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It might appear from this photo that the APU intake flap is in the \x91not closed\x92 position and generally not damaged.
The APU will automatically start in flight , irrespective of SW position, if 3 or more engine VFSGs are lost.

Subjects APU

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Quote:

Originally Posted by Fifthleg

It might appear from this photo that the APU intake flap is in the \x91not closed\x92 position and generally not damaged.
The APU will automatically start in flight , irrespective of SW position, if 3 or more engine VFSGs are lost.

Good spot, but it is possible the actuator that operates the door is damaged.
Unlikely, but possible.
This does add more credance to the complete power loss scenario.

Subjects APU

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Quote:

Originally Posted by HumbleDeer

The B787 is a way way different and much more complex and sophisticated plane than your Gulfie. The B787's two outermost (left & right) hydraulic systems are primarily driven by the engines, mechanically driving the hydraulic pumps. The center hydraulics are primarily electrically driven, and power the main flight controls. The left and right ones power the main flight controls as well, some of the less important flight control surfaces like spoilers and thrust reversers -- pardon me for not having the exact list of things. They also have a backup/supplementary electric pump each. Each of the two main engines has redundancy for the power plant a.k.a. VFSG (and motor-driven pump?) in its own right as well. All three hydraulic systems work together in a redundant fashion when it comes to the primary flight controls. The RAT can provide both electrical and mechanical sources of hydraulic support, if I'm not mistaken. The flight instrument and information systems can also be powered from two backup batteries, the APU power plant itself, and/or the RAT.

Thanks for the response. We have a Flight Test group text going about this mishap and I\x92m going to share it. We\x92ll never match the Boeing in complexity, but we\x92re getting there in capability with active matrix side sticks, touchscreens, synthetic vision, 3-D radars and a Mach 0.90 normal cruise. We completed our most recent flight from Tokyo/Haneda to our Savannah, Georgia home plate in 10 hours 38 minutes starting at 41,000 feet and finishing at 51,000 feet.

Subjects APU  Hydraulic Failure (All)  RAT (All)  RAT (Electrical)

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Quote:

Originally Posted by krismiler

Does the B787 have auto flap retract ?

Yes, but it is only designed to retract them in to the Flap 5 position which is the first stage of TE flaps. BTW you will note from the image that F5 is a barely perceptible, hence this likely flap red herring.

Subjects: None

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Quote:

Originally Posted by FullWings

This is consistent with a loss of electrical power causing a loss of hydraulic pressure

Only on the electrically-powered centre system (which does gear and flaps). Left and right have engine-driven pumps which will provide plenty of power for flight controls provided the engines remain above maybe 30-40% N2.

(I screwed up earlier and had a 767 image here...)

Quote:

Taken together, it seems that there was an event (or events) shortly after rotation that compromised both engines and the electrical system.

Compromising both engines inherently compromises the electrical system: dropping below idle N2 (plus some safety margin) disconnects generators.

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Last edited by Someone Somewhere; 14th June 2025 at 18:57 .

Subjects Generators/Alternators  Hydraulic Failure (All)

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X - Formerly Twitter

I’m not a 787 driver so for fear of looking dumb in front of those that are this still confuses me. Even IF they’ve mis-selected the flap setting (I still don’t think it’s been cemented on here that there is in fact a FMS/flap setting disagreement warning but i believe there is), had the wrong de-rated take off settings, selected flaps instead of gear up the 787 with massive high bypass engines, FBW and full envelope protections surely cannot let itself be put in such a low energy/high alpha regime as we saw in the videos IF it has both fans functioning normally, surely?

the pilots may have messed up royally and numerous times so those holes lined up but the plane is the final block in the chain and a 21st century all digital entirely clean sheet design was sold as being immune to such catastrophic outcomes from a few minor (consequential yes) and fairly common errors- aren’t all the protections and our procedures designed after decades of mistakes?

im having a hard time squaring how a fully functioning modern bird like this could allow for this outcome and almost whatever the pilots did outside of unbelievable inputs and the pilots are are a bit of a red herring IMO

Quote:

Dale Winsley
@Winsleydale
No. The LE slats are deployed therefore the flaps are as well. This is an automatic linkage. The flaps are set at Take-Off. Hard to see from the angle but they are...if slats are out (easy to see) then flaps are set. Looks like Flaps 5. Also, the 787 has the highest Thrust-to-Weight ratio of any airliner on Earth. The change in Alpha and lift is a trifling matter for it, at these settings (1-5). It will fly out of it easily, even at that density altitude. The attitude change is - in the circumstances I describe, consistent with a massive power loss (both sides). I believe based on probability that simultaneous mechanical failure is not the cause. Fuel contamination or starvation is likewise unlikely based on the 787 fuel system. The common element is the FADEC/Autothrottle/TOGO. However, each engine FADEC is dual redundant two channels. So any such common failure must happen further upstream. From a design perspective, that would be unthinkable. But this is Boeing. Given what I can see with my own eyes, I believe the flap issue is a non-starter. Also, re the landing gear: Clearly the Positive Rate challenge would be met based on normal rotation and fly-off at V2. But since we know the flaps were set correctly, that rules out an "oopsie" moment. Just as likely there was at the challenge moment an indication that something was amiss, and the Gear Up call was not made. They see both N1s unwinding and it takes a second to get past the WFT factor. They cross-check and see the airspeed also unwinding. Then they unload the Alpha and pitch to gear down Vy. And they had another 6 seconds. Whatever it was, it was not a flap, mechanical or fuel issue. We will know soon enough. But this is Boeing. My gut says "software". All 787s worldwide need to be grounded, now.
6:10 AM \xb7 Jun 14, 2025
\xb7
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Last edited by Senior Pilot; 14th June 2025 at 10:04 . Reason: Add X quote

Subjects FADEC  FBW  Fuel (All)  V2

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Jonty; "I can’t see a RAT hanging out." (Sorry Jonty for some reason I can't direct-Quote other people in my reply to posts)


It's difficult to see at the best of times - check this high-res pic of an un-connected Air France 787 with RAT deployed.
The video compression and zoom going on with the accident aircraft footage would likely lose the RAT detail - look at the windows - just a suggestion of them - so until a better video emerges it's impossible to say.

Subjects RAT (All)  RAT (Deployment)

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I hesitate to chip in in these accident threads. Keep them clean. However, as as a few comments above brushes my audio expertise, I will comment.

A very simple audio analysis give me this:
The 3 segments horisontally, are of different videos of B787s passing overhead/landing. The vertical drop you see is the doppler effect.
In other words, these are spectrograms over time which makes these distinctions easier than a simple static spectrogram.
1. B787 landing with RAT extended.
2.Air india crash
3. B787 landing without RAT


It's a 5 minute laptop job, and it would look much prettier and clearer if I spent some time with it, (Gain to color match, and spectrally match to compensate for microphone placement and type),
but it is 85% conclusive even when done as simple as this IMO.
(I do have legal forensic audio experience)
The RAT was out judging from the audio evidence. You can see the the equally spaced overtones of the propelller match when passing overhead resulting in the Doppler effect, the difference in length of the doppler is caused by distance and the slightly varying frequencies shown in the starting point is caused by a difference in speed. But the harmonic content match.
In the 3rd segment you see none of these overtones at all.

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Last edited by Kraftstoffvondesibel; 14th June 2025 at 13:02 .

Subjects RAT (All)  RAT (Deployment)

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There has been much discussion here about RAT deployment. Various claims either way have been made, based on individual perspectives of available video and audio.

I am very mindful of just how awful a tragedy this is, and have significant misgivings about disproportionate interest in others misfortune where it carries no purpose, but also recognise that for some people knowing and learning what happened ASAP could be very important, particularly given the present circumstances.

Thus while I sincerely hope that early detail from investigators will give some clarity, in an effort to reduce needless speculation regarding RAT deployment I have taken:

(1) an audio sample from the video of AI171 passing by in which people claim to hear a RAT
(2) an audio sample from a 787 video with RAT deployed on test by Boeing
(3) an audio sample from a JAL 787 video with RAT deployed

And passed these through a FFT in order to gain a more quantitative view of the noise spectra from each event.

