July 12, 2025, 11:59:00 GMT
permalink Post: 11920565
Regardless of what actually happened in that cockpit, reasoning like this seems completely backwards to me. Since when do humans reliably, instantly recognise that they've just made a mistake? If they were
that
attuned to their actions they're almost certainly attuned enough to
not
make the mistake in the first place, especially if we're talking about an action slip. I've e.g. absentmindedly added salt to my tea instead of sugar and I certainly didn't immediately realise that I'd done that - in fact it took a good few seconds even after sipping and spitting it out for my brain to catch up to what must have happened. Even if an observer had pointed out to me before drinking it that my tea had salt in it, I would just have been confused because
obviously
I wouldn't do something that silly (spoiler alert: I did)..
When they rip their hand away from the hot stove they’ve just touched.
Had this been a silly mistake, it was one with immediate, severe consequences, not something like discovering a mistake you made some time ago. As for response to the mistake, see below
On top of that I feel like people are overestimating how long ten seconds actually is, especially considering some of those seconds are reported to have been taken up by confused dialogue (that isn't even reported in its entirety). I thought it was common wisdom that accidents are never down to one thing; it would be light-years from being the first time that suboptimal crew response turned a maybe-recoverable error into a definite disaster without an ounce of malice in the mix.
Again, the situation isn’t a surprise to you, you know what just happened.
July 12, 2025, 18:47:00 GMT
permalink Post: 11920745
I think we need to be really careful about how we think about human factors.
To all of you who have talked about ‘muscle memory’ or ‘brain farts’ may I refer you all to post No. 183 by MaybeItIs. In it, he writes about the interactions between the cerebellum and the cerebrum – in effect, we have two brains; the cerebrum being the ‘conscious thinking part’ and the cerebellum being the ‘unconscious automatic part’ of our brains.
All of us have done very strange inexplicable things at some time or another in our lives, you only have to read about human factors to know how common such things are – even by highly trained flight crews . I know I have made mistakes like these, and I ask you all to examine your own lives and acknowledge that you may have done the same.
In my own experience, when I was a very new co-pilot, I was involved in a very nasty incident in a VC10 in which we all did inappropriate things, with the best of intentions . We very nearly ended up crashing. After that experience, I began to read books on psychology, brain structure and human behaviour. You will be surprised how easy it is to do the wrong thing and then, afterwards, to wonder why.
Later, I spent much of my career as a training pilot and as a training manager. Despite all the safeguards built in by designers and manufacturers, despite all the safeguards included in our crew procedures, and despite all the training we undergo during our careers, we are all still vulnerable to error, including the so-called ‘sky-gods’.
James Reason wrote about the Swiss Cheese model. Sometimes, one of the holes in the cheese can be our own totally improbable actions. What MaybeItIs has written in his post may help to explain such seemingly inexplicable events.
We all need to have some humility – There but for the grace of God go I.
To all of you who have talked about ‘muscle memory’ or ‘brain farts’ may I refer you all to post No. 183 by MaybeItIs. In it, he writes about the interactions between the cerebellum and the cerebrum – in effect, we have two brains; the cerebrum being the ‘conscious thinking part’ and the cerebellum being the ‘unconscious automatic part’ of our brains.
All of us have done very strange inexplicable things at some time or another in our lives, you only have to read about human factors to know how common such things are – even by highly trained flight crews . I know I have made mistakes like these, and I ask you all to examine your own lives and acknowledge that you may have done the same.
In my own experience, when I was a very new co-pilot, I was involved in a very nasty incident in a VC10 in which we all did inappropriate things, with the best of intentions . We very nearly ended up crashing. After that experience, I began to read books on psychology, brain structure and human behaviour. You will be surprised how easy it is to do the wrong thing and then, afterwards, to wonder why.
Later, I spent much of my career as a training pilot and as a training manager. Despite all the safeguards built in by designers and manufacturers, despite all the safeguards included in our crew procedures, and despite all the training we undergo during our careers, we are all still vulnerable to error, including the so-called ‘sky-gods’.
James Reason wrote about the Swiss Cheese model. Sometimes, one of the holes in the cheese can be our own totally improbable actions. What MaybeItIs has written in his post may help to explain such seemingly inexplicable events.
We all need to have some humility – There but for the grace of God go I.
Last edited by Bergerie1; 13th July 2025 at 04:04 . Reason: Changed reference to Post No. 183
July 12, 2025, 19:21:00 GMT
permalink Post: 11920769
I don\x92t know if the FDR measures the switch position or the electrical signal. The latter is probably more likely, although there has been much discussion around potential scenarios involving accidental switch movement as well as possible causes of electrical glitches. Let\x92s assume that the switches were actually moved, and ignoring the \x93bad faith\x94 scenario, we need a situation that encompasses the switches being moved to Cutoff by one pilot, this action being queried by the other pilot and denied by the pilot who moved the switches.
For consideration, here is a possible scenario that hasn\x92t been mentioned yet and encompasses the frailty of human performance. The report mentions that the flight crew on the immediately prior flight had written up a "STAB POS XDCR" status message, and that troubleshooting was carried out. I wonder if the scenario could be that the accident crew received a Stabiliser EICAS message on or around take-off and the Capt (who was PM) decided to action the first checklist item immediately from memory, by intending to move the Stab switches to Cutoff but moving the fuel switches instead. As in all modern Boeings, the Stabiliser Cutoff switches are immediately next to the Fuel Cutoff switches and operate in the same sense (i.e. down for Cutoff). They are guarded and never normally moved but, with an intent to move the stab switches, \x93muscle memory\x94 (cerebellum activation if you prefer) may have taken the Captain\x92s hand to the Fuel switches, which are operated on every flight. The FO (who is PF) is manually flying at this stage sees and queries it. The Capt denies it, as he doesn\x92t realise what he has done (confirmation bias perhaps). After a few seconds, the terrible mistake is realised, and the fuel switches are moved back to run, but sadly too late and the Capt makes a Mayday call.
