Fuel Cutoff Switches Page: 43 of 46

VicMel
December 24, 2025, 12:22:00 GMT
permalink Post: 12010375

Only 1 Failure

Quote:

Originally Posted by EDML

Like all theories that have been around so far it does not explain crucial parts of the accidents.
Most important: Why did the DFDR record a fuel shutoff commanded by the switches on the flight deck.

Furthermore: There is more than one source for the Air/Ground logic for the TCMA. There are two engines with two FADECs each. A bit flip, which might be very remotely possible, is not enough to trigger that sequence of events. Furthermore they were more or less on the ground - the A320 affected by solar flare was at FL350 which makes a huge difference.

The Landing Gear System I am familiar with determined and set WoW status, as well as computing aircraft weight from a load cell situated on the LG structure. Only one system, only one bit for WoW status, just one failure; then the TCMA does the rest. I read somewhere that the Pilots tried to do an engines restart by recycling the fuel cutoff switches, so I have no idea where the switches might have ended up - but TCMA does not care!

Last edited by VicMel; 24th December 2025 at 12:25 . Reason: missed out "with"

Subjects DFDR Fuel (All) Fuel Cutoff Fuel Cutoff Switches Relight

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TURIN
December 24, 2025, 12:33:00 GMT
permalink Post: 12010381

Quote:

Originally Posted by VicMel

I don't know where you read that but it's wrong.
The preliminary report as quoted above states that the fuel cut off switches were set to off. Some seconds later, the report goes on to say, the switches were returned to the on positions.
The engines reacted to the switch positions, the switches were not moved as a reaction to the engines doing something they shouldn't.
This TCMA red herring is becoming tiresome.
Please stop and wait for the final report.

Subjects Fuel (All) Fuel Cutoff Fuel Cutoff Switches Preliminary Report Relight

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Musician
December 24, 2025, 16:01:00 GMT
permalink Post: 12010436

Quote:

Originally Posted by VicMel

The preliminary report explicitly states that the crew did manage to restart one engine.

The EGT was observed to be rising for both engines indicating relight. Engine 1\x92s core deceleration stopped, reversed and started to progress to recovery. Engine 2 was able to relight but could not arrest core speed deceleration and re-introduced fuel repeatedly to increase core speed acceleration and recovery.

Please do read the preliminary report, it is the best source we have, and any question you might have regarding what it says are on topic here. TCMA is not mentioned because none of the conditions it needs to trigger were part of the accident sequence (it's more than WoW).

Subjects Fuel (All) Fuel Cutoff Fuel Cutoff Switches Preliminary Report Relight

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NOC40
December 24, 2025, 17:12:00 GMT
permalink Post: 12010461

Quote:

Originally Posted by VicMel

A week ago the BBC reported that 2025 was the sunniest year for the UK since records began; back in August I was diagnosed with a small spot of non-aggressive skin cancer, it is probably not a coincidence! This led me to think - could the Air India 171 crash be due to solar radiation? .

You're making the very basic mistake of mixing up sunlight/lack of clouds (which aircraft mostly fly above anyway) and cosmic rays, which were blamed for the A320 incident. It's sunniest near midday around the tropics of course. But cosmic rays are less fussy, and actual most common near the earth's magnetic poles.
The reason "solar radiation" wasn't mentioned in the Air India report was because the fuel supply to both engines was cut off.

Subjects BBC Fuel (All) Fuel Cutoff Switches

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Leonakua
December 24, 2025, 17:48:00 GMT
permalink Post: 12010481

Correction... The report was "switches t ransitioned to CutOff". Given the Ambiguous nature of the prelim in general, the team may have meant "valves transitioned to cut off". Which is what happened. I wouldn't bother with this, but what is posted tends to become gospel. I think the report is sloppy, and quite possibly purposefully so. So basing a discussion on it is a waste of time. 2\xa2

Yeah, just give me a 01 second.... Oh yeah, "Why did you Cut Off?" ( Fuel not mentioned )
And, wasn't RAT deployed prior to "transition" ?

Last edited by Leonakua; 24th December 2025 at 18:00 .

