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Remind me which airline industry made this famous?

Im not discounting any theory, no matter how crazy it seems.

Subjects: None

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As far as the \x93object falling off the glare shield in a rotating manner as to hit two switches a second apart\x94 theory supporters\x85..this is getting ridiculous.
Google is your friend.
The glareshield is angled steeply towards the windshield. Anything left there can roll almost out of reach\x85.towards the windshield.



Yes but what if? NO

Have a look at a crew taking off in a 787.
Handpositions and callouts are (almost) universal in this industry.

https://m.youtube.com/watch?v=4e5JTchiajA&pp=ygUaQm9laW5nIDc4NyBjb2NrcGl0IHRha2VvZ mbSBwkJ2AkBhyohjO8%3D

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Last edited by B2N2; 13th July 2025 at 03:45 .

Subjects: None

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Not sure if this is helpful for anyone or not but I thought a visual view of the timeline of events might be useful, in seconds since V1.

I've assumed 1Hz for the switch sampling rate and >1Hz for everything else (could be wrong) to give windows for the switch state changes.

I've also added in the ADS-B relevant data, although made no attempt to work out whether these timestamps are synchronised or not, so take them as you will.

I have assumed the cutoff is in chronological order from the report, albeit I have ignored the RAT supply timestamp in terms of chronology from the CVR recording, as that statement in the report at that time may just be due to contextual nature of the statement, rather than it happening prior to the RAT power supply. This gives a window for potentially when that statement was made (assuming also that it was made prior to reversing cutoff).

Don't think it neccessarily adds anything for me, other than:

- Would we expect ADS-B data to stop on engine transition to run? Note that ADS-B data was received between 08:08:43 and 08:08:51, so apparently only received in the time window that the switches were in "cutoff"
- The window between the switches being shut off and moved to run could be as short as 8 seconds, and the window between engine 1 and engine 2 being moved to run could be as short as 2 seconds
- The statement on the CVR could be a wide range of timepoints.

The ADS-B data is in my view odd, albeit this might be my lack of understanding. Yes, not synchronised, but unless the timestamps are way out (like 10 seconds out, and given the timestamp of max altitude, this feels incredibly unlikely), ADS-B data was transmitted without issue during phase 2 (both engines off, no RAT), and phase 3 (both engines off, RAT)...but NOT phase 4 (both engines firing back up, presumably still with RAT?). Bear in mind that phase 4 is almost half of the short flight. Also it would appear no data during phase 1 (both engines on), including during takeoff, despite receiving data during taxi?

*EDIT* - having looked into some other historical ADS-B data for this airport, albeit a bit cursory, it definitely appears that the lack of data in "phase 1" that I've outlined above is solely a coverage issue, with no other flights I can see having coverage in that area either. It's harder to determine the "phase 4" element as obviously no airplanes in a normal mode are in that geographical region at the altitude in question, but it does appear to be a reasonably safe bet that the missing datapoints are coverage related.

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Last edited by Mrshed; 13th July 2025 at 12:47 .

Subjects ADSB  CVR  Fuel (All)  Fuel Cutoff Switches  Preliminary Report  RAT (All)  Timeline (Preliminary Report)  V1

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Quote:

Originally Posted by Mrshed

Not sure if this is helpful for anyone or not but I thought a visual view of the timeline of events might be useful, in seconds since V1.

I've assumed 1Hz for the switch sampling rate and >1Hz for everything else (could be wrong) to give windows for the switch state changes.

I've also added in the ADS-B relevant data, although made no attempt to work out whether these timestamps are synchronised or not, so take them as you will.

I have assumed the cutoff is in chronological order from the report, albeit I have ignored the RAT supply timestamp in terms of chronology from the CVR recording, as that statement in the report at that time may just be due to contextual nature of the statement, rather than it happening prior to the RAT power supply. This gives a window for potentially when that statement was made (assuming also that it was made prior to reversing cutoff).

Thank you for the diagram. Picture = 1000 words

Really highlights how knowing precisely when the why did you cutoff" question was asked might have provided more clarity and less speculation as to how those fateful seconds played out

And it would have helped to know if Positive rate / Gear Up was called ... and when

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Last edited by unworry; 13th July 2025 at 13:19 .

Subjects ADSB  CVR  Fuel (All)  Fuel Cutoff Switches  Pilot "Why did you cut off"  Preliminary Report  RAT (All)  Timeline (Preliminary Report)  V1

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Quote:

Originally Posted by Someone Somewhere

I think in the Jeju thread, it was noted that one of the transponders was on an AC bus and the other was on the standby bus. If they had been using the other transponder (swapped each flight), then we would have had ADS-B for the full flight.

