GarageYears
July 12, 2025, 22:00:00 GMT
permalink Post: 11920872

Quote:

Originally Posted by RexBanner

The key point being missed here is that the question was \x93 why did you cutoff?\x94 not \x93did you cut off?\x94 Makes all the difference. The other pilot saw something.

Yes - this ^^^

And next, all this discussion on the idea of a worn locking mechanism on BOTH switches\x85? Both? No, one, maybe, but both sufficiently worn, but never written up to allow inadvertent or accidental activation. Nope.

Finally, these odd questions related to whether the data recorder recorded the *position* of the switch or the electrical signal. How does anyone imagine the position could be read??? It\x92s a switch - the electrical signal is what matters.

- GY

Subjects: None

GarageYears
July 13, 2025, 01:46:00 GMT
permalink Post: 11920981

Quote:

Originally Posted by FrequentSLF

With all due respect, you are incorrect, without power the electrical output is NOT the position of the switch

If the switches were without power (!), then the FDR could not record them \x91transistioning\x92. This obsession with \x91position\x92 is weird. The FDR is a DATA recorder. For example it knows the position of the thrust levers because position is used to determine how much thrust is demanded. But of course that\x92s a huge simplification. But binary switches are on or off and do NOT have a \x91position\x92.

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FDR

GarageYears
July 15, 2025, 13:28:00 GMT
permalink Post: 11922945

Quote:

Originally Posted by barrymung

There quite possibly are multiple contacts in use, but it's still a possibility. Statistically, pilot suicide is *very* rare and I would think switch failure or wiring loom failure is more common.

At this stage it's important not to rule anything out.

How common is two switches and/or two wiring loom failures occurring 1 second apart, that are then 'corrected' 10 seconds and then 4 seconds later?

What you're doing here is drilling holes in the cheese to make your theory fit. I don't think anyone is ruling anything out, but we need to dial back the imaginary 3rd person in the cockpit, flying books or whatever, and dare I say it almost, but not quite, simultaneous failures that then somehow fix themselves. Particularly, where the failures would have had to occurred in all 3-poles of each switch to cause the end result.

- GY

Subjects: None

GarageYears
July 15, 2025, 14:40:00 GMT
permalink Post: 11922993

Quote:

Originally Posted by BrogulT

"Quite possibly"? A qualified, informed person has taken the time the share exactly how the 4 sets of contacts work on this switch and how they are connected to the plane's electrical system. Go back and find that and read it. It's not an open question. Broken or shorted wires would show up as specific faults, not as just a misreported switch position.

As for the locking mechanism, I don't have this switch but I do have various electronic devices with multiple examples of locking toggle switches with similar functions. They all share a common attribute in that while you can sort of balance the toggle in the middle, the internal toggle mechanism will not snap and change state until you go past that point. So if the switch is in the OFF position, it will not turn on until you go over the hump--and vice versa. So to get the switch in that condition you'd have to first switch it on and then back it off to the middle position. IDK for sure if the specific switches in question behave, but snap-action toggle mechanisms are pretty universal so I'd assume they are similar unless someone with access to one says otherwise.

A few posts up (well, maybe 10 or 20 up) someone posted a link to a video of the exact switch operation - watching that many times, it would seem impossible to balance the switch in the mid-position, and the snap-action is pretty definite.

- GY

Subjects: None

GarageYears
July 15, 2025, 22:54:00 GMT
permalink Post: 11923330

Quote:

Originally Posted by appruser

That's on the EAFR. With their headsets on, are B787 pilots even able to hear the engines on the flight deck, over the wind noise and their headset sidetone? Genuinely asking - I don't know.

I do, I work on Level D sound and communications systems for full flight simulators, designing the sound models and communications as used in many of the worlds FFS, including the 787.

The overall sound environment of the 787 is surprisingly quiet, but at takeoff thrust the engines are easily heard, even with the headsets on - these are typically light-weight over-ear units. Aerodynamic noise is not really significant until the aircraft is faster/higher.

In this accident case, the engine spool-down should have been a noticeable sound cue.

