Posts about: "Fuel (All)" [Posts: 1028 Pages: 52]

Lord Farringdon
June 17, 2025, 00:36:00 GMT
permalink
Post: 11903890
Originally Posted by tdracer
Something that occurred to me after I went to bed last night: My assumption that the FDR readouts would rapidly reveal the cause may be flawed.

Let me explain.

The consensus is that both engines quit shortly after liftoff (that assumes that the RAT did in fact deploy). At least one of the data recorders has battery backup, so it should have kept functioning when all aircraft power was lost.

However...

Over the years, I've looked at lots and lots of digital flight data recorder outputs when investigating some sort of incident or other engine anomaly, So I have become rather familiar with some of the interesting characteristics of DFDR data.

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. As a result, most of the avionics boxes 'reset' - this is quick, but it's not instantaneous. This shows up in the FDR data - sometimes as 'no valid data' for a few seconds, or as garbage readings of zero or 'full scale'. Now, looking at the FDR data, it's easy to simply disregard the data, so normally no big deal.

Starting with the 777 (and on the 787 and 747-8), this electrical power glitch was 'fixed' - there is slight delay (~quarter of a second IIRC) before the fuel cutoff signal is sent to the engine - during which the electrical system reconfiguration takes place so no more 'glitch' during a normal engine shutdown...Except whatever happened to these engines wasn't 'normal'.

If there is a fuel cut at high power, the engine spools down incredibly rapidly - a second or two from max power to sub-idle. Assuming the fuel cut wasn't commanded by the flight deck fuel switches, the electrical system won't know it's coming, so it can't reconfigure until after the engine generators drop offline - and you're going to get that power glitch. Nearly every avionics box on the aircraft will reset due to this electrical glitch, and the FDR isn't going to get useful data for a few seconds (and then, only from the stuff that's on the battery bus).

Whatever happened, happened quickly - it's quite possible that whatever initiated the high-power fuel cut didn't get recorded.






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?

The thread is closed so there are no user likes are available.

Ngineer
June 17, 2025, 03:34:00 GMT
permalink
Post: 11903942
Originally Posted by C2H5OH
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\x92s control systems
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.

The thread is closed so there are no user likes are available.

Lead Balloon
June 17, 2025, 05:22:00 GMT
permalink
Post: 11903979
Originally Posted by ignorantAndroid
I'm honestly mystified by the obsession with TCMA. The FADECs control almost every aspect of the engines, so there must be numerous ways they could cause a failure or uncommanded shutdown. So, even if we assume that the engines failed due to faults in the FADECs, why assume that TCMA would be involved? Surely it's more logical to simply posit that some unspecified bug in the FADEC software caused the failure. That bug could be related to TCMA, but it could just as easily involve any one of the dozens of other subroutines that likely exist.

Various posters seem to assume that all it takes is an incorrect air/ground signal, and the engines would shut down. But in fact it would also require the FADECs to read the thrust levers as being at or near idle... AND the engines failing to respond to closure of the fuel metering valve. I've read the entirety of both threads, and I haven't seen anyone even attempt to explain how a malfunction within the airframe could cause both of those things to occur on both engines (or even one engine!).
There is at least one thing common to the TCMA on each engine: The TCMA software.

My recollection may be inaccurate, but wasn't there something in the software for 787 generator control units that would cause generator shut down if the aircraft was 'powered up' for a continuous 248 days? Same software, so all 4 generators would shut down. Is my recollection inaccurate?

What we do know, for sure, is that the TCMAs have the same 'authority' and effect as the fuel cut-off switches. The difference is that the crew control the latter.

The thread is closed so there are no user likes are available.

