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nachtmusak
2025-06-13T15:25:00 permalink Post: 11900625 |
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.
Why are people still considering a flap/gear mix-up? If that were the case, I\x92d expect that with both engines running, one should be able to compensate for the loss of lift by increasing angle of attack and thrust - the latter might not even needed with TO thrust.
At this point, a dual engine failure seems like a much more plausible explanation. As for what might have caused it, I honestly don\x92t know. 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. 7 users liked this post. |
lapp
2025-06-13T15:59:00 permalink Post: 11900654 |
Retired engineer here.
I have looked at the electrical systems on the B787 and this is my source. Book 1 Introduction to B787 Avionic/Electrical. Tried to post the URL but was unable to do so as I haven't made many posts. I wonder if there may have been some kind of complex fault in the electrical system that day. The incoming flight passengers reported faults with the air conditioning and IFE. The electrical power system block diagram is on p. 84 mentioning engine generated power and the RAT which, if deployed, feeds a backup power bus. There is a power limit on the RAT system of 10kVA which probably isn't enough to retract the undercarriage (correct me if I am wrong). The main electrical system is 235V ac from the engines which is converted to DC using ATRU units (Auto Transformer Rectifier Unit) - see p. 95. These systems get very hot so there is a liquid cooling system called PECS. If there were malfunctions in ATRU units that may explain the air conditioning issues on the incoming leg. So, what exactly triggered the deployment of the RAT?. I'd be looking at the whole electrical network and not just the engine generation systems. The emergency lighting system (p. 146) is called WELS (Wireless Emergency Lighting System). The survivor mentioned that was flickering. Power/control systems cutting in and out. Those lights would be battery backed and would stay illuminated if the primary power/control permanently ceased. Just a few thoughts for consideration. Last edited by Saab Dastard; 13th Jun 2025 at 16:49 . Reason: full quote included 1 user liked this post. |
SteinarN
2025-06-13T16:00:00 permalink Post: 11900656 |
Jump to 1:48 in this video (if the link doesn't automatically put you there):
https://youtu.be/SbDJjgN7Xbo?si=ShNJ2oA39j46iw9M&t=108
You can't hear that RAT sound at the very beginning of the flypast? Something else, there have been discussion about not much engine noise heard. Causes could have been poor mic, a lot of background noises etc. What stands out to me listening to this video is how clearly we can hear the crash itself, even from behind the buildings, but there is absolutely none/zero/zilch/nada engine noise to be heard whatsoever, not much other background noise either for that matter. This non-aviation related engineer is now convinced that the RAT was out spinning and the engines was either shut down/flamed out/whatever or alternatively at not much more than idle power setting. Considering the deployed RAT I would go for shut down engines. Now, what the cause for all this might be I have not much idea about, except possibly some very significant electrical system malfunction. Last edited by SteinarN; 13th Jun 2025 at 16:16 . Reason: spelling 3 users liked this post. |
Right Way Up
2025-06-13T16:06:00 permalink Post: 11900660 |
No, it really isn't. For one thing if they retracted flaps, their speed would have increased, however distance and time tells us that their speed substantially decreased from takeoff to impact. Hardly possible with less flaps, descending, and take off thrust.
Compare the video with a normal plane flyover. The lack of engine noise, and propellor like sound of the RAT is so blindingly obvious I don't know how people are still going over the flaps thing. |
andihce
2025-06-13T16:45:00 permalink Post: 11900682 |
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. 8 users liked this post. |
IFMU
2025-06-13T16:52:00 permalink Post: 11900688 |
Jump to 1:48 in this video (if the link doesn't automatically put you there):
https://youtu.be/SbDJjgN7Xbo?si=ShNJ2oA39j46iw9M&t=108
You can't hear that RAT sound at the very beginning of the flypast? 2 users liked this post. |
sSquares
2025-06-13T17:04:00 permalink Post: 11900697 |
The nose gear angle suggest that the "gear-up" was selected and a dual engine failure happened at the same time, with the hydraulics failing and possible RAT deployment.. The APU was not running and everything, except the flight recorders, might be powered down and restarted at a very low altitude.
Very scary. |
BugBear
2025-06-13T17:11:00 permalink Post: 11900702 |
Early number a/c
An early number 787 (in the first twenty four), had to make an emergency landing at New Orleans on a Houston to Newark flight. At this point, re Air India, with the RAT screaming in the original video, an electrical issue of some magnitude is at the fore. Each engine has two generated power unit (GPU). Total of four (NOT ground power unit). If one of these goes offline, the system adjusts. If an engine quits, two are gone, and the remaining two supply e power.