Perhaps a bit of a stretch but not as much of a stretch as many of the other scenarios in this thread. I think it is a real possibility. Sadly, the only other explanation that I can see is the deliberate \x93bad faith\x94 scenario, which we would all hope is incorrect.
Fly Safe
PJ88
For consideration, here is a possible scenario that hasn\x92t been mentioned yet and encompasses the frailty of human performance. The report mentions that the flight crew on the immediately prior flight had written up a "STAB POS XDCR" status message, and that troubleshooting was carried out. I wonder if the scenario could be that the accident crew received a Stabiliser EICAS message on or around take-off and the Capt (who was PM) decided to action the first checklist item immediately from memory, by intending to move the Stab switches to Cutoff but moving the fuel switches instead. As in all modern Boeings, the Stabiliser Cutoff switches are immediately next to the Fuel Cutoff switches and operate in the same sense (i.e. down for Cutoff). They are guarded and never normally moved but, with an intent to move the stab switches, \x93muscle memory\x94 (cerebellum activation if you prefer) may have taken the Captain\x92s hand to the Fuel switches, which are operated on every flight. The FO (who is PF) is manually flying at this stage sees and queries it. The Capt denies it, as he doesn\x92t realise what he has done (confirmation bias perhaps). After a few seconds, the terrible mistake is realised, and the fuel switches are moved back to run, but sadly too late and the Capt makes a Mayday call.
Perhaps a bit of a stretch but not as much of a stretch as many of the other scenarios in this thread. I think it is a real possibility. Sadly, the only other explanation that I can see is the deliberate \x93bad faith\x94 scenario, which we would all hope is incorrect.
Fly Safe
PJ88
July 13, 2025, 04:15:00 GMT
permalink Post: 11921010
You want these switches within reach of both pilots, in a position where hands are not constantly passing over them, able to be actioned quickly, to be internally guarded (= require 2 distinct actions to move) as well as externally protected (side guards). It also seems logical to have them near the thrust levers.
Boeing have achieved all this.
It feels like it would be an error to try and redesign these switches in light of this incident. The switches operated as they were commanded.
Boeing have achieved all this.
It feels like it would be an error to try and redesign these switches in light of this incident. The switches operated as they were commanded.
The switches must be accessible - Yes
They are where hands regularly pass over them - a No. As I see it, a certain expression regarding the back end of a male dog comes to mind!
Able to be actioned quickly - arguably, currently, it's much too quickly, IMHO.
Guarded - when it comes to Cerebellum (Yes, please search that word in this thread)-generated actions, that makes zero difference. When the Cerebellum has been trained and learned, it will repeat the most complex sequences you can think of - without you having to think of them. That's the REAL problem that needs to be solved.
Logical - Yes, but really No! Putting them close together can more easily result in the wrong action at times of high stress, confusion, fear, danger, urgency, whatever.
I say they need a major, i.e. Total redesign.
But one of the big problems is that these two switches are used at least a couple of times on every flight. So, they are true Cerebellum Fodder.
However, here's one suggestion. The modern plane is full of sensors, interlocks and logic devices. Use them a bit smarter, I say!
When the plane is on the ground, allow the Fuel Switches to be turned On and Off without debate. But using Air/Ground and /(or?) WoW, when the plane is in the air, the process must be made markedly different. At the very LEAST, make them properly guarded, so a flap must be lifted to action them. And as soon as the flap gets lifted in flight, a very loud alarm and maybe a light is triggered. Then, everybody knows, no need for guessing. Until you or your fellow pilot presses the Confirm button somewhere nearby, the switches can't be moved - or are disabled, or something.
If you don't regularly use this procedure, the Cerebellum won't be so likely to Run It Automatically in a panicked rush. The different process from what you did just at the start of the flight will trip up the cerebellum somewhat, and trigger the Higher Brain to start thinking...: "What? Is this correct?"
How about this?
Subsequent thoughts: The Confirm button would only remain live for a short period, say 3 seconds, during which time, you can operate the switch. Then it resets.
Another idea: Leave the Fuel Cutoff switches right where they are, as they are. But, when in Flight, totally disable them. Alarm if moved. Put the In-Flight Shutoff switches in the overhead panel, with the same kind of aural/visual Confirmation-required warning system permanently operative.
P.P.S. That may not be enough, maybe there needs to be a Takeoff speed transition added - i.e. Before Rotate. Maybe just after V1?
Last edited by MaybeItIs; 13th July 2025 at 04:48 . Reason: add the subs.
July 13, 2025, 05:15:00 GMT
permalink Post: 11921025
May I refer you to
MaybeItIs'
post
183
and my post
351
. I think that
tdracer
has laid to rest most (if not all) of the electrical theories that have been put forward on this thread. And I find the accusations of malicious operation of the switches by one or other of the pilots to be repugnant.
This leaves the so-called 'muscle memory' and 'brain fart' theories. Those who work in the field of psychology can show quite clearly that we are all liable to seemingly inexplicable mistakes, both in normal life and in the cockpit. MaybeItIs wrote about the cerebellum and the cerebrum in his post 183, his words are very wise.
