July 13, 2025, 12:43:00 GMT
permalink Post: 11921296
10 seconds is a long time in a life threatening situation (like most clich\xe9s, the cinematic trope of time slowing down only reflects people's real experiences, mine included). Reaction times to completely unexpected events can be in the order of 3-5 seconds, but I find it hard to think that it would have taken any pilot as much as 5-7 seconds to set the first switch back to run. It's not something that anyone trying to save the aircraft is going to take time to consider.
Possible explanations for the length of time are a physical altercation - but if that was so, then why did the switches then stay at run? We will be none the wiser on that, at least until the next report. Another, perhaps more likely possibility is that the switch movement itself was unnoticed by at least one of the pilots, and was not noticed until its effects took hold a couple of seconds later (my phrasing here is intended to leave open the question of how the switch moved, or was moved). Combined with the startle reaction time, this would start to explain a 10 second delay. So I expect the CVR comments are towards the later end of the possible range indicated in the excellent diagram.
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July 13, 2025, 13:01:00 GMT
permalink Post: 11921309
The fact is the moment the report was released all other previous theories were all but invalidated and deliberate action became 2nd or 1st most probable.
- Could a wiring fault / short circuit explain the cutoff without switch movement - someone posted the pinouts above, these are not single-pole switches, the wiring architecture is designed to mitigate such faults. If the switches didn't move but cutoff was acknowledged then they either self-resolved 10s later, or they were then cycled to cutoff and back to run. Improbable but possible, but the report doesn't support this and there is no precedent for it, even for a single switch not resulting in accident
- Could these be the previously mentioned switches without the locking mechanism - even if that were the case, nobody has presented a report in over half a decade that could align precedent with such a failure - where is the report of even 1 of these switches being bumped accidentally, or due to turbulence, or on landing impact? The probability that the first manifestation of these inadequate switches was this particular 1-by-1 sequence 3 seconds after takeoff, after several years, not at any other phase, it seems quite low
I do agree that at this point deliberate action is the most likely cause, followed by extreme psychological episode. Casual accidental movement if it was remotely probable would surely have been detected in decades of operation and mitigated with a redesign.
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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?
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July 13, 2025, 13:14:00 GMT
permalink Post: 11921316
The AAIB could have omitted the exchange between the pilots, or said something more neutral like "In response to a question, a crew member stated that he had not cut off the engines." To me, the fact that they chose to paraphrase that particular exchange in the particular way they did speaks volumes.
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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.
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July 13, 2025, 13:29:00 GMT
permalink Post: 11921325
This is excellent, thank you. It has helped me to crystallise a thought about the length of time the switches were at cut off.
10 seconds is a long time in a life threatening situation (like most clich\xe9s, the cinematic trope of time slowing down only reflects people's real experiences, mine included). Reaction times to completely unexpected events can be in the order of 3-5 seconds, but I find it hard to think that it would have taken any pilot as much as 5-7 seconds to set the first switch back to run. It's not something that anyone trying to save the aircraft is going to take time to consider.
Possible explanations for the length of time are a physical altercation - but if that was so, then why did the switches then stay at run? We will be none the wiser on that, at least until the next report. Another, perhaps more likely possibility is that the switch movement itself was unnoticed by at least one of the pilots, and was not noticed until its effects took hold a couple of seconds later (my phrasing here is intended to leave open the question of how the switch moved, or was moved). Combined with the startle reaction time, this would start to explain a 10 second delay. So I expect the CVR comments are towards the later end of the possible range indicated in the excellent diagram.
10 seconds is a long time in a life threatening situation (like most clich\xe9s, the cinematic trope of time slowing down only reflects people's real experiences, mine included). Reaction times to completely unexpected events can be in the order of 3-5 seconds, but I find it hard to think that it would have taken any pilot as much as 5-7 seconds to set the first switch back to run. It's not something that anyone trying to save the aircraft is going to take time to consider.
