Posts by user "nachtmusak" [Posts: 32 Total up-votes: 78 Pages: 2]

I don't really understand why so many people have latched so hard onto the theory that the flaps were not extended based off nothing but a poor quality video (while also ignoring other clues in that same video, such as what is almost certainly the sound of a ram air turbine - never mind that even in that video you can equally conclude that the slats and flaps are extended).

One would think it sensible to at least wait for higher quality images/video to emerge before saying it with confidence, given how incredible the claim and aspersions being cast on the crews' basic competence and professionalism are.

The crew did not take an intersection departure (despite people jumping to that conclusion off of clearly spotty ADS-B data).

In my opinion we should all find such things hard to believe, and it is very strange that people are so easily believing the incredible about this crew off of practically nothing.

In the high-def photo of the wing post-crash that has been posted in this thread, the flaps are visibly extended.

Also, unless we are all watching very different videos, I don't quite understand how anyone cannot hear the propeller buzzing in the video of the plane passing overhead. It's quite distinct. Though of course in this new age of AI we should take any and all audio/video with a grain of salt - which is exactly why confidence that the flaps are or aren't retracted based on such low-quality footage is a bit silly to me.

Question: would the ram air turbine (if truly it was deployed) have been capable of providing hydraulic power at their airspeed & altitude? I'm aware that it loses effectiveness below a certain number of knots, but I'm not sure what that number is for the 787.

Related question: I asked earlier at what speed the 787's RAT becomes effective in providing hydraulic power. Is it possible that by the time the RAT deployed, the aircraft had lost airspeed to the point that it would have struggled to produce an adequate amount of pressure? Taking the Gimli Glider incident as an example, my understanding (could be wrong, this was from a magazine article) is that as they bled off speed to land, they ended up short enough of hydraulic power that they started to experience control difficulties, with the plane responding fairly sluggishly. If that's the case and this poor crew was going through something similar, it might explain why they seem to do very little about their situation.

I'm pretty convinced that everyone is watching different videos, which wouldn't surprise me in the least given how much images and footage can get mangled from being downloaded/re-uploaded to different services. Personally I've seen at least two different videos (and slightly different variants of each): one that's a direct recording of the aircraft and one that's a recording of a phone playing a recording of the aircraft. The buzz of a propeller was quite audible in the former but not in the latter, and the engines are notably quiet compared to any 787 takeoff I've ever been close to.

I do think that at this point people are working backwards from the cause being retracting the flaps, rather than working forwards from the evidence towards an explanation. If everything else was as it should be apart from flaps being retracted instead of gear, you'd at the very least expect the aircraft to reach a higher speed than is suggested by how little distance there is between the end of the runway and the crash site. Coupled with the apparently parabolic trajectory seen in the airport CCTV video, the crew (allegedly) reporting engine problems on the radio, the surviving passenger testifying about flickering cabin lights, the plausible deployment of the RAT, the fact that the ADS-B data cuts out well before impact...surely at some point one must consider a lack of thrust, no matter how improbable. Recognising the what doesn't need a full thesis on the how .

I wonder if (given all the facts and rumours about the situation so far) the flaps would be so high on everyone's minds if they weren't already a hot topic from the initial, largely baseless speculation that they somehow took off with flaps retracted.

In the spirit of fairness there is another sensation that can be interpreted as "increased thrust" that a passenger is equally if not more likely to be talking about : a change in [perceived] engine noise level and/or quality.

Personally I don't hear much of the engines as the plane moves away from the cameraperson in the phone video, while the sound of impact is clearly discernible. If anyone can hear the engines well enough to tell if there is a significant change in their tone or volume, that would be valuable info, I think. Alternatively whatever increase in noise was heard started before the recording starts. In that case I suppose the "RAT theorists" would say it was the droning of the now-deployed RAT, with the assumption that it would be audible from inside the cabin (things like flap and landing gear actuation certainly are, so that isn't all that far-fetched). On the other hand, the "flap theorists" would probably say it was the crew firewalling the thrust levers in response to the inability to climb, which isn't far-fetched either.

Either way we will know soon enough what actions the pilots did or didn't take, since the various flight recorders should be found fairly easily in good condition.

Speaking of invalid derate, I sort of recall reading about an incident with a very heavy aircraft and some kind of mistake or fault (or maybe both?) leading to insufficient takeoff thrust on a hot day. Fortunately the crew was able to stabilise the aircraft and return safely to the airport, but unfortunately I don't remember any more details, and so finding it has been difficult.

Might that incident shed any light on this one, especially since that crew was able to recover?

