Posts about: "Preliminary Report" [Posts: 277 Pages: 14]

The Mods have stuck to this principle, which I shall try to adhere to.
This preliminary report is just that, but maybe consider the issues the Indian AAIB have had to address in publishing it. They will have a similar concern to the pP mods, maybe more so since any apparent accusations directed at the pilots may lead to physical retribution.
I therefore conclude great care has been taken to "sanitise" what the AAIB know, or at least strongly suspect, (from EAFR) into the report. They have conspicuously failed to identify which of the pilots was each half of the conversation they have not repeated the exact words, there's a lot missing (was positive rate ever called, was rotate ever called, any discussion about putting FC back to Run, who/how flying aircraft meanwhile). As a result we, the reader, should step back and not over-interpret this sanitised report.

Secondly, given the mod statement above, if a criminal act is suspected by the AAIB, this will likely trigger all sorts of 'primacy' issues in the investigation i.e. police? AAIB? or joint? and all the history that involves (SAS Linate?) - in Europe we have 996-2010 Article 12 para 2, but India?

Summary : For good reason I believe this report has been very carefully worded, sanitised with great care, and as such easy to inappropriately speculate what went on.

From my reading of the AAIB report, the delay in noticing the cut off switch position could not have been any later than 08:08:47 because the reference to the verbal exchange was written before the reference to the RAT deployment and I assume the written narrative follows the chronological sequence of events. The delay in resetting those fuel switches might therefore have been no more than 5 seconds. It is a pity that the pilot making the challenge didn't simply reset the switches to run instead of challenging the other pilot. I frequently tell people who blow their horns at pedestrians or other motorists that blowing the horn isn't going to help them avoid an accident and that what they really need to do in the limited time available to them is concentrate on applying the brakes and turning the steering wheel.

May I ask where you found the "no fault found" info? I can't see that, though I suspected it.

That will be easily answered when investigators play CVR recordings to colleagues, family and friends who can recognise and identify the voices.

They probably know that answer but it is omitted from preliminary report.

SLF. But I've read in full both original threads and this thread.

The Preliminary Report is written in excellent English, so I think one should pay close attention to what it says.

One thing I noticed is that at the bottom of P4 NTSB are stated as "..participated in the investigation". However UK AAIB are only stated as "visited the site". My reading is that UK AAIB are not participating?

Another is that some items on the timescale are v precise, others much more vague.

A question :

If the fuel switches were moved to cutoff, for whatever reason, what exactly would each pilot see as an EICAS warning. I'm still unclear why one pilot asked the other why he cut off - actual observation of the action, or message.

SLF: I have a small observation but I'm not sure what it means or if it has any relevance to the accident.

Previously I had assumed that the ADS-B data cut out at the same time as power was lost, so I imagined that whatever caused the fairly clear loss of thrust would have happened not too long before. But this report throws a bit of a wrench in my understanding of that.

According to the report, the fuel cutoff switches transition from RUN to CUTOFF at or very shortly after 08:08:42 UTC. Both engines' N2 values pass below minimum idle speed and the RAT begins supplying hydraulic power at about 08:08:47. Does this not imply that the generators have already been lost? With the APU also being off (the APU inlet door is noted to start opening at 08:08:54), I would have expected ADS-B data to cut out at or before 08:08:47. But curiously FlightRadar24 at least claims to have received data frames from the aircraft until 08:08:51.640970, almost five seconds later and almost ten seconds after the transition to CUTOFF (though the last frame containing coordinates comes at 08:08:50.871005).

Could anyone with relevant experience confirm how long it would take for AC power to be lost in this situation? Also, is it usual/unusual for a preliminary report like this to mention if/when the flight recorder switched to its independent power supply? I imagine it would definitely be in the final report, but I'd hoped it would be easily observable enough to be in this one.

Beyond idle curiosity I'm asking because the report also says the no. 1 engine's cutoff switch transitioned from CUTOFF to RUN at "about 08:08:52", which oddly coincides with the last ADS-B data frame at 08:08:51.640970, and that seems important somehow. Or more likely I'm just ignorant of some quirk of the 787's electrical system.