Those of us who have worked as instructors will have spent many hours embedding in our students essential habit patterns, most of which are life-savers. But, equally, habitual actions can very occasionally go wrong, despite our best intentions. I have a strong feeling that the root cause of this accident will be found to be psychological.
Some may simply try to put this down to 'pilot error' which, in a way, it is but it is not a culpable error . It is simply a result of being human.
This leaves the so-called 'muscle memory' and 'brain fart' theories. Those who work in the field of psychology can show quite clearly that we are all liable to seemingly inexplicable mistakes, both in normal life and in the cockpit. MaybeItIs wrote about the cerebellum and the cerebrum in his post 183, his words are very wise.
Those of us who have worked as instructors will have spent many hours embedding in our students essential habit patterns, most of which are life-savers. But, equally, habitual actions can very occasionally go wrong, despite our best intentions. I have a strong feeling that the root cause of this accident will be found to be psychological.
Some may simply try to put this down to 'pilot error' which, in a way, it is but it is not a culpable error . It is simply a result of being human.
July 13, 2025, 05:23:00 GMT
permalink Post: 11921030
slats11,
Sorry, you missed the risk I'm proposing to mitigate. It's not about malfeasance.
It's about saving us from ourselves - from our "smaller brain" - not what you're probably thinking!
If you search this thread, you'll find a number of reports of highly-trained, highly qualified and normally highly competent pilots doing absolutely daft things, for no explicable reason. Even they can't explain how it happened. Here's another pretty good example, which I discussed a bit somewhere here.
https://avherald.com/h?article=48d1e3ae&opt=0
I think understanding the role of the cerebellum and what it does and how it apparently works goes a long way to explaining the seemingly otherwise inexplicable. Have a read up?
.
Sorry, you missed the risk I'm proposing to mitigate. It's not about malfeasance.
It's about saving us from ourselves - from our "smaller brain" - not what you're probably thinking!
If you search this thread, you'll find a number of reports of highly-trained, highly qualified and normally highly competent pilots doing absolutely daft things, for no explicable reason. Even they can't explain how it happened. Here's another pretty good example, which I discussed a bit somewhere here.
https://avherald.com/h?article=48d1e3ae&opt=0
I think understanding the role of the cerebellum and what it does and how it apparently works goes a long way to explaining the seemingly otherwise inexplicable. Have a read up?
.
July 13, 2025, 06:04:00 GMT
permalink Post: 11921041
This leaves the so-called 'muscle memory' and 'brain fart' theories. Those who work in the field of psychology can show quite clearly that we are all liable to seemingly inexplicable mistakes, both in normal life and in the cockpit.
MaybeItIs
wrote about the cerebellum and the cerebrum in his post 183, his words are very wise.
It could have been an intentional, malicious act, but I think, for now, "brain fart" or "extremely inappropriate reaction to perceived anomaly" makes more sense for now.
July 13, 2025, 07:18:00 GMT
permalink Post: 11921078
The Action Slip scenario
What is an action slip?
There's a possible scenario we're discussing here that fits all of the available evidence. It proposes that one of the pilots operated the switches in an unconscious action called an "action slip". This is a rote action that we do without conscious thought when we're distracted: we mean to do something, and then we get our signals crossed and do something else. To learn more, search for "action slip" or "cerebellum" on this thread; I hope paulross adds the keyword to the next build of his excellent index at https://paulross.github.io/pprune-th...171/index.html .
How would this scenario play out?
We don't have enough evidence to pin down the exact sequence, so there are some assumptions here that I hope you find plausible. (And obviously it's not the only scenario that fits the evidence.) We especially do not know who did what and why, so that is all guesswork on my part. The times are taken from the preliminary report. The report places the verbal exchange among the pilots where I put it.
———
8:08:39 The 787 becomes airborne. The F/O is pilot flying (PF), with both hands on the yoke. The Captain is PNF (not flying).
8:08:42 The PNF unconsciously flips both fuel switches to CUT OFF, one after the other. This is a rote action performed after each flight, or as training captain in the simulator.
The action cuts power to the engines; they stop delivering thrust almost immediately, and the turbines start slowing down.
The 787 systems disconnect the electrical generators in advance of them failing. The right side
(Captain's side)
of the cockpit l oses power to most instruments. With all 4 generators offline, the RAT deploys to provide emergency power.
The PF feels the cessation of thrust. He looks at the display to see an ENGINES SHUT OFF message. He assumes the PNF shut them off, and asks him why he shut them off. This is the lowest "probe" level on the PACE assertiveness scale; see e.g. https://psychsafety.com/pace-graded-assertiveness/ or search for "probe alert" on pprune if you wish to know more. The highest level of assertiveness, E for "emergency", would have the F/O put the switches back himself immediately, but that would have required a high degree of confidence in the face of the older Captain that may have been difficult to achieve.
Since the action was unconscious, the PNF replies that he did not do that.
8:08:47 The RAT starts delivering hydraulic power, the engines decelerate past idle.
The PNF realizes that engine power is in fact cut. Eventually he checks the switches he thinks he did not touch, sees the engine 1 switch first and flips it back to RUN at 8:08:52. He then thinks to check the second switch and flips it up at 8:08:56.
The accident sequence ensues.
There's really not much the PNF can do at this point. At 8:09:05, he transmits a MAYDAY.
