2025-06-14T02:16:00
permalink Post: 11901080
As many will know, on the Boeing 787-8,
each main gear door is hydraulically actuated and powered by its respective side’s hydraulic system
— the
left gear door by the left hydraulic system
, and the
right by the right
. This leads me to propose the following hypothesis:
The Centre Hydraulic system is powered by two Electric Motor Pumps.
Obviously, the two Centre pumps are ultimately powered by electrical power from the VFSGs on the engines and/or the APU.
Note: the RAT will not (and could not!) supply hydraulic power to the gear system.
1 user liked this post.
2025-06-14T02:17:00
permalink Post: 11901082
YMML EK?
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?
Might that incident shed any light on this one, especially since that crew was able to recover?
Are you thinking of the EK A340 that departed with a 100 ton descepancy entered in the box resulting in incorrect thrust derate and under cooked V speeds? That aircraft was saved by the flight crew that fire walled the thrust leavers with about 600M remaining. Tail strike and destroyed the LOC antenta, but was able to get Airbourne then return for landing at YMML. Is this a possibility? 100 ton gross error, resulting in incorrect thrust, speeds and flap setting? Pilot mistakes lack of thrust for partial engine failure? The confusion and startle factor as the aircraft is rotating with a surprising lack of thrust and the runway end fast approaching may account for the gear not being selected up. If there were a gross error in the weight entered in the FMC, no takeoff config warning. 40 degrees C, flaps 5 instead of flaps 15 or similar? Hopefully some initial data from the FDR may be a pretty good indication.
1 user liked this post.
2025-06-14T02:39:00
permalink Post: 11901091
Are you thinking of the EK A340 that departed with a 100 ton descepancy entered in the box resulting in incorrect thrust derate and under cooked V speeds? That aircraft was saved by the flight crew that fire walled the thrust leavers with about 600M remaining. Tail strike and destroyed the LOC antenta, but was able to get Airbourne then return for landing at YMML. Is this a possibility? 100 ton gross error, resulting in incorrect thrust, speeds and flap setting? Pilot mistakes lack of thrust for partial engine failure? The confusion and startle factor as the aircraft is rotating with a surprising lack of thrust and the runway end fast approaching may account for the gear not being selected up. If there were a gross error in the weight entered in the FMC, no takeoff config warning. 40 degrees C, flaps 5 instead of flaps 15 or similar? Hopefully some initial data from the FDR may be a pretty good indication.
If RAT out ??? That tells a lot .
Not long to wait now ?
condolences to family\x92s and loved ones !
Last edited by Toruk Macto; 14th Jun 2025 at 04:30 .
2025-06-14T03:05:00
permalink Post: 11901101
Miscellaneous comments:
I have seen in manuals for other airliners that because the bogie tilt is by a hydraulic actuator, gravity deploying the gear means the gear doesn't tilt to landing position.
With the loss of centre-system pressure*, would you expect the bogies to tilt naturally? I.e. spring pressure holds the gear in the stowed tilt, a hydraulic cylinder pushes the gear to the landing tilt. No pressure means the gear returns to the 'stowed' tilt.
The tilt actuator is designed to be overridden when the bogie hits the ground, so perhaps it has some kind of intentional bypass and doesn't stay in place without continually applied hydraulic pressure.
If so, that would also point towards total loss of electrics and no attempt to raise the gear.
* 787 centre system is powered by two electric pumps, plus the RAT. The RAT hydraulic pump only powers flight controls, not the landing gear.
Electric loss:
Surely even total AC power loss shouldn't result in engine loss, even if the RAT doesn't come online. The FADECs have their own alternators, bare minimum flight control computers and actuators are available on battery (though probably result in some equivalent of Direct Law), and boost pumps are unnecessary at low altitude. Left/right EDPs will remain active if the engines are running at any serious speed; providing flight controls.
Poor crew reaction to ending up in direct law is possible but it's hard to see the electrical issues as a cause, not a symptom.
Anti-terrorism squad looks to be doing an excellent job (/s) and recovered a convenience-store-grade CCTV recorder, probably from somewhere on the campus it crashed into:
https://economictimes.indiatimes.com.../121823103.cms
With the loss of centre-system pressure*, would you expect the bogies to tilt naturally? I.e. spring pressure holds the gear in the stowed tilt, a hydraulic cylinder pushes the gear to the landing tilt. No pressure means the gear returns to the 'stowed' tilt.
