Posts by user "andihce" [Posts: 18 Total up-votes: 0 Pages: 1]

SLF here, retired physicist, but with much engineering (esp. systems engineering) background and considerable interest/experience in fault-finding in complex (not aircraft) systems.

I think it is helpful here to work through some possible failure scenarios in some detail. You could usefully partition these into two separate groups: “RAT was deployed” and “RAT was not deployed.” I’ll mostly follow the former here.

\xb7 By following this path, I think we can exclude incorrect flaps setting or premature flap retraction as the primary cause of the crash. It’s difficult to see how improper use of the flaps would be correlated with RAT deployment. Everything in this case points to a loss of engine thrust.

\xb7 The first question is, why did the RAT deploy? As I understand it, manual deployment by a pilot is possible, or automatic deployment caused by detection of major electrical or engine failures. I haven’t found an authoritative, detailed discussion of this, or about the time to deployment, which is relevant here as there is so little time involved.

\xb7 According to tdracer , if the primary issue was a major electrical failure, that should not have caused any engine rollback. Thus, absent pull back of the throttles (which surely would have been corrected by the pilots), there should not have been a loss of thrust.

\xb7 Thus we are left with engine rollback as the likely underlying problem. Absent other issues, a single engine rollback should not have been a major problem, so dual rollback, unlikely as it might be, seems a reasonable conclusion.

\xb7 This is consistent with the reported mayday call, although that report needs confirmation.

\xb7 It is difficult to understand a dual engine rollback. Various causes have been suggested but ruled “unlikely” here. However, it is not possible to rule out a unicorn event, like the dual engine rollback experienced by BA 38. Leaving aside the cause, it is useful to look at the consequences.

\xb7 There would have been a major loss of electrical power (apart from battery backup), assuming the APU was not running. I don’t know if is possible the APU might be used at takeoff (e,g., to unload the main engines), or if any evidence from the tail photo at the crash site provides a meaningful indication (e.g., intake door status).

\xb7 Are there other indications of loss of electrical power? The reported statements of the surviving passenger may have some relevance, but I would want to see the results of an interview by crash investigators.

\xb7 What about the loss of Flight Aware ADS-B data shortly after takeoff? There have been a few mentions of this, but not much discussion. Could this indicate loss of electrical power?



I hope this is of some use. I’m happy to defer to professionals or others here for better information/analysis.

To be clear, I am talking about the probability, given this crash has happened , that a particular item could be a cause.
The probability of something (or maybe several somethings) being a primary cause of this crash is near unity. The question, what possible causes are likely?

To take a specific item of speculation that might case dual engine rollback, fuel contamination was suggested. I don't remember all the points made in this context, but some were: no other aircraft presumably using the same fuel supply had issues; why would both engines apparently fail near simultaneously?; why would they fail just after rotation?; and so on. The consensus seemed to be, not impossible, but unlikely (presumably in the sense I just described).

Accidental (or even deliberate) fuel shutoff was also suggested. Again, the consensus seemed to be, possible, but unlikely for this type, since previous ergonomic causes of such accidental shutoff had long since been addressed.

I watched the NYT video version of the survivor interview in hospital. He is speaking in an Indian language, with a caption in English. Assuming the translation is accurate, he says he "I could feel the engine thrust increasing to go up, but it crashed with speed into the building".

​​​​​​​Note "feel", rather than "hear". Ordinarily you would first be aware of the sound of the engines spooling up, before you felt acceleration. Possibly he was subject to a somatogravic illusion as the plane accelerated downwards.

But if indeed the engines were spooling up, the question is, from what thrust level? They could have rolled back, and somehow were recovering. of their own accord or from pilot action.

All this is hanging on a pretty fine thread,

(Can't post links yet, not even permalinks, but see post #740 at present count)

I guess you have to make a post on just this one item to get it noticed!
But I agree that this piece of data deserves close attention, and is potentially confirmatory of certain scenarios which lead to electrical power loss.
I'm no expert on Flight Aware's ADS-B data, but other posts here show other flights taking off on this runway happily reporting data further down the runway and (well) after takeoff.

How else do you explain the cessation of ADS-B data from this flight from shortly after takeoff until the crash?

I think this is as interesting a line of inquiry as I've seen recently. The problem is getting the data and theory close enough to be meaningful.

For instance, what about induced drag (admittedly much complicated, I imagine, by varying ground effect) once rotation begins? A comparison with another 787-8 flight from the same runway and under similar conditions (meteorological, load, etc.) might be ideal.

Are there not tools accessible to ordinary users for making detailed such simulations, rather than a back of the envelope calculation? I daresay Boeing has made such simulations already, and have a pretty good idea of whether and when thrust loss might have occurred.

