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appruser
June 13, 2025, 17:43:00 GMT permalink Post: 11900730 |
The lack of obvious debris/smoke during takeoff might indicate it was something other than a birdstrike, and combined with the loss of adsb (per FR24) right over the runway threshold at 70ft agl, maybe it is indicative of something else causing the simultaneous loss of thrust. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): FlightRadar24 RAT (All) RAT (Deployment) |
appruser
June 13, 2025, 18:28:00 GMT permalink Post: 11900785 |
Why would you lower the nose and violently slam the aircraft into ground. The crew flew the aircraft exactly like you should in that situation. They traded angle of attack for descent rate and put the aircraft on the ground with the best chance of survival. Unfortunately with at least 110,000 lbs of fuel and buildings on the decent path the outcome was never going to be good. Doing so also bought them time to try and resolve the engine malfunction.
Subjects: None |
appruser
June 13, 2025, 19:02:00 GMT permalink Post: 11900816 |
Although the gear bogie isn\x92t in the initial post-liftoff position, if you can see the retraction mechanism operating in a 787 It first tilts the bogie forward. I\x92d therefore consider that a \x93gear up\x94 switch was activated but the action failed \x97most likely due to hydraulic pressure loss. In the second video (left-side view), I could interpret that gear retraction begins around 24 s and then halts before 27 s, exactly when the aircraft stops climbing.
Just my two cents, from the perspective of an aircraft engineer with a background primarily in Airbus.​​ Subjects (links are to this post in the relevant subject page so that this post can be seen in context): DGCA FlightRadar24 Hydraulic Failure (All) |
appruser
June 13, 2025, 19:20:00 GMT permalink Post: 11900831 |
Firstly, I don\x92t think an inadvertent selection of flaps up caused this accident. I think it\x92s a red herring that seemed plausible initially but it is not consistent with the RAT being deployed, and the evidence for the RAT is strong.
To answer your broader question though, how could such an error happen? It happens because us simple humans learn how to do actions to the point where we don\x92t have to think about them anymore. This allows us to effectively automate routine tasks and save our brains for more novel tasks. The problem arises when we trigger the wrong automatic action in response to a cue. You ask for gear up, I know I need to select the gear up, I know where the gear handle is and what it looks and feels like, yet something goes wrong in the wiring of my body and instead, the flap-up automatic action is run. It\x92s run before I have consciously thought about it. Sound far fetched? Well it has happened numerous times. I\x92ve seen someone do exactly that, select the flap instead of the gear, and there are incident reports publicly available. All modern passenger jets have a similar layout of the flap lever and the gear lever with the gear looking like a wheel and the flap looking like a wing, yet this error can still happen. Have you ever gone to put something in the fridge that should\x92ve been put in the cupboard? I\x92d bet that most people have made that weird error at some point in their lives, and yet the fridge doesn\x92t look like the cupboard and they\x92re nowhere near each other. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Gear Lever RAT (All) RAT (Deployment) |
appruser
June 13, 2025, 23:21:00 GMT permalink Post: 11900993 |
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. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): ADSB APU Condolences FADEC FlightRadar24 Fuel (All) Fuel Cutoff Fuel Cutoff Switches MAYDAY Memory Items RAT (All) RAT (Deployment) Relight |
appruser
June 14, 2025, 00:52:00 GMT permalink Post: 11901041 |
Regarding flickering lights.
The 787 has, as far as I know, a unique electrical system. When a light is selected on, either by pressing a button, flicking a switch or a touch screen selection there is no direct link to the lights. All instructions go through computers and are controlled by software. As a consequence lights are either off or on. A 'dicky' power supply as has been suggested by some will not cause the lights to flicker. This is not a 737. Subjects: None |
appruser
June 14, 2025, 17:21:00 GMT permalink Post: 11901674 |
This is what he said - the PF *has* to push the nose down to prevent a stall and keep the aircraft flying, and if the PF won't, the aircraft will do so to prevent a stall. How much depends on the flap setting. Subjects: None |
appruser
June 14, 2025, 17:41:00 GMT permalink Post: 11901686 |
I think someone posted a green & white exit sign in the 787 cabin earlier in the thread. Last edited by appruser; 14th June 2025 at 17:49 . Reason: removed speculative bit about APU coming online. Subjects: None |
appruser
June 14, 2025, 18:11:00 GMT permalink Post: 11901703 |
Good point. In the survivor's narrative, the sequence is: 5-10s after takeoff -> plane seemed stuck in the air -> green & white light came on -> they "gave race for more takeoff" (revved up) -> entered straight into (hostel).
