Posts about: "AAIB (All)" [Posts: 81 Pages: 5]

GroundedSpanner
2025-06-22T00:15:00
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Post: 11908173
Originally Posted by BrogulT
I don't want to refute your theory, but given your 30 years of experience---presuming it is relevant--I'd ask you to clarify a few things.

First, water in fuel is not a novel concept and I would presume that the designers of the 787 knew about it. You've simply stated that water might collect and settle out, but how much water might you expect under those conditions (57% humidity doesn't seem terribly high to me) and what features and procedures are already there to mitigage water contamination issues? Your theory would imply that there basically aren't any. IDK how the tank venting system works, but the idea that some huge amount of water could have condensed in the tank from the outside seems preposterous.

Second, how much water do you think it would take to cause a sustained flameout in one of those engines? Remember that they have automatic continous relight, so you're going to have to sustain your flame suppression long enough for them to wind down completely. I think those engines were probably using something like 2 gallons per second of fuel along with 250lbs of air heated to over 1100F. Any fuel in the mix would burn and the water would be converted to steam so you'd need mostly water for a long time. So if you think a hundred gallons of water could have gotten into each tank then perhaps I'd buy your theory--which, btw, does fit the known facts pretty well. But I think that short of some woeful neglect, Boeing and AI already know about and have methods of dealing with water contamination. At least I hope so.
OK - Fair Challenges - good post, I'll have a go at answering and simultaneously expanding my own thoughts. In fact I'm not having a go at you, I'm more working my theory....

Experience. Without wishing to dox myself, I've worked in engineering at a major airline from apprentice through (in no particular order) Line Maintenance, Heavy and Light Maintenance, to technical support and maintenance control on both Boeing and Airbus products, with various qualifications and authorisations along the way. [Hmm - Scrap this sentence?]On the day 9/11 occurred, I should have been making modifications inside a fuel tank instead of staring at the TV with mouth on the floor.
However, I would describe my experience as broad, yet shallow in respect to this incident. Some of my fleet I know every rivet. Some of my fleet I've only ever seen from a distance. I don't touch airplanes for a living any more. B787 though - is not my area of specialty. I'll dig in, but am not the expert. I am not a systems design engineer, so precise numbers and flow rates, are not what I do. But what the systems do, how they operate, what they look like, smell and taste like... yeah, I'm not a muggle. And I do have access to all the manuals and know how to use them. And - let me be clear, I am speculating. I was advancing a theory. It WILL be some flavour of wrong. The investigation will reveal all.

I Agree, Water in fuel is not a novel concept. Aircraft fuel tanks attract water - fact. How much? It varies. I've sumped tanks and got no water, I've seen drops of water beading about in the bottom of a gallon jug, I've seen gallons of water. I've been so covered in fuel I cant smell it or think straight and taken gallon after gallon not being able to tell if its fuel or water. I also agree that 57% humidity doesn't seem particularly high - its not south east Asian jungle levels - but I'm not an expert at humidity, 32Deg c at 57% humidity at 02:30 am is not going to be comfortable for me though. I looked at recent weather in DEL, and those values were at the higher end of the range.
Further, I believe the prevailing weather conditions on the ground are less important when it comes to the volume of water getting in. Fuel is cold, or gets damn cold during a 9 Hr flight. Fuel Temperature Management is an issue for our Drivers. So as the fuel is used at altitude, Air enters the tank through NACA Ducts in the outboard end of the wing. Its beneficial to maintain a slight positive pressure, amongst other things to reduce evaporation. (Added complication, there is also the Nitrogen Enrichment system due to TWA800 - but that's more about processing the air in the tank to change the properties and make it non-explosive). Then as the aircraft descends, more air enters as the air pressure increases. Its the humidity of that air in the descent that is going to determine the volume of water entering the tank and potentially the fuel. The water in the air condenses on the sides of the tank because of the cold post-flight fuel. It doesn't dissolve into the fuel, but sinks to the bottom. Ground temperature / humidity and time will likely affect how much water condenses out of that air while on the ground. There won't be a huge amount of air exchange on the ground. Likely if the AC landed at 2am, then from sunrise as the tank warmed up, there would actually be a flow out of the vents.

