Posts about: "CCTV" [Posts: 50 Pages: 3]

This discussion happened after Jeju. I note that one of the video sources here is actually leaked (camera-pointed-at-screen) airport CCTV. Do not mistake airport CCTV not being publicly available for it not existing.

We'd need to know the impedance/available fault current of the generators. 50x would be unusually high in an industrial setting.

VFDs are for frequency conversion to drive the motors (CAC/pumps/engine start). They won't be carrying the full generator load for galleys and anti-ice; that will be handled by cross-ties, which is a big black box on the 787.

Fast fuses can be faster acting than circuit breakers, but are one-shot. I'm not sure how fast-acting and effective the generator contactors/controllers are; conventional ACBs/MCCBs will blow open magnetically under sufficient fault current regardless of what the trip unit or close coil commands.

I wouldn't really expect electrical reconfiguration to happen on climbout, and I wouldn't expect it to be the first time this contactor gets used since maintenance - everything should get a good workout during sequential APU/engine starts.

Not designed to parallel, but you still need to switch each generator on/off buses and tie or separate buses.

In a very simple main-tie-main arrangement you can close any two of three breakers and still keep the sources separate. It gets much more complicated when you have ten different sources.

I suspect the 'large motor power centre' might parallel the rectified output of some generators.

The 787 flight controls remain almost entirely hydraulic except for stab trim and two spoiler pairs. The centre system is now electric- or RAT-only with no ADP backup. Left and Right systems are still driven by EDPs and will remain pressurised as long as there's fluid and the engines turn.

1.5MW is the figure for all six generators; only four can be used at once.

There's no indication they had any flight control issues.

Battery is essentially unused in normal operations other than to start the APU and keep the clocks running. It's there for emergencies (like after the engines fail). And yes, been discussed.

We're on the fourth day of this accident, and so far all that we - the public - have to go on is two grainy videos. I'm surprised that there haven't been more CCTV images and eye-witness accounts, especially in the middle of a city. I realise it was a very short flight, and didn't get high enough to be widely visible, but there seem to be a lot of buildings round there and it was early afternoon. Why so little information?

It appears that is not without risks...

The Ahmedabad Crime Branch issued a statement to say that Aryan's statement was recorded, and to clarify that no person was arrested for making the video, news agency PTI reported.
"He came with his father to give a statement as a witness. He was then sent away with his father. No arrests or detentions have been made," the police said.

why do they have to clarify that nobody was arrested?

https://www.hindustantimes.com/india...913615381.html

And then the buildings there are very close one to another, somebody on the street or lower floors would have no visual.

How long does it take for an engine to fail in terms of thrust output - what does thrust over time look like for various failure scenarios - e.g., no electrically powered fuel pumps, or contaminated fuel, or thrust set to idle or other issues?

The original mobile video (not the copy from someones phone screen) clearly sounds like a RAT but what does the engine itself sound like - is it idle or reduced in some way?

What is the minimum amount of thrust that would need to be lost to stop climbing and sink back down - it took 30 seconds from leaving the ground to impact from the CCTV and the first 15 was climbing.

I would look carefully at the fact that the PCU still has the technical ability to tell all AC generator control units to turn off via software, as proven in the documented and fixed 248-day software issue.

A later comment cast doubt on the glide ratio. But flying below wingspan altitude, which it was, will extend glide range because of the ground effect. Plus the descent glide range may have started later than the airport boundary. It seems plausible that the glide range is compatible with total and rapid loss of thrust.

Thanks as always TDR for your excellent professional input. It is therefore so much more perplexing that even you cant logic our way out of this impasse. That is, the assumption that the aircraft experienced a double engine failure (supported by a reasonably convincing argument that the RAT deployed), and yet no plausible reason (that we can see) for such an event. So some then collectively slip into the tired and lazy theories of intentional or unintentional crew actions that 1. beggar belief (intentional), 2. defy physics (flaps instead of gear despite clear evidence to the contrary) and call into question the professionalism of a very experienced Captain and crew as well as the aircraft manufacturer (because...well its Boeing so it must be software ).