Powering up all four at once can cause a shutdown of all generated power. The question becomes which failed first, the engines or the electrics. The RAT deployment signals either both engines shutting down, or four GPUs. I think negative on Pilot Error. Whatever the direct cause, this amount of grief is impossible to imagine. God have mercy |
appruser
2025-06-13T17:43:00 permalink Post: 11900730 |
The lack of obvious debris/smoke during takeoff might indicate it was something other than a birdstrike, and combined with the loss of adsb (per FR24) right over the runway threshold at 70ft agl, maybe it is indicative of something else causing the simultaneous loss of thrust. |
limahotel
2025-06-13T17:47:00 permalink Post: 11900736 |
Limahotel...
Why do you expect that? Are you in posession of the takeoff performance figures for this flight and the 2nd segment climb calculations? You are attributing something to not be possible simply due to an expectation that it can not be so? What do you expect that the clean maneuvering speed is when compared to takeoff flap in this instance? You may be right, you may be wrong. As may I - but to dismiss a potential and possible theory because you ' expect ' that increasing thrust and AoA would be enough is quite short sighted! 2 users liked this post. |
Del Prado
2025-06-13T17:49:00 permalink Post: 11900739 |
In summary,
Flaps were extended, possibly flaps 5 or 15. Looks like it in the video and clearly shown post crash. Aircraft reached a height of just over 100\x92 AGL (possibly 200\x92 if you compare wingspan to height in videos) RAT was deployed. Seen on videos and heard conclusively. Aircraft rotated at \x91usual\x92 spot. Comparing FR24 data from previous flights over the past week. Aircraft took off at \x91usual\x92 speed. Comparing other flights. FR24 data stopped being sent shortly after take off. Possibly indicating electrical fault. Green and white flashing light reported by survivor. Possibly indicating electrical fault. Gear bogies were at unusual angle indicating Gear selected up and then interrupted. No smoke or flames to indicate bird strike. (Edit - still debate about this in the video above where the aircraft is behind a building) No rudder input to indicate single engine failure. All speculation but hopefully a pretty balanced summary from the thread so far. It would be great if there was more focus now on what might have caused above rather than talking flaps, birds, 625\x92, etc. 11 users liked this post. |
Aerospace101
2025-06-13T18:48:00 permalink Post: 11900798 |
Misselection of flap, erroneous TO Performance data, dust = overrun, bird strikes\x85.all unlikely as none fit the evidence; the engines were very quiet.
The clearest bit of evidence is the RAT deployment. As someone else pointed out gear bogey position indicates Gear UP cycle had commenced. So the most evidenced sequence of events was rotation, positive rate = gear Up; \x85.catastrophic Power Loss. Flickering cabin emergency lights and Loud bang reported by survivor (was this heard RAT deployment or another system?). The 787 has some unique electrical/mechanical and air systems. Previous flight had issues (reported by passengers). So the root cause of the Power failure must be down to when either the 787 gets airborne (weight on wheels switch) or when Gear selected Up. I wonder if any 787 drivers could elaborate on what electric/hydraulic/air systems are affected at the very point of wheels up or gear up ? I\x92m wondering if the electrically powered cabin pressurisation system is affected at wheels up? |
xyze
2025-06-13T18:57:00 permalink Post: 11900808 |
In the take off video I think there is a subtle yaw to the right at lift off (the moment it begins being obscured by the building in the foreground). There is then a massive blast of dust on the airfield on the left side of the aircraft as it lifts off. Later video audio suggests the engines were not at full power ( or even operating - just wind noise) and that the RAT was whirring. It also shows the fuselage wheel bogies were tilted forward - so wheels up has commenced - but the gear doors are not open.
Possible sequence: right engine failure at rotation, firewalling of left engine, lift off and positive rate, gear up lever activated, wheels tilt forward, left engine failure, RAT deployed, insufficient hydraulics to Open gear doors to complete gear up sequence, ongoing dual engine failure? 1 user liked this post. |
violator
2025-06-13T18:58:00 permalink Post: 11900812 |
OK, another hour spent going through all the posts since I was on last night...
