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MaybeItIs
June 28, 2025, 06:41:00 GMT permalink Post: 11912358 |
https://www.federalregister.gov/d/2022-26933/p-18 This paragraph (and one before) is/are also worth a read - they see no rush to fix, obviously. https://www.federalregister.gov/d/2025-08346/p-20 100% Agree: any suggestion that it's in any way related to 171 is pure speculation. Sounds like these ADs apply only to small numbers of 787s. Don't even know if 171 was one of them. But installing lavatories directly above EE Bays? Who's the genius...? . Anyway, I make a point of not going 'there' during the last half of any long flight. They are frequently "awash" and unpleasant places to be. The washbasins themselves are also prone to the ejecting of water onto the floors. Agreed, it's a ####ty problem. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FAA |
MaybeItIs
June 29, 2025, 03:47:00 GMT permalink Post: 11912770 |
... at least one lav immediately aft of the flight deck.
... And every commercial airliner I'm familiar with has the prime electronics bay below the flight deck - for what should be obvious reasons. There is absolutely nothing unusual about the 787 arrangement in this regard. I see nothing wrong, everything right with the Main EE Bay being under the cockpit. It's the obvious place. But underneath a leak-prone lav? Even the plumbing fittings are problematic, often leaky. Water above, Electricity below... What do we anticipate? Time is the real issue here. We have two showers in our house. A few years on, both started leaking... It's not rocket science. How can we have innovation and improvement without I & I? The more I learn... Subjects: None |
MaybeItIs
June 29, 2025, 07:26:00 GMT permalink Post: 11912837 |
It has been said that there are three stages of truth: ridicule, violent opposition and acceptance as self-evident. Obviously, we're not there yet ![]() Of course the aircrew needs a lav within their easy reach. I don't have a cross section or plan to work with (Google not obliging), but if you post, I'll take a look. Likely, I'd compartmentalize the lav with the EE Bay space immediately below, and install a "bilge tray and drain" below the lav space and above the EE Bay compartment. If it has to be used for EE Bay gear, I'd probably rack the 28V Batteries there, with the required fireproof casings and exhaust ports etc. (Also absurd, but true.) And I'd make sure the batteries themselves were fully protected by moulded plastic "hats", similar to what they use on the big 12V battery pairs on large trucks. I guess you could fit a couple of TRUs there as well, again, well-protected from dripping conductive liquids... And maybe, you could house [one of?] the EE Bay air conditioner unit[s] there? But none of the flight-critical board racks or other sensitive electronic equipment. Any moisture-related faults there would be just too random and difficult to pin down. Subjects: None |
MaybeItIs
June 29, 2025, 10:43:00 GMT permalink Post: 11912942 |
If that's so true, why the ADs about leakage from the lavs, listed earlier?
with the sort of things you have described.
They are both contained in fireproof boxes that will vent to atmosphere in the event of a thermal runaway.
I have been working on 787s for over a decade and leaks from gallies and lavs has not once been on my list of snags.
![]() Subjects: None |
MaybeItIs
July 01, 2025, 00:43:00 GMT permalink Post: 11913971 |
Oops, too slow, answered already by Sailvi767 Last edited by MaybeItIs; 1st July 2025 at 00:44 . Reason: Oops... Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Centre Tank |
MaybeItIs
July 01, 2025, 02:24:00 GMT permalink Post: 11913990 |
Hi TT,
Can I ask a question that I guess a few observers will also want to know? Is L/D (Lift-over-Drag?) the same as Glide Slope? I.e. for an L/D of 13, does that equate to 13 forward for 1 down? If so, even at 17, it doesn't look like it would make it. Last edited by MaybeItIs; 1st July 2025 at 02:25 . Reason: Remove double-negative Subjects: None |
MaybeItIs
July 01, 2025, 07:08:00 GMT permalink Post: 11914055 |
Subjects: None |
MaybeItIs
July 01, 2025, 07:35:00 GMT permalink Post: 11914070 |
Interesting, interesting!