The tilt actuator is designed to be overridden when the bogie hits the ground, so perhaps it has some kind of intentional bypass and doesn't stay in place without continually applied hydraulic pressure.
If so, that would also point towards total loss of electrics and no attempt to raise the gear.
* 787 centre system is powered by two electric pumps, plus the RAT. The RAT hydraulic pump only powers flight controls, not the landing gear.
Electric loss:
Surely even total AC power loss shouldn't result in engine loss, even if the RAT doesn't come online. The FADECs have their own alternators, bare minimum flight control computers and actuators are available on battery (though probably result in some equivalent of Direct Law), and boost pumps are unnecessary at low altitude. Left/right EDPs will remain active if the engines are running at any serious speed; providing flight controls.
Poor crew reaction to ending up in direct law is possible but it's hard to see the electrical issues as a cause, not a symptom.
https://economictimes.indiatimes.com.../121823103.cms
2025-06-14T06:43:00
permalink Post: 11901167
Maybe mentioned before, maybe not.
Airplane landed 11:18 and took off 13:38, with some taxi time at both ends that\x92s about 2hrs at the gate with ramp temperatures likely about 40C.
I know there is a brake MEL/DMI that requires gear to remain down for 2 min.
Perhaps a reason for the gear down situation.
Airplane landed 11:18 and took off 13:38, with some taxi time at both ends that\x92s about 2hrs at the gate with ramp temperatures likely about 40C.
I know there is a brake MEL/DMI that requires gear to remain down for 2 min.
Perhaps a reason for the gear down situation.
2025-06-14T06:53:00
permalink Post: 11901175
Speaking as a B787 Captain..... There is so much rubbish and stupid suggestion being written here.
This aircraft was airborne for a grand total of 22 seconds, half of which was climbing to no more than 150' aal.
- No Flaps? Due to the setup of the ECL it is physically impossible to go down the runway without some sort of take-off flap set. The T/o config warning would have been singing it's head off. Despite assertions to the contrary I have seen no video clear enough to detect a lack of flaps.
- RAT out? Almost impossible, I have seen no quality footage that definitively witnesses the RAT being out. Those who think they car hear a RAT type noise might be listening to a motorcycle passing or similar. It takes a triple hydraulic failure or a double engine failure to trigger RAT deploment. They happily went through V1 without a hint of rejected take off so as they rotated the aircraft was serviceable. These are big engines, they take a long time to wind down when you shut them down. I have never tried it however engine failure detection takes 30s or for the aircraft to react and they were not even airborne that long.
- Flaps up instead of gear? The B787 flaps are slow both in and out. Given that the 'Positive rate' call is not made the second the wheels leave the ground, a mis-selection of flaps up would not cause any loss of lift for at least 20 seconds, by which time they had already crashed. I believe the gear remained down not because of mis-selection but because of a major distraction on rotate.
Discounting the impossible, two hypotheses remain:
1. Invalid derate set through incorrect cross-checking. Trundling down the runway takes very little power to reach Vr. It is only when you rotate that you create more drag and discover that you do not have sufficient thrust vs. drag to sustain a climb. Or....
2. Put 200' as the altitude target in the FCU. Immediate ALT capture and all the power comes off. PF is still hand flying trying to increase pitch but is already way behind the aircraft.
It could be after this that Boeing are forced to review the B787 practice of exploring the very edges of the performance envelope.
This aircraft was airborne for a grand total of 22 seconds, half of which was climbing to no more than 150' aal.
- No Flaps? Due to the setup of the ECL it is physically impossible to go down the runway without some sort of take-off flap set. The T/o config warning would have been singing it's head off. Despite assertions to the contrary I have seen no video clear enough to detect a lack of flaps.
- RAT out? Almost impossible, I have seen no quality footage that definitively witnesses the RAT being out. Those who think they car hear a RAT type noise might be listening to a motorcycle passing or similar. It takes a triple hydraulic failure or a double engine failure to trigger RAT deploment. They happily went through V1 without a hint of rejected take off so as they rotated the aircraft was serviceable. These are big engines, they take a long time to wind down when you shut them down. I have never tried it however engine failure detection takes 30s or for the aircraft to react and they were not even airborne that long.