EDLB
June 17, 2025, 05:38:00 GMT
permalink
Post: 11903988
We have two donks individual fuel supply cut simultaneous in split seconds. There is no rudder activity visible for any thrust asymmetry during this timeframe. TCMA is implemented via the FADECs which are independent for each engine with their own power source from each engine. TCMA is designed to shut down its engine if its power lever is in retard position and the engine is still powering with too much thrust. In addition the airplanes ground sensors must indicate that it is on the ground. For each thrust leaver there are two independent position sensors. It is similar redundant designed as in modern car acceleration pedals. A dual redundancy in each thrust leaver. For TCMA to shut down two fuel supplies within split seconds we have to assume that 4 thrust leaver sensors malfunctioned and the ground sensing logic failed at the same time. The probability that this happens is nil (may be 1 in every 10exp15 hours) which would be about 10 times the age of our universe.
Unless there is a software error in the FADEC TCMA system which only came to light on this flight. But there seem to be nothing special on this flight until rotation. If there is a software error I expect, that we get false single engine shut downs first. And that would already made the news if it happened during rotation.






The thread is closed so there are no user likes are available.

C2H5OH
June 17, 2025, 06:25:00 GMT
permalink
Post: 11903999
Originally Posted by tdracer
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. As a result, most of the avionics boxes 'reset' - this is quick, but it's not instantaneous. This shows up in the FDR data - sometimes as 'no valid data' for a few seconds, or as garbage readings of zero or 'full scale'. Now, looking at the FDR data, it's easy to simply disregard the data, so normally no big deal.
\x85
If there is a fuel cut at high power, the engine spools down incredibly rapidly - a second or two from max power to sub-idle. Assuming the fuel cut wasn't commanded by the flight deck fuel switches, the electrical system won't know it's coming, so it can't reconfigure until after the engine generators drop offline - and you're going to get that power glitch. Nearly every avionics box on the aircraft will reset due to this electrical glitch, and the FDR isn't going to get useful data for a few seconds (and then, only from the stuff that's on the battery bus).
Thank you for confirming.

This is not only happening to the FDR but to any reciever on the data busses. And likely not only when the engine spools down and power supply switches but also when power busses come offline and bus bar breakers activate or in any severe fault in the electrical system involving large currents, possibly arching shorts.
Hence my comments on SISO and input filtering and verification in the closed thread.

The thread is closed so there are no user likes are available.

TURIN
June 17, 2025, 06:28:00 GMT
permalink
Post: 11904002
Originally Posted by Lead Balloon
There is at least one thing common to the TCMA on each engine: The TCMA software.

My recollection may be inaccurate, but wasn't there something in the software for 787 generator control units that would cause generator shut down if the aircraft was 'powered up' for a continuous 248 days? Same software, so all 4 generators would shut down. Is my recollection inaccurate?

What we do know, for sure, is that the TCMAs have the same 'authority' and effect as the fuel cut-off switches. The difference is that the crew control the latter.
I'm pretty sure the software is written independently. Same as Airbus, you don't want the same software error on duplicate critical systems.

The thread is closed so there are no user likes are available.

Kraftstoffvondesibel
June 17, 2025, 10:10:00 GMT
permalink
Post: 11904165
So, also as an outsider when it comes to cockpit engineering, there is one commmon "system" in the sense of the very close physical location, the two engine systems have in common, and that is the physical cut off switches and their behind the panel connections.

It wouldn't take a kids pool of liquid to intefere with those?
(I asked this question previuously, in the middle of a long text, but the discussion had a very different direction then.)

What are possible ways of a common failure/triggering of these contact points somewhere in their physical installation in the cockpit?
Remember when the A350 had to be modified only 5 years ago to not allow coffee spill to turn off engines.
What about the same location in the B787?
What are the actual switches? Are they purely traditional electromechanical contact switches? How do they make contact, ie. what are the actual gaps and dimensions? Are they digital in some sense? How are they protected? Are both installed the exact same way, or are they installed with different physical screening/protection/orientation as so to make the failure modes different? How are they physically kept apart, isolated from each other to avoid interaction and/or common failure. What is the physical distance involved there? What about the cables and connectors to them? separate or bundled in the same wiring harness? Or even in Mil or D-sub connectors? I find one description of them as a common(both in one box) line replaceable unit with quick connects. Both of them in the same unit with a common connector? Sounds wild if so!
Just had to ask, and hope it doesn't disturb the great discussion too much.

