MikeSnow
July 15, 2025, 19:33:00 GMT
permalink Post: 11923203

Quote:

Originally Posted by Engineless

Do the STAB cutout switches and Fuel cutoff switches share any connectors that could have been inadvertantly cross-connected? Etc. It would not be the first time that an engineer had innocently done something that later caused an accident. And I haven't read anything about possible nefarious action by a (disgruntled?) engineer - but I've seen lots of accusations directed at the pilot(s)...

Quote:

Originally Posted by B2N2

A \x93status\x94 message is the lowest urgency message the crew can get on a Boeing aircraft.
Its a notification at best, requires no checklist.
Maintenance will do a system check in the Maintenance Computer terminal also known as a BITE test. Clear the status message and that\x92s it.
They are certainly not taking tools to take the throttle quadrant apart in search of a software fault.
The status message has nothing to do whatsoever with the Fuel Cutoff Switches.

"Software faults" do not usually come out of the blue, for no particular reason. Just because it's recorded by software it doesn't mean that it's not something hardware related that triggers it. In a previous reply, not sure if in this thread, it was mentioned that the message meant that there was implausible data coming from those STAB cutoff switches, if I remember correctly. Something like a channel showing both on and off at the same time, or the other way around, or some other inconsistency. That could have been an intermittent issue, that might indeed not be reproducible with a BITE test, and just be cleared. But if the STAB cutoff switches did indeed have a problem, or one was suspected due to recurring reports, is it really so unlikely that they might try to look for some hardware issues, such as a loose connector? For the Lion Air accident involving MCAS, after repeated issues during previous flights, they did exactly that: disconnected and reconnected some connectors to check for issues, among other things.

TURIN
July 15, 2025, 19:54:00 GMT
permalink Post: 11923218

Quote:

Originally Posted by MikeSnow

SLF here, but I did read all 3 threads. To me, this doesn't seem likely. But it got me thinking, what about the fuel switches being partially cross-connected left to right and right to left? If each of the 8 channels (4 for each switch) has its own connector, it could be possible. From what I understood from earlier posts, from the 4 channels of each switch, there are 2 can shut down an engine. If that's the case, assuming some cross-connection, a single switch movement might be able to affect both engines.

But, even if this were possible, there are problems with this hypothesis too. The problem would most likely be discovered during engine startup, if the engines are started one by one, not at the same time, as they probably wouldn't start unless both switches are set to RUN. And not sure how this would fit the various delays recorded on the FDR. And you still need something/somebody to move at least one of the switches after rotation to trigger the issue. Both switches being moved by the pilots still seems much more likely to me than some technical issue.

"Software faults" do not usually come out of the blue, for no particular reason. Just because it's recorded by software it doesn't mean that it's not something hardware related that triggers it. In a previous reply, not sure if in this thread, it was mentioned that the message meant that there was implausible data coming from those STAB cutoff switches, if I remember correctly. Something like a channel showing both on and off at the same time, or the other way around, or some other inconsistency. That could have been an intermittent issue, that might indeed not be reproducible with a BITE test, and just be cleared. But if the STAB cutoff switches did indeed have a problem, or one was suspected due to recurring reports, is it really so unlikely that they might try to look for some hardware issues, such as a loose connector? For the Lion Air accident involving MCAS, after repeated issues during previous flights, they did exactly that: disconnected and reconnected some connectors to check for issues, among other things.

Software faults, or non correlated maintenance messages can be induced by other factors other than a hardware fault.
EG. GPS faults are common among aircraft that fly around Turkey and other troublesome areas of the world due to GPS 'spoofing' or jamming. The problem is known and a procedure to reset the fault and verify that there is no 'hard' fault hidden in the hardware is used every day.

As I posted earlier in this thread, the Stab Trim (Posn) XDCR status message can be deferred under the MEL with a maintenance procedure that does not involve touching those switches.

Last edited by TURIN; 17th July 2025 at 11:59 .

galaxy flyer
July 15, 2025, 22:58:00 GMT
permalink Post: 11923333

Quote:

Originally Posted by appruser

Literally what the Preliminary Report says happened. Even the Pilots' exchange fits within this context.