I won't quote the relevant posts as they go back ~15 pages, but a few more comments: TAT errors affecting N1 power set: The FADEC logic (BTW, this is pretty much common on all Boeing FADEC) will use aircraft TAT if it agrees with the dedicated engine inlet temp probe - but if they differ it will use the engine probe . The GE inlet temp probe is relatively simple and unheated, so (unlike a heated probe) a blocked or contaminated probe will still read accurately - just with greater 'lag' to actual temperature changes. TCMA - first off, I have to admit that this does look rather like an improper TCMA activation, but that is very, very unlikely. For those who don't know, TCMA is a system to shutdown a runaway engine that's not responding to the thrust lever - basic logic is an engine at high power with the thrust lever at/near idle, and the engine not decelerating. However, TCMA is only active on the ground (unfamiliar with the 787/GEnx TCMA air/ground logic - on the 747-8 we used 5 sources of air/ground - three Radio Altimeters and two Weight on Wheels - at least one of each had to indicate ground to enable TCMA). TCMA will shutdown the engine via the N2 overspeed protection - nearly instantaneous. For this to be TCMA, it would require at least two major failures - improper air ground indication or logic, and improper TCMA activation logic (completely separate software paths in the FADEC). Like I said, very, very unlikely. Fuel contamination/filter blockage: The fuel filters have a bypass - if the delta P across the filter becomes excessive, the filter bypasses and provides the contaminated fuel to the engine. Now this contaminated fuel could easy foul up the fuel metering unit causing a flameout, but to happen to two engines at virtually the same time would be tremendous unlikely. Auto Thrust thrust lever retard - the TO lockup in the logic makes this very unlikely (it won't unlock below (IIRC) 400 ft., and even that requires a separate pilot action such as a mode select change or thrust lever movement). And if it did somehow happen, all the pilot needs to do is push the levers back up. Engine parameters on the FDR: I don't know what exactly is on the 787 FDR with regards to engine parameters, but rest assured that there is plenty of engine data that gets recorded - most at one/second. Getting the FDR readout from a modern FDR is almost an embarrassment of riches. Assuming the data is intact, we'll soon have a very good idea of what the engines were doing |
go-around flap 15
2025-06-13T19:02:00 permalink Post: 11900815 |
1) Incorrect flap retraction causing the aircraft to lose lift and unable to recover the energy in time. (Not unheard of and plenty of reports where this has happened - albeit usually not to a crash). 2) Loss of engine thrust backed up two potential pieces of evidence that back up the RAT was deployed (apparent RAT sound, potential RAT seen on low res video). It is impossible to know which of these is the case. Considering this summary of memory items is there the potential for a combination of both theories to have taken place? Inadvertant flap retraction by PNF leading the PF to sense a sink and loss of lift. Pushes the thrust levers forward to the firewall and still the aircraft sinks. PF looking through the HUD and so very much 'outside focused' and doesn't realise that PNF has instead moved the flaps. PF defaults to memory items for loss of thrust on both engines before PNF can realise or communicate to PF what they've done, start switches are cut off which drops the RAT and from that point they're only heading one way. This would satisfy the strongly held belief that the RAT was extended, whilst also following the more likely initial cause of an action slip by PNF starting the sequence, rather than a dual engine failure. 4 users liked this post. |
tuiallstar
2025-06-13T19:10:00 permalink Post: 11900822 |
The gear is required to be retracted within 12 seconds even on one engine. The fact that it wasn't means it was either not selected or there wasn't engine driven hydraulic pressure to do it.
Out of interest about when did the RAT include a hydraulic pump, not that it would be sufficient to retract the gear anyway. 1 user liked this post. |
appruser
2025-06-13T19:20:00 permalink Post: 11900831 |
Firstly, I don\x92t think an inadvertent selection of flaps up caused this accident. I think it\x92s a red herring that seemed plausible initially but it is not consistent with the RAT being deployed, and the evidence for the RAT is strong.