- GY

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): EAFR

GarageYears
July 15, 2025, 23:19:00 GMT
permalink Post: 11923339

Quote:

Originally Posted by appruser

Thanks for the explanation.

If a fault caused the pack compressors to go quiet, could that be mistaken as engine loss? Say on the left side?

Very unlikely, the pack sound is a low frequency broadband noise, while the engines are distinctly tonal at takeoff thrust. Loosing a pack would leave the engines more distinct.

The engines shutting down, especially at the phase of flight they were in, would have been very unnerving and clearly wrong.

- GY

Subjects: None

GarageYears
July 16, 2025, 14:32:00 GMT
permalink Post: 11923769

Quote:

Originally Posted by 1stspotter

Potential issue with the locking feature of fuel control switches of the Boeing 787 is a * red herring*. There is no such issue. There was an issue on some Boeing 737 aircraft. The FAA requested operators of other Boeing made aircraft to check if their aircraft had switches with a similar issue. No reports of such issue are known.
See https://feitoffake.wordpress.com/202...787-explained/

So your scenario is impossible.

And just to be clear the switch fitted to the 787 is NOT that same part as used on the 737. It is a newer design that is visually similar, but CANNOT be installed 'incorrectly'.

- GY

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FAA Fuel (All) Fuel Cutoff Switches

GarageYears
July 16, 2025, 14:36:00 GMT
permalink Post: 11923772

Quote:

Originally Posted by Dimitris

SLF here with engineering background.

Regardless of what happened and why regarding the switches going to off, there is now a documented failure mode of the system that needs mitigation (?):
Fuel switches off at less than XXX ft lead to unrecoverable AC.

If fuel cut off during take off leads to unrecoverable at less than XXX ft or risk of error i.e. switching one vs the other, then inhibit them. I'm putting it too simplistically, but if after V1 the AC is GO and there is a range of altitude/speed that engines loss leads to unrecoverable some mitigation is needed.

In the meantime maybe ban jump seating during such phases of flight regardless of it is relevant to this accident. If there is intention for something like that, less people with access reduces the possibility of happening.

Too much discussion I think for the 10s to bring the switches back to on.... Pilots are not super humans. By that time the situation the AC was at must have been very clear, some hands shaking is expected...

I wonder if based on the data from the flight, sim-runs have been made to see if the situation would be more survivable had the AC 'slammed' itself back to the runway.

--> Any estimation of how many seconds in 'off' would not change the end result? If it is 2-3 seconds, its better to stop discussing if 10s response by pilots was ok or not. The 'why' and 'preventive' of going to 'off' is a lot more important.

Edit: Have been reading tdracer posts for many many years now. Thank you!

The problem here with inhibiting the fuel cutoff is that what happens if you have an engine fire less than your XXX ft? You still need to turn off that engine, right? Now you could say turning off BOTH should be inhibited... what if they are both on fire and there's a nice flat space in front of you?

- GY

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All) Fuel Cutoff Fuel Cutoff Switches Jump Seat V1

GarageYears
July 16, 2025, 18:39:00 GMT
permalink Post: 11923921

Quote:

Originally Posted by Ant T

The SAIB from the FAA literally states the opposite to what you are stating.

It goes on to list models including 787-8, -9 and -10

https://ad.easa.europa.eu/blob/NM-18...SIB_NM-18-33_1

There were no \x93flaws\x94 in the switches themselves. The original SAIB came about because some switches on 737s were found to be installed incorrectly. When the switches were installed incorrectly they would not hold in the RUN position and would immediately snap back into CUTOFF. The failure mode was obvious and would be immediately recognized that the installation was incorrect.

These same switches are used on about 7,000 aircraft. A new part (766AT614-3D) with a new locking mechanism that could not be installed incorrectly was made for the 737.

The 787 uses an entirely different part number (4TL837‑3D). 1,200 787s with 30 million flight hours and 5 million departures. Not one instance of one, let alone two switches not working as designed.

