July 12, 2025, 02:26:00 GMT
permalink Post: 11920106
Regardless of how this happened I find it perplexing that a switch with such consequence in either position can be operated with a flick of the wrist.
Firewall shutoff switches are guarded, fire bottle switches are guarded or require both hands to operate, all require two deliberate actions to operate, except two switches in the middle of the console which do so many consrquential things..
Firewall shutoff switches are guarded, fire bottle switches are guarded or require both hands to operate, all require two deliberate actions to operate, except two switches in the middle of the console which do so many consrquential things..
July 12, 2025, 02:34:00 GMT
permalink Post: 11920108
Regardless of how this happened I find it perplexing that a switch with such consequence in either position can be operated with a flick of the wrist.
Firewall shutoff switches are guarded, fire bottle switches are guarded or require both hands to operate, all require two deliberate actions to operate, except two switches in the middle of the console which do so many consrquential things..
Firewall shutoff switches are guarded, fire bottle switches are guarded or require both hands to operate, all require two deliberate actions to operate, except two switches in the middle of the console which do so many consrquential things..
Over-guarding stuff can have its own issues. People become used to operating the guard as part of normal operations, and it becomes muscle memory.
Apparently Embraer aircraft inhibit the shutoff switch if the thrust lever is above idle - if you have a stuck thrust lever, you need to use the fire shutoff.
Another option would be to have a blocking solenoid (with override button) similar to the landing gear lever while airborne or at high speed.
July 12, 2025, 02:53:00 GMT
permalink Post: 11920122
I don’t know if the FDR measures the switch position or the electrical signal. The latter is probably more likely, although there has been much discussion around potential scenarios involving accidental switch movement as well as possible causes of electrical glitches. Let’s assume that the switches were actually moved, and ignoring the “bad faith” scenario, we need a situation that encompasses the switches being moved to Cutoff by one pilot, this action being queried by the other pilot and denied by the pilot who moved the switches.
For consideration, here is a possible scenario that hasn’t been mentioned yet and encompasses the frailty of human performance. The report mentions that the flight crew on the immediately prior flight had written up a "STAB POS XDCR" status message, and that troubleshooting was carried out. I wonder if the scenario could be that the accident crew received a Stabiliser EICAS message on or around take-off and the Capt (who was PM) decided to action the first checklist item immediately from memory, by intending to move the Stab switches to Cutoff but moving the fuel switches instead. As in all modern Boeings, the Stabiliser Cutoff switches are immediately next to the Fuel Cutoff switches and operate in the same sense (i.e. down for Cutoff). They are guarded and never normally moved but, with an intent to move the stab switches, “muscle memory” (cerebellum activation if you prefer) may have taken the Captain’s hand to the Fuel switches, which are operated on every flight. The FO (who is PF) is manually flying at this stage sees and queries it. The Capt denies it, as he doesn’t realise what he has done (confirmation bias perhaps). After a few seconds, the terrible mistake is realised, and the fuel switches are moved back to run, but sadly too late and the Capt makes a Mayday call.
Perhaps a bit of a stretch but not as much of a stretch as many of the other scenarios in this thread. I think it is a real possibility. Sadly, the only other explanation that I can see is the deliberate “bad faith” scenario, which we would all hope is incorrect.
Fly Safe
PJ88
For consideration, here is a possible scenario that hasn’t been mentioned yet and encompasses the frailty of human performance. The report mentions that the flight crew on the immediately prior flight had written up a "STAB POS XDCR" status message, and that troubleshooting was carried out. I wonder if the scenario could be that the accident crew received a Stabiliser EICAS message on or around take-off and the Capt (who was PM) decided to action the first checklist item immediately from memory, by intending to move the Stab switches to Cutoff but moving the fuel switches instead. As in all modern Boeings, the Stabiliser Cutoff switches are immediately next to the Fuel Cutoff switches and operate in the same sense (i.e. down for Cutoff). They are guarded and never normally moved but, with an intent to move the stab switches, “muscle memory” (cerebellum activation if you prefer) may have taken the Captain’s hand to the Fuel switches, which are operated on every flight. The FO (who is PF) is manually flying at this stage sees and queries it. The Capt denies it, as he doesn’t realise what he has done (confirmation bias perhaps). After a few seconds, the terrible mistake is realised, and the fuel switches are moved back to run, but sadly too late and the Capt makes a Mayday call.
Perhaps a bit of a stretch but not as much of a stretch as many of the other scenarios in this thread. I think it is a real possibility. Sadly, the only other explanation that I can see is the deliberate “bad faith” scenario, which we would all hope is incorrect.