I would like to raise a subject that I don't believe has been discussed here since the Preliminary Report was published, namely what happened to the aircraft's electrical systems as a consequence of the dual engine rollback and thereafter (RAT deployment, partial engine recovery, etc.). Apologies if I've missed posts on this topic here, but I have tried to review all of this thread quickly after previously reading most of it in detail.

As I understand it from previous discussions, without the APU, all electrical power except for that DC power provided by battery to essential systems would have been lost.

With the copilot as PF, would he have lost his instrument displays? If so, possibly additional startle effect and workload for him.

Why did the ADS-B information keep going on for so long? My understanding from previous threads was that loss of ADS-B was considered an indication of loss of electrical power.

What else would be expected with loss of power?

Some general speculation: I find it hard to understand the long delay from what must have been the onset of obvious issues to the time the first engine is set to "RUN". I wonder if much more cockpit dialog intervened, e.g. PF requesting PM to turn the fuel switches back on (since he had his hands full), and eventually operating the switches himself, with the delay and time gap between the two switches being turned to "RUN" being attributable to being preoccupied with flying the aircraft under trying conditions.

Meaning no disrespect to pilots (indeed, quite the opposite), and admittedly I'm no psychologist, but it strikes me that to postulate that a pilot might cause the crash of a large aircraft because of suicidal thoughts is to seriously understate the action taken , because such action also means the likely death of all passengers and aircrew, presumably all or most of whom are perceived as innocent bystanders by the actor. Whatever term you want to apply to that action, it is far more and far worse than individual suicide, and I would think it needs a pretty substantial and convincing body of evidence, including psychological evidence, to explain.

I know such cases have happened (or may have happened, as in MH370), and perhaps cannot be excluded here with what we know at present, but I for one would be far more inclined to suspect something along the lines of the various "brain fart" possibilities that have been mentioned, absent further data.

To look at this perhaps another way, the rarity of "pilot suicide" among all flights (say of transport-category aircraft) is NOT RELEVANT here.

We are looking at a selected, specific event , not "all flights". From what we know about this event, there appear to be only two likely explanations: pilot error (brain fart or whatever), and deliberate, malicious pilot action.

Some may still argue that we should prefer the "brain fart" explanation as "pilot suicide is so rare". I hope that is the case, but extensive discussion here seems to consider that the "brain fart" explanation, given the specific circumstances and information we know as perhaps comparably unlikely. One of these two "unlikely" explanations is likely true.

I regret mentioning Germanwings as it is not really relevant to my point. That point is simply that the statistical argument of the rarity of pilot suicide cannot be directly applied to a selected incident, especially an incident where pilot suicide is one seriously proposed explanation based on the information so far known to us. I agree that we presently have no evidence that would lead us to suspect either pilot might be suicidal.

[QUOTE=JustusW;11923090]How kind of you to so thoroughly engage with my overview of the facts. Feel free to point out any "abuse of statistics" I made in my post. It's not exactly rocket science to divide the number of known and suspected suicides by the number of departures...

To address this directly, the critical flaw is what a statistician would call " a posteriori analysis ".

A typical statistical approach would be to take the data you have (number of suicide-caused crashes and number of flights, both over some given time period), make some assumptions such as that this is a stationary process (not changing in time, e.g., because of improvements in aviation), a random process (non-deterministic), etc. and then generate the statistic (average number of suicides per flight).

That statistic might have some usefulness if for example you devised a priori an experiment, in which you would follow the next ten years of flights, hypothesizing that the number of suicide-crashes would correspond to your previously determined average rate, and then tested the actual result vs. the prediction (with such a low rate of suicide flights, there would of course be the possibility of large statistical uncertainty in the previously determined average, and in the subsequent measurement).

But when you select a specific flight, and not merely a flight, but one that ended in a crash, and not merely a crash but one where suicide is suspected, and expect that average to have some relevance, you have stepped deep into the quagmire of a posteriori analysis. The statistic you have simply can't be properly applied to the situation you are attempting to apply it to. The current case is not even remotely representative of (a random selection from) the population (all flights) for which the statistic was derived.

To be clear, I said nothing about a posteriori statistical analysis being intrinsically invalid, or not viable (in educated hands). I said it is a "quagmire", meaning that application of statistical method in this case can be fraught with issues. And indeed in popular and even more serious use of statistics you can find countless examples of dubious application to after-the-fact situations. For example, we often encounter reports of "cancer clusters", which are argued to be statistically improbable (especially by class-action legal teams) and therefore presumably caused by some local agent, but often that is after a specific cluster has already been identified, in which case it is not a random selection from the general population - and great care then needs to be applied in employing statistical arguments, especially as regards separating causation from correlation. (Not to say that some cancer clusters are not real, with clear causes.)

I will say that in reading your earlier post, I came away thinking you were arguing for the unlikelihood of suicide in this case, at least in part because it is unlikely in the world of commercial aviation as a historical fact. If that's not the case, I apologize. But I will add I think other commentary here has fallen into this trap, as discussed in my referenced post.