Possible explanations for the length of time are a physical altercation - but if that was so, then why did the switches then stay at run? We will be none the wiser on that, at least until the next report. Another, perhaps more likely possibility is that the switch movement itself was unnoticed by at least one of the pilots, and was not noticed until its effects took hold a couple of seconds later (my phrasing here is intended to leave open the question of how the switch moved, or was moved). Combined with the startle reaction time, this would start to explain a 10 second delay. So I expect the CVR comments are towards the later end of the possible range indicated in the excellent diagram.
If powered by the RAT or APU would that introduce a time delay before you an can effectively put them back to Run?
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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?
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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?
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July 13, 2025, 13:42:00 GMT
permalink Post: 11921331
I agree with sabenaboy.
The subject of pilot suicide is not distasteful, but for many it is taboo.
I understand this. Many historical accidents caused by pilot incompetence could well have been quickly labelled as suicide, only for their errors to show up in the subsequent investigation.
Looking for a rational explanation is a normal way to go, and suicide is not rational in most peoples' eyes.
However, this tragic event looks highly probable to have been caused by a deliberate action. And shutting off the fuel controls immediately following rotation is impossible to justify as an accidental move.
I remember calling the German Wings accident as a likely suicide event as soon as I heard about it. Nevertheless I was open to hostility and recriminations on this website for quite a few days, once my carefully-worded contribution was not deleted.
I do wonder if any further information can be gleaned from the FDR, which has not already been shared. I hope so. And of course, the CVR contents require further analysis.
Nobody in their right minds takes any pleasure, woke or not, from learning of a suicide, particularly one that involves the death of many innocent people.
The subject of pilot suicide is not distasteful, but for many it is taboo.
I understand this. Many historical accidents caused by pilot incompetence could well have been quickly labelled as suicide, only for their errors to show up in the subsequent investigation.
Looking for a rational explanation is a normal way to go, and suicide is not rational in most peoples' eyes.
However, this tragic event looks highly probable to have been caused by a deliberate action. And shutting off the fuel controls immediately following rotation is impossible to justify as an accidental move.
I remember calling the German Wings accident as a likely suicide event as soon as I heard about it. Nevertheless I was open to hostility and recriminations on this website for quite a few days, once my carefully-worded contribution was not deleted.
I do wonder if any further information can be gleaned from the FDR, which has not already been shared. I hope so. And of course, the CVR contents require further analysis.
Nobody in their right minds takes any pleasure, woke or not, from learning of a suicide, particularly one that involves the death of many innocent people.
Mental impairment is a huge and not well understood spectrum. Sometimes it\x92s dark and criminal; sometimes it\x92s long term disease related (Alzheimer\x92s, etc), sometimes acute (stroke), sometimes chemical and mental imbalance developing over a shorter time period (like the US Captain who had a paranoid like episode inflight, or the jumpseater in the US trying to shut down both engines but restrained by crew). In many cases it\x92s impossible to see coming and doesn\x92t even have to involve criminal/homicidal/psychotic intent. It can simply be a stroke or episode which causes confusion and someone to start grabbing at switches best left untouched \x97 perhaps while thinking he is doing the correct actions. So one can not ignore the possibility that a crew member suffered some sort of cognitive episode resulting in shutting off the FCS; perhaps thinking he was back in the chocks for a few minutes. And then forgetting he\x92d done it.
These events may be exacerbated by the huge stigma associated with a pilot attempting to seek counseling or mental health help (even for a relatively small problem which can untreated develop into a much larger one). Out of fear of repercussions of falling into that medical \x91black hole\x92 and trying to get re-certified for even minor mental health glitches.
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July 13, 2025, 14:02:00 GMT
permalink Post: 11921342
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.
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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?