———
Obviously there are variations to this, for example it could have been the PF who put the fuel switches back. (In the above scenario, the PF is focused on flying—aviate!—and never turns his head to see the switches.) My goal was simply to set out a possible sequence, to see whether it feels plausible. Remember, as you see other scenarios put forth, that any issues a person could wrestle with would also be distracting. While both pilots would be very focused during the takeoff run, the moment the aircraft lifted off, the PNF could well have mentally relaxed a little, opening an opportunity for the action slip.
Thoughts?
Edit: I got the roles mixed up; in a fixed scenario, either the Captain was the PF (and may have set the switches to cutoff), or flight control changed over at the power failure.
There's a possible scenario we're discussing here that fits all of the available evidence. It proposes that one of the pilots operated the switches in an unconscious action called an "action slip". This is a rote action that we do without conscious thought when we're distracted: we mean to do something, and then we get our signals crossed and do something else. To learn more, search for "action slip" or "cerebellum" on this thread; I hope paulross adds the keyword to the next build of his excellent index at https://paulross.github.io/pprune-th...171/index.html .
How would this scenario play out?
We don't have enough evidence to pin down the exact sequence, so there are some assumptions here that I hope you find plausible. (And obviously it's not the only scenario that fits the evidence.) We especially do not know who did what and why, so that is all guesswork on my part. The times are taken from the preliminary report. The report places the verbal exchange among the pilots where I put it.
———
8:08:39 The 787 becomes airborne. The F/O is pilot flying (PF), with both hands on the yoke. The Captain is PNF (not flying).
8:08:42 The PNF unconsciously flips both fuel switches to CUT OFF, one after the other. This is a rote action performed after each flight, or as training captain in the simulator.
The action cuts power to the engines; they stop delivering thrust almost immediately, and the turbines start slowing down.
The 787 systems disconnect the electrical generators in advance of them failing. The right side
The PF feels the cessation of thrust. He looks at the display to see an ENGINES SHUT OFF message. He assumes the PNF shut them off, and asks him why he shut them off. This is the lowest "probe" level on the PACE assertiveness scale; see e.g. https://psychsafety.com/pace-graded-assertiveness/ or search for "probe alert" on pprune if you wish to know more. The highest level of assertiveness, E for "emergency", would have the F/O put the switches back himself immediately, but that would have required a high degree of confidence in the face of the older Captain that may have been difficult to achieve.
Since the action was unconscious, the PNF replies that he did not do that.
8:08:47 The RAT starts delivering hydraulic power, the engines decelerate past idle.
The PNF realizes that engine power is in fact cut. Eventually he checks the switches he thinks he did not touch, sees the engine 1 switch first and flips it back to RUN at 8:08:52. He then thinks to check the second switch and flips it up at 8:08:56.
The accident sequence ensues.
There's really not much the PNF can do at this point. At 8:09:05, he transmits a MAYDAY.
———
Obviously there are variations to this, for example it could have been the PF who put the fuel switches back. (In the above scenario, the PF is focused on flying—aviate!—and never turns his head to see the switches.) My goal was simply to set out a possible sequence, to see whether it feels plausible. Remember, as you see other scenarios put forth, that any issues a person could wrestle with would also be distracting. While both pilots would be very focused during the takeoff run, the moment the aircraft lifted off, the PNF could well have mentally relaxed a little, opening an opportunity for the action slip.
Thoughts?
Edit: I got the roles mixed up; in a fixed scenario, either the Captain was the PF (and may have set the switches to cutoff), or flight control changed over at the power failure.
Last edited by Musician; 13th July 2025 at 08:03 .
July 13, 2025, 07:36:00 GMT
permalink Post: 11921087
What is an action slip?
There's a possible scenario we're discussing here that fits all of the available evidence. It proposes that one of the pilots operated the switches in an unconscious action called an "action slip". This is a rote action that we do without conscious thought when we're distracted: we mean to do something, and then we get our signals crossed and do something else. To learn more, search for "action slip" or "cerebellum" on this thread; I hope paulross adds the keyword to the next build of his excellent index at https://paulross.github.io/pprune-th...171/index.html .
How would this scenario play out?
We don't have enough evidence to pin down the exact sequence, so there are some assumptions here that I hope you find plausible. (And obviously it's not the only scenario that fits the evidence.) We especially do not know who did what and why, so that is all guesswork on my part. The times are taken from the preliminary report. The report places the verbal exchange among the pilots where I put it.
\x97\x97\x97
8:08:39 The 787 becomes airborne. The F/O is pilot flying (PF), with both hands on the yoke. The Captain is PNF (not flying).
8:08:42 The PNF unconsciously flicks both fuel switches to CUT OFF, one after the other. This is a rote action performed after each flight, or as training captain in the simulator.
The action cuts power to the engines; they stop delivering thrust almost immediately, and the turbines start slowing down.
The 787 systems disconnect the electrical generators in advance of them failing. The right side (Captain's side) of the cockpit loses power to most instruments. With all 4 generators offline, the RAT deploys to provide emergency power.
The PF feels the cessation of thrust. He looks at the display to see an ENGINES SHUT OFF message. He assumes the PNF shut them off, and asks him why he shut them off. This is the lowest "probe" level on the PACE assertiveness scale; see e.g. https://psychsafety.com/pace-graded-assertiveness/ or search for "probe alert" on pprune if you wish to know more. The highest level of assertiveness, E for "emergency", would have the F/O put the switches back himself immediately, but that would have required a high degree of confidence in the face of the older Captain that may have been difficult to achieve.
Since the action was unconscious, the PNF replies that he did not do that.
8:08:47 The RAT starts delivering hydraulic power, the engines decelerate past idle.