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

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tdracer
December 24, 2025, 19:19:00 GMT
permalink Post: 12010502

Quote:

Originally Posted by Leonakua

There is absolutely nothing ambiguous about the statement "switches t ransitioned to CutOff". The preliminary report reports the facts as currently known about the investigation - any ambiguity in the report is in areas that require conclusions - not facts (e.g. why the switches moved, or who moved them).
When you need invent stuff (or new meanings) for your hypothesis to work, it's time come up with a new hypothesis...

Last edited by tdracer; 24th December 2025 at 19:41 .

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

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Ver5pen
January 24, 2026, 18:30:00 GMT
permalink Post: 12026533

Quote:

Originally Posted by Musician

Non-paywalled version: https://www.aol.com/articles/sabotag...060100148.html
There's the old "the RAT deployed early" (assuming it always takes a full 6 seconds to spool up), the water leak, the "can't move both switches in a second", and new "the aft FDR looks like it burned before the crash". And this, which is as yet unsubstantiated, and is likely not relevant at all:

Just 15 minutes before take-off, the aircraft\x92s bus power control units (BPCUs), which manage the electrical systems, sent real-time signals to Boeing and Air India indicating malfunctions with both BPCUs.

In isolation, none of these problems is classed as major issues, but taken together, according to some experts they show a pattern of electrical problems that point to issues with the core network.

According to reports in India, in the minute before the aircraft took off, and almost certainly as it was heading down the runway, the 787\x92s aircraft communications addressing and reporting system sent a fault code to Boeing and Air India which indicated that the Fadec was receiving corrupted data from an engine monitoring probe.

Pierson says: \x93That aircraft was sending out fault messages before it took off. That is a big red flag. The aircraft health management system was also sending real-time data to Air India and Boeing so they had that information before the fires were even put out. None of that information was included in the preliminary report.

whilst intentional action is the most obvious explanation one can\x92t ignore data and technical grounds if one is also going to dismiss counter theories on technical grounds

I still don\x92t believe we have got a clear answer on the recording interval of the engine cutoff switch channel, if it\x92s 1s then the \x91debunking\x92 by saying it can be done very quickly is moot as (near) instant would record as 1s I believe

and the RAT element is obviously very relevant, if RAT deployment is not recorded then one has to infer when it deployed based on when it delivered hydraulic/electric capability. And this will come down to counting seconds, any indication that the RAT may have deployed before the fuel cutoffs were recorded as moved is obviously hugely consequential

it\x92s easy to dismiss these narratives as vested interests but let\x92s be honest everyone has a vested interest here and blaming the pilots has been the go to when in doubt for a very very long time- probably as long as aviation has existed

in the absence of explicit evidence (does the CVR have more to tell?) of deliberate action or pre-planning this is a horrifically complicated investigation as there will always be plausible deniability on all sides and different courts/judges will rule on it very differently based on their own biases and views

Subjects CVR FDR Fuel (All) Fuel Cutoff Switches Preliminary Report RAT (All) RAT (Deployment)

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Someone Somewhere
January 24, 2026, 20:21:00 GMT
permalink Post: 12026564

Quote:

Originally Posted by Musician

"The aft EAFR burned before the crash" was I believe originally an attempt to tie it to the aft battery fires the 787 had more than a decade ago, as they're both 'aft'. Never mind that the aft electronics bay (APU battery) is under the floor near the wheel well while the aft EAFR is above the ceiling near the rear doors.

Quote:

Originally Posted by Ver5pen

whilst intentional action is the most obvious explanation one can’t ignore data and technical grounds if one is also going to dismiss counter theories on technical grounds

I still don’t believe we have got a clear answer on the recording interval of the engine cutoff switch channel, if it’s 1s then the ‘debunking’ by saying it can be done very quickly is moot as (near) instant would record as 1s I believe

It's one second intervals but not necessarily recorded simultaneously. The NTSB has a few FDR reports from previous 787s that should show roughly what you would expect. I don't see any discrepancy.

Quote:

and the RAT element is obviously very relevant, if RAT deployment is not recorded then one has to infer when it deployed based on when it delivered hydraulic/electric capability. And this will come down to counting seconds, any indication that the RAT may have deployed before the fuel cutoffs were recorded as moved is obviously hugely consequential

RAT out would be recorded on the EAFR I believe, they just haven't explicitly specified when it happened.

The engines ran down after the switches were recorded moving. Even if the RAT deployed, that does not suggest that the crew switched the engines off because of an engine failure.

