June 14, 2025, 12:00:00 GMT
permalink Post: 11901407
I haven't managed to read every post in this thread, just a large percentage, so please excuse me if these points have already been raised. I'll post each separately in case the mods deem them irrelevant or redundant, in which case, my humble apologies.
First, the RAT. There has been a lot of discussion about this, and I suspect the audio analysis a few posts above pretty well confirms that the RAT was deployed. However, I don't think the following question has been asked, and I believe it's further weight in support of RAT deployment.
Q: Why does the video of the plane passing at low altitude, (potentially taken from an apartment window or balcony door), even exist?
I have lived near an airport flight path for many years, and would never bother to video a passing plane unless I perceived it was truly exceptional. Normally, I don't even look, unless it sounds off course, very loud or some such reason. I have yet to take such a video. Here, of course, I'm assuming that the video-taker lived in or near the building concerned, and was therefore equally used to the sounds of passing planes. I submit that the video was shot purely because the camera man (by the voice sound, but an assumption - maybe not the camera operator's) recognised that the sound he was hearing was indeed exceptional. The video begins with the plane out of the shot, so he 'must' (assumption) have heard it coming, and had time to get his phone and starting videoing. Of course I'm saying that he was hearing the RAT...
Secondly, I have found that different versions of the same video play differently (on the same hardware). In some, I cannot discern the RAT sound - unless I reduce the playback speed. Then, it seems to be very distinct - but whether this is an artifact of the reduced playback speed, I can't say. I suspect that different playback applications and hardware will also have a major influence on the RAT audibility. I am 100% convinced that the RAT sound was captured, but is not audible to all, for one or more of these reasons.
Oh, lastly, I'm guessing the (AI) RAT frequency in the audio spectrum analysis was probably lower because the plane was travelling slower than in the other, more controlled cases. Equally, the load on the AI RAT could have been greater, for any number of reasons.
First, the RAT. There has been a lot of discussion about this, and I suspect the audio analysis a few posts above pretty well confirms that the RAT was deployed. However, I don't think the following question has been asked, and I believe it's further weight in support of RAT deployment.
Q: Why does the video of the plane passing at low altitude, (potentially taken from an apartment window or balcony door), even exist?
I have lived near an airport flight path for many years, and would never bother to video a passing plane unless I perceived it was truly exceptional. Normally, I don't even look, unless it sounds off course, very loud or some such reason. I have yet to take such a video. Here, of course, I'm assuming that the video-taker lived in or near the building concerned, and was therefore equally used to the sounds of passing planes. I submit that the video was shot purely because the camera man (by the voice sound, but an assumption - maybe not the camera operator's) recognised that the sound he was hearing was indeed exceptional. The video begins with the plane out of the shot, so he 'must' (assumption) have heard it coming, and had time to get his phone and starting videoing. Of course I'm saying that he was hearing the RAT...
Secondly, I have found that different versions of the same video play differently (on the same hardware). In some, I cannot discern the RAT sound - unless I reduce the playback speed. Then, it seems to be very distinct - but whether this is an artifact of the reduced playback speed, I can't say. I suspect that different playback applications and hardware will also have a major influence on the RAT audibility. I am 100% convinced that the RAT sound was captured, but is not audible to all, for one or more of these reasons.
Oh, lastly, I'm guessing the (AI) RAT frequency in the audio spectrum analysis was probably lower because the plane was travelling slower than in the other, more controlled cases. Equally, the load on the AI RAT could have been greater, for any number of reasons.
June 14, 2025, 12:01:00 GMT
permalink Post: 11901409
I hesitate to chip in in these accidents thread. Keep them clean. However, as as a few comments above brushes my audio expertise, I will comment.
A very simple audio analysis give me this:
The 3 segments horisontally, are of B787s passing overhead. The drop you see is the doppler effect.
In other words, these are spectrograms over time which makes these distinctions easier than a simple static spectrogram.
1. B787 with RAT extended.
2.Air india crash
3. B787 without RAT
It's a 5 minute laptop job, and it would look much prettier and clearer if I spent some time with it, (Gain to color match, and spectrally match to compensate for microphone placement and type),
but it is 85% conclusive even when done as simple as this IMO.
(I do have legal forensic audio experience)
The RAT was out judging from the audio evidence. You can see the the equally spaced overtones of the propelller match when passing overhead resulting in the Doppler effect, the difference in length of the doppler is caused by distance and the slightly varying frequencies shown in the starting point is caused by a difference in speed. But the harmonic content match.