In my opinion, not enough attention is being paid to why the Pilot Monitoring might have *had to* execute the memory items for dual-engine failure.

Likely because the FDR readout showed the engines at the appropriate takeoff thrust, then the switches move, takeoff thrust goes away. Switches move back to RUN and the quick restart begins.

Triskelle
July 16, 2025, 18:21:00 GMT
permalink Post: 11923904

From the discussion about the switches it would seem impossible to me that someone sitting in either the pilot or co-pilot seats could almost simultaneously unlatch and move both switches - although it could be done by someone else in the cockpit using two hands? I can believe that both switches could be reset within a few seconds with one hand though. Would a brief electrical fault (at rotation) show on the FDR as equivalent to a switch to 'off' (closing the fuel valve and deploying the RAT)? Apparently the switches were found to be in the 'on' position.

LiveSpark
July 16, 2025, 21:26:00 GMT
permalink Post: 11924011

Quote:

Originally Posted by GroundedSpanner

787 has RDC's - Remote Data Concentrators. Doing the same function. Two of the switch pole-sets go each to one of 2 different RDC's, that feed the EAFR's / QAR, and the common core network so that any system that wants to know, can. The wiring is positive voltage from the RDC's to the switch and to GND through the common pin. So the RDC's would be able to detect anomalies such as both contacts open, or both contacts closed. The EAFR will see two independent channels per switch.
The other 2 contact sets feed latching relays (again driven each coil independently by dropping to GND at the switch) that then drive spar valves and reset signals to the FADEC Channels. (and more).

So - for the benefit of those that hang on to the 'possibility' of electrical gremlins and 'ghost' switch signals.

Each switch has 4 mechanically separated 'channels' - 2 of which do electromechanical things to the engines through separate paths, the other 2 feed through independent paths the FDR and the rest of the computer systems. The results of the electromechanical actions also feed back to the FDR.

Thus the readout from the EAFR will PROVE that the switches MUST have been PHYSICALLY MOVED.

Can someone please confirm whether or not the respective fuel cut-off switch is directly connected to the open/closing coils of the fuel valve actuator? Or is there some intermediate control system between the switch and valve actuator?

BrogulT
July 16, 2025, 22:20:00 GMT
permalink Post: 11924037

Quote:

Originally Posted by fgrieu

What type of switches are they: SPST, SPDT with 3 wires used ? For SPST or equivalent, is "cutoff" the "make" or "break" state ?
Is there a common connection for the two switches, like a ground return or common live?

From earlier and from the Honeywell datasheet these are 4PDT switches with all 4 section having the center as a common (ground AFAIK ) so that the FDR and other circuits can positively see that the switch is on one condition or the other--except for the brief time that both are open during switching. Snap toggles like this are most commonly break-before-make as tdracer confirms (but 50ms seems like a long time...). What this means practically is that a break or short in the wiring would cause a fault that would be recognized as such since a correctly operating circuit will have one or the other but not both of the circuits completed and there are 4 sets of circuits.

AirScotia
July 17, 2025, 13:46:00 GMT
permalink Post: 11924417

Quote:

Originally Posted by krismiler

If it was a suicide attempt, wouldn't the pilot responsible wait until the aircraft had got a bit higher before operating the fuel switches and follow it up with full forward stick ? At low level the outcome wouldn't have been in any doubt. Nose down would be instinctive to someone who wanted to crash and with the arms locked in the extended position it would be very difficult for the other pilot to override him.

This has been discussed.. If suicide, this is the only part of flight where the FDR will not identify which pilot is responsible. This may matter to the person for life insurance / reputation reasons.

I agree that it may have been a physical health issue causing momentary confusion. Or it may be related to medication. But I think it's hard to dispute that human fingers moved the switches.

za9ra22
July 17, 2025, 13:59:00 GMT
permalink Post: 11924424

Quote:

Originally Posted by AirScotia

The only problem with that argument is that (according to the WSJ and other musings), the pilot responsible HAS been identified, quite easily.

And in fact, I would be shocked if the pilot responsible didn't expect that his identity would be knowable in due course in any event - just as many here have supposed. Certainly, no life insurance policy would pay out on a claim until this was settled to the insurance company's satisfaction.