Fly Safe
PJ88
July 12, 2025, 03:48:00 GMT
permalink Post: 11920154
I don\x92t know if the FDR measures the switch position or the electrical signal. The latter is probably more likely, although there has been much discussion around potential scenarios involving accidental switch movement as well as possible causes of electrical glitches. Let\x92s assume that the switches were actually moved, and ignoring the \x93bad faith\x94 scenario, we need a situation that encompasses the switches being moved to Cutoff by one pilot, this action being queried by the other pilot and denied by the pilot who moved the switches. For consideration, here is a possible scenario that hasn\x92t been mentioned yet and encompasses the frailty of human performance. The report mentions that the flight crew on the immediately prior flight had written up a "STAB POS XDCR" status message, and that troubleshooting was carried out.
I wonder if the scenario could be that the accident crew received a Stabiliser EICAS message on or around take-off
and the Capt (who was PM) decided to action the first checklist item immediately from memory, by intending to move the Stab switches to Cutoff but moving the fuel switches instead. As in all modern Boeings, the Stabiliser Cutoff switches are immediately next to the Fuel Cutoff switches and operate in the same sense (i.e. down for Cutoff). They are guarded and never normally moved but, with an intent to move the stab switches, \x93muscle memory\x94 (cerebellum activation if you prefer) may have taken the Captain\x92s hand to the Fuel switches, which are operated on every flight. The FO (who is PF) is manually flying at this stage sees and queries it. The Capt denies it, as he doesn\x92t realise what he has done (confirmation bias perhaps). After a few seconds, the terrible mistake is realised, and the fuel switches are moved back to run, but sadly too late and the Capt makes a Mayday...
July 12, 2025, 07:28:00 GMT
permalink Post: 11920280
It's established fact both fuel control switches moved to CUTOFF 4 seconds after Vr, a deliberate guarded action, not easily done accidentally.
The CVR records one pilot asking “Why did you cut off?”, the other replies “I didn’t”. Then a bland Mayday attributed to the Captain “engine failure, returning” in the middle of the crisis.
The language, if reported correctly, feels strangely detached. No confusion, no urgency, no clear troubleshooting. Not drawing conclusions, but does anyone else see signs of performative behaviour, that is saying the right things outwardly, while being at odds with the underlying cause?
I appreciate that both crew members lost their lives, however if we avoid discussing uncomfortable patterns, we miss the point of investigation and learning.
The CVR records one pilot asking “Why did you cut off?”, the other replies “I didn’t”. Then a bland Mayday attributed to the Captain “engine failure, returning” in the middle of the crisis.
The language, if reported correctly, feels strangely detached. No confusion, no urgency, no clear troubleshooting. Not drawing conclusions, but does anyone else see signs of performative behaviour, that is saying the right things outwardly, while being at odds with the underlying cause?
I appreciate that both crew members lost their lives, however if we avoid discussing uncomfortable patterns, we miss the point of investigation and learning.
July 12, 2025, 08:49:00 GMT
permalink Post: 11920371
If anyone believes both guarded switches flipped to OFF by accident, one after the other in under a second, I’d genuinely like to hear the cockpit ergonomics that make that plausible. Because from where I sit, it doesn’t happen unless someone means it, or at minimum, fails to follow any known SOP.
July 12, 2025, 08:57:00 GMT
permalink Post: 11920381
Agree.
I can’t see it being possible with 1 hand. Those switches are not easy to move fast. Pretty sure they are same ones as on 737 Max.
You would need both hands. Which would mean you aren’t even in your seat unless you are in some extreme yoga position within your seat.
I can’t see it being possible with 1 hand. Those switches are not easy to move fast. Pretty sure they are same ones as on 737 Max.
You would need both hands. Which would mean you aren’t even in your seat unless you are in some extreme yoga position within your seat.
July 12, 2025, 08:58:00 GMT
permalink Post: 11920383
If anyone believes both guarded switches flipped to OFF by accident, one after the other in under a second, I’d genuinely like to hear the cockpit ergonomics that make that plausible. Because from where I sit, it doesn’t happen unless someone means it, or at minimum, fails to follow any known SOP.
July 12, 2025, 10:43:00 GMT
permalink Post: 11920473
It seems to me that there must have been further dialogue after the bland "I didn't". To have nothing reported after that two-line exchange, until the MAYDAY at 08:09:05, is a highly suspect omission from the interim report. In a two-crew cockpit, facing a sudden dual engine rollback just after rotation, I find it very hard to believe that this two-line exchange was the only interaction captured.