Yet, the answer must be simpler and staring us in the face since logic and experience (everything you have offered TDR), tell us that modern airliner engines generally do not just suddenly quit flying at the same time. In this regard we can recall several instances of double engine failure associated with bird strikes generally involving large birds or large flocks or both. But it seems we have discounted this theory very early in discussion. Why? Because we cant see any birds, or flocks of birds or engine flames/surges or puffs of smokes from the engines which would support this. Really?

I have read all the 100's of posts (sadly) and while some very early posters tried to analyze the imagery, I suspect the very poor quality eventually discouraged most from seeing anything of interest. However, smattered throughout this discussion from the beginning to the end there have about four posts that describe seeing something where others have not. At least two of these were related to possible smoke but which were probably just the dust blown outwards by the wingtip vortices. Two others however have mentioned possible flames and puffs of smoke.

The video of course is very poor. There should be a special place in hell for people who subject us to looking at a video with continuous zooming in and out, inability to retain focus on the subject (it was just a CCTV monitor, not the actual aircraft they had to focus on) and constant camera shake. A video of a video, and then the resolution probably reduced for social media upload. This all results in a very unwatchable record of the aircrafts departure. The only immediate information gleaned seems to be some idea of how far down the runway the aircraft was at takeoff and the parabolic curve as it very clearly described the aircrafts flight path.




Air India Flight 171 on departure
But take a look at this frame. The right engine shows an artifact (pixelation if you like) that might represent a surge flame. I can almost see a puff of smoke just inboard of the aileron that may be associated with that too.

Am I just seeing distortion? Am I just seeing some smoke because that's where I would expect to see it?
We are all very used to seeing everything in 4K today but back in the day when everything was low res we used to join the dots. If pixels existed then something was there. If they didn't, it wasn't.
So if it's just pixels caused by distortion then they have coincidentally appeared in the tailpipe of an aircraft that crashed shortly after takeoff with a presumed double engine failure.

But surely we would see the birds? Well, not in this video. You cant even see the registration number on the side of the aircraft and that is much bigger than a bird. Haze, distortion, focus and low res, and each individual bird wouldn't even make up a pixel.

So make of this what you will, but this problem may have started on the ground. Birds strikes are very common according to Some AI pilots who interviewed for this following article but I have no idea of the authenticity of this report:

https://www.rediff.com/news/report/a...h/20250613.htm "The Air India pilots also added that Ahmedabad airport has long been known for bird activity near the runway, which could have contributed to the incident.

"This issue (of the excessive presence of birds) has been flagged multiple times," a third Air India pilot said, asking not to be named."
Of course, a single engine failure would not have brought this aircraft down, nor would it have deployed the RAT, but we can't see what happened on the left engine when the aircraft slipped behind the radio antenna building.

While these high bypass engines are designed and certified to keep running after experiencing certain types of bird strike, the effect on two engines concerns have been voiced about the contribution of certification to the mitigation of the risk hazardous bird strike in the two engine case.

This from Sky Library:
https://skybrary.aero/articles/aircr...nue%20to%20fly .

" A number of concerns have been quite widely voiced about the contribution of certification to the mitigation of the risk of hazardous bird strikes:

• The case of bird ingestion into more than one engine at the same time is not addressed directly and it is clearly extremely difficult to meaningfully estimate the probability of such an occurrence. However, it has been observed that, since some of the current standards only require that a damaged engine can be safely shut down, this circumstance should be more fully considered when determining the acceptable outcome of ingestion into single engines, especially for the twin engine case.
• It has been noted that the potential effects of bird strikes on modern electronic flight control systems and flight deck instrument displays have not yet been fully assessed.

Maybe someone can do some video enhancing of this image as others have done with the audio enhancement to give strong probability of RAT deployment.