Last edited by Kraftstoffvondesibel; 17th June 2025 at 10:34 .

The thread is closed so there are no user likes are available.

EDML
June 17, 2025, 11:34:00 GMT
permalink
Post: 11904225
Originally Posted by compressor stall
I'd be interested in any history or understanding as to why Boeing went with the common tank approach on takeoff?
Actually the engines are fed by all tanks during take off. (L engine: L wing tank + Center tank (if filled) / R engine: R wing tank + Center tank (if filled)).

Due to the fuel pressures of the feed pumps (that are all running) the center tank fuel is used first. In case the pump in the center tank fails or the center tank is empty the fuel from the wing will be used w/o any switch over taking place as the wing feed pumps are already running.

The thread is closed so there are no user likes are available.

compressor stall
June 17, 2025, 11:47:00 GMT
permalink
Post: 11904234
Originally Posted by EDML
Actually the engines are fed by all tanks during take off. (L engine: L wing tank + Center tank (if filled) / R engine: R wing tank + Center tank (if filled)).
Due to the fuel pressures of the feed pumps (that are all running) the center tank fuel is used first. In case the pump in the center tank fails or the center tank is empty the fuel from the wing will be used w/o any switch over taking place as the wing feed pumps are already running.
Thanks for the clarification.

The thread is closed so there are no user likes are available.

artee
June 17, 2025, 11:58:00 GMT
permalink
Post: 11904239
Originally Posted by EDML
Actually the engines are fed by all tanks during take off. (L engine: L wing tank + Center tank (if filled) / R engine: R wing tank + Center tank (if filled)).

Due to the fuel pressures of the feed pumps (that are all running) the center tank fuel is used first. In case the pump in the center tank fails or the center tank is empty the fuel from the wing will be used w/o any switch over taking place as the wing feed pumps are already running.
Surely that's not quite right? If the center tank has fuel, both engines will be fed from the center tank. Only once/if the center tank doesn't have fuel, will the engines be fed from their respective wing tanks.

The thread is closed so there are no user likes are available.

OldnGrounded
June 17, 2025, 13:44:00 GMT
permalink
Post: 11904315
Originally Posted by ignorantAndroid
I'm honestly mystified by the obsession with TCMA. The FADECs control almost every aspect of the engines, so there must be numerous ways they could cause a failure or uncommanded shutdown. So, even if we assume that the engines failed due to faults in the FADECs, why assume that TCMA would be involved?
I think you may be inferring something that isn't actually true. It certainly isn't true in my case. Wanting to explore the details of a function known to be designed to shut down engines, in a case where unexplained shutdown of engines appears to be a likely cause or contributing factor, doesn't suggest that we are assuming TCMA is involved. It's just exploring the details of a a function that is designed to do that and doesn't put on a light, smoke and sound show, or produce obvious debris and residue, when it does.

I think those of us who are persistently trying to learn the details of the sensor inputs to and logic of TCMA (I prefer that characterization to "obsessed with") understand quite well the points you make here — at least those of us whose interest survives in this new thread. However, I at least, and I believe others as well, have also come to the tentative conclusions that (a) the accident aircraft had engines providing little to no useful thrust from nearly the first moments after rotation, and (b) the only possible reasons for that which have been considered here so far involve the sudden and approximately simultaneous shutdown of those engines, most likely by interruption of fuel flow (because that's one of the very few things we know that can do that without producing big bangs, flames and smoke, etc.).

Surely it's more logical to simply posit that some unspecified bug in the FADEC software caused the failure. That bug could be related to TCMA, but it could just as easily involve any one of the dozens of other subroutines that likely exist.
I don't agree that it's more logical to posit that something we don't know about has shut down the engines rather than something that we do know about that is intended to shut down engines. Do you know of other routines/subroutines in the FADEC that shut down fuel supply?