What Features and procedures are there to mitigate Water? I apologise if my post gave the impression that there are no mitigation processes. There are. Water is well understood in the industry.
Well for a start, Features / Design. The Aircraft has a water scavenge system. Water doesn't mix with fuel, it sinks to the bottom being about 20% denser than fuel, so at the very lowest point in the tank, the water scavenge system (Powered by the Aft Fuel Pump through a jet pump, a venturi like system) will suck up the 'fluid' at the very lowest point, where the water would collect and in Boeings words 'drip' that fluid into the path of the pump pickup inlet (but I'd describe it more as a 'squirt'). The idea being that a small amount of water injected into the fuel will be consumed by the engines harmlessly.
There is also agitation. The wing tank pumps are pretty much running constantly, from before engine startup to after engine shutdown. The pumps are quite violent to the fuel and supply more pressure then the engine could ever need. Any excess pressure is dumped right back into the tank, quite close to the pump, in a direction that would further stir up the fuel and help break up any water into suspended droplets.
This all works if there is a small amount of water in the fuel. The water scavenge pickup is right next to the pump inlet, but a bit lower. Little bits of water get managed. Looking at the pictures of the system, I'd say a couple of gallons of water would do no harm at all.
But if there was significantly more water in that tank. Guessing 10-30 + gallons, then the pump would be circulating water, or highly water rich fuel.

Then there's the suction pickup. Its in the same 'bay' as the aft fuel pump and located a little 'higher' than the pump inlet and water scavenge inlet. But also located between stringers that can separate out the settled water ( I wish I could share the pictures, but more than my job is worth ) I can imagine the suction pickup being in a pool of 'stagnant' water.

I also saw a post from Metcha about the scavenge system blocking with Algae - I don't know about that (B787 not my fleet). But possible that could aggravate things. There's also the reports of the Indian AAIB looking at the Titan Biocide incident. Its possible that might be related and could modify the theory.

Procedures - There's the (at my airline weekly I think) procedure to 'sump' the tanks. There are drain points in the tank. Valves that you can push in with a tool and fluid drains. As described earlier (and videos exist on YouTube), you drain about a gallon of fluid and examine it for water. Most often in temperate climates (my experience), there's a few 'beads' of water in the bottom of the jug, moving about like mercury. Except when there's more. Sometimes there's a clear line in the jug, half water, fuel above. And sometimes a gallon of water, that smells like fuel. You drain it until you are sure there's no water.

Could 'that much' water have condensed in the tank? Well - There's the question. I guess the basis of the theory is that on descent into DEL, the wing tanks picked up some very humid air, which settled water into the tanks through the night. Then, as the theory I posited must work, the wing pumps must have circulated and suspended that water into the fuel.
By design, the water from the CDG-DEL arrival should have been consumed in the DEL-AMD Sector. But desperately clinging to defending my theory (I appreciate this is a hole), lets assume that at DEL the pumps were running for a long time. Lets assume that the pumps allowed the water to be dispersed within the tank prior to being used through the engines. Then - in the DEL-AMD sector, the wing tanks could have picked up more water.

How much water would cause a sustained flameout? I never posited a sustained flameout. I posited a significant reduction in thrust. Listening back to the rooftop video, which at first we were all listening for evidence of RAT, there's also a rhythmic pop-pop-pop of engines struggling. I think the engines were running, albeit badly. Heavily water contaminated fuel will do that. It doesn't have to be 100% water. Just enough water to make the engine lose thrust. Your 2 gallons per second figure assumes the engine running at full flow. I'm not a figures man, I'll not challenge that, I do recall flowmeters at max thrust spin like crazy. But an engine struggling due to a high perrcentage of contamination, is that using 2 gal/sec? or just trying to? What happens if there is e.g. 20% water in the fuel?

There are also reported incidents of engine flameout / thrust reduction that have all happened at altitude. Incidents that have been recovered due to the altitude and time available. I Posited that the engines would have eventually regained full thrust once the contamination worked though. But 30 seconds of rough engine is very different at 40,000 feet than it is at 100 feet.

The theory also relies on a second part - the electrical failure. That the electrical failure causes the fuel supply to switch, a few seconds after the failure. We go, at the point of electrical failure from a pumped centre tank supply to a sucked wing tank supply. It takes time for that different fuel to reach the engine.

Ive written enough and am tired. Must stop now.

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Musician
2025-06-22T07:24:00
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Post: 11908318
Originally Posted by compressor stall
It's either 2 things....
1. That happens from time to time and its the way things are done in India and it's only newsworthy now by association (not causation), or
2. The DGCA need to be seen to be doing something, and that's some low hanging fruit in an otherwise vacuum of information.
3. The AAIB looked into crew rostering; this is a routine part of air accident investigations (maybe not in India? but they have NTSB and UK AAIB sitting in this time). The AAIB found irregularities; this is a safety issue, so they notified the DGCA. The DGCA would've told Air India, "we can pull your operator license over this, but we won't if you fire those responsible".

