July 13, 2025, 05:12:00 GMT
permalink Post: 11921023
Just a thought \x97 the fire extinguisher handles perform the same function as the fuel cut-off.
Could there have been a strap /booklet or something else that accidentally got under the fire handles and activated them when one of the pilots pulled on the item?
The fire handles are not particularly well protected against something getting underneath them
Is there any information on whether the fuel cutoff switches and fire handles register as separate events on the flight data recorder, or if both are logged under a common indication, such as 'fuel switch cut off'?
Could there have been a strap /booklet or something else that accidentally got under the fire handles and activated them when one of the pilots pulled on the item?
The fire handles are not particularly well protected against something getting underneath them
Is there any information on whether the fuel cutoff switches and fire handles register as separate events on the flight data recorder, or if both are logged under a common indication, such as 'fuel switch cut off'?
July 13, 2025, 05:16:00 GMT
permalink Post: 11921026
@Maybeitis,
how about we leave the total redesign of the fuel switch locations and operation (which have been moved billions of times in thousands of aircraft without a hitch) until the final report is out.
These were deliberately moved. It wasn't a brain-fart. Unless the interim report omits crew calls which turn the scenario on it's head.
These were deliberately moved. It wasn't a brain-fart. Unless the interim report omits crew calls which turn the scenario on it's head.
July 13, 2025, 05:36:00 GMT
permalink Post: 11921035
It is incomprehensible to conceive of someone deliberately shutting off the engines. For good reason the interim report does not state that as the cause \x85.. however it makes clear that the switches were moved to cutoff for an as yet unknown reason, and subsequently back to run.
This brought to mind a case many years ago where a pilot had a significant psychiatric disorder that among other things, caused him to have the urge to shutoff engines in flight. I am unable to post a link as I am a newby but if you search Sick Qantas Pilot wanted to crash you will find the story.
As sad as that particular case is, it does reveal that psychiatric issues may (I stress may) have been a trigger for the events that have unfolded on AI 171. There are other physiological events that may result in a person carrying out \x93memory\x94 actions at an in-opportune moment. These include brain tumour or a brain infection. Looking to the medicos for further discussion on these possibilities.
I am sure the investigation will be looking very closely at the autopsy results as well as medical history to determine if a health aspect contributed to the events.
This brought to mind a case many years ago where a pilot had a significant psychiatric disorder that among other things, caused him to have the urge to shutoff engines in flight. I am unable to post a link as I am a newby but if you search Sick Qantas Pilot wanted to crash you will find the story.
As sad as that particular case is, it does reveal that psychiatric issues may (I stress may) have been a trigger for the events that have unfolded on AI 171. There are other physiological events that may result in a person carrying out \x93memory\x94 actions at an in-opportune moment. These include brain tumour or a brain infection. Looking to the medicos for further discussion on these possibilities.
I am sure the investigation will be looking very closely at the autopsy results as well as medical history to determine if a health aspect contributed to the events.
July 13, 2025, 05:51:00 GMT
permalink Post: 11921038
@Maybeitis,
how about we leave the total redesign of the fuel switch locations and operation (which have been moved billions of times in thousands of aircraft without a hitch) until the final report is out.
These were deliberately moved. It wasn't a brain-fart. Unless the interim report omits crew calls which turn the scenario on it's head.
These were deliberately moved. It wasn't a brain-fart. Unless the interim report omits crew calls which turn the scenario on it's head.
Happy to oblige.
TBH, I'm no longer so concerned with what really happened inside the cockpit of AI171. What the final report says won't make any difference. I can see some flaws in the Boeing design (don't know Airbus so can't compare), and propose a few ideas to deal with that, and with the fact that we humans are highly flawed. Sometimes, the brain doesn't know what the right hand is doing. That's a wee problem.
My theory FWIW, says this won't have been called at all. And that "it" was done entirely without intention. The intention was to do something else. So, in that case, was it deliberate? I say No. It was an accident.
It was IMO, done with the best of intentions, but resulted in a serious blunder, with the wrong switches getting turned off. By what has been termed here "a slip". I agree with that. As I've mentioned, I now believe that when you know someone (including yourself) is doing something wrong, you seem to be more likely to make a mistake yourself. It's as if you automatically become partners in crime. (Even you and yourself!) Did you read this article? Some of the comments are also well worth reading.
https://avherald.com/h?article=48d1e3ae&opt=0
This [i.e 171] accident (I think the correct term) has absolutely fascinated me, and caused me to think a great deal. My recent posts are not really about 171. Only a result of it.
For the benefit of all. You know how people who have lost loved ones want their death to somehow benefit others? I didn't lose anyone in this crash, but that's a beautiful thing about we flawed humans.
