Posts about: "RUN/CUTOFF" [Posts: 186 Pages: 10]

Not on the take-off roll. It was 3 seconds after liftoff.

This is pure speculation but I can envision the following sequence of events that would match the timeline and the little we know from the CVR and sequence of events.
- While PF is concentrated on flying the airplane, PNF moves the switches from RUN to CUTOFF in quick succession (for whatever reason).
- PF doesn't notice that the switches have been moved (again, he is concentrated on flying) but soon perceives the loss of thrust and sees a message on EICAS.
- PF looks down to check throttle position. It takes him a couple seconds to realize that the switches are in CUTOFF position.
- PF asks PNF (and his superior) "Why did you cut off the engines?" (or something similar). PNF anwers that he didn't (a lie, but we don't know if deliberate or just confusion / mental breakdown)
- PF realizes that PNF is in a wrong mental state, and attempts to restart the engines. It takes him a couple of seconds to move both switches because his other hand is on the yoke trying to stabilize the airplane.
- By then the airplane has lost too much energy for a successful recovery. One of the pilots calls MAYDAY because he knows that they are about to crash.
This sequence would match the timeline between the initial fuel cutoff, and when the switches were moved back to run position, and would actually indicate great presence of mind and quick decision from the PF.
Again, this is pure speculation but it would match well with the little information we have.

Best theory I've seen so far.


I assume the unusual alarm cacophony that erupted after cutting the engines would have been overwhelming. Agree an error in good faith. If bad faith were involved, the switches wouldn't have returned to the run position, or at least they wouldn't have been allowed to remain there.

Yes - conflicting data issuing a warning when the system being controlled has no fault. That's a problem at considerable expense for a rare occurrence.

Literally covering all the bases with a video would not only show what the switch status was but also how it got there, if it has an immediate effect, which a second line would not do.

Sorry, stop right there.
What reason would any 787 Training Captain have for doing that at rotation, or slightly after rotation?
Really. Think about that. It makes Zero Sense.

@tdracers's point about the startle effect is at least plausible.

It's established fact both fuel control switches moved to CUTOFF 4 seconds after Vr, a deliberate guarded action, not easily done accidentally.
The CVR records one pilot asking “Why did you cut off?”, the other replies “I didn’t”. Then a bland Mayday attributed to the Captain “engine failure, returning” in the middle of the crisis.

The language, if reported correctly, feels strangely detached. No confusion, no urgency, no clear troubleshooting. Not drawing conclusions, but does anyone else see signs of performative behaviour, that is saying the right things outwardly, while being at odds with the underlying cause?

I appreciate that both crew members lost their lives, however if we avoid discussing uncomfortable patterns, we miss the point of investigation and learning.

​​​You might be technically correct here but this line of thinking doesn't fit with the rest of the events. If they weren't physically and observably set to CUTOFF, setting aside the spoken comment, then how were they subsequently reverted to RUN? You would be saying that some invisible systems fault produced a temporary 10 second condition, starting to apply to both switches 1 second apart and ceasing to apply 4 seconds apart. Even within a very low probability scenario, it doesn't seem plausible - this was all physical, for reasons unknown.

Really? It suggests to me and I would imagine the vast majority of us who have flown modern Boeings that they were physically moved, by one of the crew, one at a time, the question is why.

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 ?

in that fraught moment of engines not functioning very close to the ground, the last thing to do at this critical moment when you don\x92t really known what has happened is communicate a MayDay. With the buildings looming up fast, the action required is to attempt to restart, as seems to have been done by a pilot putting the fuel switch to \x93run\x94, but too late to rescue aircraft. I think the timing of the MayDay call is strange given that the scenario called for Aviate, Navigate\x85 then Communicate.

I don't think this answers my question? Evidently there is an interruption in power, the (quite stable, at that point) ADS-B stream cuts out and doesn't return for the final twenty seconds of flight. And there are other indications that non-essential loads were shed, like the survivor remembering what must have been emergency exit lighting in the cabin. Though I would have liked explicit confirmation of AC power loss happening or not in the report.