- Flaps up instead of gear? The B787 flaps are slow both in and out. Given that the 'Positive rate' call is not made the second the wheels leave the ground, a mis-selection of flaps up would not cause any loss of lift for at least 20 seconds, by which time they had already crashed. I believe the gear remained down not because of mis-selection but because of a major distraction on rotate.
Discounting the impossible, two hypotheses remain:
1. Invalid derate set through incorrect cross-checking. Trundling down the runway takes very little power to reach Vr. It is only when you rotate that you create more drag and discover that you do not have sufficient thrust vs. drag to sustain a climb. Or....
2. Put 200' as the altitude target in the FCU. Immediate ALT capture and all the power comes off. PF is still hand flying trying to increase pitch but is already way behind the aircraft.
It could be after this that Boeing are forced to review the B787 practice of exploring the very edges of the performance envelope.
1) The flap retraction would immediately result in progressive less lift, not only after full retraction . The time in the air could have been longer than your estimate, maybe enough time for full retraction
2) if 200 feet in MCP, why would that lead to a descent? Shouldn't that result in level flight?
3) wrong TOW / too low power setting sounds like a plausible event.Happened before. But with full power / TOGA set in the air ( which surely must have happened)I would expect at least a longer struggle rather than the constant descent. Just a gut feeling though, busdriver, no experience on 787. Maybe already in a power on stall. The only problem with this hypothesis is that it does not explain the gear down since there definitely was positive rate after rotation.
4) double engine failure too remote, no signs of flames etc. Forget it, agreed.
My guess remains inadvertant flaps retraction for what it's worth.
1 user liked this post.
2025-06-14T07:06:00
permalink Post: 11901181
Originally Posted by
B2N2
I know there is a brake MEL/DMI that requires gear to remain down for 2 min.
Perhaps a reason for the gear down situation.
Perhaps a reason for the gear down situation.
Plane crash near Ahmedabad..
Originally Posted by
Parishiltons
Is it possible that a reduced power takeoff error is a factor, similar to the EK407 near-accident in Melbourne?
Originally Posted by
B2N2
Yes, very much so.
Last edited by Capn Bloggs; 14th Jun 2025 at 07:22 . Reason: Punctuation.
2025-06-14T07:51:00
permalink Post: 11901217
How is misselected flap still being discussed? Misselected flap does not cause gear retraction to cease nor cause the RAT to deploy. Both of which are (subjectively) evidenced in the videos. What is the supporting evidence for misselected flap?
Yes absolutely. 100% catastrophic loss of power when getting airborne. No evidence for bird strikes\x85no severe eng damage symptoms in the videos, no mention of birds in the mayday\x85
they\x92ve gone TO power all the way to rotate, no power issues, no eng fuel issues, but as soon as its wheels off they lose all power. That can\x92t be coincidental. TCMA certainly fits this scenario especially with ground/air logic.
Taken together, it seems that there was an event (or events) shortly after rotation that compromised both engines and the electrical system. There is no evidence yet of birdstrikes and continued engine operation *should* not be affected by the aircraft electrical system as they are independently/internally powered, so logic would have the engines failing first leading to a cascade of other problems. Something that affects all engines pretty much simultaneously is a rare beast but it has happened in the past; outside of a deliberate selection of the fuel and/or fire switches for both power plants there is fuel contamination, FOD and not much else.
they\x92ve gone TO power all the way to rotate, no power issues, no eng fuel issues, but as soon as its wheels off they lose all power. That can\x92t be coincidental. TCMA certainly fits this scenario especially with ground/air logic.
1 user liked this post.
2025-06-14T08:43:00
permalink Post: 11901266
I’m not a 787 driver so for fear of looking dumb in front of those that are this still confuses me. Even IF they’ve mis-selected the flap setting (I still don’t think it’s been cemented on here that there is in fact a FMS/flap setting disagreement warning but i believe there is), had the wrong de-rated take off settings, selected flaps instead of gear up the 787 with massive high bypass engines, FBW and full envelope protections surely cannot let itself be put in such a low energy/high alpha regime as we saw in the videos IF it has both fans functioning normally, surely?
the pilots may have messed up royally and numerous times so those holes lined up but the plane is the final block in the chain and a 21st century all digital entirely clean sheet design was sold as being immune to such catastrophic outcomes from a few minor (consequential yes) and fairly common errors- aren’t all the protections and our procedures designed after decades of mistakes?