In the 3rd segment you see none of these overtones at all.
A very simple audio analysis give me this:
The 3 segments horisontally, are of B787s passing overhead. The drop you see is the doppler effect.
In other words, these are spectrograms over time which makes these distinctions easier than a simple static spectrogram.
1. B787 with RAT extended.
2.Air india crash
3. B787 without RAT
It's a 5 minute laptop job, and it would look much prettier and clearer if I spent some time with it, (Gain to color match, and spectrally match to compensate for microphone placement and type),
but it is 85% conclusive even when done as simple as this IMO.
(I do have legal forensic audio experience)
The RAT was out judging from the audio evidence. You can see the the equally spaced overtones of the propelller match when passing overhead resulting in the Doppler effect, the difference in length of the doppler is caused by distance and the slightly varying frequencies shown in the starting point is caused by a difference in speed. But the harmonic content match.
In the 3rd segment you see none of these overtones at all.
Last edited by pampel; 14th June 2025 at 17:46 .
June 14, 2025, 12:04:00 GMT
permalink Post: 11901414
I'm reading a lot of the comments, speculation is something we all like, but some things just do not add up, even with a RAT deployed
if they had dual engine failure around 50 feet where you raise the gear, how can they still find the energy to climb, since they would be at VR/V2 speed (not V2+20 at that altitude, what VNAV would command after take off, especially with a take off weight of around 205/210 tons, the 787 wings are amazing but not miracles
if they had a normal departure, why did they not raise the gear, they had a positive rate since they were climbing and the speed according to ADS-B was a constant. if they were single engine ! this would have saved them with this weight and weather, one of the first things you learn when EFATO with a 787, raise the gear, your climb performance increases dramatically
if they did an intersection departure with they're genex 64-70K engines, they would have had a take off limited weight of around 172 tons, I estimate that they were close to 205/210 tons, (max zfw of around 161 tons and around 45/50 tons of fuel) even full length would have been a stress for the engines, with the prevailing weather conditions, intersection take off can be ruled out, they would have never made it, full length is already difficult.
When we see the video, the airplane is still climbing / flying straight and level (not losing altitude), yet we hear what we think might be the RAT, I can't imagine that they had the kinetic energy to do this with no engines. if they had dual engine failure, they would have been a brick, Hot and High, no thrust, flaps 5, zero chance.
flickering of lights etc. seen by the survivor and the loud bang heard, I would not trust pax observations, because of the things they had to go through, also and I've said this before, if it was a loud bang, where is the smoke and fire in the engines, or in the video, its not audible
lets see what the report will say, but it it could be a lot to swallow for some
if they had dual engine failure around 50 feet where you raise the gear, how can they still find the energy to climb, since they would be at VR/V2 speed (not V2+20 at that altitude, what VNAV would command after take off, especially with a take off weight of around 205/210 tons, the 787 wings are amazing but not miracles
if they had a normal departure, why did they not raise the gear, they had a positive rate since they were climbing and the speed according to ADS-B was a constant. if they were single engine ! this would have saved them with this weight and weather, one of the first things you learn when EFATO with a 787, raise the gear, your climb performance increases dramatically
if they did an intersection departure with they're genex 64-70K engines, they would have had a take off limited weight of around 172 tons, I estimate that they were close to 205/210 tons, (max zfw of around 161 tons and around 45/50 tons of fuel) even full length would have been a stress for the engines, with the prevailing weather conditions, intersection take off can be ruled out, they would have never made it, full length is already difficult.
When we see the video, the airplane is still climbing / flying straight and level (not losing altitude), yet we hear what we think might be the RAT, I can't imagine that they had the kinetic energy to do this with no engines. if they had dual engine failure, they would have been a brick, Hot and High, no thrust, flaps 5, zero chance.
flickering of lights etc. seen by the survivor and the loud bang heard, I would not trust pax observations, because of the things they had to go through, also and I've said this before, if it was a loud bang, where is the smoke and fire in the engines, or in the video, its not audible
lets see what the report will say, but it it could be a lot to swallow for some
June 14, 2025, 12:07:00 GMT
permalink Post: 11901420
Or he may have heard the RAT spooling up. Valuable as a witness account may be, we’ll have to wait for FDR and CVR data and/or wreckage analysis before drawing conclusions.