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CVR FDR RAT (All) |
appruser
June 14, 2025, 18:43:00 GMT permalink Post: 11901720 |
There should not be a max pre-start EGT limit in-flight - that should only occur on the ground for a pilot-initiated Autostart where the starting EGT redlines are lower than for in-flight.
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. Could this mean that because there doesn't seem to have been any recovery once descent started, there was no fuel flow to support autorelight? Or that there was fuel flow and autorelight may have succeeded but there wasn't enough thrust generated before impact? From the video total descent time was only 17-20s. I guess what I'm asking is what would be the total cycle time if the first autorelight succeeded: flameout -> autorelight -> useful thrust? And if the PM executed dual-engine fail memory item fuel cutoff to run, how would that change the sequence? Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All) Fuel Cutoff Fuel Cutoff Switches Relight |
appruser
June 14, 2025, 22:11:00 GMT permalink Post: 11901887 |
It's a great question! Subjects (links are to this post in the relevant subject page so that this post can be seen in context): APU RAT (All) |
appruser
June 15, 2025, 01:40:00 GMT permalink Post: 11902038 |
Question: regardless of the intricacies of various aircraft-specific systems, is it possible to establish from sheer aerodynamics what can/cannot have happened here? Or to put it another way - leaving aside any and all rumours, theories, plausible sights/sounds, and other extraneous details, and focusing solely on the flight path, can loss of thrust be conclusively ruled in or out? Several times now I've seen someone put forth the argument that it's impossible for the flight path to have been as short as it is if the flaps were retracted but the engines were still producing (even derated) takeoff thrust. It might be helpful to reach a consensus on whether this is true or not - if it's inconclusive then we're back to where we already are, but if a conclusion
can
be reached it would probably save everyone a lot of breath going down various theoretical rabbit holes.
In the CCTV video, the aircraft stops climbing at 00:28. 3 seconds after, it starts visibly descending. At peak altitude, using the 197ft wingspan as a measure, the altitude is around 200ft or below. The fireball is at 00:48, 17s after descent starts visibly. Per google maps and the impact location mapped at avherald, the impact point is ~3990ft from the airport boundary road and about 4200ft from the midpoint of the runway threshold and the airport boundary road. 16:1 to 25:1 is what I could find for the 787 glide ratio range (unpowered) with main landing gear down and flaps 5. So the aircraft could cover 16 to 25 ft horizontally for every 1 ft of descent. With a starting altitude of 200ft, that would imply it could have covered 3200ft.to 5000ft during unpowered descent. The actual distance covered, around 4000ft, certainly seems to suggest that the descent was unpowered. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): AvHerald CCTV |
appruser
June 16, 2025, 02:31:00 GMT permalink Post: 11903067 |
The passenger specifically mentions the lights flickering green and white, this is a specific observation. Not the flickering which happens in the movies, but that they turned green. Boeing sky interior LEDs can turn green and orange (i call is Jamacan mode) during maintenace and trouble shooting (I was a LAME for 20 years). That points to power glitches and faults with the lights. The generaly public would not know Sky interior LEDs can trun green when they fail.
The translation of 1:43 - 1:56 is: "after, in the plane, light came on, green & white; after, I don't know, to make the plane takeoff more, what do they say, gave it race, something like that; it straight entered at speed, where, what was it'. To which the reporter responds, 'it was a hostel' at 1:57. Last edited by appruser; 16th June 2025 at 03:00 . Reason: removed a word "the" which can be misconstrued; there is no specificity about what light came on in the survivor's account Subjects: None |
appruser
June 16, 2025, 06:25:00 GMT permalink Post: 11903134 |
a slight more precise translation as a native speaker. \x93After take off it felt as if we were still in one place & not moving. Then the sound of the engines racing (common Indian term for revving of engines on bikes & cars with the clutch depressed) & then green & white lights came on in the cabin as we hit something.\x94 In my opinion the race sound he talking about sounds like engine surges if compared to race.