im having a hard time squaring how a fully functioning modern bird like this could allow for this outcome and almost whatever the pilots did outside of unbelievable inputs and the pilots are are a bit of a red herring IMO
Dale Winsley
@Winsleydale
No. The LE slats are deployed therefore the flaps are as well. This is an automatic linkage. The flaps are set at Take-Off. Hard to see from the angle but they are...if slats are out (easy to see) then flaps are set. Looks like Flaps 5. Also, the 787 has the highest Thrust-to-Weight ratio of any airliner on Earth. The change in Alpha and lift is a trifling matter for it, at these settings (1-5). It will fly out of it easily, even at that density altitude. The attitude change is - in the circumstances I describe, consistent with a massive power loss (both sides). I believe based on probability that simultaneous mechanical failure is not the cause. Fuel contamination or starvation is likewise unlikely based on the 787 fuel system. The common element is the FADEC/Autothrottle/TOGO. However, each engine FADEC is dual redundant two channels. So any such common failure must happen further upstream. From a design perspective, that would be unthinkable. But this is Boeing. Given what I can see with my own eyes, I believe the flap issue is a non-starter. Also, re the landing gear: Clearly the Positive Rate challenge would be met based on normal rotation and fly-off at V2. But since we know the flaps were set correctly, that rules out an "oopsie" moment. Just as likely there was at the challenge moment an indication that something was amiss, and the Gear Up call was not made. They see both N1s unwinding and it takes a second to get past the WFT factor. They cross-check and see the airspeed also unwinding. Then they unload the Alpha and pitch to gear down Vy. And they had another 6 seconds. Whatever it was, it was not a flap, mechanical or fuel issue. We will know soon enough. But this is Boeing. My gut says "software". All 787s worldwide need to be grounded, now.
6:10 AM \xb7 Jun 14, 2025
\xb7
53.8K
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Last edited by Senior Pilot; 14th Jun 2025 at 09:04 . Reason: Add X quote
2025-06-14T09:23:00
permalink Post: 11901300
Double power loss causality
A summary of the more certain things we know about the accident so far:
The takeoff run was from the full length and appeared normal, even after comparing with the same flight on previous days. This very much reduces the likelihood of it being a performance issue, e.g. wrong flaps, derate, ZFW/TOW, etc.
Shortly after takeoff, the gear started retracting but stopped in an early intermediate position. At the same time the aircraft climb rate dropped off, then it started a shallow descent. This is consistent with a loss of electrical power causing a loss of hydraulic pressure and total engine thrust from both engines reducing below that generated by one engine at the takeoff setting. The position reporting also went offline at that moment, indicating that it was likely load shed due to an electrical malfunction .
The takeoff run was from the full length and appeared normal, even after comparing with the same flight on previous days. This very much reduces the likelihood of it being a performance issue, e.g. wrong flaps, derate, ZFW/TOW, etc.
Shortly after takeoff, the gear started retracting but stopped in an early intermediate position. At the same time the aircraft climb rate dropped off, then it started a shallow descent. This is consistent with a loss of electrical power causing a loss of hydraulic pressure and total engine thrust from both engines reducing below that generated by one engine at the takeoff setting. The position reporting also went offline at that moment, indicating that it was likely load shed due to an electrical malfunction .
I personally think this is a good summary of what we can ascertain at this point from the evidence we have.
I am not a 787 driver by any means but with a fair bit of aviation experience. I would be interested in any thoughts on this suggestion regarding loss of thrust:
If we take it as a reasonable assumption as above that it is almost simultaneous loss of significant thrust, and for the good reasons already discussed, it is pretty unlikely that from what we can see/analyse, that the cause of this would be bird strike (expect to see some signs on video if it's significant enough to cause double engine failure) nor fuel contamination (reasons as above re: likelihood, other ac affected and simultaneous nature). TCMA I don't know enough about but it seems that the sensor redundancy/logic protection is so high it would not be the sole cause.
On this basis, should we perhaps consider the causality of a total electrics failure of some kind first, leading to deployment of the RAT, gear retraction cease etc. Clearly the independent FADEC power generation systems would mean this doesn't on its own prevent thrust control of the engines but could we then be looking at cascading faults (possibly exacerbated by latent faults below the MEL/defect threshold) that contribute to dual power loss and sensor/system issues in throttle response not resulting in FADEC commands to the engines to increase thrust. So even at that point 'firewalling' the throttles could tragically not recover the situation?
