Comment by yason
18 hours ago
It is known that the switches cannot effectively be flipped by accident.
It is known that the switches were set to "cut-off" because they were then later restored to "run", so it was not an electrical fault (i.e. switches pointing to run but reporting cut-off).
Pilot dialogue and engine telemetry confirms the cause of power loss was fuel cut-off.
The question I can't help but think is how did the pilot realize it was the cut-off switches?
I'm sure there's a warning message for them somewhere but in the few seconds of time when you're losing thrust right after rotate, and you're bombarded by a lot of warnings and errors on the screen and in the speakers: how likely are you to notice the fuel cut-off switches have been flipped?
Those switches are something you never, ever think about during operation because you're trained to only operate them when starting up and parking (and yes, in an emergency where you need to shut down the engine quick).
How long would it take for an average pilot to realize it's not one of the dozens of memory items pointing to more likely scenarios causing loss of thrust, ones that they've been training to check in case of an imminent emergency? And why didn't the first pilot who was recorded to notice the fuel cut-off didn't immediately flip the switches to "run" position first instead of asking the other pilot about it?
Given what you're vaguely implying -- that the switches would be nowhere near the first thing a pilot would normally think of in the kind of situation -- what are the odds the pilot asking on record "did you flip the fuel cut-off switch?" is the one who actually flipped the switches and was simply trying to fool the would-be investigation (even knowing they all are about to perish)?
> what are the odds the pilot asking on record "did you flip the fuel cut-off switch?" is the one who actually flipped the switches and was simply trying to fool the would-be investigation (even knowing they all are about to perish)?
This is such a diabolical mind-game that it never occurred to me. Like, they would all die, why would he want to incriminate someone else? But yet, people are weird and crazy. And maybe he didn't go down as a killer and decided to incriminate the other pilot? Anyway, it is totally possible to have happen. Sadly there are no cameras the cockpit, and a camera in the cockpit would really have help to find who did what.
I'd say the odds are 50%. The odds of the opposite scenario - where the pilot who said "did you flip the fuel cutoff" wasn't the one who did it are also 50%.
Based on the cutoffs for both engines being flipped 1 second apart, the above exchange being caught on the CVR, and then within 10 seconds the (presumably the other) pilot switching them back to Run, it's pretty clear that this was a deliberate act.
Reading https://news.ycombinator.com/item?id=44543536 I think we should not jump to conclusions yet.
I would assume that the engines cur of due to fault in the shared control system. And to restore power the pilots toggled the switches to off and then back on to get them running again.
Hopefully the timestamps tell if the engines lost power before switches were turned off? Or is there some time window that was not recorded due to the lost power to systems?
This is one of the first scenarios that came to mind for me as well.
i.e. hypothetically, no one flipped the switches to cutoff initially, but a glitch in a computer component caused the same effect, including some indication (a status light?) that the switches were in cutoff state. One of the pilots saw the indication, and asked the other. The other (truthfully) said they hadn't. Ten seconds of confusion later, one of them flipped the switches off and back on to reset the state to what it should have been.
That assumes that the switches are part of a fly-by-wire system, of course. I am not an aircraft engineer, so maybe that's not a safe assumption. But if they're fly-by-wire, seems like there might not be a way to know for sure without cockpit video, because the logging system might only log an event when the switches cause the state to change from what the computer thinks the current state is, not necessarily when the switches change to the state the computer thinks they're already in.
Someone bumping the switches accidentally seems worthy of investigation as well, given the potential for an "Oops! No locking feature! Our bad!" scenario on the part of Boeing that's mentioned in the BBC article.
Why would you assume that? The engines were providing thrust to achieve normal take off. If they did that to restore engine power why would the voice recorder have one asking the other why he cut off the engines?
I’m more familiar with the 737 (as a hobby, not as a pilot), but for that aircraft the “loss of thrust on both engines” checklist has the start levers as the second item on the list.
Note that in the checklist I am looking at the goal is to restart the engines rather than diagnose the failure and that involves these levers. I suspect you’d notice pretty quickly if they were not in the expected location.
Thanks, this is good information. So it then fits the overall picture that they would've actually bumped into these switches in the rush of emergency eventhough they're never expecting the switches to actually be off.
Do you know if it says anything about restarting them simultaneously or not?
I would think trying to restart engines one at a time would be preferred, over both of them at the same time - or maybe thats not how it works..?
Maybe the pilot who cut-off the fuel was the one who asked “why did you cut-off?”. Knowing full-well the conversation is recorded in order to fool investigators, lay blame and confuse his colleague.
How can it be known that the switches were moved physically and not some electrical signal occured on its own (fault) equivalent of switches operated, without actual physical moement of the switch? Some electronic fault in the line of the signal. I do not expect having an independent sensor for this switch monitoring actual physical movements of the switch in parallel of the intended fuel controlling signals occurring, so the faulty signal reaching valves may have been registered and assumed that actual physical movement of the switch caused it?
We know that they restarted a few seconds later a few seconds apart from each other, and shut off a second part from each other.
It's extremely unlikely for a pilot to decide to react by shutting both switches off, then turning them on within seconds (this is not a failure mode they'd have expected, deciding to shut the engine off a couple hundred feet in the air would be... a fairly reckless decision).
That leaves both switches spontaneously turning off, then back on, a couple seconds after takeoff, which is a failure mode that's never been seen before once let alone twice. Also the pilots didn't make a statement about an incongruity between the report from the plane's systems about the switch being off vs the physical position, which they very likely would have in such a situation.
I think it's reasonable to rule that theory out.