July 12, 2025, 22:11:00 GMT
permalink Post: 11920880
No simulator access, but I do know this much:
One EICAS and one PFD is on the battery (most likely the left seat PFD) - they might momentarily flicker but will not 'blank'.
You get an EICAS message when you set the fuel switch to CUTOFF - something like "ENGINE X CUTOFF" (not sure of the 787 wording, but it would be something to that effect.
One EICAS and one PFD is on the battery (most likely the left seat PFD) - they might momentarily flicker but will not 'blank'.
You get an EICAS message when you set the fuel switch to CUTOFF - something like "ENGINE X CUTOFF" (not sure of the 787 wording, but it would be something to that effect.
And that would explain the weird (at least to me) question of the pilot to the other one “why did you do that” because normally, every time you see the message SHUTDOWN it is always a result of crew action (and that is quite often as you do that about every sim ride).
Last edited by golfyankeesierra; 12th July 2025 at 23:10 .
July 12, 2025, 22:55:00 GMT
permalink Post: 11920904
If it was a wire strand in the wrong place, that would fit all the facts we know. (Not saying it was, only that it fits)
If you think the timing doesn\x92t quite make, bear in mind the 2 seconds error of margin between any 2 registered parameters in the FDR caused by the (assumed) 1Hz sampling sequential, non-synchronous sampling if you try to draw conclusions from time stamps.
Not been in that situation, obviously, but I have certainly been in stressed situations where somewhere, someone (or something, or even me) pressed the wrong button, and I need to find out which one.
10 seconds is really not a long time if it is unexpected. It is very short.
Please also remember:
-We have no idea of exactly what was said. Whether the conversation referred to a error message, engines spooling down or physical switch movement/position. Throw in possible translation inaccuracies, and we can conclude even less from the information about the conversation, or what the level of clarity or confusion were.
Last edited by Kraftstoffvondesibel; 12th July 2025 at 23:09 .
July 12, 2025, 23:05:00 GMT
permalink Post: 11920909
If it resulted in an eicas message, then the confused conversation, leading to (several) cycling attempts to reset them successfully to RUN, those 10 seconds later doesn\x92t sound unreasonable at all to me.
Not been in that situation, obviously, but I have certainly been in stressed situations where somewhere, someone (or something) pressed the wrong button, and I need to find out which one.
10 seconds is really not a long time if it is unexpected. It is very short.
Please also remember:
-We have no idea of exactly what was said. Whether the conversation referred to a error message, engines spooling down or physical switch movement/position. Throw in possible translation inaccuracies, and we can conclude even less from the information about the conversation, or what the level of clarity or confusion were.
-There is up to 2 seconds of margin of error in the time code of events because of the (speculated) sampling rate of 1Hz.
Not been in that situation, obviously, but I have certainly been in stressed situations where somewhere, someone (or something) pressed the wrong button, and I need to find out which one.
10 seconds is really not a long time if it is unexpected. It is very short.
Please also remember:
-We have no idea of exactly what was said. Whether the conversation referred to a error message, engines spooling down or physical switch movement/position. Throw in possible translation inaccuracies, and we can conclude even less from the information about the conversation, or what the level of clarity or confusion were.
-There is up to 2 seconds of margin of error in the time code of events because of the (speculated) sampling rate of 1Hz.
I'm talking about an electrical failure (for example a short), which is already implausibly affecting both (independent) circuits, causing an issue in a circuit that as I understand it fails open anyway, then resolving itself to become functional again - incidentally in roughly the same time frame that a pilot would notice an issue and seek to correct.
This doesn't require knowledge of the cockpit conversation or judgement on speed (or otherwise) of the recovery. It's purely that an already incredibly unlikely scenario (electrical failure) becomes even more unlikely with the spontaneous *and synchronised, but not perfectly so* removal of the fault state of whatever this failure was.
*Edit* Given my previous post has been removed it would appear that the mods also misread this to do with timing of *pilots response*, which I find a little odd as it was in response to a comment about electrical failure...