To break down the survivor's narrative into an interpretation, am including below a transliteration, direct translation, and the interpretation. The survivor is a very fast speaker, so had to slow the video down to 0.5x through X's settings menu on the video to capture everything he said. Video from 1:32 - 1:56 ------------------ Transliteration: ------------------ Takeoff ke baad, ek minute ke andar hee, jab takeoff hua naa, to suddenly paanch das second kaise lagaa jaise stuck ho gaya woh. Baad mein (sirf mere ko???) lagaa kuchch hua, baad mein plane mein light on ho gayee, green aur white. Baad mein woh pata nahin woh plane takeoff jyadaa karne ke liye woh race, (do?) bolte hain kya, race diya waisa kuchch, woh seedha (re?) .. speed mein hee ghus gaya, jahan woh, woh (l??), kya tha woh 1:57 Reporter: woh hostel thaa ek, hospital ka ------------------ As direct a translation as feasible without significant rewording or putting in my own perspective on his wording: ------------------ After takeoff, within one minute, when takeoff happened, then suddenly 5-10 seconds what I felt like it got stuck. After, (only to me???) it felt something happened. After, in the plane, light came on, green & white. After, I don't know, to make the plane takeoff more they race, what do they say, gave race, something like that, it straight (1/2 spoken word 'race'?) in speed got into, where, what, what was it Reporter: it was a hostel, of the hospital ------------------ Less literal translation, more intepretation: ------------------ After takeoff, within a minute, when takeoff occurred, then suddenly for 5-10 seconds it felt like it was stuck. After, it felt like something happened. After that, in the plane, a light came on, green & white. After, I don't know, to make the plane takeoff more they raced, what do they say - gave it race - something like that; it straight, with speed entered into, what was it - ------------------ Later on he describes the mechanics of his escape, and how he was able to get out through a broken door because there was some space on the outside on the ground floor where he landed, and on the opposite side there was a hostel wall that might have prevented others getting out. Hopefully this might be somewhat useful, even if to only lay to rest some of the theories based on mistranslations of what he said. It certainly helped me understand that the timeline here doesn't have enough information to line up his description of in-flight events with what's on the external videos. For example, using the cctv video for timing, his 5-10s lines up with the takeoff and climb from 00:18 to 00:27, and the "felt like it got stuck" part could correspond to 00:28-00:31 where the aircraft appears to 'stop climbing and float horizontally, very little descent' as compared to after 00:31 when it's visibly descending. The 'something happened' could be the RAT coming online (bang?) but we don't know because there isn't enough detail. Is the RAT even audible inside the cabin? And then the green & white light could be the ceiling light or the exit sign, we don't know, but there is definitely no flickering mentioned. The 'giving race' part is mystifying - see earlier discussion in the thread - was it changing pitch in the constant-speed RAT due to declining airspeed, something else, engines spooling up? we just don't have enough info here. When did they 'give race' within that 17s descent from 00:31 to 00:48 impact? If we knew that it might help, but that detail isn't there in his description; not surprising since it was a short descent. I think we have to wait for the data from the recorders, or another external video, or maybe even a video from the cabin if somebody was live-streaming to facebook/instagram/x etc. Last edited by appruser; 16th June 2025 at 07:24 . Reason: readability, added another example of potential error in translation, and question about RAT audibility inside the cabin Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All) |
appruser
June 16, 2025, 06:59:00 GMT permalink Post: 11903161 |
Based on the video taken from the left of the flight path, can we determine at what point of the runway rotation occurred? Is there positive confirmation that the takeoff roll started at the beginning of the runway ? Are the two indicative of trouble before rotation, as the Times states ?
Source: https://www.thetimes.com/world/asia/...rash-vhqw6b7v3 (paywalled) https://www.flightradar24.com/blog/f...rom-ahmedabad/ I don't know if I'm allowed to post pictures - my last post with a picture didn't show up, so I'll try adding it separately from this one. It's basically an overlay of the FR24 blogpost map on a google maps satellite view of VAAH. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): ADSB FlightRadar24 Takeoff Roll |
appruser
June 16, 2025, 02:31:00 GMT permalink Post: 11903738 |
The passenger specifically mentions the lights flickering green and white, this is a specific observation. Not the flickering which happens in the movies, but that they turned green. Boeing sky interior LEDs can turn green and orange (i call is Jamacan mode) during maintenace and trouble shooting (I was a LAME for 20 years). That points to power glitches and faults with the lights. The generaly public would not know Sky interior LEDs can trun green when they fail.