A spectrogram of the results is presented below. I hesitate to make any conclusions per se, but observe that there are similarities as well as divergences between them. In all three samples there is a relatively consistent signal roughly centered in the range 113-146Hz that could be what gives the characteristic 'buzz' sound of (apparently) a RAT in operation.

JAL ~141Hz
Test ~146Hz
AI171 ~113-134Hz (prob doppler variation here)


Spectral comparison AI171, B787 with RAT, JAL 787 with RAT



Spectral comparison #2 AI171, B787 with RAT, JAL 787 with RAT


These frequencies seem consistent(ish) with what I got from this video [[url]https://www.youtube.com/watch?v=O1r3CuRwjPc] in which a 787 RAT is being tested - albeit in this case the blades are hydraulically powered and not driven as a turbine. This test showed a fundamental frequency of 135Hz with relevant harmonics above (the second harmonic at 270Hz is higher SPL, no weighting):




It's important to note that the initial recordings are necessarily different; these are not controlled conditions, the recording equipment is probably quite diverse and almost certainly not ideal, and the environmental conditions will also be different. Moreover all of these audio samples have come from video files referenced here, one has no way of determining the provenance or veracity of these sources and, crucially, I have no prior experience of analysing/extracting RAT acoustic fingerprints (nor have I sampled 'control' audio of a 787 passing by /without/ RAT!).

Additionally it's been quite a long time since I did any work with [turbine] noise so given these and other variables I'm not prepared to make any declarations per se, but perhaps more knowledgeable people could. That said, my feeling from what I see is that RAT deployment is not dis proven, and that the apparent fundamental frequency difference between the samples may be explainable by - amongst other things - difference in a/c airspeed, bearing in mind that AI171 was on TO, the others were landing.

Ultimately what I've done here is extremely rudimentary and while it would be possible to go into much more depth I'd hope that more definitive answer would be forthcoming by then, however if anyone wants to discuss specific methodology etc off-line please PM, no wish to add to noise on this thread.

FP.

Subjects AI171  RAT (All)  RAT (Deployment)

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Quote:

Originally Posted by MR8

Even though there is no point speculating about the cause of this accident, it is the nature of the beast to have questions. As pilots (most of us at least), we do have an inquiring mindset.

My initial thoughts were an inadvertent flap retraction. But with the ‘evidence’ that has been presented over the last 48 hours, I think we can safely discard that option.

What we think we know is:
- RAT was deployed (highly possible)
- Gear was selected up, but did not operate (bogey tilted, doors remained closed)
- APU was ‘on’ (APU door open on after crash pictures)
- Flight path

Any of these observations, alone, would mean very little. However, in combination, they all point to a dual engine flameout just at/after the rotation. The aircaft has enough kinetic energy to reach roughly 150ft altitude, end then starts a shallow descent at ‘alpha max’ into the buildings ahead. The RAT deployed, APU attempted auto-start, gear was unable to retract.

I only wonder why the engines spooled down. Bird strike seems to be out of the question, so that leaves us with only a very few options, which include a software bug or a suicidal pilot (not a popular option, I understand, but we have to take all options into account).

What I don’t believe is incorrect FCU selections, since that would not explain the high AOA on impact. It also would not explain the RAT, no gear retraction or the APU inlet flap open. Another thing that is highly unlikely is any switching done by the pilots, especially RAT etc.. These airborne time is just too little, pilots usually don’t take any action below approximately 400ft, and these switches are so ‘underused’ that a pilot would not find them instantaneously in a high stress situation.

For me, a dual engine flameout seems the only possible explanation, now we only have to wait for its cause.

Is it possible to operate the fuel cut-off switches accidently?

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Last edited by Senior Pilot; 14th June 2025 at 20:08 . Reason: Double posting of image

Subjects APU  Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  RAT (All)  RAT (Deployment)

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This is what the Indian CAA is first focusing on

Subjects: None

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Quote:

Originally Posted by Jonty

I disagree. I think the lines of the underneath of the aircraft are quite obvious and its clear there's no RAT. Given it drops on the wing to body fairing just behind the main landing gear on the starboard side of the aircraft, it should be very obvious in this photo.