\xa7 25.903(b) includes the words: "in at least one configuration," It doesn't, that I can see, state that that configuration must be used during takeoff, though common sense would say it should. Subjects: None |
MaybeItIs
July 01, 2025, 12:20:00 GMT permalink Post: 11914234 |
Originally Posted by
MaybeItIs
...\xa7 25.903(b) includes the words: "in at least one configuration," It doesn't, that I can see, state that that configuration must be used during takeoff, though common sense would say it should. I also don't see any evidence that engine driven fuel pumps alone must be able to handle this scenario: provide enough fuel flow for takeoff and climb, even while the pitch is rotating, even in a hot environment with significant weight, even while the gear is stuck down. A lot of other posters here have stated that according to FCOM instructions, the normal, accepted 787 Takeoff configuration is "Both sides draw from centre" if the Centre tanks have enough fuel in them. I think (maybe wrongly) that this (prior few posts) is the first time this exact point has been raised. I hope I'm correct there. If not, my humble apologies. The great thing about this forum and sadly, this tragic accident, is that it's drawing a few previously little-known worms out of the woodwork. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Centre Tank FCOM Fuel (All) |
MaybeItIs
July 09, 2025, 12:35:00 GMT permalink Post: 11918363 |
Another question if I may? I've tried searching but find the search function quite perplexing! Anyway, didn't find this answered. From other posts here, it's clear that the Cutoff switches have a mechanical locking system which requires the switch handles to be pulled outwards to disengage the lock, before they can be moved to Cutoff. Question is, to a pilot who knows these switches, can both these switches be easily operated in this fashion in unison, i.e. I guess, with one hand, so that they are both unlocked and moved to off together? I imagine that would be quite difficult to do (unless that's what everyone routinely practices), so the result would not be simultaneous. 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 GEnx (ALL) |
MaybeItIs
July 10, 2025, 00:21:00 GMT permalink Post: 11918716 |
![]() Obviously, because it's going to require quick action to catch high RPM. And maybe that's what they tried.
It also seems to be indicating that fuel switch resetting should be attempted if the restart has failed to start the engine?
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Dual Engine Failure Engine Failure (All) Fuel (All) Fuel Cutoff Switches Relight |
MaybeItIs
July 10, 2025, 01:41:00 GMT permalink Post: 11918730 |
I don't have any comment on it other than to note that the manual is not specific to Air India. My B787-9 FCTM is identical as far as I can tell. The actual memory item for dual failure is to reset the fuel switches and start the RAT. It is also conditional on the engines being sub idle as noted by the other poster.
* (Or to be fair, these guys, this cockpit team were...) Last edited by MaybeItIs; 10th July 2025 at 01:55 . Reason: grammar (still bad, never mind), a bit better 2nd time 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 RAT (All) |
MaybeItIs
July 11, 2025, 22:41:00 GMT permalink Post: 11919935 |
It looks to me like they already are. If you look at the photo of such a switch in isolation near the end of the last thread, you'll see that there are many wires shown - like in a ribbon cable - leaving the switch. But electrically, what you suggest doesn't really do it.
It's possible that a contact could "open" due to oxidation, vibration etc without any real switch movement (but extremely unlikely in aviation-grade equipment - apart from liquid spillages that occurred some time previously...). However, if it was a double-throw switch - which it may be - you'll have the chance to see one side open and depending on whether it's make-before break or the opposite (break-before-make seems more likely, but as I found out, when it doesn't behave consistently, the consequences can be dire), the other set of contacts will close, either before or after the first side opens. That's MUCH more difficult to have happen due to contact faults. I'd say impossible, except never say never! Designing stuff like this is so difficult - do you eliminate one risky possibility only to create another? For example, do you say, OK, to shutdown the engine, the Run contact must be Open and the Cutoff contact must be Closed before you can shut the engine down? Then, if someone tipped coffee into the switch a year ago, and the Cutoff contact is now insulated by a nice thick layer of dried, milky, sugary coffee and can't make contact, then the engine won't shut down. What do you do? That said, I think the positions of those two, adjacent, low down Cutoff switches are simply accidents waiting to happen. (As has been said many times. When is the manufacturer going to act?) 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 |
MaybeItIs
July 12, 2025, 02:42:00 GMT permalink Post: 11920116 |
I'd like to say something here that might help us all understand what probably happened. It's sad, but now that we know some clear facts, I think this probably goes a long way to understanding this tragedy.