- GY

Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FAA RUN/CUTOFF Special Airworthiness Information Bulletin

GarageYears July 12, 2025, 22:00:00 GMT permalink Post: 11920872	Quote: Originally Posted by RexBanner The key point being missed here is that the question was \x93 *why* did you cutoff?\x94 not \x93did you cut off?\x94 Makes all the difference. The other pilot saw something. Yes - this ^^^ And next, all this discussion on the idea of a worn locking mechanism on BOTH switches\x85? Both? No, one, maybe, but both sufficiently worn, but never written up to allow inadvertent or accidental activation. Nope. Finally, these odd questions related to whether the data recorder recorded the position of the switch or the electrical signal. How does anyone imagine the position could be read??? It\x92s a switch - the electrical signal is what matters. - GY Subjects: None
GarageYears July 13, 2025, 01:46:00 GMT permalink Post: 11920981	Quote: Originally Posted by FrequentSLF With all due respect, you are incorrect, without power the electrical output is NOT the position of the switch If the switches were without power (!), then the FDR could not record them \x91transistioning\x92. This obsession with \x91position\x92 is weird. The FDR is a DATA recorder. For example it knows the position of the thrust levers because position is used to determine how much thrust is demanded. But of course that\x92s a huge simplification. But binary switches are on or off and do NOT have a \x91position\x92. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FDR
GarageYears July 15, 2025, 13:28:00 GMT permalink Post: 11922945	Quote: Originally Posted by barrymung There quite possibly are multiple contacts in use, but it's still a possibility. Statistically, pilot suicide is very rare and I would think switch failure or wiring loom failure is more common. At this stage it's important not to rule anything out. How common is two switches and/or two wiring loom failures occurring 1 second apart, that are then 'corrected' 10 seconds and then 4 seconds later? What you're doing here is drilling holes in the cheese to make your theory fit. I don't think anyone is ruling anything out, but we need to dial back the imaginary 3rd person in the cockpit, flying books or whatever, and dare I say it almost, but not quite, simultaneous failures that then somehow fix themselves. Particularly, where the failures would have had to occurred in all 3-poles of each switch to cause the end result. - GY Subjects: None
GarageYears July 15, 2025, 14:40:00 GMT permalink Post: 11922993	Quote: Originally Posted by BrogulT "Quite possibly"? A qualified, informed person has taken the time the share exactly how the 4 sets of contacts work on this switch and how they are connected to the plane's electrical system. Go back and find that and read it. It's not an open question. Broken or shorted wires would show up as specific faults, not as just a misreported switch position. As for the locking mechanism, I don't have this switch but I do have various electronic devices with multiple examples of locking toggle switches with similar functions. They all share a common attribute in that while you can sort of balance the toggle in the middle, the internal toggle mechanism will not snap and change state until you go past that point. So if the switch is in the OFF position, it will not turn on until you go over the hump--and vice versa. So to get the switch in that condition you'd have to first switch it on and then back it off to the middle position. IDK for sure if the specific switches in question behave, but snap-action toggle mechanisms are pretty universal so I'd assume they are similar unless someone with access to one says otherwise. A few posts up (well, maybe 10 or 20 up) someone posted a link to a video of the exact switch operation - watching that many times, it would seem impossible to balance the switch in the mid-position, and the snap-action is pretty definite. - GY Subjects: None
GarageYears July 15, 2025, 22:54:00 GMT permalink Post: 11923330	Quote: Originally Posted by appruser That's on the EAFR. With their headsets on, are B787 pilots even able to hear the engines on the flight deck, over the wind noise and their headset sidetone? Genuinely asking - I don't know. I do, I work on Level D sound and communications systems for full flight simulators, designing the sound models and communications as used in many of the worlds FFS, including the 787. The overall sound environment of the 787 is surprisingly quiet, but at takeoff thrust the engines are easily heard, even with the headsets on - these are typically light-weight over-ear units. Aerodynamic noise is not really significant until the aircraft is faster/higher. In this accident case, the engine spool-down should have been a noticeable sound cue. - GY Subjects (links are to this post in the relevant subject page so that this post can be seen in context): EAFR
