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sSquares
June 13, 2025, 12:48:00 GMT permalink Post: 11900479 |
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 ??? The "gear-up" places additional load on the hydraulic pumps and the result of that is step increase of load on the generators. Was this the trigger of the failures? |
violator
June 13, 2025, 12:56:00 GMT permalink Post: 11900487 |
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 ??? Let\x92s be careful about absolutes. Emirates 521 and Turkish 1951 are both examples of crews not firewalling the thrust levers despite low energy. The late pitch up could be due to the onset of a stall not an order from the crew. TCMA is function which can reduce thrust on both engines simultaneously. It had done so in error in the past resulting in an AD. It uses air/ground logic so that it only operates on the ground, however note that at the point of thrust loss the gear is still down without any movement of the gear or doors. I would expect gear retraction to start before that height. Could we imagine an air/ground logic fault inhibiting gear retraction and allowing TCMA, which triggered (for whatever reason!) causing dual thrust loss? I would expect this to be in the realms of a combination of failures shown to be extremely impossible, but\x85 |
HUTCHP
June 13, 2025, 14:18:00 GMT permalink Post: 11900557 |
One has to assume that, given the seeming lack of lateral deviation from the flight path, and with no obvious yawing or rudder input visible on the videos, there's only two realistic conclusions here? Simultaneous dual engine failure of unknown cause if the RAT was indeed deployed; or flaps reduced too early leading to a stall if the RAT wasn't deployed.
Evidence in this thread would lean me toward the RAT deployed and therefore dual engine out scenario. As for the cause of that, well, only a couple of likely scenarios exist that could cause simultaneous shutdown of both engines, including mistaken or intentional use of the fuel cutoff levers. Hutch |
nrunning24
June 13, 2025, 14:21:00 GMT permalink Post: 11900563 |
Former Boeing Engineer, actually worked on this specific airplane prior to delivery. To me this all comes down to if the RAT was actually out. If not, lots of different factors people have already debated and likely some sort of pilot error that I'll let the pilots on this forum debate.
If the RAT did come out, then we are looking at simultaneous dual engine failure basically at V2 which is so improbable (without bird strikes or purposeful actions) that it is basically impossible. This is a 330 Min ETOPS aircraft. I saw no rudder deflection or yaw indicating 1 engine failed first and then they shut down the second one on accident. Only two realistic options for me in that case are: 1. cutoff of the engines by the pilots. Either on purpose or accidental. 2. maintenance actions by the Air India ground team that caused issues with the engine system or power generation system. 2 is the only one I haven't seen mentioned here and I say this as a no longer Boeing employee. We STRUGGLED with AI during the EIS. They were notorious for just parking airplanes and then using them as spare parts and then screaming for help when they had to go back and get the planes ready to fly again. Still think 1 is much more likely but will just throw out that 2 since there were complaints from previous flights about IFE and AC which to me speaks to issues with the power generation possibly being neglected. |
Buster15
June 13, 2025, 15:24:00 GMT permalink Post: 11900624 |
Former Boeing Engineer, actually worked on this specific airplane prior to delivery. To me this all comes down to if the RAT was actually out. If not, lots of different factors people have already debated and likely some sort of pilot error that I'll let the pilots on this forum debate.