Various posters seem to assume that all it takes is an incorrect air/ground signal, and the engines would shut down.
I certainly don't assume that and I haven't seen posts from others (that I consider serious and reasonably well-informed) that "seem to assume" that.

But in fact it would also require the FADECs to read the thrust levers as being at or near idle... AND the engines failing to respond to closure of the fuel metering valve.
Yes, we know that.

I've read the entirety of both threads, and I haven't seen anyone even attempt to explain how a malfunction within the airframe could cause both of those things to occur on both engines (or even one engine!).
Right, and you won't see a serious attempt to do that until we know, at least, what specific sensor inputs the TCMA function uses to determine the air/ground state of the aircraft and the logic that uses those to make the determination.









Last edited by OldnGrounded; 17th June 2025 at 13:46 . Reason: Formatting

The thread is closed so there are no user likes are available.

JRBarrett
June 17, 2025, 13:50:00 GMT
permalink
Post: 11904318
Originally Posted by ignorantAndroid
Various posters seem to assume that all it takes is an incorrect air/ground signal, and the engines would shut down. But in fact it would also require the FADECs to read the thrust levers as being at or near idle... AND the engines failing to respond to closure of the fuel metering valve. I've read the entirety of both threads, and I haven't seen anyone even attempt to explain how a malfunction within the airframe could cause both of those things to occur on both engines (or even one engine!).
Many years ago I maintained a Hawker 1000 business jet equipped with PW305 engines with FADEC. The fuel control did not have a separate switch to control fuel flow to shut down the engines. Shutdown was accomplished by pressing a release on the power levers allowing the lever to be pulled past the idle stop all the way to the cutoff position.

One day upon returning from a flight, the crew pulled both power levers to cutoff. The right engine shutdown immediately as expected, but the left engine kept running. By the time we in maintenance got out to the airplane, the engine finally shutdown by itself.

Troubleshooting found the cause of the problem. The cutoff position of the power lever closed a micro switch that sent a ground to the FADEC. That ground went through two discrete wires. One went directly to one input on the FADEC. The other went through a squat switch on the main gear leg to a second input on the FADEC. The engine would only shutdown immediately if both inputs went to ground simultaneously. If only one input went to ground, the FADEC would delay shutdown for 30 seconds. This was to protect against an inadvertent movement of the power lever to the cutoff position in flight causing an immediate shutdown.

The squat switch on the left gear leg had failed in the open position, causing the problem.

I am wondering if more modern FADEC engines have similar protections against immediate shutdown in the air? I can see why the designers of the Hawker implemented the system the way they did, because the shutdown command was integral to the power lever, and it potentially could be pulled to the cutoff position in flight by an inadvertent release of the locking mechanism that would normally prevent it from going past the idle stop, whereas modern FADEC engines like found on the 787 have a discrete locking switch.

But, if a similar protection against immediate shutdown does exist in the 787, would the engines keep running for a period of time (in the air) even if the fuel control switch was accidentally or deliberately moved to \x93off\x94?


The thread is closed so there are no user likes are available.

PPRuNeUser548247
June 17, 2025, 16:23:00 GMT
permalink
Post: 11904442
As more days pass without the FAA/EASA issuing an emergency Airworthiness Directive re. the 787 Dreamliner, it does appear more likely the cause of the crash was specific to the Air India aircraft (as per speculation on fuel contamination, bad maintenance, crew error etc. etc.)

The thread is closed so there are no user likes are available.

PuraVidaTransport
June 17, 2025, 17:17:00 GMT
permalink
Post: 11904484
Having gone through every possible way the aircraft (or those in it) can shut down both engines, thought it would be helpful to look at what investigators have looked at/for in a somewhat similar case. Perhaps it will move the discussion to more unplowed ground.