It's a bit long, but that's probably necessary. I hope you find it worth the read. First up, I notice there's a tradition here to talk about "muscle memory". I understand it, but this is really quite the wrong term, and I think using the correct term will help clarify this a great deal. The muscles don't remember actions (at all, I think). It's part of the brain that's responsible (and I truly think that aircraft designers need to understand and take this fully into account when designing new aeroplanes/airplanes.) The part of the brain in question is called the Cerebellum. It has been called "The Brains Brain" but again, that's inaccurate. The cerebellum is actually the brain's Automaton! Pretty close to automation, and in some ways, nearly the same. The Cerebellum is located at the back, lower part of the brain. It looks quite different, and appears to have a stringy appearance. This part of the brain is responsible for all manner of physical (i.e. motor) actions. It is like an ECU or an EEC or a FADEC, or a GPU or all manner of sub-processing units in cars, planes, factories and so on, and I guess, in virtually all animals and humans. Basically, it is designed to take a lot of the workload off the brain itself. That's where the problem arises. Just think about walking. You can work along without even thinking about it. In fact, if you do think about it, your walking is likely to become "unnatural". Just think about how it feels to nervously walk on stage in front of a big crowd. Am I even walking properly...? I feel like a robot! The conscious mind has taken control, and it's not as good at walking naturally as the cerebellum is. After all, it's been the one doing it, all your life. So, think about talking, writing, signing your signature, typing, riding a bike, stirring your tea, driving a gold ball, playing a well-practised video game. Think of "Getting the hang of it" - it's the process of the cerebellum learning a new sub-routine. Slow to start, but capable of lightning fast action once learned. And some of its learning is evidently built-in from birth. Eye movement (& focussing?), for example. So, having a cerebellum allows you to walk very successfully, while watching the traffic, talking to your companion, thinking up jokes, listening to the birds singing, etc etc. You don't need to think about it, because your cerebellum has learned since you were a toddler "How to Walk". It knows very well, and can even handle trips and especially slips. All you have to do is say "Walk to A" and the cerebellum does it, unless the thinking brain says "Hold on, stop." This is where the term "muscle memory" comes from. Automated actions, not from muscles but from the cerebellum. Now, the problem here is that in effect, what I'm describing is, in a way, two brains. Scary thought! Even more scary when you recognise that it's virtually true. If you take a look at the anatomy of the brain in a suitable drawing, you'll see that the cerebellum is not fully connected to and integrated with the rest of the brain. It's actually a separate sub-unit which is not even wired directly into the brain (the cerebrum, just to be confusing) itself. It's attached / wired to the rear side of the brain stem, below the Main Brain: https://teachmeanatomy.info/neuroana...es/cerebellum/ - scroll down to Fig 1. Those of us who understand computers, networks, data-buses and so on will immediately recognise the problem. For a start, there's a bottleneck. And a source of latency. (The perfect word for this situation.) There's also a need for multiplexing - or, you could say switching. At least, there are two possible sources of control. Just like in the cockpit! Oh No! Having the cerebellum where it is had/has a huge survival advantage. It means it's much "closer" to all the nerves that control the muscles - so that in life-threatening emergencies, the cerebellum can get the commands out much, much faster than the conscious brain can even think of them. If you're falling, the cerebellum will have reacted even before you've had a chance to think. I learned this one day in England. I was riding an old bike to work, accelerating at a roundabout as hard as I could push. Suddenly, at full push, the chain came off. I don't (and didn't) even remember, maybe didn't even see, what happened next. One moment, I was up on the pedal, pushing hard. Next, I was in mid-air. Seriously, I remember this. I was in mid-air on the right-hand side of the bike, looking back towards the bike still rolling along beside me as I was falling. I was already about half turned, nearly onto my back. No idea how. (I was wearing a backpack, so apparently, it was my designated crashpad.) Next, I was on the road, completely free of any entanglement with the bike. It (cerebellum) didn't manage to get my right elbow out from under (maybe deliberately) but I landed mostly on my backpack, with my elbow pinned about under my right hip. The scars have faded now, but my forearm/elbow became a brake pad... Next thing I remember was sliding along a cold but fairly smooth section of road, head craned up, looking back down the road to see if anyone was going to run me over. A brown-haired young woman in a car was coming behind me, safely, watching, slowing. I firmly believe that my cerebellum was responsible for me landing so well. Nothing broken, just some skin off my elbow. Like I say, I didn't have a chance to even think about it. So, there's a big advantage in having a semi-autonomous processor operating in parallel, alongside the higher intellect. But every advantage seems to bring with it a downside, as I think we might all be seeing. The downside is, given a command by the cerebrum, the cerebellum will perform it. Accidentally, unintentionally, mistakenly, prematurely, casually, give it the wrong command, and guess what? To tell you the truth, the older I get, the more often this happens. My wife and I jokingly call it Autopilot. We're out shopping or whatever, a list of places to go, me at the wheel. A to B to C... Suddenly, we're back home, and I forgot to stop at the Drug Dealers... I jest - I mean, who would forget that! But talking is a great way to facilitate this. The cerebellum knows the way home far better than the way to the Candlestick maker, so, when lacking clear direction, evidently, it reverts to the most familiar. Exactly what happened here, who can really say? Not me. But this article (many thanks to https://www.pprune.org/members/198630-limahotel ) for this link. It's totally relevant, the PF the obvious cause: https://avherald.com/h?article=48d1e3ae&opt=0 I wonder what might have been the trigger here. Sudden high stress? Why didn't the gear go up? Who should have done that? When, compared with actual events? (Might have already been answered, sorry. I've been busy! ) Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Action slip FADEC Muscle Memory |
MaybeItIs
July 12, 2025, 04:41:00 GMT permalink Post: 11920192 |
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.