To be honest at this point for me we are immediately hamster wheeling again, and this time because any commentary around either electrical circuit issues (astronomical odds) or accidental device triggering cut off (no evidence nor can there be right now) are speculation in nature and have to be. Equally, while the obvious culprit is hands on the switches, any comments about why again are speculation and have to be.
There's nothing more anyone can get to on this one until further CVR data is released in my view. Bowing out.
Last edited by Mrshed; 12th July 2025 at 23:18 .
July 12, 2025, 23:30:00 GMT
permalink Post: 11920926
No simulator access, but I do know this much:
One EICAS and one PFD is on the battery (most likely the left seat PFD) - they might momentarily flicker but will not 'blank'.
You get an EICAS message when you set the fuel switch to CUTOFF - something like "ENGINE X CUTOFF" (not sure of the 787 wording, but it would be something to that effect.
While I doubt the PF would be actively monitoring EICAS during TO, with the sudden audio change to the engine noise as well as the sudden loss of acceleration, I'd expect him to take a quick look at EICAS to see what the (
) the engines are doing. Plus, if the PF was in the right seat and his PFD blanked - I'd expect him to look across to see what's on either the standby or the left seat PFC, and perhaps EICAS.
One EICAS and one PFD is on the battery (most likely the left seat PFD) - they might momentarily flicker but will not 'blank'.
You get an EICAS message when you set the fuel switch to CUTOFF - something like "ENGINE X CUTOFF" (not sure of the 787 wording, but it would be something to that effect.
While I doubt the PF would be actively monitoring EICAS during TO, with the sudden audio change to the engine noise as well as the sudden loss of acceleration, I'd expect him to take a quick look at EICAS to see what the (
) the engines are doing. Plus, if the PF was in the right seat and his PFD blanked - I'd expect him to look across to see what's on either the standby or the left seat PFC, and perhaps EICAS.
CVR should have recorded the beeper too, inhibits are for ground only.
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, 07:32:00 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, 07:37:00 GMT
permalink Post: 11921088
Does the EAFR record the electrical / physical contact of the RUN / CUTOFF switch or, does it record a software 'EVENT' which has the same 'signature' as the RUN / CUTOFF switch being toggled. My thoughts are that the RUN / CUTOFF switch never moved but, the underlying software / hardware system mal-functioned triggering a scenario similar to both RUN / CUTOFF switches being triggered
Some Boeing SB's describe circuit board failures triggering all sorts of unexpected / unpredictable failures
Some Boeing SB's describe circuit board failures triggering all sorts of unexpected / unpredictable failures
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, 10:36:00 GMT
permalink Post: 11921215
Does the EAFR record the electrical / physical contact of the RUN / CUTOFF switch or, does it record a software 'EVENT' which has the same 'signature' as the RUN / CUTOFF switch being toggled. My thoughts are that the RUN / CUTOFF switch never moved but, the underlying software / hardware system mal-functioned triggering a scenario similar to both RUN / CUTOFF switches being triggered
Some Boeing SB's describe circuit board failures triggering all sorts of unexpected / unpredictable failures
Some Boeing SB's describe circuit board failures triggering all sorts of unexpected / unpredictable failures
July 13, 2025, 13:04:00 GMT
permalink Post: 11921311
I still think that one of the most puzzling things from the Preliminary Report is the 4 second gap between Engine 1 fuel cutoff switch being returned to RUN, and that of Engine 2. It seems generally agreed one second is a reasonable time to operate both switches, so why did it take so long to move the 2nd switch?
July 13, 2025, 13:25:00 GMT
permalink Post: 11921321
I still think that one of the most puzzling things from the Preliminary Report is the 4 second gap between Engine 1 fuel cutoff switch being returned to RUN, and that of Engine 2. It seems generally agreed one second is a reasonable time to operate both switches, so why did it take so long to move the 2nd switch?
I'm not implicating either pilot, without more evidence.
July 13, 2025, 13:29:00 GMT
permalink Post: 11921326
I still think that one of the most puzzling things from the Preliminary Report is the 4 second gap between Engine 1 fuel cutoff switch being returned to RUN, and that of Engine 2. It seems generally agreed one second is a reasonable time to operate both switches, so why did it take so long to move the 2nd switch?