Ah, thank you - while this wasn't the incident in question, reading about it did jog my memory enough to recall that there was a flight engineer involved which narrowed down the possible aircraft types by a lot. Looking through a list of notable 747 incidents turned it up: https://en.wikipedia.org/wiki/Olympi...ays_Flight_411

Fascinating - I can't fathom the sheer sangfroid necessary to keep a 747 at near MTOW just barely airborne and under control for 5+ minutes (which was how long it took before they resolved the thrust issue).

Perhaps worth noting that the end of the runway is not the only possible source of dust in the aircraft's vicinity - from maps and videos of the airport, the sides would also have plenty. Couldn't the dust cloud also be indicative of a yaw? The paved surface is fairly narrow (45m/148ft), so I imagine given a 787's wingspan that it doesn't have to get particularly far off the centerline for it to start kicking up debris while rotating.

Available ADS-B data while limited does have the aircraft crossing the piano keys at a height of a good hundred or so feet, for what it's worth. (625ft reported altitude, QNH 1001, 37\xb0C, field elevation 189ft)

There are more data messages than that, which FR24 shared on the day of the accident and which have been posted a few times in this thread. I'm pretty sure there's also been a comparison of this + previous flights posted in this thread that shows that while the coverage at the airport itself is spotty, it's reasonable to expect further messages to have been received before impact.

Not sure how permanent the content at this URL is, but here's a link to FR24's update which has a CSV with all frames received https://www.flightradar24.com/blog/f...rom-ahmedabad/

I seem to remember it taking quite a bit longer than three days for fleets to be grounded after the last serious design flaw leading to the loss of an airliner.

In fact, it took so long that plenty of people still blame the "common theme" for JT610 and ET302.

I'm a bit bemused by all the confidence that a few days passing means anything other than operational error can be ruled out. These are a few "serious flaws" (you can quibble about the definition of "serious") involved in fatal catastrophe that I can recall:

- The DC-10 cargo door issues involved in the loss of Turkish 981

- The 747 cargo door issues involved in the United 811 accident

- The 737 rudder issues involved in the loss of United 585 and USAir 427

- The 737 MCAS issues involved in the loss of Lion Air 610 and Ethiopian 302

I would mention Lauda Air 004, but in fairness the loss of the flight data recorder hampered the investigation.

Anyway, I don't recall the case being cracked and fleets worldwide being grounded within mere days of any of these accidents. In fact several of them had fingers pointed at primarily flight crew or ground crew error before deeper investigation brought these flaws to light. You can chalk the first three up to ancient times, but the MCAS saga is recent enough to have had all the telemetry and other fancy modern tools and methods that this accident's investigators will have at their disposal. And there's also (thankfully) non-fatal flaws like with the Pratt & Whitney 4000 that ultimately led to affected 777s being grounded, but not immediately after the first fan blade failure incident in 2018 either.

Again I'm not saying that this accident definitely falls one way or the other but that's my point really - closing your mind to the possibility of anything other than operational error because "we'd know by now" seems a bit premature. If anything it seems to me like a design/procedural/mechanical flaw would take more time to surface than simple pilot error.

I'm not quite sure that one counts as a design flaw? If we were to try to list all the times that cocked-up maintenance/repair led to an accident we'd probably run afoul of the character limit...I tried to keep the list down to things in the design that actively increased the probability of or exacerbated the outcome of an accident (like the DC-10 cargo door loss being able to collapse the cabin floor). In any case the grounding came two weeks after the accident, no? Pretty quickly, but not exactly three days.

This accident too could well be down to a maintenance error, but given that the investigators are not magicians, I don't see how they'd be able to say so with confidence after just a few days. Surely they'd need to review logs, do some lab analysis, etc for that? Perhaps worth noting that an inspection of Air India's 787 fleet has been ordered, but I've seen it dismissed as a CYA move. Might not be...

I must admit I'm confused. If there was a maintenance error involved in this accident (which is what I said would take some time to uncover), how exactly would either flight data or cockpit voice recordings tell the investigators this? Please correct me if I'm wrong but every maintenance screw-up leading to an accident that I can think of was surfaced by actually examining the wreckage and logs, the former sometimes using quite sophisticated lab methods.

Pilot error still seems to me like the only thing that could be conclusively ruled in after only a few days, and it may well be the case here, I'm not contesting that. But that does not mean that other factors can be ruled out after a few days - absence of evidence is not evidence of absence and all that.

That is exactly what I am saying - that the only cause that can be positively identified at this point is pilot action whether accidental or deliberate. It's the only thing that can be conclusively ruled either in or out by now. However the tone of several of the messages here is that everything else has conclusively been ruled out because it has been three days, which makes no logical sense to me.

