Posts about: "Bird Strike" [Posts: 52 Pages: 3]

As discussed 40 pages earlier two possible root causes for simultaneous rollback or flameout without signatures of bird strike remain:
- Shutdown by crew
- Involuntary shutdown by aircraft’s control systems

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?

It seems pretty unlikely that a bird strike that took out both of those very big engines simultaneously would not have been fairly obvious in ways that nearby observers (e.g., the crew, ATC, airport personnel?) would have noticed. Possible, of course, but I don't think we've seen any evidence that points in that direction. Also, for what it's worth, the Times of London June 15 story " New clues point to engine failure for cause of Air India plane crash " cited here in the closed thread includes this:

A poster in the closed thread pointed out, properly I think, that the Times shouldn't be relied upon for presentation or interpretation of technical information. Like most general news organizations, their reporters and editors (mostly) just don't have the background to assess, filter and explain complex processes and technology. Unlike many, though, the Times can generally be relied upon to seek appropriate sources and report accurately what those sources say. I think it's very likely that Indian authorities have ruled out a bird strike, and I also think those authorities are competent to make that decision.

Pretty much what I was thinking. Maybe someone turned off the fuel switches, or a rare software glitch. Guys I have been working with have suggested fuel contamination which I have thought unlikely. Or maybe a structural failure upon wing loading that caused fuel lines to rupture.

Hopefully the route cause will be found, and I would not be surprised one bit if it is something totally left field that no one had considered, simple or complex.

On Jun 13th 2025 the DIRECTORATE GENERAL OF CIVIL AVIATION (DGCA) reported, that initial preliminary findings rule out a bird strike as no bird carcasses have been found.

Hardly surprising they have ruled out bird strikes.
Just take a look at the video of the Thomson 757 bird strike at Manchester, quite dramatic visual evidence from the affected engine, smoke and flames, none of which is observed in the IA accident video.

Agreed.
Also, I expect the airport would've sent a car out to check the runway for evidence. Since we agree that the engine failure occurred near rotation, and that rotation occured well inside the runway ( see e.g. fdr here , or the granular ADS-B data), that car would've encountered a bloody mess, and we'd all know about it by now.

The problem with these reports is that the Indian AAIB and DGCA websites ( aaib.gov.in www.dgca.gov.in ) are mute on the subject of this crash, so even the DGCA inspection mandate quoted above is shakily sourced. On Friday, AvHerald had already updated with "On Jun 13th 2025 the DGCA reported, that initial preliminary findings rule out a bird strike as no bird carcasses have been found." I searched for a source for this, and found an "exclusive" which read, "The initial probe report of the Ahmedabad Air India crash, accessed by CNN-News18, reveals key findings from the Directorate General of Civil Aviation\x92s assessment led by the director of security." Other media simply quoted News18. There are two reasons to be skeptical here:
\x95 first, we have seen fake reports circulating;
\x95 secondly, News18 rates badly on mediabiasfactcheck.com: "Launched in 2005, CNN-News18 (formerly CNN-IBN) is an English-language Indian news television channel based in India. We also rate them Questionable based on a poor fact-checking record with numerous false claims."
That leads me to consider that this "exclusive" might be sloppy reporting based on a fake\x97I have no way to know whether it is legitimate or not.

At this point, I feel we can only rely on information being official if it's published through an official website, or if there's independent reporting or a video clip from an official press briefing.

I do believe the accident was not caused by an animal strike, for many reasons.
But I wouldn't believe it based on unsourced reporting alone.

Thanks for straightening me out on that one. Strange though that bird strike theory was ruled out so quickly without examining the wreckage or hearing the CVR? And still, the video potentially shows an right engine surge on the runway. If not a bird strike, then for what reason? Maybe I'm just seeing things since no one else seems to see this so I'll leave it there.

The second box has been recovered and the CVR is being analyzed so hopefully they will give an interim update shortly.

As regards the pixelation in the take off image that you posted, I'd say that is certainly well spotted, but I think we all have to acknowledge that pixelation really denotes the absence' of information rather than it's presence. I would say that if this image were followed by indications of asymmetric thrust and an irregular take off and initial climb, it would tell us something, even in the absence of bird remains. But it didn't, and the aircraft took off with all appearing normal.

To me, the video shows that whatever happened to the aircraft was symmetrical in as far as it continued in an (almost) straight line. That said, it is entirely possible that however grainy the video evidence is, somewhere within it there may well be a significant - even if momentary - clue, so this was a good catch, even if not the smoking gun.

I don't find your experience with the Times overly surprising. Sloppy research and reporting makes its way into the best news publications, which is why I was careful to use the modifier "generally" in the post you quoted. Copying and pasting from Wiki without attribution is certainly egregious. Still, I feel comfortable with the assumption that the Times/Sunday Times does indeed generally follow good journalistic practices. I accept that the reporter(s) did speak with "Indian authorities" and that those authorities did tell the reporter(s) that a bird strike had been ruled out.

As I said, I'm also pretty confident that the Indian authorities are competent to determine whether there was a bird strike. It would be fair to ask whether I'd be confident in that if they told the reporters that there was a bird strike or that they hadn't ruled it out. I'd have to admit that I'd probably have some difficulty with that, given that I think it would be obvious to us , even with as little evidence we have so far, if birds had taken out those engines. But I hope I wouldn't be too sure that I'm right and they were wrong.