July 13, 2025, 13:34:00 GMT
permalink Post: 11921328
I still think that one of the most puzzling things from the Preliminary Report is the 4 second gap between Engine 1 fuel cutoff switch being returned to RUN, and that of Engine 2. It seems generally agreed one second is a reasonable time to operate both switches, so why did it take so long to move the 2nd switch?
July 13, 2025, 14:11:00 GMT
permalink Post: 11921348
I still think that one of the most puzzling things from the Preliminary Report is the 4 second gap between Engine 1 fuel cutoff switch being returned to RUN, and that of Engine 2. It seems generally agreed one second is a reasonable time to operate both switches, so why did it take so long to move the 2nd switch?
July 13, 2025, 14:49:00 GMT
permalink Post: 11921371
I just read this on avherald.com, and I haven't seen this being discussed here (I may have missed it, in which case please delete my post)
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. Service Bulletins by Boeing issued in year 2018 recommending to upgrade the fuel switches to locked versions to prevent inadvertent flip of the switches, as well as the FAA/GE issued Service Bulletin FAA-2021-0273-0013 Attachment 2 relating to loss of control issue (also see above) were NOT implemented by Air India. The stated MN4 computer with faulty soldering, that might weaken and lose contact due to the thermal stress after a number of cycles, interprets data and commands fuel metering valves - with the lost contact attaching the MN4 processor to the EEC intermittent electrical contact, loss of signal processing and engine control faults can occur. The SB writes under conditions for the SB: "An LOTC (Loss Of Thrust Control) event has occurred due to an EEC MN4 microprocessor solder ball failure." According to discussions in the industry it may be possible with the number of cycles VT-ANB had already completed, the solder balls were weakened sufficiently to detach the MN4 from the EEC momentarily due to loads during the takeoff rotation leading to the loss of control of thrust and shut down of the engines.
I had a quick look at the SB and it refers to a computer mounted directly on the engine. I find it extremely unlikely that BOTH computers on two different engines might fail simultaneously. So I take this latest information with a grain of salt ("India's media report").
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. Service Bulletins by Boeing issued in year 2018 recommending to upgrade the fuel switches to locked versions to prevent inadvertent flip of the switches, as well as the FAA/GE issued Service Bulletin FAA-2021-0273-0013 Attachment 2 relating to loss of control issue (also see above) were NOT implemented by Air India. The stated MN4 computer with faulty soldering, that might weaken and lose contact due to the thermal stress after a number of cycles, interprets data and commands fuel metering valves - with the lost contact attaching the MN4 processor to the EEC intermittent electrical contact, loss of signal processing and engine control faults can occur. The SB writes under conditions for the SB: "An LOTC (Loss Of Thrust Control) event has occurred due to an EEC MN4 microprocessor solder ball failure." According to discussions in the industry it may be possible with the number of cycles VT-ANB had already completed, the solder balls were weakened sufficiently to detach the MN4 from the EEC momentarily due to loads during the takeoff rotation leading to the loss of control of thrust and shut down of the engines.
I had a quick look at the SB and it refers to a computer mounted directly on the engine. I find it extremely unlikely that BOTH computers on two different engines might fail simultaneously. So I take this latest information with a grain of salt ("India's media report").
Last edited by katekebo; 13th July 2025 at 15:01 .
July 13, 2025, 15:03:00 GMT
permalink Post: 11921378
I just read this on avherald.com, and I haven't seen this being discussed here (I may have missed it, in which case please delete my post)
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. Service Bulletins by Boeing issued in year 2018 recommending to upgrade the fuel switches to locked versions to prevent inadvertent flip of the switches, as well as the FAA/GE issued Service Bulletin FAA-2021-0273-0013 Attachment 2 relating to loss of control issue (also see above) were NOT implemented by Air India. The stated MN4 computer with faulty soldering, that might weaken and lose contact due to the thermal stress after a number of cycles, interprets data and commands fuel metering valves - with the lost contact attaching the MN4 processor to the EEC intermittent electrical contact, loss of signal processing and engine control faults can occur. The SB writes under conditions for the SB: "An LOTC (Loss Of Thrust Control) event has occurred due to an EEC MN4 microprocessor solder ball failure." According to discussions in the industry it may be possible with the number of cycles VT-ANB had already completed, the solder balls were weakened sufficiently to detach the MN4 from the EEC momentarily due to loads during the takeoff rotation leading to the loss of control of thrust and shut down of the engines.