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July 13, 2025, 14:27:00 GMT
permalink Post: 11921357
On the site that I maintain that covers this thread here:
https://paulross.github.io/pprune-th...171/index.html
I removed the subject that described deliberate action on the part of the pilot(s) for reasons I explained here:
Air India Ahmedabad accident 12th June 2025 Part 2
I would restore that subject if any hard evidence appears that suports that theory, not on the basis of speculation (and out of respect to the families and memories of the flight crew).
For those thinking along those lines could I offer this challenge: All the civil aviation pilot suicide cases that I have heard about have been achieved by a rapid descent from cruising altitude. It is a pretty sure outcome. But to switch off the fuel just after takeoff, would you really expect that to succeed? Supposing the other pilot noticed and corrected this in one or two seconds rather than ten, then you would have failed.
I'm not saying people intent on this behaviour are being rational but even by the laws of un-rationality it seems an unlikely way of trying to achieve your goal.
I would restore that subject if any hard evidence appears that suports that theory, not on the basis of speculation (and out of respect to the families and memories of the flight crew).
For those thinking along those lines could I offer this challenge: All the civil aviation pilot suicide cases that I have heard about have been achieved by a rapid descent from cruising altitude. It is a pretty sure outcome. But to switch off the fuel just after takeoff, would you really expect that to succeed? Supposing the other pilot noticed and corrected this in one or two seconds rather than ten, then you would have failed.
I'm not saying people intent on this behaviour are being rational but even by the laws of un-rationality it seems an unlikely way of trying to achieve your goal.
There are only two parts of the flight where the PF's attention will be entirely focused in front of him - takeoff and landing. Cutting the fuel switches on landing is pointless - the plane will in all likelihood land safely as a glider.
Above a certain altitude after takeoff, there will be time for the PF to recover the situation. Doing it as soon as the wheels have left the ground pretty much guarantees a crash.
Doing it in cruise - FO off to the toilet etc. - it will be obvious which yoke was the one doing the pushing, unless of course you switched seats when your colleague left.
The fuel switches are effectively anonymous.
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July 13, 2025, 14:45:00 GMT
permalink Post: 11921364
It would have been useful if more of the CVR data had been released so as to see the crew interaction. Also the language used on what was released seems to refer to a third person.
However, from an operator perspective. Captain PM, FO PF. PF selects TOGA and follows the thrust levers, Captain confirms Thrust Set and replaces FO hands on the Thrust Levers. 80Kt call by PM, acknowledged by PF. Aircraft calls V1, Captain should withdraw hands from Thrust Levers and calls Rotate at Vr. PM is looking for confirmation the aircraft is climbing and calls Positive Rate. PF confirms and calls Gear Up. At this point the PF will be looking through the HUD looking to follow the flight director, the PM would be checking LNAV had engaged and at 400\x92 checking THR REF and VNAV SPD. However, at this point a loss of thrust occurred. So how was this apparent to the PF who would have been looking out with both hands on the control wheel. Reduction in pitch? GPWS call-out? Decreasing N1 on the engine instruments? EICAS ENG SHUTDOWN? What did the PM see? Who called out the situation? Were any actions called for? At some point as the generators went off line all the FO instruments would have blanked. Did the Captain assume control? I don\x92t think I would have been thinking about the Fuel Cut-Off switches at that point, yet they were specifically mentioned which does mean the switches were moved and it wasn\x92t some internal fault.
Hopefully, as the CVR is further analysed some more information will come to light.
However, from an operator perspective. Captain PM, FO PF. PF selects TOGA and follows the thrust levers, Captain confirms Thrust Set and replaces FO hands on the Thrust Levers. 80Kt call by PM, acknowledged by PF. Aircraft calls V1, Captain should withdraw hands from Thrust Levers and calls Rotate at Vr. PM is looking for confirmation the aircraft is climbing and calls Positive Rate. PF confirms and calls Gear Up. At this point the PF will be looking through the HUD looking to follow the flight director, the PM would be checking LNAV had engaged and at 400\x92 checking THR REF and VNAV SPD. However, at this point a loss of thrust occurred. So how was this apparent to the PF who would have been looking out with both hands on the control wheel. Reduction in pitch? GPWS call-out? Decreasing N1 on the engine instruments? EICAS ENG SHUTDOWN? What did the PM see? Who called out the situation? Were any actions called for? At some point as the generators went off line all the FO instruments would have blanked. Did the Captain assume control? I don\x92t think I would have been thinking about the Fuel Cut-Off switches at that point, yet they were specifically mentioned which does mean the switches were moved and it wasn\x92t some internal fault.