As I've previously posted, there is the fact that the ADS-B data (in your diagram) continues long after electrical power from the engines would have been lost. Someone recently posted that the engines don't even need to run down for this to happen, saying that operation of the FCS to cutoff would shut down the engine VFSG's.

As an aside, I have no knowledge of the software used by Flight Aware reporters, but I would be surprised if, at the very least, the computer involved was not set up with NTP (Internet Network Time Protocol) to synchronize its clock. This would set the computer's clock to within a small fraction of a second of correct time. For even greater accuracy, an inexpensive GPS device could be interfaced with the computer.

I find that significant too, but consider (*assuming* the captain was responsible for deliberately turning the FCS's to CUTOFF)

* that the captain knew the terrain in front of the runway offered no "safe" spot to set the aircraft down
* that he knew there was a high fuel load
* that all he had to do was guard the FCS's (already set to CUTOFF) with his hand, which would make it very difficult for the FO to intervene while desperately trying to fly the aircraft as best he could under the circumstances
* that without autopilot in this phase of flight the FO had to continue to fly the aircraft
* that at this very low altitude, there would be no option like a turn back to the reciprocal runway
* that engine cutoff at this time would be almost certainly be unrecoverable with even a short delay before the FCS's were set back to RUN
(add your thought here)

and this choice, perverse (insane) as it is, makes more sense.


I want to add one separate thought: the authors of the Preliminary Report had to know that people reading it, reading what it actually said, and inevitably reading between the lines, would likely focus on deliberate action by the captain as a highly probable cause.

Don't you think, that if there was any mitigating factual information available to them, that they would have included it?

Secondly, regarding recently "leaked" information, if it indeed comes from the investigating team, is certainly a breach of protocol, but since the Preliminary Report would seem to clearly exonerate Boeing and GE, and point to pilot error at the very least, what would be the motivation for a leak at this point?

I would guess it might come from frustration that the Preliminary Report has failed to state facts that make almost inevitable a conclusion as to probable cause (for instance, who in the cockpit said what and when, and what else was said that we weren't told about). Possibly it also reflects concern that the investigation has not focused more on factors relevant to that conclusion.

I did look at a satellite view of the area earlier. To my non-expert eye, the less built-up area to the right of the flight path does not look very promising, and given where the aircraft came down, there did not seem any hope of reaching the river. If the captain was responsible, with his experience, I assume he had a pretty good idea of the likely outcome. Of course, we're assuming a rational decision was involved.

Perhaps he is looking at the opposite direction of takeoff (runway 05)?

Just to be clear, I'm referring to the article at https://archive.ph/2QYNP , I assume you are too.

That article tells us the following new (relative to the Preliminary Report) information:

"The first officer who was flying the Boeing 787 Dreamliner asked the more-experienced captain why he moved the switches to the \x93cutoff\x94 position after it climbed off the runway, these people said. The first officer expressed surprise and then panicked, these people said, while the captain seemed to remain calm."

I would say that information (if true) is significant, especially about the pilots' demeanor. It implies that further words were spoken in the cockpit, beyond what was mentioned in the Preliminary Report. What these unknown words were may be of great significance.

Now you may argue this is "fake news", but I find it hard to believe that the WSJ would publish such information without some reliable source.

I understand the sentiment and sometimes wonder if myself I'm too easily accepting a very damning verdict on what happened, while trying to remain open to alternative possibilities (like the "brain fart" explanation).

We are all of course (perhaps rather morbidly) fascinated and curious about this incident, and trying to reason out what happened with insufficient data - well, at least I am. And to be honest, I am not nearly as concerned about "throwing someone [dead] to the wolves" (to put it rather harshly) than if the pilots had survived and their reputations and livelihoods would be threatened - I have read about plenty of cases where surviving pilots were innocent, even heroic and masterful in their efforts to save life, yet at least in the beginning, were falsely pilloried for what happened.

The difficulty with waiting for the Final AAIB Report comes with the possibility of malicious action. I don't know anything about Indian law, but I would imagine that if this incident had happened in the US, it would already be part of a criminal inquiry (not to mention lawsuits), and not simply under the jurisdiction of the NTSB.

I'm certainly not a lawyer, but my understanding is that the "presumption of innocence" and "proof beyond a reasonable doubt" apply to criminal trials. For civil trials, a "preponderance of evidence" with the burden of proof on the plaintiff is what I understand to be the usual, and lower standard.

We are not conducting either a criminal trial, or a civil trial here. I would rather call it (perhaps optimistically) a "scientific enquiry". I think the standard to be applied is whatever we (individually or collectively) think is reasonable, is order to fairly reach a meaningful conclusion. The standard for a criminal trial need not apply.

For instance, a determination of "probable cause" for an aircraft accident is hardly something that would pass muster in a criminal trial, yet it is commonly the output of an air accident investigation.