July 12, 2025, 10:48:00 GMT
permalink Post: 11920479
July 12, 2025, 11:21:00 GMT
permalink Post: 11920518
Just read all 16 pages - been flying! I think comment \x93why did you cutoff\x94 is not the reaction I would expect from a Training Captain who has just witnessed the co-pilot turn both fuel control switches off. They would possibly utter an exclamation, but would surely correct the error immediately - this didn\x92t happen for 10secs. The words are more likely to have come from an FO who has both hands on the control column and is concentrating on the rotation.
Every flight we do as PM we move both fuel control switches to cutoff, 1 after the other, with a gap of about 1 sec between each one. It\x92s a learnt action in response to the phrase \x93shutdown\x94.
Every sim the TC has conducted he will have moved critical switches without much thought in order to setup the sim for the exercise. I remember being slightly shocked one day on the aircraft, having been training in the sim the previous day, that I nearly operated a critical control without thought. It\x92s something I had to consciously guard against after that.
There is no rational explanation for doing it though - moving both fuel control switches down instead of moving the gear lever up is not a likely action slip. It seems either a totally subconscious act or a totally deliberate act.
Every flight we do as PM we move both fuel control switches to cutoff, 1 after the other, with a gap of about 1 sec between each one. It\x92s a learnt action in response to the phrase \x93shutdown\x94.
Every sim the TC has conducted he will have moved critical switches without much thought in order to setup the sim for the exercise. I remember being slightly shocked one day on the aircraft, having been training in the sim the previous day, that I nearly operated a critical control without thought. It\x92s something I had to consciously guard against after that.
There is no rational explanation for doing it though - moving both fuel control switches down instead of moving the gear lever up is not a likely action slip. It seems either a totally subconscious act or a totally deliberate act.
Last edited by Propellerhead; 12th July 2025 at 12:11 .
July 12, 2025, 11:36:00 GMT
permalink Post: 11920539
It's established fact both fuel control switches moved to CUTOFF 4 seconds after Vr, a deliberate guarded action, not easily done accidentally.
The CVR records one pilot asking \x93Why did you cut off?\x94, the other replies \x93I didn\x92t\x94. Then a bland Mayday attributed to the Captain \x93engine failure, returning\x94 in the middle of the crisis.
The language, if reported correctly, feels strangely detached. No confusion, no urgency, no clear troubleshooting. Not drawing conclusions, but does anyone else see signs of performative behaviour, that is saying the right things outwardly, while being at odds with the underlying cause?
I appreciate that both crew members lost their lives, however if we avoid discussing uncomfortable patterns, we miss the point of investigation and learning.
The CVR records one pilot asking \x93Why did you cut off?\x94, the other replies \x93I didn\x92t\x94. Then a bland Mayday attributed to the Captain \x93engine failure, returning\x94 in the middle of the crisis.
The language, if reported correctly, feels strangely detached. No confusion, no urgency, no clear troubleshooting. Not drawing conclusions, but does anyone else see signs of performative behaviour, that is saying the right things outwardly, while being at odds with the underlying cause?
I appreciate that both crew members lost their lives, however if we avoid discussing uncomfortable patterns, we miss the point of investigation and learning.
July 12, 2025, 11:55:00 GMT
permalink Post: 11920561
Beware hindsight bias
A 'unlocking' (guarded) switch, as per 787 fuel, is normally associated with normal use, but requiring a higher level of protection angainst inadvertent operation (two actions), but rarely, if at all, considers simultaneous dual operation - 2 switches.
Compare with covered / uncovered push button selections in other aircraft, and those requiring push button 'unlocking'.
A range of interchangeable words, meaning, interpretation; but the root principle is that form follows function.
Beware hindsight bias.
Last edited by safetypee; 12th July 2025 at 12:30 . Reason: form follows function.
July 12, 2025, 12:25:00 GMT
permalink Post: 11920578
AI171 Threads by Subject
I have rebuilt the site that organises these three threads by subject here:
https://paulross.github.io/pprune-th...171/index.html
Changes:
Raise issues here https://github.com/paulross/pprune-threads/issues or PM me.
Changes:
- Build threads up to July 12, 2025, 11:59:00 (built at July 12, 2025, 13:03:09).
- Add thread about the published report: Preliminary Air India crash report published
- Add subjects: "Guards", "Timeline (Preliminary Report)", "EICAS", "RUN/CUTOFF", "Special Airworthiness Information Bulletin", "SAIB NM-18-33", "Gear Lever", "Startle Effect" and "Cockpit Area Audio".