To answer your broader question though, how could such an error happen? It happens because us simple humans learn how to do actions to the point where we don\x92t have to think about them anymore. This allows us to effectively automate routine tasks and save our brains for more novel tasks. The problem arises when we trigger the wrong automatic action in response to a cue. You ask for gear up, I know I need to select the gear up, I know where the gear handle is and what it looks and feels like, yet something goes wrong in the wiring of my body and instead, the flap-up automatic action is run. It\x92s run before I have consciously thought about it. Sound far fetched? Well it has happened numerous times. I\x92ve seen someone do exactly that, select the flap instead of the gear, and there are incident reports publicly available. All modern passenger jets have a similar layout of the flap lever and the gear lever with the gear looking like a wheel and the flap looking like a wing, yet this error can still happen. Have you ever gone to put something in the fridge that should\x92ve been put in the cupboard? I\x92d bet that most people have made that weird error at some point in their lives, and yet the fridge doesn\x92t look like the cupboard and they\x92re nowhere near each other. |
Pip_Pip
2025-06-13T19:31:00 permalink Post: 11900839 |
In summary,
Flaps were extended, possibly flaps 5 or 15. Looks like it in the video and clearly shown post crash. Aircraft reached a height of just over 100\x92 AGL (possibly 200\x92 if you compare wingspan to height in videos) RAT was deployed. Seen on videos and heard conclusively. Aircraft rotated at \x91usual\x92 spot. Comparing FR24 data from previous flights over the past week. Aircraft took off at \x91usual\x92 speed. Comparing other flights. FR24 data stopped being sent shortly after take off. Possibly indicating electrical fault. Green and white flashing light reported by survivor. Possibly indicating electrical fault. Gear bogies were at unusual angle indicating Gear selected up and then interrupted. No smoke or flames to indicate bird strike. (Edit - still debate about this in the video above where the aircraft is behind a building) No rudder input to indicate single engine failure. All speculation but hopefully a pretty balanced summary from the thread so far. It would be great if there was more focus now on what might have caused above rather than talking flaps, birds, 625\x92, etc. The most productive responses would be along the lines of:- (1) I too have read all previous posts and agree that your summary reflects the current consensus, (2) I too have read all previous posts and agree your summary reflects the consensus HOWEVER I challenge that consensus because... [ [i]EITHER (a) reference to previous post that merits greater credence, OR (b) new evidence supplied], (3) I too have read all previous posts but I do NOT agree your summary reflects the consensus [explanation required]. It is not necessary for everyone who thinks (1) to say it (although some initial feedback would be useful!). However, if any of the more experienced and informed PPRuNers are thinking either (2) or (3) then it would be instructive to hear that. FWIW, yours strikes me as a reasonable summary of the best consensus I have been able to discern (as of ~30 minutes ago). There are multiple caveats to each line item, but I presume you've deliberately left those out for the sake of readability, so I'll do the same! The only comments I would add are:- - It's a stretch to say the RAT is seen or heard "conclusively". Doubts have been expressed about the video quality and there are dissenting views regarding the audio. If a few more people were able to wade in on the audio point in particular, this could be very beneficial in moving the discussion forward because the presence or otherwise of the RAT is significant to several competing theories. - On the subject of audio, I am surprised there has not been more discussion regarding engine noise. In the primary eye witness video the (alleged) RAT can be heard distinctly, as can the sounds of distant impact. If the engines were working as expected when overflying the camera and then flying directly away from it, do we really not think the engine noise would be more conclusive, i.e. louder (notwithstanding quiet engines and derated takeoffs)? Whichever way readers are leaning in the flaps versus power loss debate, surely these two points are pivotal, and we have actual evidence available to discuss? - Gear bogies: I'm not sure a consensus has yet been reached regarding the angle of the bogies. (I am not personally qualified to comment on this - I am purely saying I don't see a clear consensus just yet among those who are) - Mayday call: I don't recall seeing a confirmed source for the widely reported mayday. Others have brought this up in the thread but nobody appears to be able to confirm one way or the other. If accurate, its contents are informative. Am I right to presume that you have left it out of your summary due to a lack of confirmation? 9 users liked this post. |
PJ2
2025-06-13T19:59:00 permalink Post: 11900851 |
The only other way the RAT can be deployed is manually, using the p/b on the overhead panel. Almost certainly this is a highly unlikely action given time & distractions. But it is one possibility that needs examination and elimination in the data.
2 users liked this post. |
flapassym
2025-06-13T20:04:00 permalink Post: 11900854 |
Question is why both engines lost power . Foreign object ingestion , contaminated fuel or both cutoff levels operated ? We do not know .
Any autothrust discussion is misleading since every pilot in that situation will firewall the levers whatever thrust reduction was selected for TO . the same is true for the RAT discussion- if enough hydraulic pressure was generated or not . The plane pitched up last second so there obviously was control until the end . Of course , without energy pulling alone will not bring you anywhere . Why did both engines fail the same second as they would be cut off ??? Actually not true. Remember the 737 with iced up itt probes that hit the Washington bridge? a simple \x93yugga\x94 on the power levers would have prevented disaster. probably irrelevant to this topic however |
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