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Kraftstoffvondesibel
July 11, 2025, 21:01:00 GMT permalink Post: 11919791 |
If you look at the mechanism, and imagine the physical obstacle that makes the lift necessary not being there, it could conceivably be connecting, yes. It would then be like any other switch, really.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Switch Guards |
Kraftstoffvondesibel
July 11, 2025, 21:51:00 GMT permalink Post: 11919856 |
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Cockpit Area Audio EAFR |
Kraftstoffvondesibel
July 11, 2025, 21:57:00 GMT permalink Post: 11919867 |
It can only know their electrical, not mechanical positions. Think about it, how would that work?
Would love to see some kind of accelerometer reading of the moment the switches went to cut off. Or even cockpit area audio. They will figure it out. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Cockpit Area Audio Fuel (All) Fuel Cutoff Switches |
Kraftstoffvondesibel
July 11, 2025, 22:04:00 GMT permalink Post: 11919875 |
Actually, why are switches that are only really required on the ground or in an engine shut down event where they are? Embraer's have the switches out of the way on an overhead panel and as well as detent locked, have a protective guard, one has to physically lift. If the PF had to physically carry out the engine shut down on an Embraer, he would have to raise his arm. Would be obvious to the PnF.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All) Fuel Cutoff Switches Fuel Cutoff Switches (detent) Human Factors Switch Guards |
Kraftstoffvondesibel
July 11, 2025, 22:26:00 GMT permalink Post: 11919913 |
And indeed they are 4 pole on-on switches, but one set of poles signals the spar valve directly while the other goes to the digital systems. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FDR Spar Valves |
Kraftstoffvondesibel
July 11, 2025, 23:02:00 GMT permalink Post: 11919962 |
I\x92d like to add for emphasis that we do not know what was said. We only have the investigators summary/narrative. We don\x92t know which exact words were used, or in which language they were spoken, or even which way across the command gradient those unknown words were uttered.
Having a non-english first language myself, I can find several translations from english to my own language of which all will be equally correct but fit each of the various interpretations in this thread. Someone said the data and audio must be interprered together, but we don\x92t have the audio. The other language bit os the \xabtransitioned\xbb rather than \xabmoved\xbb. We don\x92t know from the report whether it was moved. We know it electrically transitioned between states. If it was a short because of contamination, or the gate was wrongly installed or worn, cycling it back(or simply fiddling with it in high stress) explains both the sequence and time used. The only thing we know is that the switches were physically in run when found. Right next to the throttles in Idle\x85 There is also the sample rate issue raised by several. A millisecond difference can be sampled as a second difference. They might also not be sampled at the same time. Not aviation, but a automated system I owned recorded all positions and values of thousands of switches and potentiometers sequentially over about a second. The 787 is a much newer system, but processor speed isn\x92t necessarily the top priority. So maybe try and not put so much effort into analyzing words we don\x92t know and sub-second FDR data? The cockpit area microphone just might have picked up discernable clicks or plonks from the switches being moved. how about this: A nice, uncontroversial alternative to cockpit video could be a small microphone array. It would, when visualising audio data, show where and when to the millimeter a sound changes or emanates in the cockpit, any switch or mechanical fault, but not arms moving, facial expressions or who does what. It would be an easy add on/expansion to the existing battery powered area mic. They do it in large factories to pin-point loose bolts or mechanical wear well ahead of tgem needing to be changed. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Cockpit Area Audio FDR |
Kraftstoffvondesibel
July 11, 2025, 23:16:00 GMT permalink Post: 11919980 |
Yet seconds later the transition from CUTOFF to RUN was recorded and was effective for both switches. "Effective" means all poles made contact, the spar fuel valves and EECs. Independently, on each side. We know this because both engines re-lit at different times.
Doesn't sound like spilled coffee or "a short." It happens, you cycle(ie.fiddle) with them until you make contact again. We don\x92t know how the switches moved, we only know when they made contact. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RUN/CUTOFF |
Kraftstoffvondesibel
July 11, 2025, 23:59:00 GMT permalink Post: 11920023 |
Respectfully, your explanation is invented from your personal experience. It does not cleanly fit the facts as provided in the report, and in fact must assume the report authors intentionally omitted all description of cycling/fiddling. It also assumes spilling and shorting that are not described anywhere.
