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There have been a couple of fatal incidents involving Airbus aircraft, namely Indonesia AirAsia Flight 8501 and Air France Flight 447, that could have been prevented had the captains orders / input been the only accepted one. In both cases the captain was commanding push down to recover from a stall, while the FO was pulling up. Because of the dual-input system they cancelled each-other out and the stalls were not recovered from.

Has Airbus done anything to address this? It seems to me that if the aircraft is in alternate law, as it was in both cases, perhaps it should only accept input from the left seat.

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    $\begingroup$ You mean besides each side's priority switch, never mind CRM? For what it's worth, there have been many accidents where the captain has been in the wrong, too, so clearly "blindly trust the captain's input" wouldn't be the correct approach either. See Who has the final authority over sidesticks? and Why is the Priority Takeover button used? and probably some others. $\endgroup$
    – user
    Sep 27 '18 at 8:57
  • $\begingroup$ @MichaelKjörling It was just an example. I don't know about the priority switch. $\endgroup$
    – Cloud
    Sep 27 '18 at 9:11
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    $\begingroup$ "Only accept input form the left seat" is a very bad idea. What if the reason the airplane is in alternate law is an accident that not only damaged the airplane systems but also knocked the captain unconscious? Also, the assumption that the captain is also the pilot flying is on thin ice. Yes, in case of unforeseen circumstances, often the most experienced pilot will take the controls, but … who is to say that the captain is actually the most experienced pilot for this particular type of aircraft in these particular circumstances? Also, what if flying the aircraft isn't actually the most … $\endgroup$ Sep 27 '18 at 9:38
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    $\begingroup$ … demanding task at the moment, but rather figuring out what the hell happened? In that case, you want the most experienced person (which might be the captain) to work on figuring out the problem, and "the other guy" flying the plane. What if the left seat is unusable as a result of the accident? $\endgroup$ Sep 27 '18 at 9:39
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    $\begingroup$ re: "In both cases the captain was commanding push down to recover from a stall": In the case of AF447 the captain was NOT at the controls during the accident sequence. He was not even in the cockpit at first and had to be called into the cockpit urgently. He then took place behind the two First Officers and remained there until impact. $\endgroup$
    – summerrain
    Dec 9 '18 at 20:02
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Nothing was changed in the stick design or logic.

The side stick design and logic are not addressed by the final recommendations of both accident reports. Of the issues were the training and lack of crew resource management (CRM). Recommendations toward the manufacturer, for example, are with regard to the barrage of warnings the crew of Indonesia AirAsia had, even though Airbus aircraft already have an EMER CANC button to mute spurious alerts:

The KNKT recommends that Airbus to consider in developing a means for flight crews to effectively manage multiple and repetitive Master Caution alarms to reduce distraction. (PK-AXC accident report)

(There are already buttons to take priority, as well as aural and visual cues as to which seat currently has priority.)

Active sticks

Coupled digital side sticks weren't there when Airbus first introduced the A320, as a technology they became feasible in the early 90s. And were first introduced in c. 2015 on the Gulfstream 500 and 600 business jets.

Imagine panicked, under-trained, and uncommunicative pilots in an active sticks cockpit; they might think their sticks got jammed or the coupling motors are acting up. And seeing how long it took for the active sticks to make it into a business jet already hints at the snail pace (and cost) of aviation hardware certification and approval in general.

As for the captain's / left seat inputs being correct, as others have commented, there have been numerous accidents where the captain was in control and the first officer's recommendations were not heard or they kept silent, again, bad CRM.


Re comments on visually noticing the other yoke (not really a side stick design/logic issue):

That did not help Flash Airlines Flight 604 and Atlas Air Flight 3591. Tunnel vision and/or not speaking up is the main problem. Same with the thrust levers; despite moving automatically on Boeing planes -- showing the current setting -- they did not help Asiana Airlines Flight 214 and Turkish Airlines Flight 1951.

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It's not clear that there is an issue.

Is the lack of coupling actually a lack?

The lack of coupling between the two side-sticks to provide feedback between the pilots is, intuitively, a lack in the interface.

We are used, in the physical world, to being able to feel what another person is doing through the things that we're manipulating, the machinery and tools we operate together.

However, flying a plane is not like carrying a ladder up a narrow staircase, or riding with someone on a tandem bike. That kind of implicit bodily feedback isn't part of the Airbus cockpit system.

Cockpit communication is supposed to be explicit

Instead, the communication is supposed to be explicit, so the pilots say what they are doing when operating the controls. Introducing physical feedback into that environment might seem like an enhancement, but in fact it would be the opposite: it would be the introduction of a source of doubt, that draws habit and practice away from the explicit communication around which the system has been designed, towards an implicit form of communication.

Even implicit communication requires verbal confirmation

It would then be necessary to introduce also a new system under which the pilots would decide whether their explicit verbal communication is now in operation ("I have the controls"), or the implicit physical communication (you feel the other pilot doing something).

Now there is a new burden! As well as deciding what they should be doing with the controls, the pilots must also decide whether they will be prioritising explicit/verbal or implicit/physical communications - two things to manage.

And working that out will require explicit verbal communication, so they may have well just stuck with that in the first place.

And if implicit physical communication is allowed to have weight, they still need explicit verbal confirmation of it, because that's what pilots always do. By the time I have asked my co-pilot "WTF are you doing with the stick and why?" it's already later and more stressful than if they had said in the first place that they were taking the controls to climb over an unexpected mountain.

It's not a lack, it's the removal of something unwanted

Implicit communication through the side-stick is not a free gift of additional useful communication. In the Airbus cockpit system, it's the introduction of something dangerous and unnecessary, that would require extra cockpit management and would harm communication in the cockpit.

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