For reference FR24's CSV containing all ADS-B frames supposedly received from the aircraft can be found in their post here: https://www.flightradar24.com/blog/f...rom-ahmedabad/

Quote:

"The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec."

This might have been discussed but as has been suggested upthread; a possible scenario is that at some point, PIC took their hands off the thrust levers and/or placed them in a guarding position behind the thrust levers at their base - but by doing so unfortunately nudged the Fuel cut-off switches to 'Off' - perhaps 'helped' by there either being incorrectly fitted locking mechanisms or worn locking mechanisms ?

I believe the fuel cutoff switches are one of the exceptions to this. They are direct wired. Stab trim may well be too.

I think they're called remote data concentrators - in many cases it is a conversion from a direct digital input to a bus signal; electronics would not call it an 'analog' input unless it was actually measuring a quantitative value.

I think I have seen a previous reference that the generators are disconnected when you select the switches to cutoff (or very shortly afterwards), not when the engine actually drops below idle. That could account for a few seconds of spool down time.

That is a very good question IMHO.

Aside from anything technical, I find this attitude really strange. This is a discussion forum, of course there is (and should be!) significant discussion about a bizarre crash of a modern widebody aircraft. There will naturally be speculation and some nonsense but this is a discussion forum and that is to be expected. What's the point in locking threads until the final report comes out?

You can always not read it.

indeed, it was valid to have closed earlier threads as we were all purely speculating but now the prelim report is out surely it\x92s fair game? The AF447 threads I\x92ve gone back and read have gone into 100s of pages multiple times

As long as things are mostly civil surely there\x92s zero reason to be shutting down organic conversations now

If the thrust levers were found in idle but, according to the EAFR, were set to TO thrust until the end, doesn\x92t that also raise further questions? I mean: Of course, the impact causes compression at the nose, but the centrifugal forces act in the opposite direction. So, if there is an objective inconsistency here, and we have a pilot who says he did not operate the fuel cut-off switches, while the EAFR indicates otherwise, then we have yet another inconsistency.

Relevant section in the preliminary report

I have rebuilt the site that organises these three threads by subject here: https://paulross.github.io/pprune-th...171/index.html

Changes:

• Build threads up to July 12, 2025, 11:59:00 (built at July 12, 2025, 13:03:09).
• Add thread about the published report: Preliminary Air India crash report published
• Add subjects: "Guards", "Timeline (Preliminary Report)", "EICAS", "RUN/CUTOFF", "Special Airworthiness Information Bulletin", "SAIB NM-18-33", "Gear Lever", "Startle Effect" and "Cockpit Area Audio".
• Minor improvements to the index.html page.

Project is here: https://github.com/paulross/pprune-threads
Raise issues here https://github.com/paulross/pprune-threads/issues or PM me.

Two things I would like to add:

1: in the context of 'evidentiary' posts, the fact we discuss an issue here which is then embedded in a YouTube expert's analysis, doesn't then make that YT video credible evidence to prove a point here. It's a hamster wheel in action.
2: The absence of some detail or another from the preliminary report doesn't speak to a cover up. What it does is tell us that either that detail was absent from the investigatory evidence, so not available to consider, or it was present but not considered (at this stage at least) a material detail which was useful to report.

(First, I've read the whole thread, and most of the content in the previous threads, though they are obviously of less relevance in some areas now.)
This notion has caused me some concern, since seeing at least one very similar remark when I read the other threads (possibly by the same poster, though?).
It seems extremely undesirable for TCs to end up habituated to taking actions like this without thought. I wonder if it creates a case for the sim setups being performed by non-flying personnel?