Question: I imagine the accident crew /Captain at least would have been aware of this status message, or at least that it had been looked into. Is that fair comment, or known anywhere? Or maybe he even knew what they did, which may well have been FNF.* I mean, possibly the Captain decided, since he had a young pilot flying, that he would try to avoid any potential Stabiliser problems from startling his junior pilot by pre-emptively cutting off the Stab control while they were still good. And didn't announce the intention because he didn't want to distract the PF, or make him even more nervous. Stuff like this does happen. If he happened, as you say, to flip the Fuel Cutoffs instead, that's all that would show on the FDR. Knowing who said what would be a big help. *Fault Not Found, in case that's not an Aviation acronym. Last edited by MaybeItIs; 12th July 2025 at 04:56 . Subjects (links are to this post in the relevant subject page so that this post can be seen in context): EICAS FDR Fuel (All) Fuel Cutoff Switches |
MaybeItIs
July 12, 2025, 05:26:00 GMT permalink Post: 11920212 |
When I read that transcript, even I, a non-pilot, thought WTF!? (In that case, maybe the PNF thought "(He)'s trying to chat me up, and at the worst possible time," which could really have unsettled her, caused her to be reactive and 'snappy'.) Funny how, when you think someone's doing something wrong, you're more likely to stuff up as well. The Staines crash had a big element of that. It seems to be contagious. We are suggestible creatures, or something. P.S.
Most airlines would have a 'no action until 400 feet' requirement.
Last edited by MaybeItIs; 12th July 2025 at 05:35 . Reason: delete redundant word, add PS Subjects (links are to this post in the relevant subject page so that this post can be seen in context): EICAS |
MaybeItIs
July 12, 2025, 08:46:00 GMT permalink Post: 11920368 |
May I ask where you found the "no fault found" info? I can't see that, though I suspected it.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Preliminary Report |
MaybeItIs
July 12, 2025, 11:15:00 GMT permalink Post: 11920513 |
Has anyone answered whether there is any message when the engine CutOff switches are transitioned in this situation?
If there isn't then the asker must have seen it being done. If there is, then it's still not absolutely pinned to a pilot, is it? 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 |
MaybeItIs
July 12, 2025, 12:22:00 GMT permalink Post: 11920577 |
Don't the Checklist instructions for an engine restart throw a spanner in the works, in terms of what conditions you are supposed to perform the restart in? Could that account for the delay, if they were being followed? I find this:
![]() to be very confusing, due to the Condition: statement. Having probably never actually done it before, did they think the engine speeds had to be below idle before attempting a restart? Relevant links from previous thread: Air India Ahmedabad accident 12th June 2025 Part 2 Air India Ahmedabad accident 12th June 2025 Part 2 Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Relight |
MaybeItIs
July 12, 2025, 22:40:00 GMT permalink Post: 11920899 |
\x94STAB POS XDCR\x94 Fault Not Found, No Fault Found - True/False?
Guys,
I have seen several comments now, all reporting that the STAB POS XDCR report was examined by maintenance on the morning in question and that there was No Fault Found , or words to that effect. I believe it was me who first raised this possibility, not as a fact but as a likelihood, on noting that the plane was released from maintenance exactly one hour before the flight. This seemed very tight, which led me to suspect they had not managed to find the fault, and had to quit and carry on regardless - handing over the plane at the last minute. I've asked the first poster I saw to post this as a fact where they got it from but haven't seen that answered. Now, a few others have also included it as a fact. If it's all down to my original post ( Preliminary Air India crash report published ), my apologies, though I don't see what I wrote as that ambiguous. Can anyone confirm that there is an official statement anywhere that substantiates that there was No Fault Found. Otherwise, it's become a rumour, which of course, is not surprising. I'd just like that cleared up. ![]() Last edited by MaybeItIs; 12th July 2025 at 22:48 . Reason: link added Subjects: None |