GarageYears July 15, 2025, 23:19:00 GMT permalink Post: 11923339	Quote: Originally Posted by appruser Thanks for the explanation. If a fault caused the pack compressors to go quiet, could that be mistaken as engine loss? Say on the left side? Very unlikely, the pack sound is a low frequency broadband noise, while the engines are distinctly tonal at takeoff thrust. Loosing a pack would leave the engines more distinct. The engines shutting down, especially at the phase of flight they were in, would have been very unnerving and clearly wrong. - GY Subjects: None
GarageYears July 16, 2025, 14:32:00 GMT permalink Post: 11923769	Quote: Originally Posted by 1stspotter Potential issue with the locking feature of fuel control switches of the Boeing 787 is a * red herring. There is no such issue. There was an issue on some Boeing 737 aircraft. The FAA requested operators of other Boeing made aircraft to check if their aircraft had switches with a similar issue. No reports of such issue are known. See https://feitoffake.wordpress.com/202...787-explained/ So your scenario is impossible. And just to be clear the switch fitted to the 787 is NOT that same part as used on the 737. It is a newer design that is visually similar, but CANNOT be installed 'incorrectly'. - GY Subjects* (links are to this post in the relevant subject page so that this post can be seen in context): FAA Fuel (All) Fuel Cutoff Switches
GarageYears July 16, 2025, 14:36:00 GMT permalink Post: 11923772	Quote: Originally Posted by Dimitris SLF here with engineering background. Regardless of what happened and why regarding the switches going to off, there is now a documented failure mode of the system that needs mitigation (?): Fuel switches off at less than XXX ft lead to unrecoverable AC. If fuel cut off during take off leads to unrecoverable at less than XXX ft or risk of error i.e. switching one vs the other, then inhibit them. I'm putting it too simplistically, but if after V1 the AC is GO and there is a range of altitude/speed that engines loss leads to unrecoverable some mitigation is needed. In the meantime maybe ban jump seating during such phases of flight regardless of it is relevant to this accident. If there is intention for something like that, less people with access reduces the possibility of happening. Too much discussion I think for the 10s to bring the switches back to on.... Pilots are not super humans. By that time the situation the AC was at must have been very clear, some hands shaking is expected... I wonder if based on the data from the flight, sim-runs have been made to see if the situation would be more survivable had the AC 'slammed' itself back to the runway. --> Any estimation of how many seconds in 'off' would not change the end result? If it is 2-3 seconds, its better to stop discussing if 10s response by pilots was ok or not. The 'why' and 'preventive' of going to 'off' is a lot more important. Edit: Have been reading tdracer posts for many many years now. Thank you! The problem here with inhibiting the fuel cutoff is that what happens if you have an engine fire less than your XXX ft? You still need to turn off that engine, right? Now you could say turning off BOTH should be inhibited... what if they are both on fire and there's a nice flat space in front of you? - GY Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All) Fuel Cutoff Fuel Cutoff Switches Jump Seat V1
GarageYears July 16, 2025, 18:39:00 GMT permalink Post: 11923921	Quote: Originally Posted by Ant T The SAIB from the FAA literally states the opposite to what you are stating. It goes on to list models including 787-8, -9 and -10 https://ad.easa.europa.eu/blob/NM-18...SIB_NM-18-33_1 There were no \x93flaws\x94 in the switches themselves. The original SAIB came about because some switches on 737s were found to be installed incorrectly. When the switches were installed incorrectly they would not hold in the RUN position and would immediately snap back into CUTOFF. The failure mode was obvious and would be immediately recognized that the installation was incorrect. These same switches are used on about 7,000 aircraft. A new part (766AT614-3D) with a new locking mechanism that could not be installed incorrectly was made for the 737. The 787 uses an entirely different part number (4TL837‑3D). 1,200 787s with 30 million flight hours and 5 million departures. Not one instance of one, let alone two switches not working as designed. - GY Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FAA RUN/CUTOFF Special Airworthiness Information Bulletin

Posts by user "GarageYears" [Posts: 9 Total up-votes: 0 Pages: 1]