It's a speculation, but I'd be surprised if it didn't fit the facts.
Also, we can't draw any conclusions about the accident crew; the discovery could've been incidental, or the accident crew might be affected, but the investigation is ongoing, so that's not public yet. It will be in the report, perhaps in the preliminary report even. (I expect NTSB and UK AAIB insist on a preliminary report, but who knows.)
Gary Brown
2025-06-22T08:15:00
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Post: 11908347
Originally Posted by JPI33600
Huh??? I can't find any indication of that dose in the report:

So it seems they didn't keep any record of the quantity, but they think they did it as prescribed. Is there a public source for the numbers you gave?
Originally Posted by Gary Brown
For the Gatwick indident, read p2 of the AAIB Final Report for the figure of 38 x correct dosage. The rest of the report will tell you how AAIB arrived at that figure (mostly, though not entirely, by testing the fuel post landing...).

I'll double check my claim of 100 x for the Japan incident tomorrow. I'm on cooking duty this evening.....
You're right that I am wrong about the 100 x figure ..... The Japan report doesn't fully resolve the concentrations issue (see below), but at p. 10 of the report they summarise similar incidents where they believe 10 x the recommended dose (1000ppm instead of 100ppm) was used. I'll correct the original post. But, we have incidents where the over-dosage is between 10 and 38 x that recommended....

The difficulty in ascertaining the over-dosage in all these instances is that a) there was no general requirement to keep a record of the concentration calculated and used, and b) in each case the biocide admixture was done several days, several flight cycles, and several re-fuellings before the incident, and in most cases at a maintenance facility a long way from the incident route.

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Icarus2001
2025-06-22T10:19:00
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Post: 11908414
having a brand new FDR lab, might not be sufficient in case you have to reconstruct the melted data access paths to the core memory modules
Well if a brand new, completed in April purpose built facility is not up to the task, then what hope is there. That is why it was built, for just this eventuality. Knowing a little about things, I would venture that know how is more critical here than the equipment available.

Either way, the US facility is avaible, so why take a week to decide to send it there?

Here is their reasons…

The ministry said the AAIB will determine the location for analysis after a "due assessment of technical, safety, and security factors".
​​​​​​​Some interesting words in there. Yes Minister.

Last edited by Icarus2001; 22nd Jun 2025 at 13:24 .
DaveReidUK
2025-06-22T11:25:00
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Post: 11908461
Originally Posted by MarineEngineer
India is the first country to put a lander and a rover on the south pole of the moon. I'm sure they can get the data from the EAFR!
At least one previous investigation report by the Indian AAIB has used CVR and FDR data downloaded from an (intact) EAFR.

4 users liked this post.

DIBO
2025-06-22T11:56:00
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Post: 11908486
Originally Posted by DaveReidUK
At least one previous investigation report by the Indian AAIB has used CVR and FDR data downloaded from an (intact) EAFR.
With 'intact' being the crucial part of these recent posts. It is my understanding that a suitably equipped LAME can simply download the FDR data from an installed EAFR (CVR requires dismounting). So downloading as such, isn't the issue.

However more importantly, as implied by another poster 'patience' is of the essence in this thread ...

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MarineEngineer
2025-06-22T12:26:00
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Post: 11908502
Originally Posted by DaveReidUK
At least one previous investigation report by the Indian AAIB has used CVR and FDR data downloaded from an (intact) EAFR.
But has AAIB India ever had to get data directly from the memory chips due to a badly damaged data recorder? I think it would have the capability.
za9ra22
2025-06-22T13:20:00
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Post: 11908536
Originally Posted by MarineEngineer
But has AAIB India ever had to get data directly from the memory chips due to a badly damaged data recorder? I think it would have the capability.
India has become one of the foremost global centres of IT hardware and software development, so I'd agree that it seems quite probable that it would have the capability to work with data extraction at component level.

It seems likely also that in setting up a lab to allow the reading of data recorders, they would know in advance that in many instances, the devices would likely be in a damaged condition when recovered, and ensure they were equipped for that.

It seems to me more likely that any actual delay in retrieving data, presuming there is anything to retrieve in the first place, would be in the form of pressures from competing interests than in competing capabilities.

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za9ra22
2025-06-22T18:25:00
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Post: 11908740
Two minor points regarding competence and who gets the task of data extraction from the data recorders: Firstly, that it's the AAIB (India) which will decide where and when to hand over the data recorders, and secondly, the supposed comment attributed to the Ministry of Civil Aviation in the press release dated June 19 ( https://www.pib.gov.in/PressReleaseP...x?PRID=2137718 ), that "t he decision regarding the location for decoding the flight recorders will be taken by the AAIB after due assessment of all technical, safety, and security considerations " would likely have been phrased rather differently if the lab in India were not considered capable of the work involved.