No crew is going to shut down the engines down simply because a RAT deploys unexpectedly.

Quote:

it’s easy to dismiss these narratives as vested interests but let’s be honest everyone has a vested interest here and blaming the pilots has been the go to when in doubt for a very very long time- probably as long as aviation has existed

in the absence of explicit evidence (does the CVR have more to tell?) of deliberate action or pre-planning this is a horrifically complicated investigation as there will always be plausible deniability on all sides and different courts/judges will rule on it very differently based on their own biases and views

It is very, very, very hard to argue that the EAFR records valid data for A/B/C/D but generates fake data for X/Y/Z, but the fake data is still externally and internally consistent. Which seems to be where we are now.

I don't think you can or will effectively prove whether it was intentional or some kind of an action slip, and by which pilot.

I think the accident report will be able to very clearly and with no reasonable doubt show that the switches were physically moved.

From the article:

Quote:

The alternative is too awful for them to contemplate : that one of the pilots murdered hundreds of people as collateral damage in a suicide.

And there you have the answer. If you refuse to consider the scary option, whatever remains must be the 'truth'.

Quote:

Because the aft flight recorder was destroyed, investigators cannot retrieve the one piece of information that it alone contained – the moment it stopped working, which might have provided a vital clue about a fire or electrical failure in the moments before the crash.

Have we had actual confirmation that the aft EAFR was completely unrecoverable? I don't believe so; the preliminary report said this:

Quote:

The aft EAFR was substantially damaged and could not be downloaded through conventional means. The CPM was opened to inspect the memory card. The damage was extensive.

The forward EAFR will have shown when each bus lost power and if they don't believe there's any unique data on the aft EAFR, attempting to recover data from it is basically an academic exercise.

Last edited by Someone Somewhere; 24th January 2026 at 20:32 .

Subjects APU Action slip CVR DFDR EAFR Electrical Failure Engine Failure (All) FDR Fuel (All) Fuel Cutoff Switches NTSB Preliminary Report RAT (All) RAT (Deployment)

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Someone Somewhere
January 25, 2026, 06:41:00 GMT
permalink Post: 12026747

Selecting the fuel system controls (i.e. fuel pumps) off will not work AFAIK , as the engines will gravity/suction feed under most circumstances.

Fire handle will work as the backup shutdown. As the fire handle is not regularly used, I don't think action slips are inadvertently going to operate them.

Option A is to ignore the cutoff switch unless the thrust lever is at idle - Embraer already does this.

Option B is a landing-gear-lever style solenoid interlock on the cutoff switches. Unless the aircraft is on ground and slow, that engine has failed, or that engine has a fire warning, you have to push override.

I think Jeju have fairly conclusively shown that you need to not switch an engine off within ten seconds.

If you want a system to stop the pilot(s) deliberately and competently crashing the plane (as is posited for MH370), it gets much much harder. I posted some thoughts about that in the 'too much automation' (IIRC) thread, but it boiled down to needing a lot of redundancy and a self-flying aircraft. Enforcing 'must have M of N enabled' is the easy part.

Subjects Action slip Fuel (All) Fuel Cutoff Switches

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Someone Somewhere
January 25, 2026, 09:43:00 GMT
permalink Post: 12026797

Quote:

Originally Posted by Jonty

The responses to the article are very interesting. And pretty much go to reaffirming my point about vested interests.

it was the same with the MH370 accident.

If you’re American or worked/flew Boeing aircraft you’re more likely to blame the pilots. If you’re Indian or Asian you’re more likely to blame the aircraft.

Unless someone produces a smoking gun, which is very unlikely, then the causes will always be up for debate.

Here in the U.K. we had the Chinook crash, where the pilots were instantly blamed. It makes me very uncomfortable to blame one individual for mass murder without a smoking gun as such.

Do you not consider the EAFR showing the cutoff switches switching to cutoff, followed by the engines spooling down, a smoking gun? Especially coupled with the engines restarting once re-enabled?

We had some discussions over in 787 GEnx loss of aircraft data will result in engine shutdown which I won't repeat in full, but there doesn't seem to be any credible way to get that result from a system failure without dealing in one-in-a-quadrillion events. The monitoring channel going to the RDCs and EAFRs is independent from the relay logic that closes the fuel valves.