June 14, 2025, 12:19:00 GMT
permalink Post: 11901426
It was hard to let it go, so I spent a bit more time with the audio, using filtering and matching to see if I could be even more sure.
It's a pity uploading audio to this site isn't as easy as uploading photos, but I can say it took very little filtering and matching to make the Air India audio become nearly indistinguishable from audio taken of B787 with known RAT extended during landing.
I can't see it in the photos either, but in these circumstances the audio is a lot more trustworthy, and from my audio point of view RAT deployment is 100% confirmed.
In the off chance that the audio I borrowed from a confirmed RAT event was somehow faked, I plotted the technical data I could find of the B787 RAT (4000rpm, 2 blades) combined with a height estimate and asked the O3 model with deep research to estimate doppler shift and speed.
The result matches the above documented 270-200Hz (in one of the harmonics) Doppler shift observed in 1.7 seconds.
It's a pity uploading audio to this site isn't as easy as uploading photos, but I can say it took very little filtering and matching to make the Air India audio become nearly indistinguishable from audio taken of B787 with known RAT extended during landing.
I can't see it in the photos either, but in these circumstances the audio is a lot more trustworthy, and from my audio point of view RAT deployment is 100% confirmed.
In the off chance that the audio I borrowed from a confirmed RAT event was somehow faked, I plotted the technical data I could find of the B787 RAT (4000rpm, 2 blades) combined with a height estimate and asked the O3 model with deep research to estimate doppler shift and speed.
The result matches the above documented 270-200Hz (in one of the harmonics) Doppler shift observed in 1.7 seconds.
Also, while I'm barely a pilot, I am a qualified cognitive scientist with an interest in memory. Without going into any detail, even assuming no concussion or other insults, given what the single witness has gone, and is going through, I wouldn't trust a word he says about his experiences, especially about timings and orders of things happening. I'm not implying any dishonesty, just a very high risk of entirely innocent confabulation about such a short and intense experience that nothing could prepare him for. Flight crew, with vast amounts of training and years of trying to imagine their way through the impossible, would probably do better, but even then post hoc confabulation would be hard to avoid.
Last edited by Subsy; 14th June 2025 at 12:32 .
June 14, 2025, 12:22:00 GMT
permalink Post: 11901428
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.
June 14, 2025, 12:22:00 GMT
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.
June 14, 2025, 12:24:00 GMT
permalink Post: 11901432
The B787 is a way way different and much more complex and sophisticated plane than your Gulfie. The B787's two outermost (left & right) hydraulic systems are primarily driven by the engines, mechanically driving the hydraulic pumps. The center hydraulics are primarily electrically driven, and power the main flight controls, amongst other things like the gear. The left and right ones power the main flight controls as well, some of the less important flight control surfaces like spoilers and thrust reversers -- pardon me for not having the exact list of things. They also have a backup/supplementary electric pump each. Each of the two main engines has redundancy for the power plant a.k.a. VFSG (and motor-driven pump?) in its own right as well. All three hydraulic systems work together in a redundant fashion when it comes to the primary flight controls. The RAT can provide both electrical and mechanical sources of hydraulic support, if I'm not mistaken. The flight instrument and information systems can also be powered from two backup batteries, the APU power plant itself, and/or the RAT.
The Global Express has 4 engine driven generators, one APU generator, one RAT generator that provide AC and DC power to the aircraft's systems. On the hydraulic side, the aircraft has 3 fully independent and redundant hydraulic systems which power all flight control surfaces the exception being, the slats and flaps are AC power driven and are available even with only the RAT providing power. The 3 hydraulic systems are powered from each engine backed up by 2 EDPs (system 1 and 2) and system 3 is powered by 2 EDPs only. The RAT powers system 3 via one of its EDPs. In the event of a dual engine failure the RAT would deploy automatically and power the AC essential plus DC essential busses and one EDP on system 3. The APU is available to you up to FL450 and will supply full AC power but bleed air only up to FL300.
June 14, 2025, 12:26:00 GMT
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.
June 14, 2025, 12:31:00 GMT
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.
June 14, 2025, 12:43:00 GMT
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 June 2025 at 19:08 . Reason: Double posting of image
June 14, 2025, 12:48:00 GMT
permalink Post: 11901455
Sorry but before you make a statement like this, you better read up on the "complexity and sophistication" of the latest business jets like the Gulfstreams and Global Express.