Very happy to be corrected by those with much more experience and understanding of big jets operations and systems!
2025-06-14T09:28:00
permalink Post: 11901302
Originally Posted by
Sisiphos
Not sure where the idea comes from the gear was partially retracted...
Plane crash near Ahmedabad..
3 users liked this post.
2025-06-14T11:49:00
permalink Post: 11901397
I think they meant the retraction had "commenced". A previous post said the bogeys on the -8 tip forward, then the doors open. In the video, the bogeys are tipped forward but the doors remain closed.
Plane crash near Ahmedabad..
Plane crash near Ahmedabad..
1 user liked this post.
2025-06-14T12:22:00
permalink Post: 11901429
What evidence do we have that the RAT was deployed? All I can find is people talking about a "noise" which seems very thin evidence indeed.
Think about living next to a flight path. I do. I never take videos of passing planes. I doubt this video-taker did either.
But something incited him to pick up his phone (I guess) and start videoing, even before he could see the plane, which is out of view at the start. I suggest that he heard the RAT coming, knew it was totally out of the ordinary and thought it worth filming.
Why else would you film just another passing plane?
Also, looking at that video, I can see a "shadow" where the RAT would be. The RAT is very small compared with the landing gear, but there's something there. Largely lost to video compression, but it adds up.
And I can hear it, but not on every copy of that video. Try slowing the video down, but I don't know if that's reliable.
5 users liked this post.
2025-06-14T12:26:00
permalink Post: 11901435
Someone will surely be able to correct me, but the "door" that opens to deploy the RAT remains open. That could go some way to explaining the "shadow" you refer to.
2025-06-14T12:31:00
permalink Post: 11901444
Even though there is no point speculating about the cause of this accident, it is the nature of the beast to have questions. As pilots (most of us at least), we do have an inquiring mindset.
My initial thoughts were an inadvertent flap retraction. But with the ‘evidence’ that has been presented over the last 48 hours, I think we can safely discard that option.
What we think we know is:
- RAT was deployed (highly possible)
- Gear was selected up, but did not operate (bogey tilted, doors remained closed)
- APU was ‘on’ (APU door open on after crash pictures)
- Flight path
Any of these observations, alone, would mean very little. However, in combination, they all point to a dual engine flameout just at/after the rotation. The aircaft has enough kinetic energy to reach roughly 150ft altitude, and then starts a shallow descent at ‘alpha max’ into the buildings ahead. The RAT deployed, APU attempted auto-start, gear was unable to retract.
I only wonder why the engines spooled down. Bird strike seems to be out of the question, so that leaves us with only a very few options, which include a software bug or a suicidal pilot (not a popular option, I understand, but we have to take all options into account).
What I don’t believe is incorrect FCU selections, since that would not explain the high AOA on impact. It also would not explain the RAT, no gear retraction or the APU inlet flap open. Another thing that is highly unlikely is any switching done by the pilots, especially RAT etc.. The airborne time is just too little, pilots usually don’t take any action below approximately 400ft, and these switches are so ‘underused’ that a pilot would not find them instantaneously in a high stress situation.
For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.
My initial thoughts were an inadvertent flap retraction. But with the ‘evidence’ that has been presented over the last 48 hours, I think we can safely discard that option.
What we think we know is:
- RAT was deployed (highly possible)
- Gear was selected up, but did not operate (bogey tilted, doors remained closed)
- APU was ‘on’ (APU door open on after crash pictures)
- Flight path
Any of these observations, alone, would mean very little. However, in combination, they all point to a dual engine flameout just at/after the rotation. The aircaft has enough kinetic energy to reach roughly 150ft altitude, and then starts a shallow descent at ‘alpha max’ into the buildings ahead. The RAT deployed, APU attempted auto-start, gear was unable to retract.
I only wonder why the engines spooled down. Bird strike seems to be out of the question, so that leaves us with only a very few options, which include a software bug or a suicidal pilot (not a popular option, I understand, but we have to take all options into account).