Hopefully, as the CVR is further analysed some more information will come to light.
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July 13, 2025, 14:48:00 GMT
permalink Post: 11921368
At this point, I agree that intentional operation of the FCS switches is the most likely cause of the shutdown. But that doesn't mean that we know or can know what the intent of the intentional action was. And I don't think we have any compelling evidence that the intent was to crash the aircraft and kill everyone aboard.
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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 .
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July 13, 2025, 15:02:00 GMT
permalink Post: 11921377
With the greatest respect, I don't think any deliberate act has been proven. Allocating blame on assumptions should be avoided. People should work on facts, and then unconfirmed assumptions.
The only known fact is that engines for some reason were shut down. The other known fact is that there is a recorded indication that the start lever command was recorded as both cutoff in short succession then followed by idle detent causing a restart attempt.
I think the key unknowns here are important.
1. Was the start lever position recorded, or only the electrical signal? My money is on an electrical signal not position, therefore the manual positioning of the start levers is not conclusively proven.
2. The bulletin for locking mechanism for the start levers has been mentioned in the preliminary report. This is a huge unknown. Did that mean that in a failure that the levers could both move into cutoff at the same time? This occurred exactly as the aircraft was rotating and increasing pitch.
3. The information from the CVR if taken at face value must not be discounted. No pilot actually confirmed conclusively seeing the other move the switch. This could have been an assumption noticing an engine failure, seeing the start levers positions in cutoff or indeed seeing the start levers moved deliberately. This is a huge critical unknown.
4. One pilot asked 'why did you cutoff' and the other responded 'I didn't'. This is not a confirmation of anything for sure. In fact it is equally a suggestion nobody pilot moved the switches as it is saying they did. This is not conclusive. This raises an important question, was this genuine, did either pilot have any reason in their life to attempt to do this and then cover their actions? There is zero suggestion here either way, but hopefully investigators will already be looking at their backgrounds and state of affairs.
5. There is no indication who or what commanded the engines back to idle detent again. There is proof of both engines attempting to restart. I would take this as confirmation of teamwork existing on the flight deck, and this would suggest a lack of deliberate interference by either pilot. Should that have been deliberately done, so much more could have happened. It just hasn't been alluded to in the preliminary report.
My own impression is that it did not appear to be a situation of a deliberate act to crash. I say this as they appear to have both tried to save the aircraft and immediately restart the engines and recover taking some critical timely actions demonstrating competent reaction.
The timing of the commanding fuel to cutoff os critical imo. The aircraft was pitching. If an accidental command to cutoff occurred then I feel this however unlikely would have been made instead of another action. The only likely thing happening at that exact time or due 2-3 seconds after lift off was gear up. The CVR and recorded timing of engine failure in relation to that challenge and response in SOP will be key imo. Did the challenge for gear up occur before the idle detent electrical signals? Also, the focus should be on that bulletin for the locking mechanism for the start levers.
I just cannot imagine an experienced crew doing this by accident and the information just doesn't suggest a deliberate act.
My post is just to highlight huge lists of unknowns. The media appears to have made their mind up that the flight crew did this. I just highlight that is definitely not confirmed yet. We have a whole list of unknowns and conflicting communication that raises more questions than they solve.
I would urge zero conclusions be made, and RIP the crew and passengers. There are zero conclusions to what happened yet in my opinion, and I think the suggestion to relatives of the flight crew and families tragically killed that this is a known pilot deliberate action simply cannot be made at this point. We must not blame the flight crew prematurely or pretend we know what happened. I think the media should take note and back off from all the assumptions.