To put it another way: if pilot action isn't the root cause, then what exactly is the investigation supposed to say right now other than the utterly redundant "well this is a headscratcher, and we're going to take a while to figure it out"? Are they supposed to turn into Chicken Little screaming that the sky is falling with no evidence-based justification? To be fair, you could perhaps argue that they should come out and "clear" the pilots' names, but that implies an obligation to social media hucksters and mobs that I don't think should exist.

Also we should be wary of treating it like an either/or; poor crew response to a manageable fault stemming from a design weakness or maintenance issue is also an option. See e.g. the Swirijaya crash that was initiated by a faulty autothrottle, but the resulting upset was quite preventable and also recoverable even after it had developed.

Erm - to be clear I was responding to/disagreeing with the recent surge of posts saying that because the investigation has been silent so far, then "obviously" it must have been pilot action and they are simply embarrassed and trying to come up with a cover. Several people have outright said that if there was a design flaw at play then the worldwide 787 fleet would already have been grounded by now, as though such a flaw is something that can be definitively uncovered in three days.

I'm not purporting to know what actions of the crew have been positively ruled in or out; what I'm saying is that only pilot action can have been ruled out as a root cause at this point. My impression is that any other potential cause would need further investigation to positively identify and is thus still on the table of options.

Edited to add: personally I strongly believe that there is either insufficient thrust or a total loss of thrust here. I struggle to see what else could produce the observed flight path. Whatever caused the loss of thrust, I can't claim to know. But investigators' "silence" says nothing about what that cause is IMO.

(disclaimer: not a pilot, just some experience in petroleum and power engineering)
Re: the Jetstar incident and accumulation of crystals in the fuel system: I don't think a sample size of one is necessarily representative of all possible failure modes.

For one thing, the mass of salts present seems quite dependent on the magnitude of the error made with the biocide, and isn't specific to biocide at all (a sufficient amount of any stable-enough crystal in the fuel system would do the trick - see e.g. ice crystals in BA 38).

For another, would the increased fuel demand of (near-)full power not cause a blockage by residue to develop quicker? That's not a rhetorical question: I don't know enough about the GEnx-1B's fuel system or these specific magnesium salts to tell if the accretion of crystals would be directly or inversely proportional to the fuel's volumetric flow rate. In the case of BA 38 the fuel-oil heat exchanger blockage only became apparent (or perhaps only developed fully?) when increased thrust was commanded, no? And the thrust on each engine reduced within several seconds of each other - a far cry from the minutes that the Jetstar situation developed over.

I suppose my other question would be what possible sources of chemical contamination there are, apart from water and biocide. I think that for the theory of a quickly-manifesting fuel system blockage to work, it must be something on the microscopic scale (for lack of better phrasing); larger physical debris would surely cause a more externally-spectacular failure than a quiet rollback, and is extremely unlikely to manifest in both engines at anything close to the same time.

Now I'll admit that this is pretty out there as far as speculation goes: any petroleum product can produce flow-inhibiting crystals by itself if it's at a low enough temperature, or at higher temperatures in the presence of a suitable contaminant/gellant. As I understand it the fuel tanks of modern airliners are heated as necessary to prevent the temperature of the fuel from dropping too low. But if that system was malfunctioning or there was an inadvertently introduced gellant in the tanks, could that have resulted in a dangerous buildup of paraffin wax? Unfortunately due to the post crash fire I'm not sure the investigators will be able to collect fuel samples for testing, as was done for BA 38 to rule out fuel waxing...

Bringing part of my previous question back up: I know that fuel waxing was at some point one of the suspects in the BA 38 accident, but was ruled out via testing fuel samples. However I've been unable to find any records of airliner accidents or incidents that did involve fuel waxing, which I thought most likely existed if it was a possibility the investigation was considering? Does anyone know of any such incidents?

More accidents/incidents where fuel starvation was triggered by crystalline contaminants blocking fuel lines might also be useful - I'm trying to establish a range of how quickly and under what conditions such blockages could cause a loss of thrust in both engines.

625 feet is straight from ADS-B data, which is just pressure altitude using sea-level STP. I don't know if it has been mentioned in this thread yet but in the other thread it was pointed out several times that this would have come out to ~100ft in true altitude AGL. The mathematics of that checks out to me (QNH 1001, temperature 37\xb0C, and field elevation of 189 feet).

The aircraft also visibly never gets much more than roughly its own wingspan above the ground in CCTV footage, at least to my eyes.

News articles tend to be fairly unreliable sources of info as far as parameters like altitude go in my experience.