What I don’t believe is incorrect FCU selections, since that would not explain the high AOA on impact. It also would not explain the RAT, no gear retraction or the APU inlet flap open. Another thing that is highly unlikely is any switching done by the pilots, especially RAT etc.. The airborne time is just too little, pilots usually don’t take any action below approximately 400ft, and these switches are so ‘underused’ that a pilot would not find them instantaneously in a high stress situation.
For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.
16 users liked this post.
2025-06-14T12:43:00
permalink Post: 11901451
Even though there is no point speculating about the cause of this accident, it is the nature of the beast to have questions. As pilots (most of us at least), we do have an inquiring mindset.
My initial thoughts were an inadvertent flap retraction. But with the ‘evidence’ that has been presented over the last 48 hours, I think we can safely discard that option.
What we think we know is:
- RAT was deployed (highly possible)
- Gear was selected up, but did not operate (bogey tilted, doors remained closed)
- APU was ‘on’ (APU door open on after crash pictures)
- Flight path
Any of these observations, alone, would mean very little. However, in combination, they all point to a dual engine flameout just at/after the rotation. The aircaft has enough kinetic energy to reach roughly 150ft altitude, end then starts a shallow descent at ‘alpha max’ into the buildings ahead. The RAT deployed, APU attempted auto-start, gear was unable to retract.
I only wonder why the engines spooled down. Bird strike seems to be out of the question, so that leaves us with only a very few options, which include a software bug or a suicidal pilot (not a popular option, I understand, but we have to take all options into account).
What I don’t believe is incorrect FCU selections, since that would not explain the high AOA on impact. It also would not explain the RAT, no gear retraction or the APU inlet flap open. Another thing that is highly unlikely is any switching done by the pilots, especially RAT etc.. These airborne time is just too little, pilots usually don’t take any action below approximately 400ft, and these switches are so ‘underused’ that a pilot would not find them instantaneously in a high stress situation.
For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.
My initial thoughts were an inadvertent flap retraction. But with the ‘evidence’ that has been presented over the last 48 hours, I think we can safely discard that option.
What we think we know is:
- RAT was deployed (highly possible)
- Gear was selected up, but did not operate (bogey tilted, doors remained closed)
- APU was ‘on’ (APU door open on after crash pictures)
- Flight path
Any of these observations, alone, would mean very little. However, in combination, they all point to a dual engine flameout just at/after the rotation. The aircaft has enough kinetic energy to reach roughly 150ft altitude, end then starts a shallow descent at ‘alpha max’ into the buildings ahead. The RAT deployed, APU attempted auto-start, gear was unable to retract.
I only wonder why the engines spooled down. Bird strike seems to be out of the question, so that leaves us with only a very few options, which include a software bug or a suicidal pilot (not a popular option, I understand, but we have to take all options into account).
What I don’t believe is incorrect FCU selections, since that would not explain the high AOA on impact. It also would not explain the RAT, no gear retraction or the APU inlet flap open. Another thing that is highly unlikely is any switching done by the pilots, especially RAT etc.. These airborne time is just too little, pilots usually don’t take any action below approximately 400ft, and these switches are so ‘underused’ that a pilot would not find them instantaneously in a high stress situation.
For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.
Last edited by Senior Pilot; 14th Jun 2025 at 19:08 . Reason: Double posting of image
2025-06-14T13:15:00
permalink Post: 11901474
Since it was spotted we're assuming that the MLG bogie position indicates that gear had been selected up, but the sequence was interrupted. It's been suggested that the bogies might droop nose-down if hydraulic pressure is lost, even if Gear Up has
not
been selected.
Is this the case?
Is this the case?
2 users liked this post.
2025-06-14T14:05:00
permalink Post: 11901513
I agree it is helpful to seek a consensus on some of these matters.
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?
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?
- The bogie could be explained by the Flap/Slat priority valve giving priority to the flaps if the PM suddenly realised his mistake and quickly put the flap lever back to the TO position and then selected the gear lever to UP. Those systems are both heavy hitters and would\x92ve sucked the life out of the CTR hydraulic system pumps.
- There is no way loss of AC (alleged RAT deployment) could've caused a spool down of both engines. Think QF A380 incident in SIN - The entire #1 engine wiring harness in the wing was completely severed and yet it continued (by design) to run at its previous thrust setting. They had to shut it down using a fire truck!
