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> It's difficult to conclude anything other than murder-suicide. Is it possible it could have been an accident or a mistake by one of the pilots? How intention

> It's difficult to conclude anything other than murder-suicide. Is it possible it could have been an accident or a mistake by one of the pilots? How intention-proofed are engine cutoffs?

ummonk 1y ago
You have to pull the switches out (against a spring) to be able to move them over a notch and flip them. Not really something you can just mistake for another switch or bump into by accident. I'd liken it to turning off the ignition by turning the key while driving your car. Possibly something that could happen if you're really fatigued, but requires quite a mental lapse.
- magicalhippo 1y ago
  Is it possible to rest the switch on the notch? Does the switch make contact if the switch is in the RUN position but the switch is not completely down? That is, is it possible they flipped the switches over to RUN but did not seat the switches properly, and instead leaving them on top of the notch, with later vibration causing the switches to disengage? Just trying to think of some semi-plausible non-active causes.
- deleted 1y ago
  [deleted]
- joezydeco 1y ago
  Report says the switches went to cutoff one second apart from each other. Can a human do the physical operation on two switches that quickly?
  - snypher 1y ago
    There's a good photo of them here; https://theaircurrent.com/aviation-safety/ai171-investigation-fuel-control-switches/ https://theaircurrent.com/aviation-safety/ai171-investigatio... You can do them both with one hand.
    - zihotki 1y ago
      Are you completely sure you can considering that they are spring loaded and they are like 7-10cm apart judging by the size of other controls?
      - snypher 1y ago
        I don't understand your question. I have done this myself, am I completely sure?
        cosmicgadget 1y ago
        Did you mean to say you can activate the switches with one hand simultaneously? That is probably what the above commenter assumed you meant. Since lifting and twisting two switches simultaneously with one hand seems challenging.
        mvdtnz 1y ago
        It didn't happen simultaneously so this is irrelevant.
        cosmicgadget 1y ago
        It is relevant to the interaction I replied to.
        ryandrake 1y ago
        You’re the only one who said “simultaneously.”
        cosmicgadget 1y ago
        See above.
        deleted 1y ago
        [deleted]
  - heisenbit 1y ago
    The timing is really curious. 08:08:35 Vr 08:08:39 Liftoff 08:08:42 Engine 1 cut-off 08:08:42 Engine 2 cut-off 08:08:47 minimum idel speed reached ?? One pilot to other: why cut-off. Other: Did not do it 08:08:52 Engine 1 run 08:08:52 Engine 2 run 1 second to switch them both off and then 4 seconds to switch them both on. No one admitted to switch them off. They are probably going with fine comb over the audio and also the remains of the chared switches. Looks like the engines react very quickly to cut-off so it is not clear whether the question about the cut-off is prompted by a glance to the switches or the feel of the airplane. The big question is whether the switches were moved or something made it seem as if the switches were moved.
    - ExoticPearTree 1y ago
      > Looks like the engines react very quickly to cut-off so it is not clear whether the question about the cut-off is prompted by a glance to the switches or the feel of the airplane. The workload is pretty high during the takeoff phase. The engines react right away when fuel flow is stopped. The engine displays can have some lag before data is updated. Relighting an engine at low speed is not feasible - most need 230-250kts IAS before attempting the operation. Maybe you could do it if the APU was still running and could provide compressed air, but it takes about 20-30 seconds to start up amd then probably 5-10 more to spool up to full thrust. I am speculating here a bit, but the pilot did not have enough time to save the plane even if he did everyting right and as fast as humanly possible. All this aside is overshadowed by the limited amount of time the pilot flying (I would assume the captain in this case since there was only one ATPL pilot in the cockpit) had to troubleshoot the issue of a dual engine failure - as this is what would have felt to him - during takeoff.
      - leetrout 1y ago
        > I would assume the captain The report states the FO was pilot flying.
        ExoticPearTree 1y ago
        My bad. I assumed it was the captain since the report says the FO only has a CPL license. And I was a bit surprised he could fly on a comercial airplane with only that kind of license and not an ATPL one.
xenadu02 1y ago
It could be defective switch springs, fatigue-induced muscle memory error, or something else. The pilot who did it saying he did not may not have realized what he did. It's pretty common under high workload when you flip the wrong switch or move a control the wrong way to think that you did what you intended to do, not what you actually did. That said Boeing could take a page out of the Garmin GI275. When power is removed it pops up a "60s to shutdown dialog" that you can cancel. Even if you accidentally press SHUTDOWN it only switches to a 10s countdown with a "CANCEL" button. They could insert a delay if weight on wheels is off. First engine can shutdown when commanded but second engine goes on 60s delay with EICAS warning countdown. Or just always insert a delay unless the fire handle is pulled. Still... that has its own set of risks and failure modes to consider.
- yard2010 1y ago
  I'm doing it all the time while rebasing commits or force pushing to my branch. Sometimes I would just click the wrong buttons and end up having to stay late to clean the mess. It's a great thing I'm not a pilot. I would be dead by now.
- rogerrogerr 1y ago
  Delay is probably worse - now you're further disassociating the effect of the action from the action itself, breaking the usual rule: if you change something, and don't like the effect, change it back.
  - Yokolos 1y ago
    This makes me wonder. Is there no audible alarm when the fuel is set to cutoff?
    - aaronmdjones 1y ago
      Shutting off both engines would display "ENG SHUTDOWN" in yellow text (caution) on the EICAS. If only one engine was shut down, it would say "ENG SHUTDOWN L" or "ENG SHUTDOWN R". Any of these would trigger an unmistakable audible "BLEEP BLEEP BLEEP" to draw your attention to the screen so that you could see what the caution was. These messages are right next to the engine N1 indications anyway, so it would be immediately obvious that one or more of the engines was spooling down.