Going through AAIB Bulletin10/2008 from the British AAIB in the BA 38 case. Before finding the exact cause, they had investigated the following with findings in quotes:

1. General aircraft examination - "no pre‑existing defects with the electrical systems, hydraulics, autoflight systems, navigation systems or the flying controls."
2. Spar valves - "Extensive testing to induce an uncommanded movement, that remained unrecorded, could not identify any such failure modes."
3. High Intensity Radiated Field (HIRF) and Electro- Magnetic Interference(EMI) - "There is therefore no evidence to suggest that HIRF or EMI played any part in this accident."
4. Fuel System - "The examination and testing found no faults in the aircraft fuel system that could have restricted the fuel flow to the engines."
5. Engines - "No pre‑existing defects or evidence of abnormal operation were found with the exception of signs of abnormal cavitation erosion on the delivery side of both HP pumps. Some small debris was recovered from the left FOHE inlet chamber but this would not have restricted the fuel flow."
6. Fuel Loading/Fuel Testing - "No evidence of contamination was found." "The properties of the sampled fuel were also consistent with the parameters recorded in the quality assurance certificate for the bulk fuel loaded onto G‑YMMM at Beijing."
7. Water in Fuel - "It is estimated that the fuel loaded at Beijing would have contained up to 3 ltr (40 parts per million (ppm)) of dissolved water and a maximum of 2 ltr (30 ppm) of undissolved water (entrained or free). These quantities of water are considered normal for aviation turbine fuel."

Knowing the history of this flight, the previous flights and the climate that day, I left out all the discussion in the report of fuel waxing/ice. That seems as irrelevant as 'vapor lock'.

I too am beginning to think this will be, as an earlier poster termed it, a "unicorn" event.

Source: Bulletin_10-2008.pdf

The thread is closed so there are no user likes are available.

nachtmusak
June 17, 2025, 17:34:00 GMT
permalink
Post: 11904500
Originally Posted by nachtmusak
Unfortunately due to the post crash fire I'm not sure the investigators will be able to collect fuel samples for testing, as was done for BA 38 to rule out fuel waxing...
Bringing part of my previous question back up: I know that fuel waxing was at some point one of the suspects in the BA 38 accident, but was ruled out via testing fuel samples. However I've been unable to find any records of airliner accidents or incidents that did involve fuel waxing, which I thought most likely existed if it was a possibility the investigation was considering? Does anyone know of any such incidents?

More accidents/incidents where fuel starvation was triggered by crystalline contaminants blocking fuel lines might also be useful - I'm trying to establish a range of how quickly and under what conditions such blockages could cause a loss of thrust in both engines.

The thread is closed so there are no user likes are available.

PC767
June 17, 2025, 18:04:00 GMT
permalink
Post: 11904524
Originally Posted by The Brigadier
As more days pass without the FAA/EASA issuing an emergency Airworthiness Directive re. the 787 Dreamliner, it does appear more likely the cause of the crash was specific to the Air India aircraft (as per speculation on fuel contamination, bad maintenance, crew error etc. etc.)
One would hope, but, whilst there has been confirmation that the EAFRs have been recovered, nothing has been reported about their state or whether they have been downloaded or examined.

If the data is readable there may be a lot of politics and reputation on how that data may be interpreted. Behind the veneer of international cooperation vested interests will be being considered, advocated and agreed.

It, unfortunately, is naive to think that politics will not have a silent presence in agreeing a press release. Boeing and GE are flagship USA companies. Air India is the flagship carrier of India.

Investigations of all types first establish what happened, then how and why, before recommendations and actions. There is a possibility that they know the what, but the how and why incur liability.

The thread is closed so there are no user likes are available.

604driver
June 17, 2025, 18:54:00 GMT
permalink
Post: 11904568
Originally Posted by PC767
One would hope, but, whilst there has been confirmation that the EAFRs have been recovered, nothing has been reported about their state or whether they have been downloaded or examined.

If the data is readable there may be a lot of politics and reputation on how that data may be interpreted. Behind the veneer of international cooperation vested interests will be being considered, advocated and agreed.

It, unfortunately, is naive to think that politics will not have a silent presence in agreeing a press release. Boeing and GE are flagship USA companies. Air India is the flagship carrier of India.

