Can't find a definitive source right now, but everything is implying there are discrete lines - at least one for command signal to the FADECs, and a separate sense line to the DFDAU for packaging up and sending to the EAFR. That lines up with design philosophy on this stuff of sensing control input data as close to the source as you can get.
Thanks for looking. I worked for Boeing (satellites, not airplanes) for a good part of my career, and I was there when Dennis Muilenburg pushed through his cost saving measures. It was the same culture that created the problems with the 737-MAX. Experienced design engineers were replaced/outsourced and the culture of safety was sacrificed. One example here:
787 (Dreamliner) was pushing hard for weight reduction, and it would not surprise me at all if the switch output fed a digital computer input rather than routing directly to the fuel shutoff valves, but I don't have any direct knowledge of this.
Then why do we see the pilots notice the cutoff, move the switches back, and the engines respond as expected? The switched cannot move themselves. We’d expect to hear more commentary and confusion if the cutoff was active and the switches still in Run.
There would have likely been an indication on the glass cockpit displays that the fuel had been cut off, perhaps the pilot flying noticed this and asked the captain.
Yes, there is, but the reaction to that would be to look at the position the cutoff switches were in. We didn’t hear “wtf, they’re in Run” - the report says they just moved them from Cutoff to Run and the engines responded as expected.
I think you have to really reach to make this not pilot error. I know it’s appealing to call this a Boeing problem, but the evidence just from this prelim report is very compelling.
Until we hear the actual CVR audio, I don't think we can assume much. They are under a very high stress at that point in the flight, and while the "WTF?" might be going through their minds, all they could've resorted to is toggling the switches off and on again.