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. Service Bulletins by Boeing issued in year 2018 recommending to upgrade the fuel switches to locked versions to prevent inadvertent flip of the switches, as well as the FAA/GE issued Service Bulletin FAA-2021-0273-0013 Attachment 2 relating to loss of control issue (also see above) were NOT implemented by Air India. The stated MN4 computer with faulty soldering, that might weaken and lose contact due to the thermal stress after a number of cycles, interprets data and commands fuel metering valves - with the lost contact attaching the MN4 processor to the EEC intermittent electrical contact, loss of signal processing and engine control faults can occur. The SB writes under conditions for the SB: "An LOTC (Loss Of Thrust Control) event has occurred due to an EEC MN4 microprocessor solder ball failure." According to discussions in the industry it may be possible with the number of cycles VT-ANB had already completed, the solder balls were weakened sufficiently to detach the MN4 from the EEC momentarily due to loads during the takeoff rotation leading to the loss of control of thrust and shut down of the engines.
AD 2021-15-05 requires initial and repetitive replacement of the full authority digital engine control (FADEC) integrated circuit (MN4) microprocessor.
The MN4 is part of the FADEC in the engine, the probability of both engines having identical unrelated failures at the same time is very unlikely.
Edited: I see katekebo has already raised this as very unlikely
Last edited by mh370rip; 13th July 2025 at 15:05 . Reason: Duplicate of a previous poster
July 13, 2025, 15:35:00 GMT
permalink Post: 11921397
Since some posters seem focused on the theory that the fuel control switches didn't move - just the electric output did (and as I posted earlier, the FDR only knows electrical states, there is literally no other way for the FDR to monitor the switch position).
So I did a little thought experiment. Uncommanded engine shutdowns (for all causes) are already rare - a 10-6 event. Now, during my 40 year career, I can't remember ever encountering a case where the fuel shutoff was commanded without a corresponding movement of the fuel switch. However in this industry it's a good idea to 'never say never', so let's assume it's happened. It would take something like a hot short to cause it to happen (moving the voltage from RUN to CUTOFF) since an open circuit will simply leave the valves where they were. That would put its probability way out there - something like 10-8/hr.
The left and right engine wiring is physically isolated from the other engine - nothing gets routed in common bundles between the engines. Hence there is simply no way a localized issue could affect both engine's wire bundles. So we're talking two independent events that cause the switch output to electrical change state between RUN and CUTOFF without associated switch movement. So now were out in a 10-16/hr. territory. Now, these independent events both occur a second apart - 3,600 seconds/hr., so we've just added ~8 orders of magnitude to the dual failure probability number (10-24/hr.). Now, they both somehow return to normal withing a few seconds of each other - another ~8 orders of magnitude so we're talking 10-32.
That means the probability of this happening at any time since the Big Bang is way less than one....
Space aliens look reasonable in comparison. So can we discuss things that might actually have happened?
So I did a little thought experiment. Uncommanded engine shutdowns (for all causes) are already rare - a 10-6 event. Now, during my 40 year career, I can't remember ever encountering a case where the fuel shutoff was commanded without a corresponding movement of the fuel switch. However in this industry it's a good idea to 'never say never', so let's assume it's happened. It would take something like a hot short to cause it to happen (moving the voltage from RUN to CUTOFF) since an open circuit will simply leave the valves where they were. That would put its probability way out there - something like 10-8/hr.
The left and right engine wiring is physically isolated from the other engine - nothing gets routed in common bundles between the engines. Hence there is simply no way a localized issue could affect both engine's wire bundles. So we're talking two independent events that cause the switch output to electrical change state between RUN and CUTOFF without associated switch movement. So now were out in a 10-16/hr. territory. Now, these independent events both occur a second apart - 3,600 seconds/hr., so we've just added ~8 orders of magnitude to the dual failure probability number (10-24/hr.). Now, they both somehow return to normal withing a few seconds of each other - another ~8 orders of magnitude so we're talking 10-32.