- History and design would dictate that a big 180 minutes ETOP\x92s twin such as the 787 having a dual engine failure or significant power loss at such a critical phase of flight would be a billion to one chance at best. Only the Airbus A400 had a software issue causing all 4 engine fuel shutoff valves to close causing it to crash killing the flight test crew - But this was during its development and flt testing.
- Wide body twin\x92s delivering in the region of 60,000 to 115,000 lbs of thrust at TO rarely , if at all, flame out from multiple bird strike(s) like the baby Bus\x92s and Boeing\x92s. If anyone has seen the frozen chickens at TO power video would know what I\x92m talking about. And the Fan Blade being \x91blown off\x92 as well. In both cases the engine was was able to maintain full TOGA thrust for significantly longer than the AI aircraft.
But it\x92s early days and anything could happen. And nothing surprises me anymore.
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2025-06-14T14:09:00
permalink Post: 11901517
Max EGzt and autorelight
Combining all the bits and pieces of info from this thread so far, IMO we can theoretically sequence it thus using the video from the left:
00:18 Rotation. Normal takeoff config.
00:24 Gear up starts. per Raffael with FF.
......... FR24 ADSB last transmission (71ft, 172kt) just before runway threshold. Matches with video aircraft altitude at 1/2 wingspan.
......... ? Full power flameout leaves N2 ~ 60%; Airspeed < 200k so N2 will decay to 15% in 8-10s?
......... ? Takeoff EGT of 900C needs 25-35s to fall below 250C ?
00:27 Gear up stops. per Raffael with FF. Bogies tilted.
......... ? APU starts. 20-55s to 95%N?
......... Per 787 dual-engine fail/stall memory items, PM initiates Fuel Cutoff and Run.
00:28 Visible loss of thrust. Alt ~ 200ft using aircraft wingspan as measure.
......... Matches with eyewitness "within 5-10s ... it was stuck in the air".
......... Per 787 dual-engine fail/stall memory items, PM initiates RAT Switch for 1s. Whether auto or manual, the RAT initiates.
......... RAT "bang" heard by survivor
......... RAT coming online accounts for eyewitness "lights started flickering green and white".
......... Per 787 QRH below 1000ft, PF makes no change to Main Landing Gear and flaps, aircraft pointed straight for best glide.
00:31 Descending visibly, somewhere beyond the runway threshold. Alt ~ 200ft using aircraft wingspan as measure.
......... ? Because EGT > 250C FADEC blocks fuel (T-HOT hot restart inhibit?) so no relight though N2 > 15% ?
......... 787 glide ratio between 16:1 to 25:1 with MLG down, Flaps 5. About 15-20s and 3-5000ft of glide from 200ft?
......... Some flap accounts for the ground pictures.
00:34 ? N2 has presumably decayed to 15%, FADEC flips to X-START: airspeed outside envelope? No hope of relight now.
......... PM/PF transmits Mayday?
......... Video showing RAT deployed.
00:46 APU reaches some fraction of 95%N (APU sound accounting for survivor's perception of thrust?).
00:48 Impact. 4200ft from descent start, 3990ft from airport boundary road. 17s from visible descent start.
if this is a valid sequence, the only remaining question is why the dual-engine failure at ~200ft agl?
with condolences to the families and people affected.
00:18 Rotation. Normal takeoff config.
00:24 Gear up starts. per Raffael with FF.
......... FR24 ADSB last transmission (71ft, 172kt) just before runway threshold. Matches with video aircraft altitude at 1/2 wingspan.
......... ? Full power flameout leaves N2 ~ 60%; Airspeed < 200k so N2 will decay to 15% in 8-10s?
......... ? Takeoff EGT of 900C needs 25-35s to fall below 250C ?
00:27 Gear up stops. per Raffael with FF. Bogies tilted.
......... ? APU starts. 20-55s to 95%N?
......... Per 787 dual-engine fail/stall memory items, PM initiates Fuel Cutoff and Run.
00:28 Visible loss of thrust. Alt ~ 200ft using aircraft wingspan as measure.
......... Matches with eyewitness "within 5-10s ... it was stuck in the air".
......... Per 787 dual-engine fail/stall memory items, PM initiates RAT Switch for 1s. Whether auto or manual, the RAT initiates.
......... RAT "bang" heard by survivor
......... RAT coming online accounts for eyewitness "lights started flickering green and white".
