Posts by user "appruser" [Posts: 29 Total up-votes: 0 Pages: 2]

Yes, this is the odd part - from the videos it didn't look like there was any attempt to put the nose down for best glide, and even the pitch up (if presumably from fear) was not very pronounced. It basically came down in the same attitude as during the takeoff. That has me wondering if they even had any controls at all. Very low probability, true, but then both engines out is also a low probability event. 'RAT Push and hold 1 second' seems to be a dual-engine fail memory item on a 787, so both engines out would explain the loss of thrust and the RAT deployment.

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.

Nose down would be to get best glide - longest time in the air and max distance. Raising the nose up leads to a stall and brings the aircraft down faster than best glide. It's counter-intuitive, hence the tendency to pull the nose up in a stall or loss of power has to be trained out of pilots.

Thank you, and to HI288 too! this combined with the FR24 blog post about adsb loss just over the runway threshold, and the latest DGCA ask for Air India 787 maintenance adds more weight to the theory, IMO, that there was a major technical issue in play here.

Neurotypically an error in an automatic action will occur when the routine that encompasses that action is changed. Hence babies being left in back seats of cars, and probably a factor for the sterile flight deck rule. Any reason to think that might have been in play here?

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.

As it turns out, the survivor just says that the light came on, green & white. No mention of flickering by him. Looks like a translation issue. Am not allowed to post the url yet; the interview is on X, DDNewslive.

So I called a 787 Captain to ask him about this - in dual-engine fail, at 200ft or below, 170kts, flaps 5, does the PF push the nose down for best glide, do nothing, or push nose up in transition to flare?

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.

Thank you! the DDNewslive interview is posted on X, and seems to be mistranslated by most of the news agencies - no mention of "thrust" by the survivor, and he doesn't mention flickering lights either, just that a green & white light came on.

I think someone posted a green & white exit sign in the 787 cabin earlier in the thread.

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).

Thank you for the correction.

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?

Have been thinking about this a bit in this thread. First I thought it might be the APU spooling up, but apparently the APU isn't very audible in seat 11A - good 787 sound insulation. Cabin Air Compressors are not started either if power loss induces APU start, so that might not be it either. Since his sequence doesn't give a good idea of when, is the RAT a potential source of this noise? would it be audible in the cabin? Apparently the RAT is variable pitch constant speed, so as the aircraft speed decayed from 170kt to 120kt, would it become louder as the RAT prop pitch adjusted to the lower airspeed?

It's a great question!

IMO

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.

"Flickering" is a mistranslation that's made its way around the world's news services. He said 'light came on, green & white'.


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.

May I make a friendly suggestion - might be best to avoid putting in our own interpretations/perspectives of what he said - for example, he doesn't mention "sound" anywhere - we would interpret 'sound' based on experience, but that isn't quite what he said - he only used the word 'race' (a.k.a 'revved' elsewhere). Another example would be interpreting that he said "we were still in one place & not moving" - what he really said was that it felt like they were "stuck" - his word, nothing about movement or standing still or one place. A third one would be 'green & white lights came on in the cabin as we hit something' makes those two events very close together or simultaneous, when his narrative doesn't actually do that, just that they hit something in the end, and before that they 'gave race', and before that a green & white light came on.

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.

IMO, I don't know if that is trustworthy - the FR24 ADSB data seems to show that the aircraft was at 21ft AGL between the 1500ft and 2000ft markers from the end of the runway.

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.

"Flickering" is a mistranslation that's made its way around the world's news services. He said 'light came on, green & white'.


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.

May I make a friendly suggestion - might be best to avoid putting in our own interpretations/perspectives of what he said - for example, he doesn't mention "sound" anywhere - we would interpret 'sound' based on experience, but that isn't quite what he said - he only used the word 'race' (a.k.a 'revved' elsewhere). Another example would be interpreting that he said "we were still in one place & not moving" - what he really said was that it felt like they were "stuck" - his word, nothing about movement or standing still or one place. A third one would be 'green & white lights came on in the cabin as we hit something' makes those two events very close together or simultaneous, when his narrative doesn't actually do that, just that they hit something in the end, and before that they 'gave race', and before that a green & white light came on.

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.

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.

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

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.