On edit:
And mods, apologies, this is getting rather more tangential to the incident than I intended!
Senior Pilot
2025-06-26T16:01:00
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Post: 11911339
https://www.pib.gov.in/PressReleseDe...x?PRID=2139785

Status Report on recovery and examination of data from Black Boxes – Air India Flight AI-171

On the evening of 24 June 2025, the team led by DG AAIB with technical members from AAIB and NTSB began the data extraction process. The Crash Protection Module (CPM) from the front black box was safely retrieved, and on 25 June, 2025, the memory module was successfully accessed and its data downloaded at the AAIB Lab.The analysis of CVR and FDR data is underway. These efforts aim to reconstruct the sequence of events leading to the accident and identify contributing factors to enhance aviation safety and prevent future occurrences.
Note the front EAFR is the one with RIPS battery backup.

26 users liked this post.

D Bru
2025-06-26T22:05:00
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Post: 11911534
Originally Posted by grumpyoldgeek
I have to disagree with point 1. They did not give a reason for using the front unit and I don't see why you would assume one.
Really, Grumpy? If aft EAFR (not RIPS supported) would have had any data/voice after elec failure following T/O, I think the AAIB would have been more than happy to extract everything from that one since it was found earlier and most likely more intact than the front one. Regards

Last edited by D Bru; 26th Jun 2025 at 22:17 . Reason: Sorry but I didn't want to sound too "grumpy" ;)

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Pilot DAR
2025-06-27T23:46:00
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Post: 11912237
I have opened this thread for a period, as I have read a news report updating the status of the data recorders:

https://www.cbc.ca/news/world/air-in...-box-1.7573145

From the article:

Indian authorities flew the black boxes from Ahmedabad to the national capital in an Indian Air Force aircraft amid tight security early this week.
The investigation could take weeks or months.

India set up a state-of-the-art laboratory in New Delhi in April to help the AAIB repair damaged black boxes and retrieve data to enhance the accuracy of investigations.

A multidisciplinary team led by AAIB director general GVG Yugandhar is probing the Air India crash with assistance from aviation and air traffic control specialists and experts from the U.S. National Transportation Safety Board.
Posts with additional information about retrieving and disseminating data recorder information are welcomed here for while. Let's keep the speculation posts to a very minimum please, hoping that this thread can remain open for a while as authoritative information becomes available...

Pilot DAR

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V1... Ooops
2025-06-28T02:28:00
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Post: 11912290
Originally Posted by WillowRun 6-3
...the article asserts, in a thematic sense, that the timing of information release is not consistent with factual information about the investigation. (It also generally suggests that information typically is released by investigation authorities earlier within the initial 30-day time period provided for by Annex 13....
I think that it is understandable that the Indian accident investigation team leaders are being very cautious about when and what information to release. This is probably the first "really big" accident investigation they have done that has achieved so much international attention. I am sure that they want to be certain that when they do release information it is accurate and carefully presented, simply to avoid any embarrassment that might arise from a hasty or less than carefully thought out disclosure.

For that reason, I think we ought to give the Indian investigators the benefit of the doubt and assume that they simply want to make sure that when they do make a statement it is 'bulletproof' and reflects well on their skill, professionalism, and the processes that they have followed.

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WillowRun 6-3
2025-06-28T02:58:00
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Post: 11912300
Regarding benefit of the doubt being warranted: While I agree, the more important point is the AW&ST writer probably would also agree. The message the article centers upon is that the relevance of, or need for, giving benefit of the doubt appears substantial. In that sense, the writer makes the same point as "This is probably the first 'really big' accident investigation they have done that has achieved so much international attention" - and citing that there have been three "fatal airline accident[s] in the country since 2000".

Among other facts supporting both the theme of article and the propriety of allowing benefit of the doubt, as the article notes, "Unlike their counterparts from Europe and the U.S., AAIB experts are not regularly dispatched as technical advisors in foreign investigations involving products built and certified at home."
Innaflap
2025-06-28T14:14:00
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Post: 11912510
Originally Posted by V1... Ooops
I think that it is understandable that the Indian accident investigation team leaders are being very cautious about when and what information to release. This is probably the first "really big" accident investigation they have done that has achieved so much international attention. I am sure that they want to be certain that when they do release information it is accurate and carefully presented, simply to avoid any embarrassment that might arise from a hasty or less than carefully thought out disclosure.