- Minor improvements to the index.html page.
Raise issues here https://github.com/paulross/pprune-threads/issues or PM me.
July 12, 2025, 18:11:00 GMT
permalink Post: 11920724
(First, I've read the whole thread, and most of the content in the previous threads, though they are obviously of less relevance in some areas now.)
This notion has caused me some concern, since seeing at least one very similar remark when I read the other threads (possibly by the same poster, though?).
It seems extremely undesirable for TCs to end up habituated to taking actions like this without thought. I wonder if it creates a case for the sim setups being performed by non-flying personnel?
Meanwhile, I read the prelim report. The English is generally fairly good but I note multiple mistakes/typos, and some oddities. One such oddity is that the timestamp of the second cutoff switch change isn't listed explicitly anywhere I can find, but instead just a relative time: "gap of 01 second". To write "1" as "01" like this invites speculation that it's a typo for 0.1; this is unlikely, given the polling frequency mentioned by some posts above, but nonetheless seems odd. (I am aware that Indian conventions differ from those in US/UK English, including placement of commas in large numbers, but I don't think this is such a case.)
Another indication to suggest it hasn't been proof-read very effectively: the FADEC is also described as a "... Dual ..." instead of "... Digital ...".
Every sim the TC has conducted he will have moved critical switches without much thought in order to setup the sim for the exercise. I remember being slightly shocked one day on the aircraft, having been training in the sim the previous day, that I nearly operated a critical control without thought. It\x92s something I had to consciously guard against after that.
It seems extremely undesirable for TCs to end up habituated to taking actions like this without thought. I wonder if it creates a case for the sim setups being performed by non-flying personnel?
Meanwhile, I read the prelim report. The English is generally fairly good but I note multiple mistakes/typos, and some oddities. One such oddity is that the timestamp of the second cutoff switch change isn't listed explicitly anywhere I can find, but instead just a relative time: "gap of 01 second". To write "1" as "01" like this invites speculation that it's a typo for 0.1; this is unlikely, given the polling frequency mentioned by some posts above, but nonetheless seems odd. (I am aware that Indian conventions differ from those in US/UK English, including placement of commas in large numbers, but I don't think this is such a case.)
Another indication to suggest it hasn't been proof-read very effectively: the FADEC is also described as a "... Dual ..." instead of "... Digital ...".
July 12, 2025, 18:46:00 GMT
permalink Post: 11920744
A question from an accepted standpoint of relative ignorance - neither a pilot nor hugely familiar with 787s although have spent a lot of time around both.
The accident report indicates that the aircraft had a STAB master caution warning on the previous sector. A maintenance action took place during the turnaround in AMD before the accident flight.
Noting that the two guarded stab cutoff switches are directly adjacent to the two guardedfuel run/cutoff switches at the base of the throttle quadrant, is there any condition that could have led a pilot to reach for the stab cutoff at the critical moment? Recurrence of the tech defect from the previous sector or switches being left in the wrong position but not noticed under the red guards ?
If that\x92s possible then accidental action of the fuel cutoff switches when the intent was some intervention with the stab switches seems more likely than a wilful pilot action to cut off fuel flow.
Is that remotely possible, given the defect history?
The accident report indicates that the aircraft had a STAB master caution warning on the previous sector. A maintenance action took place during the turnaround in AMD before the accident flight.
Noting that the two guarded stab cutoff switches are directly adjacent to the two guardedfuel run/cutoff switches at the base of the throttle quadrant, is there any condition that could have led a pilot to reach for the stab cutoff at the critical moment? Recurrence of the tech defect from the previous sector or switches being left in the wrong position but not noticed under the red guards ?
If that\x92s possible then accidental action of the fuel cutoff switches when the intent was some intervention with the stab switches seems more likely than a wilful pilot action to cut off fuel flow.
Is that remotely possible, given the defect history?
July 12, 2025, 18:54:00 GMT
permalink Post: 11920748
Couple of things.
If the red stab trim guards are closed, the switches are in the correct position.
After a 78 dual eng failure the RHS instruments return after the APU comes on line and even then it\x92s slowish as all the previous load-shedding gets reversed.
There would have been no time anyway.
If the red stab trim guards are closed, the switches are in the correct position.
After a 78 dual eng failure the RHS instruments return after the APU comes on line and even then it\x92s slowish as all the previous load-shedding gets reversed.
There would have been no time anyway.