If the RAT did come out, then we are looking at simultaneous dual engine failure basically at V2 which is so improbable (without bird strikes or purposeful actions) that it is basically impossible. This is a 330 Min ETOPS aircraft. I saw no rudder deflection or yaw indicating 1 engine failed first and then they shut down the second one on accident. Only two realistic options for me in that case are: 1. cutoff of the engines by the pilots. Either on purpose or accidental. 2. maintenance actions by the Air India ground team that caused issues with the engine system or power generation system. 2 is the only one I haven't seen mentioned here and I say this as a no longer Boeing employee. We STRUGGLED with AI during the EIS. They were notorious for just parking airplanes and then using them as spare parts and then screaming for help when they had to go back and get the planes ready to fly again. Still think 1 is much more likely but will just throw out that 2 since there were complaints from previous flights about IFE and AC which to me speaks to issues with the power generation possibly being neglected. Hopefully you might be able to answer this. Many thanks. I am a retired gas turbine engineer who worked on safety systems and assessments and assisted on a number of accident investigations (military fast jets) and would be interested to know this. |
violator
June 13, 2025, 18:58:00 GMT 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
June 13, 2025, 19:02:00 GMT 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. |
sTeamTraen
June 13, 2025, 19:42:00 GMT permalink Post: 11900845 |
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EDML
June 13, 2025, 19:45:00 GMT permalink Post: 11900847 |
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flapassym
June 13, 2025, 20:04:00 GMT 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 |
EXDAC
June 13, 2025, 20:19:00 GMT permalink Post: 11900866 |
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neila83
June 13, 2025, 20:50:00 GMT permalink Post: 11900886 |
We're all shouting each other down with two main different theories on why the aircraft lost lift so shortly after takeoff.
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. As has been said many times as well, the landing gear retraction process appears to start as the bogies tilt, and then suddenly stops. Which rather suggests they did pull the gear lever. Based on the videos and the amount of speed the plane lost in the very brief sequence ovents, I'd say that the plane lost power a lot earlier than it would have in your theory. Last edited by neila83; 13th June 2025 at 21:03 . |
jumpseater
June 13, 2025, 20:55:00 GMT permalink Post: 11900891 |
The aircraft as I understand was on a turnround. Is there any element that a ground engineer would have adjusted or checked incorrectly in that standard turnround check, that may have led to duel fuel starvation, or similar issue end up with a unrecoverable loss of power. Obviously I\x92m assuming that involves the time taken for start, pushback, taxiing and TO roll before it manifests itself.
(bio many years in airport ops/atc, and watched an a/c trash engines as it rolled for TO. Reason, equipment was left in an intake that gently moved into the engine after start/push/taxi and commenced roll) |
maxmanx
June 13, 2025, 21:30:00 GMT permalink Post: 11900926 |
Having read all the posts, watched the videos and with a 30 year background interest in air safety, I have a nagging feeling that the engine fuel cut off switches were pulled just after take-off. I am not saying this with the intention of idle speculation, it is just that to me nothing else seems to make sense. To anyone disagreeing with this, I really hope you are right and I am wrong.
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jxksz
June 13, 2025, 21:33:00 GMT permalink Post: 11900929 |
Something I've been wondering about this accident is the phase of the flight where the apparent power loss happened. It seems like the engines were running normally through the takeoff, until the aircraft lifted off the ground. After that the loss of power seemed to happen very quickly.
Could there be a scenario where aircraft's fuel supply is interrupted by change in aircraft's attitude (for example faulty pumps, partially contaminated fuel)? Frankly I have no idea how 787's fuel pumps operate, or if fuel contamination could happen in a way that blocks the flow only when aircraft reaches certain nose-up attitude. |
Europa01
June 13, 2025, 21:33:00 GMT permalink Post: 11900930 |
Cutoff Switches
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Sailvi767
June 13, 2025, 21:48:00 GMT permalink Post: 11900942 |
The requirement to lift the cutoff switch out of the detent before moving it is an important point. However, those switches are close together and unless the the detent requires significant force I suggest that they could be operated together with one hand if that was an intentional action.
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andihce
June 13, 2025, 21:51:00 GMT permalink Post: 11900947 |
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. |
Turkey Brain
June 13, 2025, 21:57:00 GMT permalink Post: 11900954 |
At this stage, at least two scenarios seem highly plausible:
1. Technical issue Airliners rely on air/ground logic , which is fundamental to how systems operate. There have been numerous crashes and serious incidents linked to this logic functioning incorrectly. Some engineering tests require the air/ground switch to be set in a particular mode. If it's inadvertently left in engineering mode—or if the system misinterprets the mode—this can cause significant problems.