How about here….

Subjects RAT (All)

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Here’s another screen shot from an unknown source showing both the RAT and a bit of symmetric spoiler float due to lack of hydraulic pressure to close side.

Subjects Hydraulic Failure (All)  RAT (All)

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Quote:

Originally Posted by ATC Watcher

from the EASA statement yesterday :

No mention of UK

I'm not sure why one would rely on EASA for confirmation (or otherwise) of the AAIB's involvement.

Subjects: None

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Quote:

Originally Posted by galaxy flyer

Here\x92s another screen shot from an unknown source showing both the RAT and a bit of symmetric spoiler float due to lack of hydraulic pressure to close side.

Considering everything that's possibly to be found in the vicinity of the plane in the picture, I don't think we can conclusively say that's the RAT deployed.

Subjects Hydraulic Failure (All)  RAT (All)  RAT (Deployment)

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Quote:

Originally Posted by galaxy flyer

Here\x92s another screen shot from an unknown source showing both the RAT and a bit of symmetric spoiler float due to lack of hydraulic pressure to close side.

I don't think you can infer no hyd pressure from the spoiler "float. I've read elsewhere that they are biased up slightly to be used in slow speed roll control.

Subjects Hydraulic Failure (All)  RAT (All)

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Quote:

Originally Posted by Shep69

This to me makes more sense; perhaps I`ve got it wrong but in the video the trailing edge flaps definitely look up. Maybe there`s more and they weren`t.

I\x92m now convinced the whole \x91mis-selected flaps\x92 is a complete red herring. Based on the wreckage on the ground which clearly showed the flaps extended and a still from the witness video which I am 100% sure shows the flaps extended. I always believed it was a total loss of thrust and now can\x92t see any other explanation and so need to know why that happened.


Accident aircraft with TE flaps visible.

\x91Normal\x92 787 takeoff with flaps

Subjects: None

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Quote:

Originally Posted by FL370 Officeboy

I\x92m now convinced the whole \x91mis-selected flaps\x92 is a complete red herring. Based on the wreckage on the ground which clearly showed the flaps extended and a still from the witness video which I am 100% sure shows the flaps extended. I always believed it was a total loss of thrust and now can\x92t see any other explanation and so need to know why that happened.


Accident aircraft with TE flaps visible.

\x91Normal\x92 787 takeoff with flaps

Honestly can`t tell from the still or video.

But if the TE flaps were down in TO position in the wreckage pic (haven`t seen it) that`s that.

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Quote:

Originally Posted by QDM360

People really need to stop using FR24 data if they don't understand it.
This FR24 recording of AI171
https://www.flightradar24.com/data/f.../ai171#3ac3097
only consists of 4 unique ADS-B data messages. The first two were on the apron/taxiway. Then one at the runway intersection. And the fourth and last one just after the aircraft became airborne. That's all.

The two last ADS-B data messages are more than 4 minutes apart. It was 8:04 UTC when they entered the runway at the intersection. The next and last data point was received at 8:08 UTC.

The map view connects these dots, so it looks like a proper track. But in reality the ADS-B receiver barely received anything. It's therefore silly to argue the aircraft stopped transmitting ADS-B data based on this poor recording. The only thing you can say with certainty is that FR24's ADS-B receiver at Ahmedabad has really, really poor coverage...

Flightradar24 published the CSV with all received data. It had EIGHT datapoints of the aircraft after its rotation showing its altitude. https://www.flightradar24.com/blog/f...rom-ahmedabad/

Subjects ADSB  AI171  FlightRadar24

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Quote:

Originally Posted by 1stspotter

Flightradar24 published the CSV with all received data. It had EIGHT datapoints of the aircraft after its rotation showing its altitude. https://www.flightradar24.com/blog/f...rom-ahmedabad/

Please stop posting information from this commercial aircraft spotter site. It is frequently inaccurate. ADS-B site free to use and more accurate IMHO.

Subjects ADSB  FlightRadar24

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