The translation of 1:43 - 1:56 is: "after, in the plane, light came on, green & white; after, I don't know, to make the plane takeoff more, what do they say, gave it race, something like that; it straight entered at speed, where, what was it'. To which the reporter responds, 'it was a hostel' at 1:57. Subjects: None |
appruser
June 16, 2025, 06:25:00 GMT permalink Post: 11903744 |
a slight more precise translation as a native speaker. \x93After take off it felt as if we were still in one place & not moving. Then the sound of the engines racing (common Indian term for revving of engines on bikes & cars with the clutch depressed) & then green & white lights came on in the cabin as we hit something.\x94 In my opinion the race sound he talking about sounds like engine surges if compared to race.
To break down the survivor's narrative into an interpretation, am including below a transliteration, direct translation, and the interpretation. The survivor is a very fast speaker, so had to slow the video down to 0.5x through X's settings menu on the video to capture everything he said. Video from 1:32 - 1:56 ------------------ Transliteration: ------------------ Takeoff ke baad, ek minute ke andar hee, jab takeoff hua naa, to suddenly paanch das second kaise lagaa jaise stuck ho gaya woh. Baad mein (sirf mere ko???) lagaa kuchch hua, baad mein plane mein light on ho gayee, green aur white. Baad mein woh pata nahin woh plane takeoff jyadaa karne ke liye woh race, (do?) bolte hain kya, race diya waisa kuchch, woh seedha (re?) .. speed mein hee ghus gaya, jahan woh, woh (l??), kya tha woh 1:57 Reporter: woh hostel thaa ek, hospital ka ------------------ As direct a translation as feasible without significant rewording or putting in my own perspective on his wording: ------------------ After takeoff, within one minute, when takeoff happened, then suddenly 5-10 seconds what I felt like it got stuck. After, (only to me???) it felt something happened. After, in the plane, light came on, green & white. After, I don't know, to make the plane takeoff more they race, what do they say, gave race, something like that, it straight (1/2 spoken word 'race'?) in speed got into, where, what, what was it Reporter: it was a hostel, of the hospital ------------------ Less literal translation, more intepretation: ------------------ After takeoff, within a minute, when takeoff occurred, then suddenly for 5-10 seconds it felt like it was stuck. After, it felt like something happened. After that, in the plane, a light came on, green & white. After, I don't know, to make the plane takeoff more they raced, what do they say - gave it race - something like that; it straight, with speed entered into, what was it - ------------------ Later on he describes the mechanics of his escape, and how he was able to get out through a broken door because there was some space on the outside on the ground floor where he landed, and on the opposite side there was a hostel wall that might have prevented others getting out. Hopefully this might be somewhat useful, even if to only lay to rest some of the theories based on mistranslations of what he said. It certainly helped me understand that the timeline here doesn't have enough information to line up his description of in-flight events with what's on the external videos. For example, using the cctv video for timing, his 5-10s lines up with the takeoff and climb from 00:18 to 00:27, and the "felt like it got stuck" part could correspond to 00:28-00:31 where the aircraft appears to 'stop climbing and float horizontally, very little descent' as compared to after 00:31 when it's visibly descending. The 'something happened' could be the RAT coming online (bang?) but we don't know because there isn't enough detail. Is the RAT even audible inside the cabin? And then the green & white light could be the ceiling light or the exit sign, we don't know, but there is definitely no flickering mentioned. The 'giving race' part is mystifying - see earlier discussion in the thread - was it changing pitch in the constant-speed RAT due to declining airspeed, something else, engines spooling up? we just don't have enough info here. When did they 'give race' within that 17s descent from 00:31 to 00:48 impact? If we knew that it might help, but that detail isn't there in his description; not surprising since it was a short descent. I think we have to wait for the data from the recorders, or another external video, or maybe even a video from the cabin if somebody was live-streaming to facebook/instagram/x etc. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All) |
appruser
June 16, 2025, 23:27:00 GMT permalink Post: 11903870 |
Reviewed audio again both at normal speed and slowed down, with the potential word 'brace' in mind. He's definitely using the word 'race', in my opinion.