I'll shut up now. Thanks for allowing me to participate.
July 13, 2025, 06:13:00 GMT
permalink Post: 11921045
This accident emphasises the sad fact that HUMANS are the weakest link in the FS chain - particularly now that engineering is much more reliable.
How close are we to having PILOTLESS passenger aircraft ?
I would guess many years?
Computers don\x92t have heart attacks and \x91brain farts \x91 ! BUT garbage IN = garbage OUT !
PS reading the many reports that these cut off switches have been \x91moved \x91 in error they appear to be located in a much too accessible position !
(On the B707 ( AWACS ) they were on the roof panel.)
The explanation that they were switched OFF in error after a STAB TRIM warning seems possibly the most likely cause but would be a major mistake !! is a STAB TRIM problem shortly after T/O potentially a major problem on th B787 ?
How close are we to having PILOTLESS passenger aircraft ?
I would guess many years?
Computers don\x92t have heart attacks and \x91brain farts \x91 ! BUT garbage IN = garbage OUT !
PS reading the many reports that these cut off switches have been \x91moved \x91 in error they appear to be located in a much too accessible position !
(On the B707 ( AWACS ) they were on the roof panel.)
The explanation that they were switched OFF in error after a STAB TRIM warning seems possibly the most likely cause but would be a major mistake !! is a STAB TRIM problem shortly after T/O potentially a major problem on th B787 ?
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, 07:31:00 GMT
permalink Post: 11921085
If we assume that the report is factual, as there is no good reason to think otherwise, then the aircraft was serviceable and there were no faults, messages or warnings right up to the point the FCSs were moved to cutoff, as they would have been detailed in the report. The only unresolved question is why was this done?
Putting deliberate action to one side, if the FO was the PF in manual flight, as SOP the captain as PM would be making any configuration changes, MCP selections or switch movements. We know that the captain was a trainer and as such, it is likely that he was used to running details both from the instructor station and either seat. Given the constraints on simulator time and ever-increasing syllabi it is not uncommon for trainers to physically reset the sim to save time and that includes moving critical controls without diagnosis or confirmation in ways inappropriate for the phase of flight, even if frozen. It is likely that if you were doing a lot of training, you would become more practiced at this than the SOP multi-crew interactive method and unknowingly build a semi-autonomous routine in your mind that allowed these type of actions as there was no jeopardy. Normal line pilots are only trained/practiced/checked on the correct way of doing these.
I\x92m not saying that this is what happened, just offering one possibility as to how a competent crew could end up in a disastrous scenario and experience post-decision dissonance over what had just transpired.
Putting deliberate action to one side, if the FO was the PF in manual flight, as SOP the captain as PM would be making any configuration changes, MCP selections or switch movements. We know that the captain was a trainer and as such, it is likely that he was used to running details both from the instructor station and either seat. Given the constraints on simulator time and ever-increasing syllabi it is not uncommon for trainers to physically reset the sim to save time and that includes moving critical controls without diagnosis or confirmation in ways inappropriate for the phase of flight, even if frozen. It is likely that if you were doing a lot of training, you would become more practiced at this than the SOP multi-crew interactive method and unknowingly build a semi-autonomous routine in your mind that allowed these type of actions as there was no jeopardy. Normal line pilots are only trained/practiced/checked on the correct way of doing these.
I\x92m not saying that this is what happened, just offering one possibility as to how a competent crew could end up in a disastrous scenario and experience post-decision dissonance over what had just transpired.
July 13, 2025, 07:32:00 GMT
permalink Post: 11921086
Rather confusingly, AvHerald carries this today
"On Jul 12th 2025 (UTC) India's media report that the investigation is NOT focussing on a human action causing the fuel switches to appear in the CUTOFF position, but on a system failure."
I have no idea what provenance to attach to that!
"On Jul 12th 2025 (UTC) India's media report that the investigation is NOT focussing on a human action causing the fuel switches to appear in the CUTOFF position, but on a system failure."
I have no idea what provenance to attach to that!
Some Boeing SB's describe circuit board failures triggering all sorts of unexpected / unpredictable failures
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, 07:53:00 GMT
permalink Post: 11921100
A lot of \xabflipping\xbb and \xabflicking\xbb of fuel switches going on. You don\x92t flick or flip these switches. They require a deliberate movement.
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, 08:43:00 GMT
permalink Post: 11921144
The switches were operated at 3s after liftoff\x85exactly the time positive rate would be confirmed\x85so I\x92m still thinking third party isn\x92t the most likely scenario.