> It's difficult to conclude anything other than murder-suicide. Is it possible it could have been an accident or a mistake by one of the pilots? How intention-proofed are engine cutoffs?

ummonk 1y ago

You have to pull the switches out (against a spring) to be able to move them over a notch and flip them. Not really something you can just mistake for another switch or bump into by accident. I'd liken it to turning off the ignition by turning the key while driving your car. Possibly something that could happen if you're really fatigued, but requires quite a mental lapse.

magicalhippo 1y ago
Is it possible to rest the switch on the notch? Does the switch make contact if the switch is in the RUN position but the switch is not completely down? That is, is it possible they flipped the switches over to RUN but did not seat the switches properly, and instead leaving them on top of the notch, with later vibration causing the switches to disengage? Just trying to think of some semi-plausible non-active causes.
deleted 1y ago
[deleted]
joezydeco 1y ago
Report says the switches went to cutoff one second apart from each other. Can a human do the physical operation on two switches that quickly?
- snypher 1y ago
  There's a good photo of them here; https://theaircurrent.com/aviation-safety/ai171-investigation-fuel-control-switches/ https://theaircurrent.com/aviation-safety/ai171-investigatio... You can do them both with one hand.
  - zihotki 1y ago
    Are you completely sure you can considering that they are spring loaded and they are like 7-10cm apart judging by the size of other controls?
    - snypher 1y ago
      I don't understand your question. I have done this myself, am I completely sure?
      - cosmicgadget 1y ago
        Did you mean to say you can activate the switches with one hand simultaneously? That is probably what the above commenter assumed you meant. Since lifting and twisting two switches simultaneously with one hand seems challenging.
        mvdtnz 1y ago
        It didn't happen simultaneously so this is irrelevant.
        cosmicgadget 1y ago
        It is relevant to the interaction I replied to.
        ryandrake 1y ago
        You’re the only one who said “simultaneously.”
        cosmicgadget 1y ago
        See above.
        deleted 1y ago
        [deleted]
- heisenbit 1y ago
  The timing is really curious. 08:08:35 Vr 08:08:39 Liftoff 08:08:42 Engine 1 cut-off 08:08:42 Engine 2 cut-off 08:08:47 minimum idel speed reached ?? One pilot to other: why cut-off. Other: Did not do it 08:08:52 Engine 1 run 08:08:52 Engine 2 run 1 second to switch them both off and then 4 seconds to switch them both on. No one admitted to switch them off. They are probably going with fine comb over the audio and also the remains of the chared switches. Looks like the engines react very quickly to cut-off so it is not clear whether the question about the cut-off is prompted by a glance to the switches or the feel of the airplane. The big question is whether the switches were moved or something made it seem as if the switches were moved.
  - ExoticPearTree 1y ago
    > Looks like the engines react very quickly to cut-off so it is not clear whether the question about the cut-off is prompted by a glance to the switches or the feel of the airplane. The workload is pretty high during the takeoff phase. The engines react right away when fuel flow is stopped. The engine displays can have some lag before data is updated. Relighting an engine at low speed is not feasible - most need 230-250kts IAS before attempting the operation. Maybe you could do it if the APU was still running and could provide compressed air, but it takes about 20-30 seconds to start up amd then probably 5-10 more to spool up to full thrust. I am speculating here a bit, but the pilot did not have enough time to save the plane even if he did everyting right and as fast as humanly possible. All this aside is overshadowed by the limited amount of time the pilot flying (I would assume the captain in this case since there was only one ATPL pilot in the cockpit) had to troubleshoot the issue of a dual engine failure - as this is what would have felt to him - during takeoff.
    - leetrout 1y ago
      > I would assume the captain The report states the FO was pilot flying.
      - ExoticPearTree 1y ago
        My bad. I assumed it was the captain since the report says the FO only has a CPL license. And I was a bit surprised he could fly on a comercial airplane with only that kind of license and not an ATPL one.

xenadu02 1y ago

It could be defective switch springs, fatigue-induced muscle memory error, or something else. The pilot who did it saying he did not may not have realized what he did. It's pretty common under high workload when you flip the wrong switch or move a control the wrong way to think that you did what you intended to do, not what you actually did. That said Boeing could take a page out of the Garmin GI275. When power is removed it pops up a "60s to shutdown dialog" that you can cancel. Even if you accidentally press SHUTDOWN it only switches to a 10s countdown with a "CANCEL" button. They could insert a delay if weight on wheels is off. First engine can shutdown when commanded but second engine goes on 60s delay with EICAS warning countdown. Or just always insert a delay unless the fire handle is pulled. Still... that has its own set of risks and failure modes to consider.

yard2010 1y ago
I'm doing it all the time while rebasing commits or force pushing to my branch. Sometimes I would just click the wrong buttons and end up having to stay late to clean the mess. It's a great thing I'm not a pilot. I would be dead by now.
rogerrogerr 1y ago
Delay is probably worse - now you're further disassociating the effect of the action from the action itself, breaking the usual rule: if you change something, and don't like the effect, change it back.
- Yokolos 1y ago
  This makes me wonder. Is there no audible alarm when the fuel is set to cutoff?
  - aaronmdjones 1y ago
    Shutting off both engines would display "ENG SHUTDOWN" in yellow text (caution) on the EICAS. If only one engine was shut down, it would say "ENG SHUTDOWN L" or "ENG SHUTDOWN R". Any of these would trigger an unmistakable audible "BLEEP BLEEP BLEEP" to draw your attention to the screen so that you could see what the caution was. These messages are right next to the engine N1 indications anyway, so it would be immediately obvious that one or more of the engines was spooling down.