The PNF realizes that engine power is in fact cut. Eventually he checks the switches he thinks he did not touch, sees the engine 1 switch first and flips it back to RUN at 8:08:52. He then thinks to check the second switch and flips it up at 8:08:56.
The accident sequence ensues.
There's really not much the PNF can do at this point. At 8:09:05, he transmits a MAYDAY.
\x97\x97\x97
Obviously there are variations to this, for example it could have been the PF who put the fuel switches back. (In the above scenario, the PF is focused on flying\x97aviate!\x97and never turns his head to see the switches.) My goal was simply to set out a possible sequence, to see whether it feels plausible. Remember, as you see other scenarios put forth, that any issues a person could wrestle with would also be distracting. While both pilots would be very focused during the takeoff run, the moment the aircraft lifted off, the PNF could well have mentally relaxed a little, opening an opportunity for the action slip.
Thoughts?
There's a possible scenario we're discussing here that fits all of the available evidence. It proposes that one of the pilots operated the switches in an unconscious action called an "action slip". This is a rote action that we do without conscious thought when we're distracted: we mean to do something, and then we get our signals crossed and do something else. To learn more, search for "action slip" or "cerebellum" on this thread; I hope paulross adds the keyword to the next build of his excellent index at https://paulross.github.io/pprune-th...171/index.html .
How would this scenario play out?
We don't have enough evidence to pin down the exact sequence, so there are some assumptions here that I hope you find plausible. (And obviously it's not the only scenario that fits the evidence.) We especially do not know who did what and why, so that is all guesswork on my part. The times are taken from the preliminary report. The report places the verbal exchange among the pilots where I put it.
\x97\x97\x97
8:08:39 The 787 becomes airborne. The F/O is pilot flying (PF), with both hands on the yoke. The Captain is PNF (not flying).
8:08:42 The PNF unconsciously flicks both fuel switches to CUT OFF, one after the other. This is a rote action performed after each flight, or as training captain in the simulator.
The action cuts power to the engines; they stop delivering thrust almost immediately, and the turbines start slowing down.
The 787 systems disconnect the electrical generators in advance of them failing. The right side (Captain's side) of the cockpit loses power to most instruments. With all 4 generators offline, the RAT deploys to provide emergency power.
The PF feels the cessation of thrust. He looks at the display to see an ENGINES SHUT OFF message. He assumes the PNF shut them off, and asks him why he shut them off. This is the lowest "probe" level on the PACE assertiveness scale; see e.g. https://psychsafety.com/pace-graded-assertiveness/ or search for "probe alert" on pprune if you wish to know more. The highest level of assertiveness, E for "emergency", would have the F/O put the switches back himself immediately, but that would have required a high degree of confidence in the face of the older Captain that may have been difficult to achieve.
Since the action was unconscious, the PNF replies that he did not do that.
8:08:47 The RAT starts delivering hydraulic power, the engines decelerate past idle.
The PNF realizes that engine power is in fact cut. Eventually he checks the switches he thinks he did not touch, sees the engine 1 switch first and flips it back to RUN at 8:08:52. He then thinks to check the second switch and flips it up at 8:08:56.
The accident sequence ensues.
There's really not much the PNF can do at this point. At 8:09:05, he transmits a MAYDAY.
\x97\x97\x97
Obviously there are variations to this, for example it could have been the PF who put the fuel switches back. (In the above scenario, the PF is focused on flying\x97aviate!\x97and never turns his head to see the switches.) My goal was simply to set out a possible sequence, to see whether it feels plausible. Remember, as you see other scenarios put forth, that any issues a person could wrestle with would also be distracting. While both pilots would be very focused during the takeoff run, the moment the aircraft lifted off, the PNF could well have mentally relaxed a little, opening an opportunity for the action slip.
Thoughts?
July 13, 2025, 07:41:00 GMT
permalink Post: 11921093
What is an action slip?
There's a possible scenario we're discussing here that fits all of the available evidence. It proposes that one of the pilots operated the switches in an unconscious action called an "action slip". This is a rote action that we do without conscious thought when we're distracted: we mean to do something, and then we get our signals crossed and do something else. To learn more, search for "action slip" or "cerebellum" on this thread; I hope paulross adds the keyword to the next build of his excellent index at https://paulross.github.io/pprune-th...171/index.html .
How would this scenario play out?
We don't have enough evidence to pin down the exact sequence, so there are some assumptions here that I hope you find plausible. (And obviously it's not the only scenario that fits the evidence.) We especially do not know who did what and why, so that is all guesswork on my part. The times are taken from the preliminary report. The report places the verbal exchange among the pilots where I put it.
———
8:08:39 The 787 becomes airborne. The F/O is pilot flying (PF), with both hands on the yoke. The Captain is PNF (not flying).
8:08:42 The PNF unconsciously flicks both fuel switches to CUT OFF, one after the other. This is a rote action performed after each flight, or as training captain in the simulator.
The action cuts power to the engines; they stop delivering thrust almost immediately, and the turbines start slowing down.
The 787 systems disconnect the electrical generators in advance of them failing. The right side (Captain's side) of the cockpit loses power to most instruments. With all 4 generators offline, the RAT deploys to provide emergency power.
The PF feels the cessation of thrust. He looks at the display to see an ENGINES SHUT OFF message. He assumes the PNF shut them off, and asks him why he shut them off. This is the lowest "probe" level on the PACE assertiveness scale; see e.g. https://psychsafety.com/pace-graded-assertiveness/ or search for "probe alert" on pprune if you wish to know more. The highest level of assertiveness, E for "emergency", would have the F/O put the switches back himself immediately, but that would have required a high degree of confidence in the face of the older Captain that may have been difficult to achieve.