Meanwhile, I read the prelim report. The English is generally fairly good but I note multiple mistakes/typos, and some oddities. One such oddity is that the timestamp of the second cutoff switch change isn't listed explicitly anywhere I can find, but instead just a relative time: "gap of 01 second". To write "1" as "01" like this invites speculation that it's a typo for 0.1; this is unlikely, given the polling frequency mentioned by some posts above, but nonetheless seems odd. (I am aware that Indian conventions differ from those in US/UK English, including placement of commas in large numbers, but I don't think this is such a case.)
Another indication to suggest it hasn't been proof-read very effectively: the FADEC is also described as a "... Dual ..." instead of "... Digital ...".

That account, which is posted as being authoritative, appears to disregard SAIB NM-18-33 which states, in part:

"In order to move the switch from one position to the other under the condition where the locking feature is engaged, it is necessary for the pilot to lift the switch up while transitioning the switch position. If the locking feature is disengaged, the switch can be moved between the two positions without lifting the switch during transition, and the switch would be exposed to the potential of inadvertent operation. Inadvertent operation of the switch could result in an unintended consequence, such as an in-flight engine shutdown.'

Since the preliminary report does not specify that this SAIB was actioned on this aircraft we do not know if it was fitted with defective switches.

In my personal opinion a defective locking feature does not explain the reported event sequence. That does not mean the switches were not defective.

I've been on record in the past advocating for this, but not as the means for intervention. - in the kind of instance we may have seen here, that likely wouldn't have helped anyway - but as a moderating influence on a crew member who may have been contemplating wayward actions. Being observed is often a powerful influence in behavioural extremes.

On edit: and No, I doubt the preliminary report was written to avoid the risk of copycat actions or delay public reaction. The investigatory team are not at all likely to be considering that kind of audience in what is essentially a finding of fact. An altercation would have been caught on the CVR... and reported upon.

Both of them? 1-2 seconds apart? That\x92s extremely unlikely.

Earlier today I watched Mentour Pilot's YouTube discussion, one of the things Petter said was "Brain fart of the century" regarding the erroneous selection of cut-off 3 seconds after leaving the ground. Somewhere else I saw this sort of thing described as a "Car keys put in the fridge" event.

I'm also reminded of the Moorgate tube train crash in 1975, no one has ever determined why an experienced driver who had driven the short out and return route 4 times that day suddenly accelerated while bringing his train into a terminus station with a closed tunnel beyond the platform end.

As someone married to a person who suffers with epilepsy, I'm used to short term memory interruption events where my wife will have done something and then not remember doing it 10 seconds later. I suppose such a thing in a pilot is a possibility, a new sufferer may not even realise that they have this kind of condition or even know they have performed an action.

I don't have anything else I can add to this, I read the preliminary report twice and checked every word. It doesn't offer any clear suggestions without expanding on the limited information provided. Undoubtedly the investigators have a lot more information they can examine but it will take time. One thing is that it doesn't mention a positive rate call, in the circumstances that suggests that this wasn't made and was replaced with the "Why did you cut-off?" question.

I note that this crash might have been more survivable with a 15 degree change of heading to the left towards a more open area to the south of the 5 buildings involved, but of course there would be no reason for the crew to have done this or indeed any time to do it.

With all due respect I disagree I think the prelim report was very sanitised to achieve the aim of a prelim report (are there any urgent safety actions relevant to this accident to be addressed?) whilst avoiding 1) Extreme public reaction 2) Addressing potential criminal behaviour - which the AAIBs are not experts in, nor the correct investigatory authority.
Your final sentence similarly I doubt - I suspect the CVR does reveal a lot more - certainly the timings of the reported interactions. It's just sensitive information... The report was written at 4AM ish Indian time and released shortly afterwards, and I surmise most of the delay was not "what to include" but "what NOT to include" to (only) achieve the aims of a prelim report.
I am not trying to be disrespectful, just put forward a different point of view, and you may well be right...

This takes the trouble of going through the preliminary report in some detail, and picks up on the inclusion of a psychologist in the investigation team, which I don't think has been mentioned here yet.

Is there anything professional pilots would take exception to in the explanation by the pilot in this video?