Assuming the 787 is similar, perhaps the aircraft was broadcasting ADS-B for the full flight (with the transponder running off main battery/RAT power) but the reception was marginal, resulting in no reception until just after liftoff and no reception once they start to sink again.

That could make sense, the data received is centred around the recorded max altitude - amended diagram below:

Subjects ADSB

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Quote:

Originally Posted by njc

Very helpful, thanks! One recommendation for change: since we don't know what words were used by the pilots, how about using "CVR: query cutoff" rather than "why did you cutoff"?

Seems fair, thanks! I rattled it off in 10 minutes so suggestions/error checking welcome

Latest version:

Subjects CVR  Fuel (All)  Fuel Cutoff Switches  Pilot "Why did you cut off"

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Quote:

Originally Posted by Easy Street

It might be 3.01 seconds, due to the sampling rate. Still not quick, but a lot quicker than 4 seconds in the context. If it was being done by PF while trying to fly the aeroplane, then it wouldn't be as slick as the shutdown routine (and it would be against muscle memory of that routine as the switches are being moved in the opposite direction).

I'm pleased you said this as I've realised that my image is wrong, as the timestamp is not +/- 1 second, but only -0-1 seconds.

Corrected (FWIW):

Subjects Muscle Memory

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Quote:

Originally Posted by cargun

Hi,

I have a couple of questions. Forgive me for being late into this thread if any of them is already discussed:

1) I just read this in a Boeing manual:

The fuel control switches send signals to open or close fuel valves to operate or shutdown the engines.
- They send signals to the remote data concentrators (RDC) and the spar valve start switch relays.
- The spar valve start switch relays use these signals to control the spar valve and the high pressure shut off valve (HPSOV) in the fuel metering unit (FMU).
- The RDCs send the signals to the common data network (CDN) and then to the electronic engine control (EEC) to operate the FMU fuel valves (FMV and HPSOV).
The fuel control switches have 2 positions:
- RUN
- CUTOFF.
You must pull the switch out of a detent to select a position.

There seems to be RDC's (remote data concentrators) and CDN (common data network) between those fuel switches and the fuel valves. Is there any possibility that there may have been an electronic control module or sensor fault to generate such a signal rather than mechanical switch movements?

2) Looking at the incident timeline, one of the pilots takes corrective action to reswitch to RUN position 10 seconds after maximum air speed is reached and 5 seconds after RAT is deployed. Is this normal?
It's not clear however that whether their conversation is after or before the RAT is deployed.
(No visual or auditory cues in the cockpit for a critical fuel switch action? Not hearing the engines shutting down?)


3) The same pilot that turns on Engine 1's fuel switch, turns on Engine 2's switch 4 whole seconds later. Why not consecutively, right one after the other, just like they were turned off one second apart?
If only he had done so the second engine might have recovered in time as well.

4) This aircraft's TCM has been replaced in 2019 and 2023, not related to a fuel switch issue. And there had been no fuel switch defect reports since 2023. One begs to ask if there had been a fuel switch defect report back in 2023 and what was the nature of it?
Are TCM's replaced as a whole, including the switches, twice? If so, why wouldn't they install a TCM version at least in 2023 with redesigned switches (w/ enhanced locking mechanism) mentioned in the FAA SAIB? Have they installed old/used TCM's manufactured prior to 2018 SAIB?
Please note that the RH and LH GE engines of the aircraft were only installed in March 2025 and May 2025 respectively, but they were used and dating from 2013 and 2012. Is this normal for a 12 year old Boeing aircraft to change so many mission critical components?
Electronic parts somehow, but how durable are those GE engines?

Thanks,

C.A.

The data frame is recording the state of the fuel control switch system, being OFF or RUN. It does not monitor the physical position of the switch itself. It is normally reasonable to infer that the state has followed the switch but at the risk of sounding like a broken record, electrical systems on aircraft are prone to issues with water ingress, and we have learnt that computer systems are also prone to bit flipping from cosmic radiation. I doubt that this is anything like Kev's big day out at Learmonth, with QF072, but I also remain concerned over the potential for deluge of pooled water into the E&E bay, which has happened before. The evidence to put that to bed will be a spectral analysis of the time from liftoff onwards, looking for the signature of a switch being repositioned to OFF and then back to RUN. The Fuel Control Switches have an audible snap in most cases when repositioned. I would also spend a lot of time looking at the engine start case to detect the switch being positively locked into the RUN position.

When reading any of the data when it comes out, pay some attention to the sampling rate of the data being provided, it is quite possible to make erroneous assumptions where that is not taken into consideration. The data buses used to get data from the aircraft system to the recorder, and the recorders themselves use sequential sentences, and varyious rates.