Most of the "we'll never know" accidents don't have full FDR and CVR data. This one does.

I'm usually not on Boeing's side but the evidence is pretty overwhelming here.

Subjects CVR EAFR Engine Failure (All) Engine Shutdown FDR Fuel (All) Fuel Cutoff Switches GEnx (ALL)

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Musician
January 25, 2026, 09:58:00 GMT
permalink Post: 12026812

Quote:

Originally Posted by Jonty

All of this is factually incorrect.

It's incorrect to say we're blaming the pilots; the prevailing opinion seems to be that ONE pilot (but we don't know who) inadvertantly flipped the switches in lieu of another task ("action slip").
It's incorrect to call this "mass murder", and I don't think anyone did (and stayed unmoderated).
It's also incorrect to say there's no smoking gun: the preliminary report is very clear that the fuel cutoff switches transitioned, i.e. somebody moved them such that one set of contacts was registered by the electronics and the FDR, and another set of contacts operated the fuel valve. The whole accident sequence follows from this logically and without contradictions.

It is clear that MH370 deviated off course intentionally, but we cannot say if a pilot planned this, or if the aircraft was hijacked.

It is false to say that the pilots were blamed "instantly" for the 1994 Chinook crash; the RAF board of inquiry did not do that. That ruling was overturned at first, but two subsequent inquiries re-overturned that, so that the pilots stand exonorated today.

Please do review the facts.

Subjects Action slip FDR Fuel (All) Fuel Cutoff Fuel Cutoff Switches Preliminary Report

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Kiltrash
January 25, 2026, 11:32:00 GMT
permalink Post: 12026852

The bottom line will be in the report as" The fuel switches were operated incorrectly for reasons unknown "

Like the Marie Celeste it will be one of the great unknowns

Subjects Fuel (All) Fuel Cutoff Switches

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Jonty
January 25, 2026, 11:50:00 GMT
permalink Post: 12026864

Quote:

Originally Posted by Kiltrash

The bottom line will be in the report as" The fuel switches were operated incorrectly for reasons unknown "

Like the Marie Celeste it will be one of the great unknowns

I think that\x92s true. It will be something along those lines.

Subjects Fuel (All) Fuel Cutoff Switches

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Someone Somewhere
January 26, 2026, 07:33:00 GMT
permalink Post: 12027289

I don't think we have any real evidence for intentional vs action slip. From what I've seen, the moderation has been light since the preliminary report came out showing the cutoff switches were used.

From what I've seen here, the consensus is somewhere around 70% intentional 30% action slip.

I agree that we're unlikely to ever know; several of the discussions around cockpit video recorders were kicked off by that.

Last edited by Someone Somewhere; 27th January 2026 at 05:02 .

Subjects Action slip Fuel (All) Fuel Cutoff Switches Preliminary Report Thread Moderation

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DBYO
January 26, 2026, 11:40:00 GMT
permalink Post: 12027436

Quote:

Originally Posted by Musician

The idea is to protect the engines against inadvertant dual shutdown in some way.
(There's always another way to deliberately crash an aircraft.)
The problem is, what do you do when the shutdown protection fails and doesn't let you shut down an engine you really need to shut down?

Action slips generally result from confusing two different but frequently-performed actions. The obvious safety mechanism is to ensure that use of the cut-off switches is not a frequently-performed action. Future aircraft designs could move the end-of-fight engine shutdown process to a software screen, leaving the use of the physical buttons for emergencies only.

I agree that addressing potential deliberate action is far more challenging.

Subjects Action slip Engine Failure (All) Engine Shutdown Fuel (All) Fuel Cutoff Switches

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ignorantAndroid
January 26, 2026, 22:24:00 GMT
permalink Post: 12027684

Quote:

Originally Posted by Kiltrash

The bottom line will be in the report as" The fuel switches were operated incorrectly for reasons unknown "

Like the Marie Celeste it will be one of the great unknowns

Unless the CVR captured the sounds of a physical struggle. I suspect that those who have heard it have a better understanding of what happened than we do.

Subjects CVR Fuel (All) Fuel Cutoff Switches

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Someone Somewhere
February 01, 2026, 20:55:00 GMT
permalink Post: 12030826

The switches IIRC have both 'run' and 'cutoff' contacts monitored. So if the switches are moved to cutoff, the 'run' contacts open, and the 'cutoff' contacts close. If (big if), instead, loss of power resulted in switches appearing open, you would see both 'run' contacts and 'cutoff' contacts as open, which would be a fault.

