Posts by user "MaybeItIs" [Posts: 43 Total up-votes: 0 Pages: 3]

MaybeItIs
June 28, 2025, 06:41:00 GMT
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Post: 11912358
Originally Posted by Someone Somewhere
The FAA is saying it's a problem . Any suggestion that it's related to this incident is pure speculation. Possibly brought on by that slop 'report', which may have itself been somewhat inspired by the ADs.
Agreed. But the FAA itself does speculate - on what basis, I have no idea. They use the word "may", see here, last sentence (and in other ADs in the sequence):

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
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Post: 11912770
Originally Posted by tdracer
... 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.
Yes, that was fairly much my point. The "Dream" was supposed to be revolutionary, "all" electric..., but it doesn't take a genius to copy an old, out-dated layout.

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
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Post: 11912837
Originally Posted by tdracer
So how are you going to allow the pilot to relieve themselves - while maintaining post 9/11 security - without a lav up front?
Ask the Apollo astronauts? The ISS Crew members? But don't mention 9/11! The fireballs just don't compare.

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
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Post: 11912942
Originally Posted by TURIN
It will come as no surprise to anyone that EE bays are well protected
If that's so true, why the ADs about leakage from the lavs, listed earlier?

with the sort of things you have described.
Thanks, that's nice of you to confirm. Despite never working on one, I must have some idea...

They are both contained in fireproof boxes that will vent to atmosphere in the event of a thermal runaway.
Didn't I just say that? "with the required fireproof casings and exhaust ports etc." Ok, didn't mention thermal runaway, but that's the purpose of the fireproof boxes and exhaust ports. But the whole risk/ danger of thermal runaway is another issue, isn't it? There are safer batteries that are not lead-acid whales. Are the any other planes out there that need fireproof boxes and vent pipes to contain and purge burning battery fumes etc to the outside? It's not just the fumes that are the issue, of course.

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.
Good to hear, hope you know them inside out and catch every issue. Please keep an eye out for trickles down walls in the EE Bays though.

Subjects: None

MaybeItIs
July 01, 2025, 00:43:00 GMT
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Post: 11913971
Originally Posted by B2N2
​​
  • Engines run on their own tank for take off.
Is this correct? I'm sure I've seen contradictory views, such as (paraphrasing): For TO, All pumps are On; the centre (tank) pumps have higher delivery pressure so they win the "Supply the Fuel" contest, unless they fail or their tank goes empty; in either case, their delivery pressure goes to zero and the wing tank pump(s) then get their turn.

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
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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
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Post: 11914055
Originally Posted by Musician
I remember that someone used some kind of tool to confirm that the aircraft could've gone unpowered for as long as we assume it did, but of course I can't find it again now. :-(
Here?
Air India Ahmedabad accident 12th June 2025 Part 2

Subjects: None

MaybeItIs
July 01, 2025, 07:35:00 GMT
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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
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Post: 11914234
Originally Posted by adfad
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.
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.
Sorry, you missed the point I was trying to make. \xa7 25.903(b) does say that the fuel system must be able to operate in an isolated, two-sided mode (for a twin engined jet), such that nothing on one side, such as bad fuel, will adversely affect the other engine. Of course, during Takeoff, both sides drawing fuel from a Centre Tank containing a lot of contaminants (e.g. Fuel Bug matter, water) is a scenario that could bring down the plane. We are all aware of that. But the point I was trying to make is that although \xa7 25.903(b) requires "at least one configuration" that separates both systems entirely (such as Left engine drawing from Left Main Tank, and Right from Right) which can be configured, the Rule doesn't appear to make that compulsory for Takeoff.

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
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Post: 11918363
Originally Posted by OliTom
Obvious questions, Is the procedure applicable to the GEnx engines installed on the accident aircraft [...]?

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
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Post: 11918716
Originally Posted by AirScotia
Nobody seems to have discussed this. If I'm reading it right (and I'm not a pilot), it seems to be suggesting that in the event of a dual engine failure, a restart should be attempted while the engine still has high RPM?
That's how I read this:


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?
Not sure about this. I think it's saying Resetting to initiate a Restart attempt. Not repeating it.

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
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Post: 11918730
Originally Posted by AerocatS2A
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.
Excellent, thank you. More and more I'm convinced, as I was at Day One, that this guy* was a genuinely excellent pilot. More sad than ever.
* (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
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Post: 11919935
Originally Posted by Engineless
A douple-pole switch.
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
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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
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Post: 11920192
Originally Posted by Propjet88
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.
Excellent point!

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
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Post: 11920212
Originally Posted by Hollywood1
You shouldn't be doing anything but flying the airplane soon after rotation, regardless of any EICAS messages appearing.
Totally agree. But look at the Luxair article linked earlier. ALL the PF did to apparently throw the PNF off and cause the crash was say "Looks like spring".

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.
That's a funny rule. When one pilot breaks the rule and does something wrong, is the other pilot is not bound to follow?

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
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Post: 11920368
Originally Posted by Natterjak
\x94STAB POS XDCR\x94 ... was released from maintenance (according to the preliminary report) at 06:40UTC ahead of an 07:40UTC departure (the crash flight) with \x94no fault found\x94.
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
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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
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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
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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