2. Pilot misselection of fuel control switches to cutoff This is still a very real possibility. If it occurred, the pilot responsible may not have done it consciously—his mindset could have been in a different mode. There’s precedent: an A320 pilot once inadvertently shut down both engines over Paris. Fortunately, the crew managed to restart them. Afterward, the pilot reportedly couldn’t explain his actions. If something similar happened here, then when the pilots realized the engines had stopped producing thrust, pushing the levers forward would have had no effect. It’s easy to overlook that the fuel switches are in the wrong position—they're far from the normal scan pattern. And with the ground rushing up, the view outside would’ve been far more commanding. Speaking personally, when I shut down engines at the end of a flight, I consciously force myself to operate each fuel switch independently and with full attention. I avoid building muscle memory that might lead to switching off both engines in a fast, well-practiced habit. If this is a technical issue, I assume we’ll know soon enough. |
fdr
June 13, 2025, 22:13:00 GMT permalink Post: 11900962 |
At this stage, at least two scenarios seem highly plausible:
1. Technical issue Airliners rely on air/ground logic , which is fundamental to how systems operate. There have been numerous crashes and serious incidents linked to this logic functioning incorrectly. Some engineering tests require the air/ground switch to be set in a particular mode. If it's inadvertently left in engineering mode—or if the system misinterprets the mode—this can cause significant problems.
2. Pilot misselection of fuel control switches to cutoff This is still a very real possibility. If it occurred, the pilot responsible may not have done it consciously—his mindset could have been in a different mode. There’s precedent: an A320 pilot once inadvertently shut down both engines over Paris. Fortunately, the crew managed to restart them. Afterward, the pilot reportedly couldn’t explain his actions. If something similar happened here, then when the pilots realized the engines had stopped producing thrust, pushing the levers forward would have had no effect. It’s easy to overlook that the fuel switches are in the wrong position—they're far from the normal scan pattern. And with the ground rushing up, the view outside would’ve been far more commanding. Speaking personally, when I shut down engines at the end of a flight, I consciously force myself to operate each fuel switch independently and with full attention. I avoid building muscle memory that might lead to switching off both engines in a fast, well-practiced habit. If this is a technical issue, I assume we’ll know soon enough. On item 2, the video shows no asymmetry at any time, so there is only a symmetric failure of the engines possible. Back on a B747 classic, you could chop all 4 engines at the same time with one hand, on a B737, also, not so much on a B777 or B787. I would doubt that anyone used two hands to cut the fuel at screen height. Note, there was a B744 that lost one engine in cruise when a clip board fell off the coaming. Didn't happen twice, and it only happened to one engine.
Yes indeed, the moment they pulled the gear lever, as we see the gear begin the retraction process, and then suddenly stop. Almost as if they suddenly lost power.
We can see the landing gear retraction process begin. We see the bogies tilted in the second video. We can hear the RAT. We can see the RAT. We can see the flaps extended in the video and at the crash site. There isn't actually a single piece of evidence the flaps were raised, it's just a conclusion people jumped too before evidence began to emerge. The crazy thing is, when the report comes out and there is no mention of flaps none of the people who have been pushing the flap theory will self reflect or learn anything. They'll think those of us who didn't buy into it were just lucky, rather than it being down to use of fairly simple critical thinking. Neila83 is correct, the gear tilt pre retraction is rear wheels low, and at the commencement of the selection of the retraction cycle (generally), There is enough in the way of anomalies here to end up with regulatory action, and airlines themselves should/will be starting to pore over their systems and decide if they are comfortable with the airworthiness of the aircraft at this moment. A latent single point of failure is not a comfortable place to be. Inhibiting TCMA might be a good interim option, that system could have been negated by having the ATR ARM switches....(Both)... ARM deferred to the before takeoff checks. The EAFR recovery should result in action within the next 24-48 hours. Boeing needs to be getting their tiger teams warmed up, they can ill afford to have a latent system fault discovered that is not immediately responded to, and the general corporate response of "blame the pilots" is not likely to win any future orders. I think we are about to have some really busy days for the OEM. Not sure that Neila83 is that far off the mark at all. Last edited by fdr; 14th June 2025 at 01:21 . Reason: corrected for B788 by Capt Bloggs! |
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