IMHO.

Subjects FAA  Fuel (All)  Fuel Cutoff Switches  Fuel Cutoff Switches (detent)  High Pressure Shutoff Valve  RAT (All)  RAT (Deployment)  RUN/CUTOFF  Spar Valves  Special Airworthiness Information Bulletin

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Electrical effects of engine rollback

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Quote:

Originally Posted by Mrshed

I'm pleased you said this as I've realised that my image is wrong, as the timestamp is not +/- 1 second, but only -0-1 seconds.

Corrected (FWIW):

I would like to raise a subject that I don't believe has been discussed here since the Preliminary Report was published, namely what happened to the aircraft's electrical systems as a consequence of the dual engine rollback and thereafter (RAT deployment, partial engine recovery, etc.). Apologies if I've missed posts on this topic here, but I have tried to review all of this thread quickly after previously reading most of it in detail.

As I understand it from previous discussions, without the APU, all electrical power except for that DC power provided by battery to essential systems would have been lost.

With the copilot as PF, would he have lost his instrument displays? If so, possibly additional startle effect and workload for him.

Why did the ADS-B information keep going on for so long? My understanding from previous threads was that loss of ADS-B was considered an indication of loss of electrical power.

What else would be expected with loss of power?

Some general speculation: I find it hard to understand the long delay from what must have been the onset of obvious issues to the time the first engine is set to "RUN". I wonder if much more cockpit dialog intervened, e.g. PF requesting PM to turn the fuel switches back on (since he had his hands full), and eventually operating the switches himself, with the delay and time gap between the two switches being turned to "RUN" being attributable to being preoccupied with flying the aircraft under trying conditions.

Subjects ADSB  APU  Fuel (All)  Fuel Cutoff Switches  Preliminary Report  RAT (All)  RAT (Deployment)  RUN/CUTOFF  Startle Effect

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Quote:

Originally Posted by tdracer

It doesn't really matter - the FADEC will do it's best to get the engine running again regardless of the lever position - in that regard the only real difference is once the engine reaches min idle, it'll simply keep accelerating to the target N1 (or EPR). There is no need to move the thrust lever to idle to get a successful start.

There have been a few cases that I know about where the flight crew did a normal ground start with the thrust lever at mid-power, and the engine simply continues to accelerate to the 'commanded' N1 or EPR. In one case (a 777), this happened during pushback. As the engine continued to accelerate above idle, the thrust caused the aircraft to jackknife around the tug, causing the tug driver to have to dive for cover to prevent serious injury. That even happened while we were doing the development of the 747-8 - it prompted me to ask the 747 Chief Pilot if we wanted to consider a 'start inhibit' in the FADEC logic that would prevent a ground start attempt if the thrust lever wasn't at idle (ground starts only - for what should be obvious reasons). He didn't like the idea, and it went no further...

Thanks, makes sense. It was the above note that confused me.

Subjects FADEC

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At the time I hoped I was wrong. I wasn’t .Now I am going to say that whilst not impossible, I think it unlikely that this was a technical issue. Again, I hope I am wrong.

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Looking at some past FDR data, it appears that the fuel cutoff switches are sampled at 1 Hz, but the actual valve position is sampled at 4 Hz. The position of the fire switch (fire handle) is also recorded. N1 and N2 are sampled at 1 Hz.

Subjects FDR  Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches

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Quote:

Originally Posted by Mrshed

He is of course incorrect in stating a 10 second delay between CVR statement and FC switch to RUN.

He's talking about a 10 sec delay between fuel cutoff and back to run (after 4min15sec into the video)

Subjects CVR  Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  RUN/CUTOFF

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Quote:

Originally Posted by Musician

A way to cross-check would be to track the aircraft position over time from the point of rotation, or to use the new photo in the report that shows the RAT over the runway to triangulate where that was.

This was posted sometime ago, but if anyone would still find it useful to pinpoint the location of the aircraft in the 'new' photo from the Preliminary Report (with RAT deployed) I made a crude attempt which placed it roughly midway between the two sets of identical touchdown zone markings, ~245m (803 ft) from the displaced threshold of RW05.

The deemed position of the CCTV camera is only an estimate, based on visual cues. I'm happy to share my workings, should anyone find it useful to cross-reference this with other data they are working on, but I will avoid cluttering up the thread any further until/unless it becomes relevant.