Investigations of all types first establish what happened, then how and why, before recommendations and actions. There is a possibility that they know the what, but the how and why incur liability.

Investigators will try to establish a single source or truth. For them, that\x92s an ideal outcome. But due to the nature of investigations, the aim gets derailed as established facts versus possible/potential scenarios based on missing links of the chain are pieced together. But for sure, commercial considerations and liability wont enter into a proper investigation. The task of the investigators is to determine the how and why.

Theres a saying, and it may even have been the title of a book\x85 Lift is a gift but Thrust is a must. In this case, certainly one or both were absent.

For 2 (maybe 3 if it was a training flight) professional people, the day started with waking up, getting ready, saying goodbye to loved ones, who they believed they would see again soon in 2-3 days. Sadly, that won\x92t happen, and it\x92s the job of the investigators to find out why and liability isn\x92t a hindrance to them.

They will look at every piece of evidence and recreate the events. But it will take time.

information worthy of note is:

A) The gear was still down.
B) It would appear (due to some work by amazing members) that the RAT was indeed deployed.

Other observances:

1. Bits flying off the aircraft. (From experience of operating in this area, they like to fly kites, and waste thermals and floats around, notably plastic bags) I have no idea if that la what we see or not.

2. Generally in India, they love using their horns. So whilst you can compare the frequencies of a potential RAT to a motorbike, appreciate there would be a million horns going off too.

3. Some posters have spoken of the \x93startle effect\x94 like they know what they are talking about. The most startling effect of a professional flight deck during an emergency is how calm it is. There aren\x92t hands flying around everywhere. In fact:

V1 > Rotate > Positive Rate > Gear Up > Confirm FD/AP Modes is adjusted to:
V1 > Rotate > Positive Rate > Gear Up > Silence the bell (Or your SOP Variation) FD/AP modes and the PF flies the aircraft.

the next step is to identify the problem, agree on it and then perform the actions. That won\x92t happen below 400\x92.

4. There\x92s no company in the world where Pilots are being fed and watered between V1 and 1000\x92 so spilling drinks on run switches isn\x92t a thing on this departure.

5. Temperature inversion. Yes it\x92s possible and it degrades performance. However, if it\x92s present, it\x92s usually announced on the ATIS. IF other aircraft have reported it.

6. Fuel contamination. Without knowing the systems, yes it\x92s potentially possible, but it would appear no other aircraft have reported being affected by it.

I think, this accident is especially interesting to Professional Aviators and Engineers because I think none of us would ever believe that it could happen. The aircraft is highly automated, the crew have been properly trained and the operation was a regular or possibly training flight.

A query I have is, do later Gen aircraft like the 777/787/747 A330/A350/A380 constantly send Airframe/Engine data home to ops/engineering/oem\x92s. Is it likely the data is out there?

Anyway, I just wanted to post this to reassure the travelling public that Pilots don\x92t try to shut down engines before they raise the gear.


The thread is closed so there are no user likes are available.

tdracer
June 17, 2025, 21:41:00 GMT
permalink
Post: 11904694
Originally Posted by Lord Bracken
I was referring to CVR/FDRs in general being specialist equipment requiring specialist facilities to process. In any case, I would be very interested to find out where those from this accident are read. It appears from a post upthread there are new facilities in New Dehli that could be used. Having said that, for the EK 521 accident in Dubai the recorders were sent to the UK for analysis, despite a "flight data recorder centre" in Abu Dhabi being opened (again with much fanfare) by the UAE GCAA five years before the occurrence.
Given the number of times I reviewed DFDR data supplied by an operator after some sort of event/incident, I think most major operators have access to the equipment needed to download a healthy data recorder. So I'd be a bit surprised if Air India does not have this capability. OldnGrounded has also posted that the Indian AAIB also has that ability.