Since the action was unconscious, the PNF replies that he did not do that.
8:08:47 The RAT starts delivering hydraulic power, the engines decelerate past idle.
The PNF realizes that engine power is in fact cut. Eventually he checks the switches he thinks he did not touch, sees the engine 1 switch first and flips it back to RUN at 8:08:52. He then thinks to check the second switch and flips it up at 8:08:56.
The accident sequence ensues.
There's really not much the PNF can do at this point. At 8:09:05, he transmits a MAYDAY.
———
Obviously there are variations to this, for example it could have been the PF who put the fuel switches back. (In the above scenario, the PF is focused on flying—aviate!—and never turns his head to see the switches.) My goal was simply to set out a possible sequence, to see whether it feels plausible. Remember, as you see other scenarios put forth, that any issues a person could wrestle with would also be distracting. While both pilots would be very focused during the takeoff run, the moment the aircraft lifted off, the PNF could well have mentally relaxed a little, opening an opportunity for the action slip.
Thoughts?
There's a possible scenario we're discussing here that fits all of the available evidence. It proposes that one of the pilots operated the switches in an unconscious action called an "action slip". This is a rote action that we do without conscious thought when we're distracted: we mean to do something, and then we get our signals crossed and do something else. To learn more, search for "action slip" or "cerebellum" on this thread; I hope paulross adds the keyword to the next build of his excellent index at https://paulross.github.io/pprune-th...171/index.html .
How would this scenario play out?
We don't have enough evidence to pin down the exact sequence, so there are some assumptions here that I hope you find plausible. (And obviously it's not the only scenario that fits the evidence.) We especially do not know who did what and why, so that is all guesswork on my part. The times are taken from the preliminary report. The report places the verbal exchange among the pilots where I put it.
———
8:08:39 The 787 becomes airborne. The F/O is pilot flying (PF), with both hands on the yoke. The Captain is PNF (not flying).
8:08:42 The PNF unconsciously flicks both fuel switches to CUT OFF, one after the other. This is a rote action performed after each flight, or as training captain in the simulator.
The action cuts power to the engines; they stop delivering thrust almost immediately, and the turbines start slowing down.
The 787 systems disconnect the electrical generators in advance of them failing. The right side (Captain's side) of the cockpit loses power to most instruments. With all 4 generators offline, the RAT deploys to provide emergency power.
The PF feels the cessation of thrust. He looks at the display to see an ENGINES SHUT OFF message. He assumes the PNF shut them off, and asks him why he shut them off. This is the lowest "probe" level on the PACE assertiveness scale; see e.g. https://psychsafety.com/pace-graded-assertiveness/ or search for "probe alert" on pprune if you wish to know more. The highest level of assertiveness, E for "emergency", would have the F/O put the switches back himself immediately, but that would have required a high degree of confidence in the face of the older Captain that may have been difficult to achieve.
Since the action was unconscious, the PNF replies that he did not do that.
8:08:47 The RAT starts delivering hydraulic power, the engines decelerate past idle.
The PNF realizes that engine power is in fact cut. Eventually he checks the switches he thinks he did not touch, sees the engine 1 switch first and flips it back to RUN at 8:08:52. He then thinks to check the second switch and flips it up at 8:08:56.
The accident sequence ensues.
There's really not much the PNF can do at this point. At 8:09:05, he transmits a MAYDAY.
———
Obviously there are variations to this, for example it could have been the PF who put the fuel switches back. (In the above scenario, the PF is focused on flying—aviate!—and never turns his head to see the switches.) My goal was simply to set out a possible sequence, to see whether it feels plausible. Remember, as you see other scenarios put forth, that any issues a person could wrestle with would also be distracting. While both pilots would be very focused during the takeoff run, the moment the aircraft lifted off, the PNF could well have mentally relaxed a little, opening an opportunity for the action slip.
Thoughts?
Seeing that the gear remained down after liftoff, there was CVR confusion after the event, and there was an attempt to rectify the situation…. I’m now thinking aviation is witnessing its most bizarre action-slip it’s ever seen and we’ll learn that the human automatic system is capable of making the most inappropriate and illogical responses to a given situation. I suspect fatigue and the captains sim experience of flicking switches plays a part.
As a result of this, I think we’ll see a renewed interest in slowing down actions at all times…touch a control, look at it, pause, consciously think about what you are touching before you execute it. This needs to be habitual, especially on LH fleets where fatigue inevitably plays into the operation.
We’ll also be discouraging the “insta-pilot” trend of showing how slick you are (usually on A320) where your hands flick round the flight deck at lightning speed. Even in more benign scenarios like shutdown flows etc, this isn’t a good habit.
July 13, 2025, 08:08:00 GMT
permalink Post: 11921110
A statement that completely underestimates the human subconscious system. You need a deliberate movement to raise the gear or drop the flaps too…I’d say nearly every operator has instances of pilots accidentally doing one instead of the other. There will be people saying that there is no way you can have such an extreme action slip but I don’t think we should ever underestimate the power of the human to do the most random things, even if it is one-in-a-million event.
July 13, 2025, 08:16:00 GMT
permalink Post: 11921117
A statement that completely underestimates the human subconscious system. You need a deliberate movement to raise the gear or drop the flaps too\x85I\x92d say nearly every operator has instances of pilots accidentally doing one instead of the other. There will be people saying that there is no way you can have such an extreme action slip but I don\x92t think we should ever underestimate the power of the human to do the most random things, even if it is one-in-a-million event.