If my suggestion can be corroborated at all, then the question of what happened next becomes somewhat easier to answer. Perhaps neither engine stopped running but they did so with limited thrust? If anything from the pilots mayday call can believed, it wasn't engines shut down..it was no thrust. So why did the RAT deploy? Cant answer that. And, I cant imagine it would be manually deployed if both engines were still running.
However, TDR did say.

"On the 767 and 747-400, when you shutdown an engine and the IDG goes offline, there is a momentary 'glitch' in the electrical power system as it reconfigures for the available power source - this is why you see the flight deck displays flicker and return, and the cabin lights momentarily flicker."

Startle factor that electrically systems were about to fail? Manually deploy RAT?

Edit: I might add, they would have found remains on the runway if this did indeed happen. But we have heard anything from anybody?

625 feet is straight from ADS-B data, which is just pressure altitude using sea-level STP. I don't know if it has been mentioned in this thread yet but in the other thread it was pointed out several times that this would have come out to ~100ft in true altitude AGL. The mathematics of that checks out to me (QNH 1001, temperature 37\xb0C, and field elevation of 189 feet).

The aircraft also visibly never gets much more than roughly its own wingspan above the ground in CCTV footage, at least to my eyes.

News articles tend to be fairly unreliable sources of info as far as parameters like altitude go in my experience.

Could you please elaborate on that?

FR24 did do that raw ADS-B data comparison. Remember the GPS position and barometric altitude are sent by the aircraft itself. The altitude is sent in 25 ft intervals, so a shallow curve that is smooth in reality looks janky in the data, due to the rounding of the numbers. From https://www.flightradar24.com/blog/f...rom-ahmedabad/ :
The red line is the accident flight, and it covers approximately 4.3 seconds.
Obviously the altitudes are all uncorrected for barometric pressure, which would've varied with the weather on that day; you kind of have to mentally shift the lines vertically downward. Now I looked for, but couldn't find, the post in the old thread where the rotation was triangulated\xb9, but I remember that it was near the turnoff to the high-speed taxiway, so a few seconds ahead of this ADS-B capture. We only have the video to show us what occurred then.

That means the ADS-B data doesn't really tell us whether the first few seconds of the climb were normal or not.

When we compare the red line to the blue lines, the data tells us the climb rate had already decayed significantly before the accident aircraft passed over the end of the runway, because the red flight path is much more shallow than the blue flight paths.

Please correct me if I'm wrong: to my eye, the data alone does not show that the engines must have failed after rotation, because the data does not demonstrate a normal climb rate.

But likewise, the engines can't have failed much before rotation:
For completeness' sake: you can look at the CCTV video, consider the 787's wingspan a flying 200 ft yardstick, and hopefully agree that the aircraft did not get much higher than 200 ft AAL, if that.

-----
\xb9 I found one of them, anyway. The reference is the CCTV video:

I'd like to stick my neck out and say what I think I know. And I do mean "know", not what I think "likely" or "possible".

1. The aircraft reached an altitude AGL rather more than one wingspan. This can be clearly seen in the still from the CCTV video posted by Cape Bloggs on 2025-06-18 at 0401. The 787-8 wingspan is 197+ ft. So it got at least 200 feet up in the air. (Info from CCTV screen shot.)

2. (a) Ground effect on lift essentially disappears on TO when the wheels are at screen height. (Info from an eminent colleague who performed the analysis.) I believe it follows that (b) he didn't get up to 200 ft by performing a zoom climb on unstick. It further follows that (c) there must have been some initially adequate lift out of GE to establish for a few seconds positive RoC.

3. The FR24 graphic posted by Musician shows that the aircraft became initially airborne "as usual", compared with other TO profiles. (Info from FR24.)

4. The aircraft lacked adequate thrust even to maintain altitude shortly after unstick.

5. Flaps 5 is minimal for TO. If you don't set it, you are told very clearly that you are misconfigured, well before TO roll. (Info from others.)

6. At Flaps 5 and likely loading (fuel, PAX, token sum for baggage) and in the atmospheric conditions pertaining, there is more than enough nominal thrust available to establish positive RoC. That obviously also holds for Flaps-more-than-5. (Info from others.)