To add: This is pertinent because it really does show that if this were a suicide by pilot, the pilot either knew he would be identified and named, or didn't care.

Icarus2001
July 17, 2025, 15:07:00 GMT
permalink Post: 11924452

Quote:

If suicide, this is the only part of flight where the FDR will not identify which pilot is responsible.

Why is that then?

za9ra22
July 17, 2025, 15:23:00 GMT
permalink Post: 11924460

Quote:

Originally Posted by jimtx

Why would AAIB include that red herring in the prelim when they had the switches in their possession and included pics of them in the report? I have to admit that I took a bite of that herring and still have a nagging issue with myself not being able to see a dog on the lower part of the left switch. But I'm more inclined to think badly of the AAIB for including the herring.

Not sure why you would think the paragraph in the preliminary report was a red herring - it's a statement of historical context directly relating to the fuel control switches which the investigation had found in the FDR record as having 'transitioned' to OFF before 'transitioning' ack to ON.

To not detail the background would have been to omit a clearly pertinent fact which would have left others questioning the authority of the report for not covering it. The report itself then clearly states: "At this stage of investigation, there are no recommended actions to B787-8 and/or GE GEnx-1B engine operators and manufacturers." to ensure it is known that no defects were found at the time of the report being issued.

I suspect it is written as it is because at this point, there is no evidence the investigation can provide as to how the switches 'transitioned', let alone why.

jimtx
July 17, 2025, 17:06:00 GMT
permalink Post: 11924525

Quote:

Originally Posted by za9ra22

Why "There has been no defect reported pertaining to the fuel control switch since 2023 on VT-ANB." instead of: The mishap switches have been checked and have no defects. Their locking feature is operational.

They have the switches.

Chernobyl
July 17, 2025, 17:27:00 GMT
permalink Post: 11924531

Quote:

Originally Posted by AirScotia

This has been discussed.. If suicide, this is the only part of flight where the FDR will not identify which pilot is responsible. This may matter to the person for life insurance / reputation reasons.

Quote:

Originally Posted by Nick H.

I'm sorry to say that OhForSure's suicide theory fits well because:

[...] he may have wanted the investigators not to reach a firm conclusion of suicide so that his family would receive an insurance payout [...]

[emphasis mine]

I'm genuinely puzzled about the statements above (and many more similar examples in previous posts too numerous to count). I checked the language in my own policy (a common term life insurance policy in Canada) and it explicitly states under exclusions: "Suicide within 2 years of the effective date of coverage or reinstatement, or the date of any increase in coverage, is not covered." [again, emphasis mine] Beyond the 2 year exclusion period, suicide is considered an insured risk.

So, is everyone just presuming that insurance policies don't/won't pay out in the event of suicide? If so, I have at least one example that counters that common knowledge. Perhaps this is an exclusion in flight crew life insurance -- I don't rightly know (as simple SLF I'm not aware of those Ts & Cs). Can anyone point to an authoritative source (as opposed to just surmised knowledge) which states that a life insurance policy will not pay out in the event of suicide (past any exclusion period) and hence could be motivating factor in the decision-making of this incident? Further, it should be from an Indian life insurance company that would typically cover pilots (as this is the relevant scenario).

For further clarity: I take no position on whether this incident was triggered by intent or not. I just want to better understand whether this particular aspect may or may not have been a contributing factor.