July 13, 2025, 08:16:00 GMT
permalink Post: 11921118
Action slip seems highly unlikely to me. Even if one cutoff switch was moved in response to a gear up request I can\x92t believe anyone would then move a second switch, one second later.
July 13, 2025, 08:21:00 GMT
permalink Post: 11921123
July 13, 2025, 11:13:00 GMT
permalink Post: 11921238
I\x92d counter that order of likelihood by suggesting
(1) It\x92s still a likely response to ask that question if your colleague had just switched them off by action-slip.
(2) See my post above. Routine use of these switches is in one \x93event\x94\x85below OAT 40C you start both simultaneously and at shutdown you operate one straight after another.
(3) The interim report seems to leave out all information on verbal exchanges not specifically involved with a response to the abnormal situation.
Not saying you aren\x92t correct, but it doesn\x92t change the order of likelihood in my mind.
(1) It\x92s still a likely response to ask that question if your colleague had just switched them off by action-slip.
(2) See my post above. Routine use of these switches is in one \x93event\x94\x85below OAT 40C you start both simultaneously and at shutdown you operate one straight after another.
(3) The interim report seems to leave out all information on verbal exchanges not specifically involved with a response to the abnormal situation.
Not saying you aren\x92t correct, but it doesn\x92t change the order of likelihood in my mind.
By precedent in routine operations I mean: is there a single example of these switches being cut off at takeoff like this? There is precedent for the wrong engine being shut down in a fire sure, and there is perhaps precedent for mishaps with the fuel switches in other cockpit layouts - but in the case of this layout, with this model of switch or even this 'style' of switch and placement, I cannot find a single example that would come close to the level of catastrophic action slip of pulling out and setting to cutoff both switches one by one.
I think the preliminary report is supposed to present all factual information - they could have left out "why did you cutoff / I did not" - I could understand if they left out sounds that could be ambiguous, perhaps indicating a struggle but not clear enough to present as fact. However, "positive rate / gear up" followed by 2 switches instead of gear handle is completely factual and relevant information, to exclude it makes no sense.
July 13, 2025, 11:27:00 GMT
permalink Post: 11921247
AI171 Thread by Subject
I have rebuilt the site that organises this thread by subject here:
https://paulross.github.io/pprune-th...171/index.html
It studies 3703 posts (and discards 1043 of them).
Changes:
- Add subjects: "Action slip", "AvHerald", "Human Factors", 'Pilot "Why did you cut off"'.
- Build threads up to July 13, 2025, 10:57:00 (built on July 13, 2025, 12:02:17).
Project is here: https://github.com/paulross/pprune-threads
Raise issues here https://github.com/paulross/pprune-threads/issues or PM me.
It studies 3703 posts (and discards 1043 of them).
Changes:
- Add subjects: "Action slip", "AvHerald", "Human Factors", 'Pilot "Why did you cut off"'.
- Build threads up to July 13, 2025, 10:57:00 (built on July 13, 2025, 12:02:17).
Project is here: https://github.com/paulross/pprune-threads
Raise issues here https://github.com/paulross/pprune-threads/issues or PM me.
July 13, 2025, 11:28:00 GMT
permalink Post: 11921248
(1) is true I give you that, but there is no followup "I didn't.. oh crap", denial is a reasonable response if you truly haven't registered doing something, but it is also a reasonable response if you want to confuse to delay
By precedent in routine operations I mean: is there a single example of these switches being cut off at takeoff like this? There is precedent for the wrong engine being shut down in a fire sure, and there is perhaps precedent for mishaps with the fuel switches in other cockpit layouts - but in the case of this layout, with this model of switch or even this 'style' of switch and placement, I cannot find a single example that would come close to the level of catastrophic action slip of pulling out and setting to cutoff both switches one by one.
I think the preliminary report is supposed to present all factual information - they could have left out "why did you cutoff / I did not" - I could understand if they left out sounds that could be ambiguous, perhaps indicating a struggle but not clear enough to present as fact. However, "positive rate / gear up" followed by 2 switches instead of gear handle is completely factual and relevant information, to exclude it makes no sense.
By precedent in routine operations I mean: is there a single example of these switches being cut off at takeoff like this? There is precedent for the wrong engine being shut down in a fire sure, and there is perhaps precedent for mishaps with the fuel switches in other cockpit layouts - but in the case of this layout, with this model of switch or even this 'style' of switch and placement, I cannot find a single example that would come close to the level of catastrophic action slip of pulling out and setting to cutoff both switches one by one.
I think the preliminary report is supposed to present all factual information - they could have left out "why did you cutoff / I did not" - I could understand if they left out sounds that could be ambiguous, perhaps indicating a struggle but not clear enough to present as fact. However, "positive rate / gear up" followed by 2 switches instead of gear handle is completely factual and relevant information, to exclude it makes no sense.
July 13, 2025, 18:47:00 GMT
permalink Post: 11921526
Former Boeing Engineer on the 787 (prob should put this in my profile at some point but newbie on the forum), but personally flown nothing bigger than a 172.
Longer I think about this the more I lean towards purposeful but not intentional action slip cutoffs by the captain. Some people have commented on sim training captains doing this to reset quicker (i wouldn't know).
We know FO was flying and initial cut offs are 1 then 2, which to me says CAPT did it. But also relights were 1 then 2 which tells me CAPT also did that one most likely.