I am not au fait with audio spectral analysis so, unlike some others here, including some whose views and experience I value highly, I am agnostic at this point about the RAT. (This is neither to deprecate those who performed this analysis, nor the views of those who know more about practical spectral analysis than I do and are convinced by it.)

Now for my personal inference so far from this.
Items 2 and 3 above suggest to me that the aircraft was adequately configured to conduct a normal TO and initially establish positive RoC for a second or two.
For me, the big question is: why wasn't there adequate thrust to maintain that? (We've been talking about those possibilities for some days now - I won't attempt to summarise.)

PBL

I have to agree with you PBL . It is amazing that people are still arguing about the height the aircraft reached during the first 11s of the flight. It is almost measurable to the metre from the aircraft wingspan on the video. Do not mistake the power required to reach Vr within in the TORA with the power required to maintain a stable climb at V2 to V2+10 in the second and third segments. They are very different numbers, that's why Perf A is one of the dark arts of aviation! It is quite probable that this aircraft rotated below a suitable Vr speed for the weight and ambient conditions and was unable to establish a stable climb due lack of applied power. Big engines take time to spool up, your immediate future depends on how late you recognise the situation and go for TOGA.

But you ask..... How can an aircraft possibly get airborne with a stalled wing? Look at Air France 7775 . At rotate the wing was already stalled (albeit for different reasons) but the airborne profile of the aircraft was rather similar to Air India.

Non-aviation engineer here: I have a question about the low level altitude capture theory that I've been a bit hesitant to ask, since no-one else seemed to be bringing it up.

My understanding of altitude capture is that the autopilot will automatically adjust both thrust and pitch to intercept the requested altitude. However to my eyes there is very little pitch adjustment in the CCTV video of the plane taken from behind, until the very end of the video when it pitches up somewhat (obscured by buildings, more visible in the smartphone video). Please correct me if I'm wrong but I'd have thought that if the autopilot was trying to capture a very low altitude it would start pitching down (quite noticeably!) to do so, not remain at what looks like 10+ degrees nose-up. I honestly struggle to reconcile what I'm looking at in the video with an attempt to level off at 0ft, 200ft, or any of the other mentioned low-level altitudes.

Also maybe I'm missing something 787-specific but generally doesn't the autopilot have to be activated for the aircraft to automatically attempt to capture the pre-selected altitude? That was the case in this incident involving a Dash 8 and a target altitude of 0 feet that I am reading about ( https://www.gov.uk/aaib-reports/aaib...-dash-8-g-ecoe ). I'd have thought the PF would still be hand-flying the departure at the point that things went wrong, considering that the gear hadn't even been retracted yet...

The autopilot would not have been in and the pilot would have been hand flying maintaining the takeoff attitude. The flight director might have commanded a level off which obviously would not have been followed.

Minimum autopilot engagement altitude is 200\x92 for the 78 (from others on the forum). It\x92s 400\x92 AGL on the 777.

My interest is in how the auto throttles would have behaved in such a situation\x97where VNAV would not be engaged yet and the automatics gone into SPD/ALT. ; would they have pulled off thrust assuming a level off and then come back in to maintain bug speed (perhaps confusing the crew in the process ?).

That\x92s a very good question, and clearly one that those postulating the theory haven\x92t thought about either.

No, it's not. You got that value from ADS-B, which is barometric altitude at standard pressure, and when you correct for that, the highest value is ~100 ft. AAL.

Instead, look at the CCTV video, and consider that the wing span of the aircraft is ~200 ft. I hope you'll agree AI171 didn't come close to 400 ft. AAL at any point.

Reported 625' pressure altitude, elevation 189', QNH 1001.

So they only got to around 100' height, half the wing span of a Boeing 787? I think it looks higher than that.

189' elevation, QNH1001, the pressure altitude should be around 550'. First readout from ADS-B is 575', highest is 625'. I did not look up if runway departure end is much different there than aerodrome elevation.

