bonin
misinterpreted the situation as meaning that the plane was
flying too fast and actually reduced the thrust and moved
to apply the speedbrakes – the opposite of what was
required to recover from the stall. Robert overruled him
and attempted to take control, but Bonin continued to try
and fly the plane. He and Robert made simultaneous and
contradictory inputs, without realizing that they were
doing so. By the time the crew worked out what was going
on, there was insufficient altitude left to recover, and
AF447 crashed into the ocean, with the loss of all 228
passengers and crew.
But I've had the stick back the whole time!
At last, Bonin tells the others the crucial fact whose
import he has so grievously failed to understand himself.
I know what the Popular Mechanics article says, but I cannot find any confirmation of the key points in the official accident report, which I take to be much more reliable.
Page 28: The right-seat co-pilot Bonin says "j’ai l’impression qu’on a une vitesse de fou non qu’est-ce que vous en pensez ? "(I feel like we're speeding like crazy, what do you think?")
Page 31: Same co-pilot "mais je suis à fond à cabrer depuis tout à l’heure " (But I've pulling back completely for a while), and this while the cockpit is screaming "Dual Input" (so this means that the other pilot was inputting as well, thus "unbeknownst" in my original comment).
Same page, right after, the captain says, "non non non ne remonte plus là" (No, no, no, don't pull back any further".
If you read the entire transcript, it's clear that there was persistent confusion as to who was in control, despite the dual-input warnings. AF447 is widely considered to be a failure in CRM, and a failure to recognize that they were in an aerodynamic stall (again, despite the warnings).
They didn't trust the plane with the information it was providing, which is probably why they ignored these warnings.
>Page 31: Same co-pilot "mais je suis à fond à cabrer depuis tout à l’heure " (But I've pulling back completely for a while), and this while the cockpit is screaming "Dual Input" (so this means that the other pilot was inputting as well, thus "unbeknownst" in my original comment).
Perhaps you didn't notice this, but immediately after the point in the transcript you refer to, there's an exchange between the pilots where they establish who's in control (see "vas-y tu as les commandes" at 2 h 13 min 46,0). There is no way to be sure, but it seems probable that this exchange was prompted by the dual input warnings.
>They didn't trust the plane with the information it was providing, which is probably why they ignored these warnings.
There is no indication that they ignored the dual input warnings.
Linking the control sticks doesn't magically resolve problems caused by a breakdown in cockpit discipline. If both pilots are going for the controls at the same time, you're going to have problems. The warning system seems to have done its job, insofar as it prompted the pilots to figure out who was in control.
Oh, I don't think I alluded to linking the control sticks... perhaps you intended to respond to another comment?
As for the dual input thing, there are 6 instances of the the warning. We can't really know what the pilots were thinking, but I believe page 31, from when Bonin says, "je suis à fond à..."... and then Robert à "attends moi j’ai des j’ai des commandes moi hein" a little later, "alors donne moi les commandes à moi les commandes", and 4 warnings Dual Input between them (in the space of about a minute and a half)...
I think it's fair to say that it wasn't super clear who was in control.
I'll make no comments about which system is better since I have no direct experience of flying in such environments (have only piloted small aircraft with mirrored controls, but with clear "Commande à droite/gauche" to establish PF, with my instructor). But à priori, I would imagine both systems work fine if used well.
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?
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.
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).
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 (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.
See in particular 2 h 13 min 39,7 and 2 h 13 min 40,6. Both of the pilots at the controls thought that they needed to climb. The captain realizes the mistake, but he's not at the controls, so linked sticks would have made zero difference to his perception of the situation. The accident report concludes that the stall was probably unrecoverable by this point anyway.
The section I'm citing is right there on page 31 of your second link. See 2 h 13 min 39,7. More dual input at 2 h 14 min 03,2. Crash at 2 h 14 min 28,4.
That is the point where both pilots at the controls still think that they need to climb. The captain, who realizes the mistake, is not at the controls, so whether or not the side sticks were linked would have made no difference to his perception of the situation.
The official report does not identify the side sticks as a factor in the accident.
If you think you can do a better job of identifying the cause of the accident than the professionals who investigated it, you should explain clearly why.
With regard to dual input, it's clear from the transcript that the pilots noticed the dual input alarms.
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). In Boeing airplanes, the movement of the two yokes is synchronized.