The only known fact is that engines for some reason were shut down. The other known fact is that there is a recorded indication that the start lever command was recorded as both cutoff in short succession then followed by idle detent causing a restart attempt.
I think the key unknowns here are important.
1. Was the start lever position recorded, or only the electrical signal? My money is on an electrical signal not position, therefore the manual positioning of the start levers is not conclusively proven.
2. The bulletin for locking mechanism for the start levers has been mentioned in the preliminary report. This is a huge unknown. Did that mean that in a failure that the levers could both move into cutoff at the same time? This occurred exactly as the aircraft was rotating and increasing pitch.
3. The information from the CVR if taken at face value must not be discounted. No pilot actually confirmed conclusively seeing the other move the switch. This could have been an assumption noticing an engine failure, seeing the start levers positions in cutoff or indeed seeing the start levers moved deliberately. This is a huge critical unknown.
4. One pilot asked 'why did you cutoff' and the other responded 'I didn't'. This is not a confirmation of anything for sure. In fact it is equally a suggestion nobody pilot moved the switches as it is saying they did. This is not conclusive. This raises an important question, was this genuine, did either pilot have any reason in their life to attempt to do this and then cover their actions? There is zero suggestion here either way, but hopefully investigators will already be looking at their backgrounds and state of affairs.
5. There is no indication who or what commanded the engines back to idle detent again. There is proof of both engines attempting to restart. I would take this as confirmation of teamwork existing on the flight deck, and this would suggest a lack of deliberate interference by either pilot. Should that have been deliberately done, so much more could have happened. It just hasn't been alluded to in the preliminary report.
My own impression is that it did not appear to be a situation of a deliberate act to crash. I say this as they appear to have both tried to save the aircraft and immediately restart the engines and recover taking some critical timely actions demonstrating competent reaction.
The timing of the commanding fuel to cutoff os critical imo. The aircraft was pitching. If an accidental command to cutoff occurred then I feel this however unlikely would have been made instead of another action. The only likely thing happening at that exact time or due 2-3 seconds after lift off was gear up. The CVR and recorded timing of engine failure in relation to that challenge and response in SOP will be key imo. Did the challenge for gear up occur before the idle detent electrical signals? Also, the focus should be on that bulletin for the locking mechanism for the start levers.
I just cannot imagine an experienced crew doing this by accident and the information just doesn't suggest a deliberate act.
My post is just to highlight huge lists of unknowns. The media appears to have made their mind up that the flight crew did this. I just highlight that is definitely not confirmed yet. We have a whole list of unknowns and conflicting communication that raises more questions than they solve.
I would urge zero conclusions be made, and RIP the crew and passengers. There are zero conclusions to what happened yet in my opinion, and I think the suggestion to relatives of the flight crew and families tragically killed that this is a known pilot deliberate action simply cannot be made at this point. We must not blame the flight crew prematurely or pretend we know what happened. I think the media should take note and back off from all the assumptions.
Kudos to the crew for trying to re-light the engines so quickly.
My 10 cents is on the switches and there is not a aireworthiness directive out there for nothing.
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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
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July 13, 2025, 15:22:00 GMT
permalink Post: 11921391
The graph based on the preliminary timeline would indicate 2-3 seconds to establish the RAT power. Having used RATs in the sim and on test flights on two types, that\x92s seems correct. It\x92s very quick and, if the switches were cutoff on the runway, no way would the plane achieved that flight path, probablt overrun the runway.
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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.
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July 13, 2025, 16:06:00 GMT
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If the intent was suicide, in order to make the situation unrecoverable, pulling both fire handles would be the next item to ensure the engines would not restart in the time available, therefore if only the run/cutoff switches were moved to cut off, then the situation was not foreseeably unrecoverable and can only questionably be construed as a suicide.
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