Also comments around 10 seconds of delay being a long time, that's REALLY fast in my opinion especially considering, 1. this is a situation that is never trained for and 2. All sorts of lights changing, displays flickering, whole right side of the cockpit basically turning off and 3. Your really close to the ground and transitions (from takeoff to climb) lend themselves hard things to break your mind out of. That has to be a very jarring experience that needs likely a few seconds just to re-orient themselves. I'm honestly impressed they got them re-lit that fast, but assuming training with engine out and re-start procedures likely gave them a hint fuel switches from the EICAS messages.
Very confident Boeing FlightOps engineers and training captains have run through this in the sim quite a few times now.
Longer I think about this the more I lean towards purposeful but not intentional action slip cutoffs by the captain. Some people have commented on sim training captains doing this to reset quicker (i wouldn't know).
We know FO was flying and initial cut offs are 1 then 2, which to me says CAPT did it. But also relights were 1 then 2 which tells me CAPT also did that one most likely.
Also comments around 10 seconds of delay being a long time, that's REALLY fast in my opinion especially considering, 1. this is a situation that is never trained for and 2. All sorts of lights changing, displays flickering, whole right side of the cockpit basically turning off and 3. Your really close to the ground and transitions (from takeoff to climb) lend themselves hard things to break your mind out of. That has to be a very jarring experience that needs likely a few seconds just to re-orient themselves. I'm honestly impressed they got them re-lit that fast, but assuming training with engine out and re-start procedures likely gave them a hint fuel switches from the EICAS messages.
Very confident Boeing FlightOps engineers and training captains have run through this in the sim quite a few times now.
July 13, 2025, 20:42:00 GMT
permalink Post: 11921631
Action slips - further information
Non-pilot here.
For those interested in reading more about 'action slips', including performing one routine function in place of another, the following free-access article goes into more detail:
Wiley Online Library: Oops! I Did it Again: The Psychology of Everyday Action Slips
As other people have perspicaciously pointed out, assuming that it was the Pilot Monitoring that transitioned the Fuel Cut-Off Switches from RUN to CUTOFF, what action would they likely have been attempting to perform
at that stage of the flight
for an action slip to be a likely possibility?
Alternatively, given that the PM was used to operating simulators, what conditions could have prompted him to do a sequence that was familiar to him of resetting the simulator (including operating the FCS switches), doing things that are inadvisable in a real aircraft?
If these are stupid questions, I apologise for taking up a mod's time processing the comment deletion.
For those interested in reading more about 'action slips', including performing one routine function in place of another, the following free-access article goes into more detail:
Wiley Online Library: Oops! I Did it Again: The Psychology of Everyday Action Slips
Type of slip: Habit intrusion/'double capture slip'
Analysis: Incorrect motor schema is activated during a task due to failure of sustained focal attention to the task in working memory
Example: Going to the kitchen sink to wash a dish but finding yourself washing one's hands instead
Analysis: Incorrect motor schema is activated during a task due to failure of sustained focal attention to the task in working memory
Example: Going to the kitchen sink to wash a dish but finding yourself washing one's hands instead
Alternatively, given that the PM was used to operating simulators, what conditions could have prompted him to do a sequence that was familiar to him of resetting the simulator (including operating the FCS switches), doing things that are inadvisable in a real aircraft?
If these are stupid questions, I apologise for taking up a mod's time processing the comment deletion.
July 13, 2025, 20:53:00 GMT
permalink Post: 11921645
Non-pilot here.
For those interested in reading more about 'action slips', including performing one routine function in place of another, the following free-access article goes into more detail:
Wiley Online Library: Oops! I Did it Again: The Psychology of Everyday Action Slips
As other people have perspicaciously pointed out, assuming that it was the Pilot Monitoring that transitioned the Fuel Cut-Off Switches from RUN to CUTOFF, what action would they likely have been attempting to perform at that stage of the flight for an action slip to be a likely possibility?
Alternatively, given that the PM was used to operating simulators, what conditions could have prompted him to do a sequence that was familiar to him of resetting the simulator (including operating the FCS switches), doing things that are inadvisable in a real aircraft?
If these are stupid questions, I apologise for taking up a mod's time processing the comment deletion.
For those interested in reading more about 'action slips', including performing one routine function in place of another, the following free-access article goes into more detail:
Wiley Online Library: Oops! I Did it Again: The Psychology of Everyday Action Slips
As other people have perspicaciously pointed out, assuming that it was the Pilot Monitoring that transitioned the Fuel Cut-Off Switches from RUN to CUTOFF, what action would they likely have been attempting to perform at that stage of the flight for an action slip to be a likely possibility?
Alternatively, given that the PM was used to operating simulators, what conditions could have prompted him to do a sequence that was familiar to him of resetting the simulator (including operating the FCS switches), doing things that are inadvisable in a real aircraft?
If these are stupid questions, I apologise for taking up a mod's time processing the comment deletion.
I\x92m inclined to give equal wait to intentional shutting down the engines (suicide, if you will) and \x93action-slip\x94. Three seconds after WOW and calling for \x93gear up\x94 is quick but not hugely so. We don\x92t have the transcript, we don\x92t know if the voices were associated with which pilots. It\x92s entirely possible, there was \x93positive rate\x94, \x93gear up\x94 exchange followed by the movement of the switches by the PM, followed by \x93why did you cut off\x94 by the PF who is soon without a PFD.
As to timing, in high stress situations, the mind can run like a computer slowing time or just the opposite, time speeds up and seconds go by trying to comprehend the situation. I was in an ejection, I could spends 15 minutes describing what happened in 500 milliseconds.