You're looking for the point where the LEFT of the two white lines intersects the runway (ignore the white dots):

Subjects CCTV  Preliminary Report  RAT (All)  RAT (Deployment)

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Quote:

Originally Posted by GroundedSpanner

Switching off the engines would cut power. (the RAT deployed before they overflew the end of the runway) The HUD would go blank. As would most of the display units. The lighting would change. The hissing of conditioned air would stop. Various 'noises' would cease. The engines sound would change dramatically, and they would feel the deceleration. The one EICAS screen remaining would be generating all sorts of messages. It would be obvious that power was lost.
I cant speak for how long it would take to connect the dots though.

Display and Crew Alert (DCA)/EICAS would indeed receive signal about Fuel Cutoff switches (L&R) position and written to EAFR (source:
https://data.ntsb.gov/Docket/Documen...man-Master.PDF )

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Last edited by D Bru; 14th July 2025 at 23:39 .

Subjects EAFR  EICAS  Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  RAT (All)  RAT (Deployment)

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Air India 171: Energy-Consistent Flight Profile

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This energy-based model illustrates Air India 171's flight profile from liftoff to impact. It uses the initial data point from FlightRadar24 of 184 kts G/S, 21 ft height, Google Earth for the crash location, and CCTV footage (originally posted on X) for timing.



A key observation is the calculated average ground speed of 150 knots from the initial point, just after takeoff, to the crash site, derived using the CCTV elapsed time. The model incorporates "best-guess" mid-points inferred from the CCTV footage, which help depict approximate indicated airspeeds consistent with the aircraft's energy state throughout the flight.



The analysis assumes zero thrust during the flight and an average Lift-to-Drag ratio of approximately 12. For this model, a takeoff mass of 210 tonnes and an estimated V2 of 160 knots were used.



Note: This analysis was conducted prior to the release of the AAIB preliminary report, and therefore does not account for the correct take off mass and the actual V2 of 162. The differences are small and as this is a rough best guess, it\x92s just a basic energy model to show the possible trade between speed and height. No account was made of an engine spooling up at the end of the flight. Visual review of the video suggests the thrust from any restarting engine must have been very low, as no significant yaw is discernible.

Subjects AAIB (All)  CCTV  FlightRadar24  Preliminary Report  V2

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Subjects: None

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Quote:

Originally Posted by Occy

What about electrical wiring? If there's an intermittent wiring connection connection or the switch contacts were worn the circuit can indeed go off and come on again seemingly at random.

Subjects: None

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After all the analysis on PPRuNE, fuel switch failure (well, dual switch failure, at practically the same time) seems so unlikely it's no longer worthy of consideration. However, I'm still open to the idea of a failure elsewhere that may have signalled the fuel switches had transistioned from Run to Cutoff wthout physical movement of either switch. Why? Firstly, because of this (taken from the preliminary report)

Quote:

The crew of the previous flight (AI423) had made Pilot Defect Report (PDR) entry for status
message “STAB POS XDCR” in the Tech Log. The troubleshooting was carried out as per
FIM by Air India’s on duty AME, and the aircraft was released for flight at 0640 UTC.

The STAB cutout switches are located next to the Fuel cutoff switches. What did Air India’s on duty AME do as part of their troubleshooting? Were panels removed to gain access to the rear of the switches and wiring? What about wiring and data connections elsewhere? What may have been disconnected/disturbed as part of this process? Do the STAB cutout switches and Fuel cutoff switches share any connectors that could have been inadvertantly cross-connected? Etc. It would not be the first time that an engineer had innocently done something that later caused an accident. And I haven't read anything about possible nefarious action by a (disgruntled?) engineer - but I've seen lots of accusations directed at the pilot(s)...

Secondly, the preliminary report's version of (part of) the conversation in the cockpit -

Quote:

In the cockpit voice recording, one of the pilots is heard asking the other why did he cutoff.
The other pilot responded that he did not do so.

Until proven beyond reasonable doubt I'm chosing to take the cockpit conversation at face value, because I really don't want to believe any of the following scenarios:
A) one of the pilots lied
B) one of the pilots attempted to deflect blame onto the other pilot for the benefit of the CVR
C) One of the pilots unknowingly operated the fuel cutoff switches.
D) One of the pilots deliberately operated the fuel cutoff switches.

It is all too easy to blame one of the pilots when in reality no one outside of the official investigation may yet know what most likely happened.

Subjects CVR  Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  Pilot "Why did you cut off"  Preliminary Report

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Since the preliminary report neglected including when the RAT deployment occurred, I've tried to estimate it based on the picture they did include:




Baro altitude should be around 150ft; using the public cctv video, I estimate this picture was taken between 4-7 seconds after rotation. A wide range, but that was the best estimate I could come up with. Maybe someone else could narrow it down further.

Subjects Preliminary Report  RAT (All)  RAT (Deployment)

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