MikeSnow July 15, 2025, 19:33:00 GMT permalink Post: 11923203	Quote: Originally Posted by Engineless Do the STAB cutout switches and Fuel cutoff switches share any connectors that could have been inadvertantly cross-connected? Etc. It would not be the first time that an engineer had innocently done something that later caused an accident. And I haven't read anything about possible nefarious action by a (disgruntled?) engineer - but I've seen lots of accusations directed at the pilot(s)... SLF here, but I did read all 3 threads. To me, this doesn't seem likely. But it got me thinking, what about the fuel switches being partially cross-connected left to right and right to left? If each of the 8 channels (4 for each switch) has its own connector, it could be possible. From what I understood from earlier posts, from the 4 channels of each switch, there are 2 can shut down an engine. If that's the case, assuming some cross-connection, a single switch movement might be able to affect both engines. But, even if this were possible, there are problems with this hypothesis too. The problem would most likely be discovered during engine startup, if the engines are started one by one, not at the same time, as they probably wouldn't start unless both switches are set to RUN. And not sure how this would fit the various delays recorded on the FDR. And you still need something/somebody to move at least one of the switches after rotation to trigger the issue. Both switches being moved by the pilots still seems much more likely to me than some technical issue. Quote: Originally Posted by B2N2 A \x93status\x94 message is the lowest urgency message the crew can get on a Boeing aircraft. Its a notification at best, requires no checklist. Maintenance will do a system check in the Maintenance Computer terminal also known as a BITE test. Clear the status message and that\x92s it. They are certainly not taking tools to take the throttle quadrant apart in search of a software fault. The status message has nothing to do whatsoever with the Fuel Cutoff Switches. "Software faults" do not usually come out of the blue, for no particular reason. Just because it's recorded by software it doesn't mean that it's not something hardware related that triggers it. In a previous reply, not sure if in this thread, it was mentioned that the message meant that there was implausible data coming from those STAB cutoff switches, if I remember correctly. Something like a channel showing both on and off at the same time, or the other way around, or some other inconsistency. That could have been an intermittent issue, that might indeed not be reproducible with a BITE test, and just be cleared. But if the STAB cutoff switches did indeed have a problem, or one was suspected due to recurring reports, is it really so unlikely that they might try to look for some hardware issues, such as a loose connector? For the Lion Air accident involving MCAS, after repeated issues during previous flights, they did exactly that: disconnected and reconnected some connectors to check for issues, among other things.
TURIN July 15, 2025, 19:54:00 GMT permalink Post: 11923218	Quote: Originally Posted by MikeSnow SLF here, but I did read all 3 threads. To me, this doesn't seem likely. But it got me thinking, what about the fuel switches being partially cross-connected left to right and right to left? If each of the 8 channels (4 for each switch) has its own connector, it could be possible. From what I understood from earlier posts, from the 4 channels of each switch, there are 2 can shut down an engine. If that's the case, assuming some cross-connection, a single switch movement might be able to affect both engines. But, even if this were possible, there are problems with this hypothesis too. The problem would most likely be discovered during engine startup, if the engines are started one by one, not at the same time, as they probably wouldn't start unless both switches are set to RUN. And not sure how this would fit the various delays recorded on the FDR. And you still need something/somebody to move at least one of the switches after rotation to trigger the issue. Both switches being moved by the pilots still seems much more likely to me than some technical issue. "Software faults" do not usually come out of the blue, for no particular reason. Just because it's recorded by software it doesn't mean that it's not something hardware related that triggers it. In a previous reply, not sure if in this thread, it was mentioned that the message meant that there was implausible data coming from those STAB cutoff switches, if I remember correctly. Something like a channel showing both on and off at the same time, or the other way around, or some other inconsistency. That could have been an intermittent issue, that might indeed not be reproducible with a BITE test, and just be cleared. But if the STAB cutoff switches did indeed have a problem, or one was suspected due to recurring reports, is it really so unlikely that they might try to look for some hardware issues, such as a loose connector? For the Lion Air accident involving MCAS, after repeated issues during previous flights, they did exactly that: disconnected and reconnected some connectors to check for issues, among other things. Software faults, or non correlated maintenance messages can be induced by other factors other than a hardware fault. EG. GPS faults are common among aircraft that fly around Turkey and other troublesome areas of the world due to GPS 'spoofing' or jamming. The problem is known and a procedure to reset the fault and verify that there is no 'hard' fault hidden in the hardware is used every day. As I posted earlier in this thread, the Stab Trim (Posn) XDCR status message can be deferred under the MEL with a maintenance procedure that does not involve touching those switches. Last edited by TURIN; 17th July 2025 at 11:59 .