July 12, 2025, 19:12:00 GMT
permalink Post: 11920764
If anyone believes both guarded switches flipped to OFF by accident, one after the other in under a second, I\x92d genuinely like to hear the cockpit ergonomics that make that plausible. Because from where I sit, it doesn\x92t happen unless someone means it, or at minimum, fails to follow any known SOP.
July 12, 2025, 19:21:00 GMT
permalink Post: 11920769
I don\x92t know if the FDR measures the switch position or the electrical signal. The latter is probably more likely, although there has been much discussion around potential scenarios involving accidental switch movement as well as possible causes of electrical glitches. Let\x92s assume that the switches were actually moved, and ignoring the \x93bad faith\x94 scenario, we need a situation that encompasses the switches being moved to Cutoff by one pilot, this action being queried by the other pilot and denied by the pilot who moved the switches.
For consideration, here is a possible scenario that hasn\x92t been mentioned yet and encompasses the frailty of human performance. The report mentions that the flight crew on the immediately prior flight had written up a "STAB POS XDCR" status message, and that troubleshooting was carried out. I wonder if the scenario could be that the accident crew received a Stabiliser EICAS message on or around take-off and the Capt (who was PM) decided to action the first checklist item immediately from memory, by intending to move the Stab switches to Cutoff but moving the fuel switches instead. As in all modern Boeings, the Stabiliser Cutoff switches are immediately next to the Fuel Cutoff switches and operate in the same sense (i.e. down for Cutoff). They are guarded and never normally moved but, with an intent to move the stab switches, \x93muscle memory\x94 (cerebellum activation if you prefer) may have taken the Captain\x92s hand to the Fuel switches, which are operated on every flight. The FO (who is PF) is manually flying at this stage sees and queries it. The Capt denies it, as he doesn\x92t realise what he has done (confirmation bias perhaps). After a few seconds, the terrible mistake is realised, and the fuel switches are moved back to run, but sadly too late and the Capt makes a Mayday call.
Perhaps a bit of a stretch but not as much of a stretch as many of the other scenarios in this thread. I think it is a real possibility. Sadly, the only other explanation that I can see is the deliberate \x93bad faith\x94 scenario, which we would all hope is incorrect.
Fly Safe
PJ88
For consideration, here is a possible scenario that hasn\x92t been mentioned yet and encompasses the frailty of human performance. The report mentions that the flight crew on the immediately prior flight had written up a "STAB POS XDCR" status message, and that troubleshooting was carried out. I wonder if the scenario could be that the accident crew received a Stabiliser EICAS message on or around take-off and the Capt (who was PM) decided to action the first checklist item immediately from memory, by intending to move the Stab switches to Cutoff but moving the fuel switches instead. As in all modern Boeings, the Stabiliser Cutoff switches are immediately next to the Fuel Cutoff switches and operate in the same sense (i.e. down for Cutoff). They are guarded and never normally moved but, with an intent to move the stab switches, \x93muscle memory\x94 (cerebellum activation if you prefer) may have taken the Captain\x92s hand to the Fuel switches, which are operated on every flight. The FO (who is PF) is manually flying at this stage sees and queries it. The Capt denies it, as he doesn\x92t realise what he has done (confirmation bias perhaps). After a few seconds, the terrible mistake is realised, and the fuel switches are moved back to run, but sadly too late and the Capt makes a Mayday call.
Perhaps a bit of a stretch but not as much of a stretch as many of the other scenarios in this thread. I think it is a real possibility. Sadly, the only other explanation that I can see is the deliberate \x93bad faith\x94 scenario, which we would all hope is incorrect.
Fly Safe
PJ88
July 12, 2025, 19:32:00 GMT
permalink Post: 11920776
Couple of things.
If the red stab trim guards are closed, the switches are in the correct position.
After a 78 dual eng failure the RHS instruments return after the APU comes on line and even then it\x92s slowish as all the previous load-shedding gets reversed.
There would have been no time anyway.
If the red stab trim guards are closed, the switches are in the correct position.
After a 78 dual eng failure the RHS instruments return after the APU comes on line and even then it\x92s slowish as all the previous load-shedding gets reversed.
There would have been no time anyway.
of course when both engines spool down they\x92ll be left in the Boeing equivalent of EMER ELEC, I can\x92t say I know but I would assume this episode take out everything in front of the FO who was PF at the time, the RAT would\x92ve taken time to come online
it would\x92ve been a truly startling event, I wonder if that is when the FO went \x91heads inside\x92 and saw the position of the cut offs or cycled them?