The Global Express has 4 engine driven generators, one APU generator, one RAT generator that provide AC and DC power to the aircraft's systems. On the hydraulic side, the aircraft has 3 fully independent and redundant hydraulic systems which power all flight control surfaces the exception being, the slats and flaps are AC power driven and are available even with only the RAT providing power. The 3 hydraulic systems are powered from each engine backed up by 2 EDPs (system 1 and 2) and system 3 is powered by 2 EDPs only. The RAT powers system 3 via one of its EDPs. In the event of a dual engine failure the RAT would deploy automatically and power the AC essential plus DC essential busses and one EDP on system 3. The APU is available to you up to FL450 and will supply full AC power but bleed air only up to FL300.
The Global Express has 4 engine driven generators, one APU generator, one RAT generator that provide AC and DC power to the aircraft's systems. On the hydraulic side, the aircraft has 3 fully independent and redundant hydraulic systems which power all flight control surfaces the exception being, the slats and flaps are AC power driven and are available even with only the RAT providing power. The 3 hydraulic systems are powered from each engine backed up by 2 EDPs (system 1 and 2) and system 3 is powered by 2 EDPs only. The RAT powers system 3 via one of its EDPs. In the event of a dual engine failure the RAT would deploy automatically and power the AC essential plus DC essential busses and one EDP on system 3. The APU is available to you up to FL450 and will supply full AC power but bleed air only up to FL300.
Elsewhere, there is a picture of the tail wreckage showing what looks likethe APU door partially open. The panel is otherwise undamaged indicating not caused by post-impact. I’ll try to poach it
its here, but wrong file extension on the photo
https://www.nytimes.com/interactive/...smid=url-share
Last edited by galaxy flyer; 14th June 2025 at 13:52 .
June 14, 2025, 13:14:00 GMT
permalink Post: 11901473
Yes but reduced power is not complete loss of thrust which leads to RAT deployment is it ?
June 14, 2025, 13:20:00 GMT
permalink Post: 11901478
It was hard to let it go, so I spent a bit more time with the audio, using filtering and matching to see if I could be even more sure.
It's a pity uploading audio to this site isn't as easy as uploading photos, but I can say it took very little filtering and matching to make the Air India audio become nearly indistinguishable from audio taken of B787 with known RAT extended during landing.
I can't see it in the photos either, but in these circumstances the audio is a lot more trustworthy, and from my audio point of view RAT deployment is 100% confirmed.
In the off chance that the audio I borrowed from a confirmed RAT event was somehow faked, I plotted the technical data I could find of the B787 RAT (4000rpm, 2 blades) combined with a height estimate and asked the O3 model with deep research to estimate doppler shift and speed.
The result matches the above documented 270-200Hz (in one of the harmonics) Doppler shift observed in 1.7 seconds.
It's a pity uploading audio to this site isn't as easy as uploading photos, but I can say it took very little filtering and matching to make the Air India audio become nearly indistinguishable from audio taken of B787 with known RAT extended during landing.
I can't see it in the photos either, but in these circumstances the audio is a lot more trustworthy, and from my audio point of view RAT deployment is 100% confirmed.
In the off chance that the audio I borrowed from a confirmed RAT event was somehow faked, I plotted the technical data I could find of the B787 RAT (4000rpm, 2 blades) combined with a height estimate and asked the O3 model with deep research to estimate doppler shift and speed.
The result matches the above documented 270-200Hz (in one of the harmonics) Doppler shift observed in 1.7 seconds.
Last edited by mechpowi; 14th June 2025 at 14:08 .
June 14, 2025, 13:45:00 GMT
permalink Post: 11901503
RAT deployment
Not clear which post you are responding to - but throttle can only command engine down to idle, whereas RAT deployment due to dual-engine failures (not the only cause of deploy) would require the engines to go sub-idle (such as flameouts that the autorelight function could not catch before falling sub-idle).
June 14, 2025, 13:58:00 GMT
permalink Post: 11901509
June 14, 2025, 14:05:00 GMT
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.
June 14, 2025, 14:09:00 GMT
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.
June 14, 2025, 14:16:00 GMT
permalink Post: 11901521
Maybe the person filming had seen the a/c doing something unusual and grabbed their phone to film?
Misty.
June 14, 2025, 14:47:00 GMT
permalink Post: 11901546
As SLF with non-aviation engineering background, but an interest in aircraft, I offer no theories on what happened, as I haven't got a clue.