......... Per 787 QRH below 1000ft, PF makes no change to Main Landing Gear and flaps, aircraft pointed straight for best glide.
00:31 Descending visibly, somewhere beyond the runway threshold. Alt ~ 200ft using aircraft wingspan as measure.
......... ? Because EGT > 250C FADEC blocks fuel (T-HOT hot restart inhibit?) so no relight though N2 > 15% ?
......... 787 glide ratio between 16:1 to 25:1 with MLG down, Flaps 5. About 15-20s and 3-5000ft of glide from 200ft?
......... Some flap accounts for the ground pictures.
00:34 ? N2 has presumably decayed to 15%, FADEC flips to X-START: airspeed outside envelope? No hope of relight now.
......... PM/PF transmits Mayday?
......... Video showing RAT deployed.
00:46 APU reaches some fraction of 95%N (APU sound accounting for survivor's perception of thrust?).
00:48 Impact. 4200ft from descent start, 3990ft from airport boundary road. 17s from visible descent start.
if this is a valid sequence, the only remaining question is why the dual-engine failure at ~200ft agl?
with condolences to the families and people affected.
In-flight, the Autorelight function should attempt to restart the engine as soon as a flameout is detected, and for an engine flaming out at high power it might catch it before it even goes sub-idle. Generally, Autorelight will continue attempting until some cutoff N2 at which time it will stop attempting, or if the pilot move the fuel switch to Cutoff. And while the EEC is still powered (via its own PMA) down to roughly 10% N2, the ignition exciters required for Autorelight do get their power from the airplane.
2025-06-14T15:06:00
permalink Post: 11901555
- The bogie could be explained by the Flap/Slat priority valve giving priority to the flaps if the PM suddenly realised his mistake and quickly put the flap lever back to the TO position and then selected the gear lever to UP. Those systems are both heavy hitters and would’ve sucked the life out of the CTR hydraulic system pumps.
- There is no way loss of AC (alleged RAT deployment) could've caused a spool down of both engines. Think QF A380 incident in SIN - The entire #1 engine wiring harness in the wing was completely severed and yet it continued (by design) to run at its previous thrust setting. They had to shut it down using a fire truck!
- History and design would dictate that a big 180 minutes ETOP’s twin such as the 787 having a dual engine failure or significant power loss at such a critical phase of flight would be a billion to one chance at best. Only the Airbus A400 had a software issue causing all 4 engine fuel shutoff valves to close causing it to crash killing the flight test crew - But this was during its development and flt testing.
- Wide body twin’s delivering in the region of 60,000 to 115,000 lbs of thrust at TO rarely , if at all, flame out from multiple bird strike(s) like the baby Bus’s and Boeing’s. If anyone has seen the frozen chickens at TO power video would know what I’m talking about. And the Fan Blade being ‘blown off’ as well. In both cases the engine was was able to maintain full TOGA thrust for significantly longer than the AI aircraft.
- There is no way loss of AC (alleged RAT deployment) could've caused a spool down of both engines. Think QF A380 incident in SIN - The entire #1 engine wiring harness in the wing was completely severed and yet it continued (by design) to run at its previous thrust setting. They had to shut it down using a fire truck!
- History and design would dictate that a big 180 minutes ETOP’s twin such as the 787 having a dual engine failure or significant power loss at such a critical phase of flight would be a billion to one chance at best. Only the Airbus A400 had a software issue causing all 4 engine fuel shutoff valves to close causing it to crash killing the flight test crew - But this was during its development and flt testing.
- Wide body twin’s delivering in the region of 60,000 to 115,000 lbs of thrust at TO rarely , if at all, flame out from multiple bird strike(s) like the baby Bus’s and Boeing’s. If anyone has seen the frozen chickens at TO power video would know what I’m talking about. And the Fan Blade being ‘blown off’ as well. In both cases the engine was was able to maintain full TOGA thrust for significantly longer than the AI aircraft.
As for history and design making a dual-engine failure a billion to one chance: I'd be more inclined to agree that it's unlikely to be what happened if the actual manufacturing of planes (Boeings in particular) and the maintenance procedures were both carried out "by the book" at all times by the manufacturer and the airlines... This is clearly not the case though.
Last edited by Saab Dastard; 14th Jun 2025 at 19:35 . Reason: reference to deleted posts removed