galaxy flyer July 15, 2025, 22:58:00 GMT permalink Post: 11923333	Quote: Originally Posted by appruser Literally what the Preliminary Report says happened. Even the Pilots' exchange fits within this context. In my opinion, not enough attention is being paid to why the Pilot Monitoring might have had to execute the memory items for dual-engine failure. Likely because the FDR readout showed the engines at the appropriate takeoff thrust, then the switches move, takeoff thrust goes away. Switches move back to RUN and the quick restart begins.
Triskelle July 16, 2025, 18:21:00 GMT permalink Post: 11923904	From the discussion about the switches it would seem impossible to me that someone sitting in either the pilot or co-pilot seats could almost simultaneously unlatch and move both switches - although it could be done by someone else in the cockpit using two hands? I can believe that both switches could be reset within a few seconds with one hand though. Would a brief electrical fault (at rotation) show on the FDR as equivalent to a switch to 'off' (closing the fuel valve and deploying the RAT)? Apparently the switches were found to be in the 'on' position.
LiveSpark July 16, 2025, 21:26:00 GMT permalink Post: 11924011	Quote: Originally Posted by GroundedSpanner 787 has RDC's - Remote Data Concentrators. Doing the same function. Two of the switch pole-sets go each to one of 2 different RDC's, that feed the EAFR's / QAR, and the common core network so that any system that wants to know, can. The wiring is positive voltage from the RDC's to the switch and to GND through the common pin. So the RDC's would be able to detect anomalies such as both contacts open, or both contacts closed. The EAFR will see two independent channels per switch. The other 2 contact sets feed latching relays (again driven each coil independently by dropping to GND at the switch) that then drive spar valves and reset signals to the FADEC Channels. (and more). So - for the benefit of those that hang on to the 'possibility' of electrical gremlins and 'ghost' switch signals. Each switch has 4 mechanically separated 'channels' - 2 of which do electromechanical things to the engines through separate paths, the other 2 feed through independent paths the FDR and the rest of the computer systems. The results of the electromechanical actions also feed back to the FDR. Thus the readout from the EAFR will PROVE that the switches MUST have been PHYSICALLY MOVED. Can someone please confirm whether or not the respective fuel cut-off switch is directly connected to the open/closing coils of the fuel valve actuator? Or is there some intermediate control system between the switch and valve actuator?
BrogulT July 16, 2025, 22:20:00 GMT permalink Post: 11924037	Quote: Originally Posted by fgrieu What type of switches are they: SPST, SPDT with 3 wires used ? For SPST or equivalent, is "cutoff" the "make" or "break" state ? Is there a common connection for the two switches, like a ground return or common live? From earlier and from the Honeywell datasheet these are 4PDT switches with all 4 section having the center as a common (ground AFAIK ) so that the FDR and other circuits can positively see that the switch is on one condition or the other--except for the brief time that both are open during switching. Snap toggles like this are most commonly break-before-make as tdracer confirms (but 50ms seems like a long time...). What this means practically is that a break or short in the wiring would cause a fault that would be recognized as such since a correctly operating circuit will have one or the other but not both of the circuits completed and there are 4 sets of circuits.
AirScotia July 17, 2025, 13:46:00 GMT permalink Post: 11924417	Quote: Originally Posted by krismiler If it was a suicide attempt, wouldn't the pilot responsible wait until the aircraft had got a bit higher before operating the fuel switches and follow it up with full forward stick ? At low level the outcome wouldn't have been in any doubt. Nose down would be instinctive to someone who wanted to crash and with the arms locked in the extended position it would be very difficult for the other pilot to override him. This has been discussed.. If suicide, this is the only part of flight where the FDR will not identify which pilot is responsible. This may matter to the person for life insurance / reputation reasons. I agree that it may have been a physical health issue causing momentary confusion. Or it may be related to medication. But I think it's hard to dispute that human fingers moved the switches.
