Comment by manquer
2 days ago
Given the fly by wire nature of 787 there is an also fourth option.
The physical switch was not touched at all , and the software has a bug under some rare conditions which cut off the supply to both engines.
2 days ago
Given the fly by wire nature of 787 there is an also fourth option.
The physical switch was not touched at all , and the software has a bug under some rare conditions which cut off the supply to both engines.
Extremely unlikely, since we can hear the other pilot ask why he turned the fuel switches. If it was an electrical glitch, he wouldn’t be able to see that they are in the cutoff position.
All we know is the pilot flying is only asking whether the pilot monitoring if he cut off
- We don't know if he meant the switch specifically at all. He could also have meant engines or thrust in general. There are many other visual signals and UX indicators to know if engines are spinning down. Thrust levels, to RPM to falling speed, change in angle of attack, rate of climb, even engine noise, vibrations you expect at full thrust etc.
- We also don't know if the switch was physically in cut off position in the first place or even if was the pilot noticed that specific visual signal and meant that when he spoke.
If it was a software issue, it is possible the switch was properly positioned, and software issue cut engine was cutoff, the display screens and other lights would show that.
In such a scenario, the pilot(s) would have likely checked with each other first if they did something as in the audio and manually tried restarting the engine as they seem to have done.
I am not saying it is a bug or any specific fault scenario, Just that it too early, we don't yet have enough information to say what is likely at all.
I think there are a couple of factors that disprove these theories:
- The specific mention of "cut off" in the CVR is very telling. If both pilots were genuinely surprised, you'd expect they'd say something like "engine failure" or "loss of thrust" first. Noone thinks the engines have been shut down as a knee-jerk reaction to a sudden loss of thrust.
- If investigators had the slightest indication there's a software or hardware bug out there that randomly causes dual engine failures, an emergency airworthiness directive would have been issued by now. This hasn't happened.
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