That means the probability of this happening at any time since the Big Bang is way less than one....
Space aliens look reasonable in comparison. So can we discuss things that might actually have happened?
Now my operator had an incident on a 757 in cruise about 10 years ago where the spar valve closed without command. The SPAR VALVE light will probably have lit up (can\x92t remember) but the engine died. From crz thrust to no thrust in seconds.
So such things are not unknown.
July 13, 2025, 15:38:00 GMT
permalink Post: 11921398
Engine 1 transition to RUN, reported at 08:08:52, which is 19 seconds post V1. However, at 1Hz this change could have occurred up to 1 second before, i.e. 18 seconds post V1.
Engine 2 transition reported at 08:08:56, 23 seconds post V1, but same logic, so either 22 seconds post or 23 seconds post.
This does indeed give a maximum window of 4.99 seconds, although this is still approximate as it presumes that both switches are sampled at the same point in time, and it also ignores the fact that a second isnt a discrete point in time, but its close enough.
Note that if both switches arent sampled at the same point in time, which I'd assume they probably aren't, this makes the maximum possible actually 5.98 seconds, and the minimum possible elasped time just 2.02 seconds.
e.g. Engine 1 switch is sampled at the 990th ms per second, hence recording the time as 08:08:52, but this was actually 08:08:52.99, and assume this is when the switch actually changed. Engine 2 samples exactly on the second, but changed 990ms ago. Recorded as 08:08:56, but actually occurred t/f at 08:08:55.01. This makes the difference 2.02.
This assumes the timing is recorded as "within" the second in question, rather than rounding to the nearest second, but I'd strongly presume it does this as its fundamentally how computer clocks work.
Basically, when looking at two 1Hz samples and comparing, you need to add +/- 1.98 seconds to the timestamp differences to give true range. Of course, assuming stochastic sampling and assuming that the events are independent to clocks (i.e. are not triggered by a time event), then on average the most likely difference in time between them by the distribution will be exactly what it says on the tin - i.e. 4 seconds. But other time differences are possible across the distribution.
It should be noted though that under these assumptions, the probability of an actual time difference of <3 seconds reporting as 4 seconds is pretty vanishingly small (less than 0.01%), although the chances then increase significantly. But an actual 4 to 4.5 second time difference only has about 68% chance of being *reported* as a 4 second time difference, so the time deltas here do have only around a two thirds accuracy given the time granularity reported in the report.
Last edited by Mrshed; 13th July 2025 at 16:12 .
July 13, 2025, 16:29:00 GMT
permalink Post: 11921426
I do assume that, *but* we dont have data records with millisecond or better accuracy, these havent been shared. So with accuracy to the second, these are the realistic possibilities.
Even with millisecond accuracy, it's not generally held practice that you would round to the nearest second using those milliseconds when reporting to a lower accuracy, generally speaking you simply remove the milliseconds, although this will vary case by case. In this case, as we don't have the methodologies, the *possibility* is very much that they have just removed the milliseconds, and as such this method gives the *possible* (albeit not probable) range of actual time deltas.
Even with millisecond accuracy, it's not generally held practice that you would round to the nearest second using those milliseconds when reporting to a lower accuracy, generally speaking you simply remove the milliseconds, although this will vary case by case. In this case, as we don't have the methodologies, the *possibility* is very much that they have just removed the milliseconds, and as such this method gives the *possible* (albeit not probable) range of actual time deltas.
I fully expect that the investigators will have reported the times as the separation observed from the sampling, thus \xb11 sec accuracy (for this particular input). There doesn't need to be any further inaccuracy. We are free to turn a quoted four seconds into three or five, but not two or six.
Edit: sorry, I see what you mean now. I was misunderstanding, because their reporting on the switches to CUTOFF was a duration - 'time gap of 01 sec' - whereas restoration to RUN is described in real timestamps, e.g. '08:08:56 UTC'. I'd sort of forgotten the latter and assumed four seconds was quoted. Mea culpa.