And yes, thanks for correcting those fuel levels. I'd want them to be right if I consulted that Wiki entry. I often use Wikipedia as a starting place, but I remember that it's an encyclopedia and if I have more than a passing interest in the material of an entry, I follow and assess the cited sources there before reaching any conclusions.

I think it's not a coincidence that tdracer's post was chosen to be the thread starter of part 2. I'll wait for the preliminary report to see it confirmed or disproved.

I read the whole threads, keeping my hands on the mousewheel so far since I'm not a pilot, just a EE / safety / systems engineer.
The hamsterwheel ist spinning a lot here, and of course it could be anything including some VHDL FPGA code line or a broken RAM cell in a cheap memory bar within the computer it was compiled with. Anything is possible, but to be honest: development processes, if followed, are usually pushing the probability to a level where it becomes pure theory. BOSCH uses FPGA+\xb5C on the brake control box of cars. They sold 100 millions of those, used 4000h each (car lifetime) without error, with less strict development process. Most errors are made on requirement level, not code.

Also, so far there is no evidence I've seen regarding the 'chicken-egg' problem, did the engines fall below idle (fuel, stall...) and this caused an electrical blackout (-> battery, RAT...) or did an EE problem cause the engines to reduce thrust (FADEC, SW bug...). And where is the common cause in all this?
There has to be a systematic error common to both engines, an external failure affecting both or a dependent fault with one affecting the other within seconds. This is the only thing I think everyone agrees here. And I refuse to beleave the external failure or dependent fault was sitting in the cockpit.
I think it is something not common to every aircraft type for the last 50 years.
So I started searching and found a candidate.

I read myself into the EE architecture of this unique 'bleed-less' design and it's megawatt powergrid since this is the part where I may be able to contribute (and I'm most curious about). Generators on the 787 are >250kW instead of <100kW each and there are two per engine instead of just one. In fact, they can go up to 516 kW and shear off the gearbox at >2200Nm (equal to >2 MW, per generator).
https://www.easa.europa.eu/en/downloads/7641/en (page 11)
So while on any other aircraft the generator is more like the dynamo on your bicycle, those generators are massive (x10).
The gearbox is connected to the HP shaft (N2) on the GEnx. I learned from Wikipedia that RR moved this gearbox to the IP shaft on the Trend 1000. And RR is happy that the A330neo Trend 7000 uses bleed air and less load on the gearbox, since this maintains stability on the HP shaft at light load (also Wikipedia).
Those generators are not in phase and frequency sync, or in other words: If you parallel them, they fight each other, it's like a short. They will almost block if this is not handled by the control box if possible (or some melting fuse blows at some point).
787 electrical system - variable frequency generators?
Somehow I find it hard to believe that they are not able to disturb the engines despite that everyone here so far is claiming that there is no way an electrical problem could influence them because FADEC has it's own supply. I read that one is sufficent to start the engine, usually both are used.
In my mind I find lot's of ways this could influence both engines simultanously. If just the BTBs on the 230V grid got some humidity (hot, no AC, water cooling...) and went up in one big arc (I think they made them semiconductor relays, too).
Could those gearboxes and engines handle 4500Nm / almost 5 MW on each HP shaft, applied within a fraction of a second without any problem?
Or if the engines were in a condition not far from compressor stall, one was stalling and 400kW load jumped from one engines generators to the other...
I did some rough estimation and one of the generators could push N2 below idle in a second or less without fuel just with its normal 250kW load (just inertia).
This is one point which is unique to this airplane model, so maybe worth a closer look.

I know that those engines are burning at >100MW at full power, but how fragile in the balance between compressor load and this one turbine stage on the HP shaft / N2, without the inertia of a 2.8 meter fan? This is just out of my background, any thermodynamic expert here?
Of course I also have no insight in SW and communication within the control boxes, how much they are talking to each other, delaying/ramping load redistribution etc. If FADEC recognizes a flameout, could it instantly command the generators to cut the load, even above idle rpm?

I would assume that some fuel contamination, valve blockade, even compressor stall would pop up slower. But such a generator could kick in within milliseconds.

As a safety guy I learned that one tends to look first at things one is familiar with (SW, HW, mechanics, pilot behaviour, maintainance, depending on one's profession) and in the end it's often the interface and dependent faults within which are not carefully considered (e.g. takeoff situation vs. thermodynamics vs. mechanics vs. power generation vs. humidity vs. generator control...) together with transient behaviour. It was the same with MCAS (safety culture vs. pilot training vs. SW design (repeated action) vs. single AOA input vs. bird strike probability close to ground vs. trim loading/blockade vs. stickshaker noise/distraction).
In fact, I was trying to find information on all those systems and directly found slides on how the engines and generators could be simulated and the power grid tested in a HIL (hardware in the loop) environment. My experience from automotive is that such simulated environments are often far from reality and HIL environment programming finished after the product is already at the customer. But of course its far easier and cheaper to apply and test faults there. But then, some programmer programms what he thinks the reaction of the engine would be.
This 'bleed-less' design was some massive change in airplane EE architecture with hugh consequences on the whole airplane design and extremely hard to fully analyze.

I'm just asking questions and hope that we all learn a lot and this was fully considered or just not an issue. It's just an aspect I found worth mentioning and not only spinning the wheel.

PS: I doubt it was TCMA. The air/ground decision is done in a different box, evaluating 5 inputs in a 1/3 and 1/2 decision according to this discussion. This is then safely sent to the FADEC (as one input) and combined with the thrust lever position and N2. But if the thrust lever position is sensed (redundant and direct) close to idle, you do not need TCMA or ground mode to expect reduced thrust.