A more straightforward explanation is that the controls were manually moved to CUTOFF. Then, seconds later they were manually and individually moved to RUN. According to the report, expected effects occurred with each "transition." "P1 Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position" "Engine 1 fuel cutoff switch transitioned from CUTOFF to RUN" "Engine 2 fuel cutoff switch also transitions from CUTOFF to RUN" You are absolutely correct insofar that is the most likely explanation, but see answer above. While I have found, as I suspect most, the deliberation angle most likely, since day one, it isn\x92t really fit for discussion, so the other, admittedly slightly more unlikely avenues are more appropriate and more interesting imho. But you also underestimate my history with spilling coffee on large amounts of switches, but while tangentially relevant, that is for another thread in another forum.o-) Intermittent faults with spillage and switches fixed by cycling/fiddling is a thing, and it is not contrary to the facts from the report. It is possible. It is also, admittedly not the most likely. Last edited by Saab Dastard; 12th July 2025 at 00:01 . Reason: Reference to deleted post removed 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 RUN/CUTOFF |
Kraftstoffvondesibel
July 12, 2025, 22:08:00 GMT permalink Post: 11920877 |
What you are asking is for a camera to take a picture of the handle. IMHO, and with all due respect, I think a lot of people on this thread with little experience of installing switches, knobs, soldering connectors and wiring looms and the banality of how they sometimes fail in complex electromechanical systems underestimate the chances of a technical fault. Yes, the switches are supposed to be electrically isolated, and I am sure they feel super solid to the touch for the operator when working as intended, but that is not the end of it. They are better than common switches, but they aren\x92t magical beings. They are the same switches of the same manufacturer, used the same number of times, in the exact same ways, installed in the same LRU centimeters away from each other. The poles many seem to think are impossible to unintentionally hit at the same time are mere millimeters apart. These factors alone rises the probability of a common mode fault many orders of magnitude imho. Is it unlikely? Yes. But as has been pointed out by many, this accident was caused by something unikely but possible. A strand of un-isolated wire in the LRU. A bit of liquid like what happened to the A350. All possible. Someone wnt as far as saying, with very vague numbers to back it up, it would have been unlikely for something like that to happen even from the big bang until today. I can only agree with one word of that: Today. A common fault of two isolated, but physically close switches due to something or other, has happened today, as it did yesterday and the day before. I am really only playing the devils advocate here, in response to a few posts that I feel expresses over confidence in established, but maybe a tad too grandfathered design practices of designing such a system, that has no real redundancy in this day and age. It is not necessarily my \xabpreferred\xbb guess as to what happened either. Subjects: None |
Kraftstoffvondesibel
July 12, 2025, 22:55:00 GMT permalink Post: 11920904 |
If it was a wire strand in the wrong place, that would fit all the facts we know. (Not saying it was, only that it fits) If you think the timing doesn\x92t quite make, bear in mind the 2 seconds error of margin between any 2 registered parameters in the FDR caused by the (assumed) 1Hz sampling sequential, non-synchronous sampling if you try to draw conclusions from time stamps. Not been in that situation, obviously, but I have certainly been in stressed situations where somewhere, someone (or something, or even me) pressed the wrong button, and I need to find out which one. 10 seconds is really not a long time if it is unexpected. It is very short. Please also remember: -We have no idea of exactly what was said. Whether the conversation referred to a error message, engines spooling down or physical switch movement/position. Throw in possible translation inaccuracies, and we can conclude even less from the information about the conversation, or what the level of clarity or confusion were. Last edited by Kraftstoffvondesibel; 12th July 2025 at 23:09 . Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FDR Parameters RUN/CUTOFF |
Kraftstoffvondesibel
July 12, 2025, 23:22:00 GMT permalink Post: 11920919 |
Sorry you are missing my point.
I'm talking about an electrical failure (for example a short), which is already implausibly affecting both (independent) circuits, causing an issue in a circuit that as I understand it fails open anyway, then resolving itself to become functional again - incidentally in roughly the same time frame that a pilot would notice an issue and seek to correct. This doesn't require knowledge of the cockpit conversation or judgement on speed (or otherwise) of the recovery. It's purely that an already incredibly unlikely scenario (electrical failure) becomes even more unlikely with the spontaneous *and synchronised, but not perfectly so* recovery of whatever this failure was. I also think the time fits, sampling margins taken into accounts. I don\x92t know what happened, but I think something in this vein of common mode failure in closely placed switches, connectors and looms, though completely dismissed by some, is in the realm of possible, and does not nearly demand the the impossible set up some claims it does. I talk from experience with large broadcast installs, some made for posterity, some temporary, in which I would dare say the number of connectors looms and switches dwarfs any aircraft, in a fraction of the time, and I have seen some weird s***. At the same time, doesn\x92t nearly has to answer to the same life or death standards, and there is certainly a much larger number of much better paid people involved with the aircraft design. I agree there is a bit of hamsterwheeling, especially with people thinking they know what was said on the flight deck, and about some of the systems. But I find there has been some good points made, especially regarding human factors, interaction design, robustness of old and tried designs. I have seen input from several experts in tangential fields that I find very interesting just in a general sense. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Electrical Failure Human Factors |
Kraftstoffvondesibel
July 17, 2025, 16:03:00 GMT permalink Post: 11924490 |
There where open land ahead equidistant from the runway centerline. Certainly as much room as BA38 used and SAS751 had available.
A bit further out there is a river. Death was anything but assured taking these into account. Subjects: None |