For that reason, I think we ought to give the Indian investigators the benefit of the doubt and assume that they simply want to make sure that when they do make a statement it is 'bulletproof' and reflects well on their skill, professionalism, and the processes that they have followed.
Not to mention the political pressure and Tata involvement
Hot 'n' High
2025-06-28T21:21:00
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Post: 11912668
Originally Posted by Machinbird
...... This might be a useful starting point for understanding what could have gone wrong.
Sadly Machinbird , I think this has been covered, especially re the engines, in some depth already. Several who post here have extensive knowledge in FADEC and associated protections. It's all a mystery tbh and I guess we just need to wait now until some concrete evidence is produced by the AAIB.

Not wishing to dampen enthusiasm to find out a cause but, 2 Threads in, no-one is much the wiser. Just my opinion but that seems to be where we are. What a dreadful accident - I can't even begin to imagine what the crew went through in those final moments.

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za9ra22
2025-06-29T17:13:00
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Post: 11913135
Originally Posted by EDLB
I find it very disconcerting that with downloaded recorders the investigators seem to have no clue how and why the dual engine shut down happened.
I don't see any direct confirmation that the flight recorder(s) have been read and their data determined, just that the AAIB have them in their custody, and they aren't going anywhere else.

To be honest, I don't see any detail in this reported conversation that tells me the Minister has any actual knowledge of the state of play in the investigation itself, just the process and a general round-up of what we basically already know.

My guess is that the investigation has not provided any feedback yet - or at least none that the Minister is able to pass on.

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silverelise
2025-06-30T13:05:00
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Post: 11913609
India's Minister of State for Civil Aviation appears to be confirming in this this interview that the cause of the accident was a dual engine failure. Which is, I think, the first vaguely official confirmation of what happened that has been released? He also confirmed that all the data from the recorders has been downloaded and is being processed by the Indian AAIB, no boxes have been sent abroad.
The 30 day deadline for the preliminary report is July 12th.

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Lonewolf_50
2025-06-30T13:08:00
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Post: 11913613
Originally Posted by The Brigadier
We know that the right-hand GEnx-1B was removed for overhaul and re-installed in March 2025 so it was at “zero time” and zero cycles, meaning a performance asymmetry that the FADEC would have to manage every time maximum thrust is selected. If the old engine was still on the pre-2021 EEC build while the fresh engine carried the post-Service Bulletin software/hardware, a dual “commanded rollback” is plausible.
A latent fault on one channel with the mid-life core can prompt the other engine to match thrust to maintain symmetry, leading to dual rollback.
Then why didn't that happen on the previous flight from Deli to Ahmedabad, or any of the previous flights since that engine install in March?
Originally Posted by silverelise
He also confirmed that all the data from the recorders has been downloaded and is being processed by the Indian AAIB, no boxes have been sent abroad.
The 30 day deadline for the preliminary report is July 12th.
Thanks for the update, and in particular that bolded bit.
Originally Posted by the linked article
Investigators still haven’t ruled out the possibility of sabotage being behind the Air India crash in Ahmedabad earlier this month that killed 274 people , according to India’s aviation minister. The Aircraft Accident Investigation Bureau (AAIB) has confirmed that the aircraft’s flight recorders – known as black boxes – will not be sent outside the country for assessment and will be analysed by the agency, said Murlidhar Mohol, the minister of state for civil aviation.l
adfad
2025-06-30T15:49:00
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Post: 11913716
Originally Posted by silverelise
India's Minister of State for Civil Aviation appears to be confirming in this interview that the cause of the accident was a dual engine failure. Which is, I think, the first vaguely official confirmation of what happened that has been released? He also confirmed that all the data from the recorders has been downloaded and is being processed by the Indian AAIB, no boxes have been sent abroad.
The 30 day deadline for the preliminary report is July 12th.
It's hard to find a full and reliable translation of his statement but here is another snippet from Yahoo (I can't post links sorry)

The minister called the crash a \x93rare case\x94 and, referring to claims by veteran pilots and experts that a dual-engine failure may have led to the crash, said: \x93It has never happened that both engines have shut down together.\x94 \x93Once the report comes, we will be able to ascertain if it was an engine problem or fuel supply issue or why both engines had stopped functioning.
I think it's very important to define "engine failure" vs e.g., reduced thrust - BA38 for example was described as "restricted fuel flow when thrust was demanded" and there was no evidence of engine driven generator power stopping as the engines were still running at idle at impact. It's pretty clear from the available evidence that Air India lost electrical power within 20 seconds of leaving the ground, and based on the landing gear orientation theories that time may be significantly shorter <10 seconds.