Interesting that the readout of pressure altitude doesn't get lower again, after 625', which could support the total loss of all AC (and most DC power?). Transponder possibly stopped working, but one of the pilots was able to transmit a mayday call. So they must have had some kind of electricity available.

So what I mentioned about THR REF / VNAV SPD is probably not applicable. Yes, I did not account for the QNH initially, which makes closer to 100' than 400' AGL.

I will revert to await the official findings then, with a substantial loss of electricity seeming more and more plausible.

slf/ppl here - with a respectable amount of experience in software delivery for real-time/embedded/safety critical systems. Software development in this area really is an engineering discipline and bears no resemblance to common practice in other areas. Couple that with the requirements for function duplication/triplication, harness separation et al then IMHO the chances of FADEC etc software errors are effectively zero.


I'm commenting to make that point but also to link the videos and the FR-24 dataset - (below with my deltas for height/time added)



Extract from FR24 csv dataset


As noted in both threads to date everything was normal until it wasn't - the two values for fpm above are subject to FR24 variance of +/- 25' so even these suggest a normal climb at this stage of flight ca 2,000fpm. FR24 Lat/Longs all follow the centre line.


On this data the climb stops at around 70' AGL and electrical failure around 2s later. Again, as noted in the threads, this aligns with when gear up might have been expected. If the climb stopped because of fuel shutoff then 2s for spool down to electrical failure isn't out of the question.


Looking at the two videos.

The CCTV video indicates a total flight time, from rotation, of about 32s, subjectively levelling off ~14s after rotation.

The rooftop video has a flight time ~14s suggesting the video starts ~18s after rotation.


The rooftop video evidences the RAT as deployed from the beginning - meaning it must have been deployed by at least 16s after rotation - which aligns with the ADS-B indicated electrical failure.


If the forward flight recorder really is being sent to the US for recovery then it's reasonable to assume that the rear recorder contains nothing after the electrical failure and they are hoping the forward recorder captured something from the cockpit in the final 16s.


I don't have any experience of flight deck CRM but I don't see how those timings allow problem identification/misidentification and subsequent action - ie it wasn't down to the crew.


However:

The maximum aircraft height in the CCTV video, as judged by wingspan, appears higher than 71' - though it is certainly less than a wingspan height at the beginning of the rooftop video.


I haven't seen, in the threads, any statement of what happens on the flight deck with a total electrical failure - is it a 4s blackout whilst the RAT deploys and systems restart? - or are there batteries that keep something alive?

The Indian Express is carrying a story ( https://indianexpress.com/article/ci...lues-10077117/ ) that includes the following:"Investigators probing the June 12 crash of Air India flight AI-171 from Ahmedabad to London Gatwick are taking a close look at a February 2020 incident in Gatwick, involving an Airbus A321, in which both engines malfunctioned immediately after takeoff. It led to a Mayday call before the aircraft returned to Gatwick 11 minutes later after a turnaround." ...

..."it was \x93clear from visual observation and wreckage\x94 that the flight suffered a power failure." ...

..."The black boxes and the DVR have been recovered but the officer said that the devices were damaged and file extraction would \x93be a complicated process\x94." ...

... "We will check the technical logs to see if any of the engineering teams or pilots of the previous flight left comments on the performance of both engines"
Assuming there is some credence to the article, dual engine failure due to water contamination is the leading theory. It certainly fits much of the speculation in this thread. It may be that the flight data was not captured and much more reliance will be on forensic examination of the CCTV footage and the wreckage. Those waiting for the flight data to be published may be disappointed.

If the original CCTV footage was made available, together with a detailed survey map of the airport, it will be possible to accurately estimate the takeoff speed and altitude during all the critical periods. My guess is thrust was reduced or lost very early and perhaps before the aircraft left the tarmac. Then shortly after becoming airborne, power was lost resulting in the deployment of the RAT. It is doubtful that the pilots shut down the engines or the wrong engine. Likewise flap/slat misconfiguration is unlikely.