Have a listen - he uses the english word 'race' at 1:48, it isn't a translation: Additionally, within context of "to make the plane takeoff more, they ____, what do they say - gave it ____ - something like that", the word 'race' is a much better fit than 'brace'. His hand gesture also appears to corroborate the takeoff intent. Subjects: None |
appruser
July 12, 2025, 01:28:00 GMT permalink Post: 11920070 |
Can someone with the engineering knowledge build a timeline/timeframe for fuel cutoff switch RUN to CUTOFF -> fuel stops -> engine flameout -> N2 drops to ? -> VFSGs quit -> RAT deployment starts -> RAT full power -> APU deployment start?
Does the RAT really start providing power in 4 seconds from the E2 fuel cutoff switch RUN -> CUTOFF? Timeline from AAIB and the public CCTV video: 08:08:33 v1 153 kts . 08:08:35 vr 155 kts . . . 08:08:39 Liftoff, A/G Air Mode, rotation at 00:18 in public CCTV video . . 08:08:42 E1 Fuel Cutoff Switch RUN -> CUTOFF, 180 kts 08:08:43 E2 Fuel Cutoff Switch RUN -> CUTOFF .............? N1 N2 begin to decrease .............? "Why did you cutoff", "I didn't" .............? Airport CCTV shows RAT .............? N2 < idle speed 08:08:47 RAT hydraulic power . 08:08:49 Public CCTV video: visible loss of thrust, Alt < 200ft using wingspan . . 08:08:52 E1 Fuel Cutoff Switch CUTOFF -> RUN, CCTV video: visible descent . 08:08:54 APU inlet door begins opening . 08:08:56 E2 Fuel Cutoff Switch CUTOFF -> RUN 08:09:05 MAYDAY 08:09:11 EAFR Recording stops 08:14:44 Crash Fire Tender leaves airport Last edited by appruser; 12th July 2025 at 01:29 . Reason: readability Subjects (links are to this post in the relevant subject page so that this post can be seen in context): AAIB (All) APU CCTV EAFR Fuel (All) Fuel Cutoff Fuel Cutoff Switches Hydraulic Failure (All) MAYDAY Pilot "Why did you cut off" Preliminary Report RAT (All) RAT (Deployment) RUN/CUTOFF Timeline (Preliminary Report) |
appruser
July 15, 2025, 16:59:00 GMT permalink Post: 11923087 |
Having read through most of the posts in this and the other threads, and the preliminary report a few times in parts, am mystified by this:
The Preliminary Report states: "The CCTV footage obtained from the airport showed Ram Air Turbine (RAT) getting deployed during the initial climb immediately after lift-off (fig. 15). No significant bird activity is observed in the vicinity of the flight path. The aircraft started to lose altitude before crossing the airport perimeter wall." Does this mean the RAT deployed "immediately after" in the sense of within 1 second after lift-off? We, as a group, certainly seem to be interpreting the "immediately thereafter" in a prior paragraph to mean that the E1 and E2 fuel cutoff switches went RUN -> CUTOFF within 1 second or so after max airspeed of 180kts at 08:08:42. The prior paragraph for quick ref: "The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec. The Engine N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cut off." Additionally, have to say, this PR has a few major weaknesses in it: - no timestamp for RAT deployment, though RAT hydraulic power coming online has one; also is it for initial power or rated power? - no timestamp for the pilot conversation about 'cutoff', though it is provided for the MAYDAY. - no timestamps for E1/E2 Fuel Cutoff Switches going from RUN -> CUTOFF, though they're provided for CUTOFF -> RUN. Last edited by T28B; 15th July 2025 at 17:15 . Reason: formatting errors fixed. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CCTV Fuel (All) Fuel Cutoff Fuel Cutoff Switches Hydraulic Failure (All) MAYDAY Preliminary Report RAT (All) RAT (Deployment) RUN/CUTOFF Timeline (Preliminary Report) |