With no power, the RDCs reading those switch contacts would of course also be unpowered, so you would expect to simply get no data.

If the switches appeared to close when the RAT came online, then how would you explain:

The ten-second time with the first engine switches being off being significantly longer than the time needed for the RAT to start supplying power
The fact that the switches did not switch simultaneously, especially when being switched back to run (four-second gap)

It's a nonsense theory with ChatGPT written all over it. It's been discussed at some length previously.

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

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Musician
February 01, 2026, 22:18:00 GMT
permalink Post: 12030849

Quote:

Originally Posted by nikplane

Hello everyone.
There's this rumor and/or question going around:
Someone was promoting the idea that a diode failure in the backup battery had disabled the battery and both buses.
He claimed that the FDR inputs from the switch sensors were coming from opto-isolators, and since they had lost power, they showed the switches going into the open state until power returned from the RAT.
For this theory to be valid, a single diode failure would have had to disable the entire aircraft.

Please,
- just comments on technical aspects?
- It's unclear this refers to the forward EAFR backup battery or
the Hot Battery Bus (Hot BB).

Thanks

The engines have their own power supply, separate connections to the cutoff switches and thrust lever angle resolvers, and would be unaffected in this scenario.

Notwithstanding the fact that this failure mode is also technically implausible/impossible. Here's a 787 that landed with the battery on fire:
https://skybrary.aero/accidents-and-...and-japan-2013

On 16 January 2013, a Boeing 787-8 (JA804A) being operated by All Nippon Airways (ANA) on a scheduled passenger flight from Yamaguchi-Ube to Tokyo Haneda in day Visual Meteorological Conditions (VMC) made an emergency diversion to Takamatsu after a main battery failure was annunciated climbing through FL320.

.
The original perpetrator of this idea is Jeremy John Thompson, with a Youtube video titled "How Air India AI171 B787 crashed - Lithium Battery Diode Module Failure" positing that the battery diode module failed, the battery overcharged and short-circuited, and disaster ensued. This was half a year ago.

Last edited by Musician; 1st February 2026 at 22:41 .

Subjects AI171 EAFR FDR Fuel (All) Fuel Cutoff Switches RAT (All)

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JustusW
February 02, 2026, 13:20:00 GMT
permalink Post: 12031080

Quote:

Originally Posted by Den2020

On Feb 2nd 2026 the crew of an Air India Boeing 787-9, registration VT-ANX performing flight AI-132 from London Heathrow,EN (UK) to Bangalore (India), observed during engine start, that the left hand fuel control switch failed to remain in the RUN position two times and moved towards the CUTOFF position.

So here's what we'll be discussing next:
1) How Air India faked this emergency.
2) How Boeing is covering up this massive safety flaw.

Although just by the description alone I can't even create a mental image of the failure mode given the actual construction of the switches. Not only are they latching into the detent, but what could possibly apply a downward force? Would gravity alone move a switch of this type even if the guard was completely removed? By their nature switches tend to be mechanically bistable, meaning they have two stable positions regardless of any switch guards.
Maybe someone with actual knowledge of the switches can chime in here. For me this sounds very strange and raises all sorts of red flags.

Subjects Fuel (All) Fuel Cutoff Switches Fuel Cutoff Switches (detent) RUN/CUTOFF Switch Guards

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Pilot DAR
February 02, 2026, 13:32:00 GMT
permalink Post: 12031086

Quote:

that the left hand fuel control switch failed to remain in the RUN position two times and moved towards the CUTOFF position.

Having operated this type of switch for about a half century, I am unconvinced that a properly selected switch could "move towards the cutoff position".

From post 166 of this thread:

Quote:

Consider this post with a picture of the switches in question:

They must be lifted over the detent (if installed correctly) in each direction.

Perhaps the switch could be defective, but that is (a) easily detectable by the pilot) and (b) still not likely to result in it moving on its own, rather just not locking well in the selected position. This is a situation where readers need to apply their understanding before accepting an unsubstantiated report. If we receive an authoritative report about how this switch "moved toward cutoff" twice on its own, I will read with great interest!

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

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