There you go, that’s the tell I expect. Someone sloshing chemicals around and it was finally been noticed in the paperwork somewhere and then they start checking the accident records or vv

https://www.gov.uk/aaib-reports/airc...-february-2020

I have read through all the first thread and much of the second before commenting; SLF here, albeit with a lot of flights in a lot of commercial, emergency and non-commercial aircraft but with a relevant background and expertise in collision reconstruction and looking for holes in Swiss Cheese.

The evidence is overwhelming that both engines lost power, and substantial that they were cut simultaneously. There is one matter that I have not seen adequately explored here, and that is the Christmas Tree hypothesis, where a plane not in use is used as a stock of spare parts, which then have to be replaced if it is then called for service.

One of the engineering experts has noted that a specific engine control circuit board must be powered down every 51 days or can cause problems, and even more so at 249 days when it has the capacity to cut both engines simultaneously. As the same expert pointed out, there are very few single points of failure in an aircraft - but this would seem to be one of them and accordingly should receive significant scrutiny. Is it possible, that on a parked aircraft, this item could have remained powered, silently ticking off the days? It then returns to service and the counter overflows at an extraordinarily unfortunate moment causing catastrophe? This is the way statistics works.

I ran over a very small rock yesterday in a car with reinforced tyre walls on the wheels. I thought nothing of it until the tyre pressure warning lit - and the tyre was indeed losing air. I have checked the CCTV (dashcam) and inspected the wheel. It was clear that I had touched the stone in the one place where it had compressed the tyre against the rim and cut the sidewall. That car has travelled 207,000km in my hands. The rock was about 5cm in diameter. The chances of that I would hit a rock that size at that moment in that precise way to destroy my tyre were over 4 billion to one. But it did.

I'd agree, without expert knowledge there would have to be big assumptions, but I expect that Aircraft Flight Engineers could do it. Probably already have.

Sure, actual data is usually more accurate than eyeballed stuff. But not always. In fact, it's often the eye that determines that something measured or calculated is "Off". How accurate is ADS-B data? I've seen FR24 tracks go way off course then suddenly get corrected / interpolated, frequently. The erroneous data seems to be "removed" by their algorithm, but where are the errors arising? Why this inaccuracy, and therefore, how accurate are the datagrams referred to? I know there were no datagrams received during the backtrack that I accept actually occurred, but that's completely different from receiving erroneous ADS-B data.

Sure, the CCTV footage I've seen is very poor, a video, moved about and zoomed, of the CCTV screen. Not easy to judge, but still useful and could be analysed frame-by-frame to compensate for all the extraneous input. Anyway, it's obvious to me that the rate of climb dropped abruptly just before the flight attained its apex, as if thrust was suddenly cut off. Knowing the momentum to altitude conversion, it might be possible to estimate whether that's true or not. The evident RAT deployment supports engine shutdown, not just engines to Idle, doesn't it? In that case, it would be useful to know at what altitude the engine shutdown took place.

Okay, didn't know that, I guess suggests means it's uncertain? Can you tell me from what height to what height it suggests this?

And why all the wrong figures for the height attained, quoted in previous thread? Can't all be the atmospheric conditions.

Haha! Even a stone (the right shape) can do that, and I'm not disputing that kinetic energy can be converted to altitude. Wings are useful for that... Just curious to get an idea of how much in this case.

To be honest, i believe that taking a lot of the evidence into consideration, it is possible to arrive at a limited number of scenarios for what is most likely to have happened.

One fact that alters things substantially is whether the survivor's impression is correct that possibly the engines started to spool up again just before impact. If that's the case then what does that do to the possibility or otherwise that the TMCA system caused a dual engine shutdown?

To me, since the world seems to be watching this forum, and we are getting no feedback from the authorities, what is posted here might be useful in helping the investigators look at things they might not have considered. Besides, as Icarus2001 has kindof suggested, it's probably a very good thing that there are clearly lots of keen eyes on this.