July 13, 2025, 09:03:00 GMT
permalink Post: 11921160
I see 3 meaningful explanations roughly by order of probability
- Switches moved deliberately - evidenced by the specific question "why did you cutoff" and circumstanced by this being the most vulnerable phase of flight to do such a thing
- Switches moved accidentally eg., 'action-slip' - is there a precedent for not 1 but both switches of this type in any similar aircraft being cut off during routine operations?
- Switches failed mechanically or electronically - the recovered switches were in the position consistent with flight data, timing data is consistent with manual 1-by-1 movement
July 13, 2025, 09:15:00 GMT
permalink Post: 11921169
I don't see any evidence here. The report doesn't mention any callout of positive rate or request for gear up. The cutoff switches were moved ~3 seconds after wheels leaving the ground which would have been just before or at roughly the same time as the callout. The report did not say "pilot flying requested gear up and then the switches were moved to cutoff". There is also no evidence of a 3rd person and I'm not even sure how that would make a difference.
I see 3 meaningful explanations roughly by order of probability
I see 3 meaningful explanations roughly by order of probability
- Switches moved deliberately - evidenced by the specific question "why did you cutoff" and circumstanced by this being the most vulnerable phase of flight to do such a thing
- Switches moved accidentally eg., 'action-slip' - is there a precedent for not 1 but both switches of this type in any similar aircraft being cut off during routine operations?
- Switches failed mechanically or electronically - the recovered switches were in the position consistent with flight data, timing data is consistent with manual 1-by-1 movement
(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.
July 13, 2025, 10:13:00 GMT
permalink Post: 11921202
Not sure if this is helpful for anyone or not but I thought a visual view of the timeline of events might be useful, in seconds since V1.
I've assumed 1Hz for the switch sampling rate and >1Hz for everything else (could be wrong) to give windows for the switch state changes.
I've also added in the ADS-B relevant data, although made no attempt to work out whether these timestamps are synchronised or not, so take them as you will.
I have assumed the cutoff is in chronological order from the report, albeit I have ignored the RAT supply timestamp in terms of chronology from the CVR recording, as that statement in the report at that time may just be due to contextual nature of the statement, rather than it happening prior to the RAT power supply. This gives a window for potentially when that statement was made (assuming also that it was made prior to reversing cutoff).
Don't think it neccessarily adds anything for me, other than:
- Would we expect ADS-B data to stop on engine transition to run? Note that ADS-B data was received between 08:08:43 and 08:08:51, so apparently only received in the time window that the switches were in "cutoff"
- The window between the switches being shut off and moved to run could be as short as 8 seconds, and the window between engine 1 and engine 2 being moved to run could be as short as 2 seconds
- The statement on the CVR could be a wide range of timepoints.
The ADS-B data is in my view odd, albeit this might be my lack of understanding. Yes, not synchronised, but unless the timestamps are way out (like 10 seconds out, and given the timestamp of max altitude, this feels incredibly unlikely), ADS-B data was transmitted without issue during phase 2 (both engines off, no RAT), and phase 3 (both engines off, RAT)...but NOT phase 4 (both engines firing back up, presumably still with RAT?). Bear in mind that phase 4 is almost half of the short flight. Also it would appear no data during phase 1 (both engines on), including during takeoff, despite receiving data during taxi?
*EDIT* - having looked into some other historical ADS-B data for this airport, albeit a bit cursory, it definitely appears that the lack of data in "phase 1" that I've outlined above is solely a coverage issue, with no other flights I can see having coverage in that area either. It's harder to determine the "phase 4" element as obviously no airplanes in a normal mode are in that geographical region at the altitude in question, but it does appear to be a reasonably safe bet that the missing datapoints are coverage related.
Last edited by Mrshed; 13th July 2025 at 11:47 .
July 13, 2025, 10:23:00 GMT
permalink Post: 11921207
Not sure if this is helpful for anyone or not but I thought a visual view of the timeline of events might be useful, in seconds since V1.
I've assumed 1Hz for the switch sampling rate and >1Hz for everything else (could be wrong) to give windows for the switch state changes.
I've also added in the ADS-B relevant data, although made no attempt to work out whether these timestamps are synchronised or not, so take them as you will.
I have assumed the cutoff is in chronological order from the report, albeit I have ignored the RAT supply timestamp in terms of chronology from the CVR recording, as that statement in the report at that time may just be due to contextual nature of the statement, rather than it happening prior to the RAT power supply. This gives a window for potentially when that statement was made (assuming also that it was made prior to reversing cutoff).
Really highlights how knowing precisely when the why did you cutoff" question was asked might have provided more clarity and less speculation as to how those fateful seconds played out
And it would have helped to know if Positive rate / Gear Up was called ... and when
Last edited by unworry; 13th July 2025 at 12:19 .