Usually when I hear of data recorders going back to the US NTSB or the recorder manufacturer, it's because the crash damage is such that specialized equipment is needed to download the data. The recorder in the tail would likely have little damage.
While the AAIB may have held off on downloading the recorders until all the major players are present, it's been several days - I'd expect everyone who matters is already there. So I think it is reasonable to believe that the investigators have done a download and have had at least a preliminary look at the data. If there is a smoking gun, they probably already know (and the longer we don't hear something regarding the rest of the 787 fleet, or at least the GEnx powered fleet, the less likely it is that they suspect a systemic problem with the aircraft and/or engine). However the proviso that I posted earlier about potential data loss/corruption due to a sudden shutdown still applies - so maybe the data simply isn't on the recorder.

As has already been posted, EMI is highly unlikely - the current cert requirements for HIRF are quite high, and due to the composite airframe construction of the 787, the lighting requirements are much higher than for conventional aluminum aircraft (the higher resistance of the composite airframe results is higher lightning induced currents).

FDR has suggested a large slug of water hitting critical aircraft electronics at rotation - it is possible that resultant electrical short circuits could falsely signal the engines that the switches are in cutoff. Highly unlikely that it would do that to both engines, but possible.
Then again, all the other plausible explanations are highly unlikely, so...

BTW, I do have a life outside PPRuNe - and I'm going to be traveling the next several days, with limited to non-existent internet access. So don't be surprised if I'm not responding posts or PMs.

The thread is closed so there are no user likes are available.

Lead Balloon
June 17, 2025, 23:14:00 GMT
permalink
Post: 11904751
Could someone post an authoritative list of the inputs to the EAFR\x92s? By \x93authoritative\x94, I mean the actual wiring diagram excerpt of the aircraft model and engine configuration (and hopefully mod state...), that labels each input.

I\x92m confidently assuming that it will, for example, include an input monitoring the state of the input controlling the fuel shut off valves in the wing roots. But does it monitor, separately, each and every one of the switches and systems that can change the input controlling the fuel shut off valves? I'm hoping and assuming \x91yes\x92, but hope and assumptions can be unhelpful and misguided.

As we know, there are some things the pilots can do that will result in fuel shut off, but other things will result in fuel shut off without pilot intervention.

Of course, it may be that the recorded data will indicate that there was no change in the state of the inputs controlling the fuel shut off valves during the short flight. Hopefully \x96 yes hopefully \x96 that will be confirmed one way or other, soon. Along with another dozen questions....

I was struck by a comment in this or the earlier thread that I cannot now find. It was to the effect \x96 I\x92m paraphrasing \x96 that fuel shut off results in an almost immediate cessation of thrust. (Please correct my paraphrasing if I\x92m off track.) I was also struck by how quiet the aircraft was in the original video, except for the RAT. (Or was it a motorcycle? Sorry couldn\x92t resist. Just joking\x85)

Someone earlier asked how the aircraft could have kept climbing if both engines stopped very late in the take-off roll or shortly after take-off. My answer: Momentum. A bullet fired into the air loses thrust immediately after \x91take off\x92 but continues climbing for a while. And my understanding of the expert opinion on the available, reliable information is that the aircraft didn\x92t climb very far.

The thread is closed so there are no user likes are available.

Squawk7700
June 17, 2025, 23:26:00 GMT
permalink
Post: 11904762
Originally Posted by Lead Balloon
I was struck by a comment in this or the earlier thread that I cannot now find. It was to the effect \x96 I\x92m paraphrasing \x96 that fuel shut off results in an almost immediate cessation of thrust.
Spot on, there's so much fuel being sucked at that power setting, it would be super quick and presumably at near enough to the exact same time.

I assume (rightly so) that you're focused on what could cause them to fail at what appears to be the exact same time given the absence of yaw and any correcting rudder input.

One the face of it, it could only be throttle or fuel supply, with fuel supply only being able to be cut off by valves so abruptly. Any kind of blockage or similar wouldn't give such a result, even if there was a low fuel condition, short of the pickups being exactly right next to each other, presumably that wouldn't give the outcome we've seen.


The thread is closed so there are no user likes are available.