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Preliminary report into Air India crash released

(www.bbc.co.uk)
308 points cjr | 8 comments | 11 Jul 25 20:23 UTC | HN request time: 1.787s | source | bottom
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sillysaurusx[dead post] ◴[11 Jul 25 22:58 UTC] No.44537641[source]▶
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anonymousiam ◴[11 Jul 25 23:06 UTC] No.44537707[source]▶
The report says the co-pilot was flying.

The report says the black box reports the fuel cutoff switches being activated. That doesn't necessarily mean that either of the two pilots activated them, it just means that the fly-by-wire system reacted to a fuel cutoff event.

"The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec. The Engine N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cutoff.

In the cockpit voice recording, one of the pilots is heard asking the other why did he cutoff.

The other pilot responded that he did not do so."

replies(1): >>44537791 #
rogerrogerr ◴[11 Jul 25 23:18 UTC] No.44537791[source]▶
> That doesn't necessarily mean that either of the two pilots activated them

It does:

1. Those switches have physical interlocks and cannot be manipulated by any computer system.

2. The flight data recorder is measuring the position of the switches; they aren't inferring the position from some system state. There's a "position of this switch" channel.

The switches were physically moved in the cockpit, that's basically ground truth. The question now is who and why.

replies(2): >>44537827 #>>44538593 #
1. anonymousiam ◴[11 Jul 25 23:25 UTC] No.44537827[source]▶
What is the path of the wires from the switch onward? Do they go into a digital input of the flight computer, or do they directly feed the fuel control valves?

https://simpleflying.com/boeing-787-technical-features-guide...

" Advanced electric controls

The 787 entered service with an improved fly-by-wire flight control system. Rather than mechanical processes, the systems convert flight deck crew inputs into electrical signals. Still, there were additional advancements with the type."

replies(1): >>44537939 #
2. rogerrogerr ◴[11 Jul 25 23:42 UTC] No.44537939[source]▶
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.
replies(1): >>44538054 #
3. anonymousiam ◴[12 Jul 25 00:02 UTC] No.44538054[source]▶
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:

https://www.cnn.com/2019/04/30/politics/boeing-sensor-737-ma...

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.

replies(1): >>44538641 #
4. unyttigfjelltol ◴[12 Jul 25 01:54 UTC] No.44538641{3}[source]▶
In that case, it could be true both that neither pilot manipulated the switch and that the system recorded a dual fuel cutoff.
replies(1): >>44538956 #
5. rogerrogerr ◴[12 Jul 25 03:05 UTC] No.44538956{4}[source]▶
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.
replies(1): >>44539008 #
6. anonymousiam ◴[12 Jul 25 03:19 UTC] No.44539008{5}[source]▶
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.
replies(1): >>44539076 #
7. rogerrogerr ◴[12 Jul 25 03:36 UTC] No.44539076{6}[source]▶
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.

If you think it’s not pilot error, you can make some fake Manifold dollars: https://manifold.markets/JohnHughes/what-will-be-the-officia...

replies(1): >>44540058 #
8. userbinator ◴[12 Jul 25 07:30 UTC] No.44540058{7}[source]▶
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.