za9ra22 July 17, 2025, 13:59:00 GMT permalink Post: 11924424	Quote: Originally Posted by AirScotia This has been discussed.. If suicide, this is the only part of flight where the FDR will not identify which pilot is responsible. This may matter to the person for life insurance / reputation reasons. The only problem with that argument is that (according to the WSJ and other musings), the pilot responsible HAS been identified, quite easily. And in fact, I would be shocked if the pilot responsible didn't expect that his identity would be knowable in due course in any event - just as many here have supposed. Certainly, no life insurance policy would pay out on a claim until this was settled to the insurance company's satisfaction. To add: This is pertinent because it really does show that if this were a suicide by pilot, the pilot either knew he would be identified and named, or didn't care.
Icarus2001 July 17, 2025, 15:07:00 GMT permalink Post: 11924452	Quote: If suicide, this is the only part of flight where the FDR will not identify which pilot is responsible. Why is that then?
za9ra22 July 17, 2025, 15:23:00 GMT permalink Post: 11924460	Quote: Originally Posted by jimtx Why would AAIB include that red herring in the prelim when they had the switches in their possession and included pics of them in the report? I have to admit that I took a bite of that herring and still have a nagging issue with myself not being able to see a dog on the lower part of the left switch. But I'm more inclined to think badly of the AAIB for including the herring. Not sure why you would think the paragraph in the preliminary report was a red herring - it's a statement of historical context directly relating to the fuel control switches which the investigation had found in the FDR record as having 'transitioned' to OFF before 'transitioning' ack to ON. To not detail the background would have been to omit a clearly pertinent fact which would have left others questioning the authority of the report for not covering it. The report itself then clearly states: "At this stage of investigation, there are no recommended actions to B787-8 and/or GE GEnx-1B engine operators and manufacturers." to ensure it is known that no defects were found at the time of the report being issued. I suspect it is written as it is because at this point, there is no evidence the investigation can provide as to how the switches 'transitioned', let alone why.
jimtx July 17, 2025, 17:06:00 GMT permalink Post: 11924525	Quote: Originally Posted by za9ra22 Not sure why you would think the paragraph in the preliminary report was a red herring - it's a statement of historical context directly relating to the fuel control switches which the investigation had found in the FDR record as having 'transitioned' to OFF before 'transitioning' ack to ON. To not detail the background would have been to omit a clearly pertinent fact which would have left others questioning the authority of the report for not covering it. The report itself then clearly states: "At this stage of investigation, there are no recommended actions to B787-8 and/or GE GEnx-1B engine operators and manufacturers." to ensure it is known that no defects were found at the time of the report being issued. I suspect it is written as it is because at this point, there is no evidence the investigation can provide as to how the switches 'transitioned', let alone why. Why "There has been no defect reported pertaining to the fuel control switch since 2023 on VT-ANB." instead of: The mishap switches have been checked and have no defects. Their locking feature is operational. They have the switches.
Chernobyl July 17, 2025, 17:27:00 GMT permalink Post: 11924531	Quote: Originally Posted by AirScotia This has been discussed.. If suicide, this is the only part of flight where the FDR will not identify which pilot is responsible. This may matter to the person for life insurance / reputation reasons. Quote: Originally Posted by Nick H. I'm sorry to say that OhForSure's suicide theory fits well because: [...] he may have wanted the investigators not to reach a firm conclusion of suicide so that his family would receive an insurance payout [...] [emphasis mine] I'm genuinely puzzled about the statements above (and many more similar examples in previous posts too numerous to count). I checked the language in my own policy (a common term life insurance policy in Canada) and it explicitly states under exclusions: "Suicide within 2 years of the effective date of coverage or reinstatement, or the date of any increase in coverage, is not covered." [again, emphasis mine] Beyond the 2 year exclusion period, suicide is considered an insured risk. So, is everyone just presuming that insurance policies don't/won't pay out in the event of suicide? If so, I have at least one example that counters that common knowledge. Perhaps this is an exclusion in flight crew life insurance -- I don't rightly know (as simple SLF I'm not aware of those Ts & Cs). Can anyone point to an authoritative source (as opposed to just surmised knowledge) which states that a life insurance policy will not pay out in the event of suicide (past any exclusion period) and hence could be motivating factor in the decision-making of this incident? Further, it should be from an Indian life insurance company that would typically cover pilots (as this is the relevant scenario). For further clarity: I take no position on whether this incident was triggered by intent or not. I just want to better understand whether this particular aspect may or may not have been a contributing factor.

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