The timing of data loss seemingly lining up with the first cutoff switch being flipped back to RUN seems a little too coincidental to me, but again hopefully someone with relevant knowledge has a mundane explanation for this.

Regardless of what actually happened in that cockpit, reasoning like this seems completely backwards to me. Since when do humans reliably, instantly recognise that they've just made a mistake? If they were that attuned to their actions they're almost certainly attuned enough to not make the mistake in the first place, especially if we're talking about an action slip. I've e.g. absentmindedly added salt to my tea instead of sugar and I certainly didn't immediately realise that I'd done that - in fact it took a good few seconds even after sipping and spitting it out for my brain to catch up to what must have happened. Even if an observer had pointed out to me before drinking it that my tea had salt in it, I would just have been confused because obviously I wouldn't do something that silly (spoiler alert: I did).

On top of that I feel like people are overestimating how long ten seconds actually is, especially considering some of those seconds are reported to have been taken up by confused dialogue (that isn't even reported in its entirety). I thought it was common wisdom that accidents are never down to one thing; it would be light-years from being the first time that suboptimal crew response turned a maybe-recoverable error into a definite disaster without an ounce of malice in the mix.

The report doesn't say WHEN the pilots spoke to each other. The one doing the asking might have been speaking ten seconds after CUTOFF, simultaneously moving switches to RUN. Or, he may have asked soon after observing the other's action, and there was a several seconds' delay before getting an answer.

Rather confusingly, AvHerald carries this today

"On Jul 12th 2025 (UTC) India's media report that the investigation is NOT focussing on a human action causing the fuel switches to appear in the CUTOFF position, but on a system failure."

I have no idea what provenance to attach to that!

Since some posters seem focused on the theory that the fuel control switches didn't move - just the electric output did (and as I posted earlier, the FDR only knows electrical states, there is literally no other way for the FDR to monitor the switch position).

So I did a little thought experiment. Uncommanded engine shutdowns (for all causes) are already rare - a 10-6 event. Now, during my 40 year career, I can't remember ever encountering a case where the fuel shutoff was commanded without a corresponding movement of the fuel switch. However in this industry it's a good idea to 'never say never', so let's assume it's happened. It would take something like a hot short to cause it to happen (moving the voltage from RUN to CUTOFF) since an open circuit will simply leave the valves where they were. That would put its probability way out there - something like 10-8/hr.

The left and right engine wiring is physically isolated from the other engine - nothing gets routed in common bundles between the engines. Hence there is simply no way a localized issue could affect both engine's wire bundles. So we're talking two independent events that cause the switch output to electrical change state between RUN and CUTOFF without associated switch movement. So now were out in a 10-16/hr. territory. Now, these independent events both occur a second apart - 3,600 seconds/hr., so we've just added ~8 orders of magnitude to the dual failure probability number (10-24/hr.). Now, they both somehow return to normal withing a few seconds of each other - another ~8 orders of magnitude so we're talking 10-32.

That means the probability of this happening at any time since the Big Bang is way less than one....

Space aliens look reasonable in comparison. So can we discuss things that might actually have happened?

Definitely the best and most important post of this thread IMO.

Well, not really, because separated wiring alone doesn't require independent events to produce a common outcome. I mean, pour a drink into the panel, or something more exotic like panel-localised EM interference (I have absolutely no idea how realistic that is, just illustrative).

For other reasons, I think it very unlikely that the switches were anything other than physically moved, so this is kind of pedantry rather than useful. But the probability analyses that folk (including experts) come up with often loses sight of the above. I posted much the same in one of the earlier threads about a month ago when all we knew was twin engine failure.

​​​​​

No simulator access, but I do know this much:

One EICAS and one PFD is on the battery (most likely the left seat PFD) - they might momentarily flicker but will not 'blank'.

You get an EICAS message when you set the fuel switch to CUTOFF - something like "ENGINE X CUTOFF" (not sure of the 787 wording, but it would be something to that effect.

While I doubt the PF would be actively monitoring EICAS during TO, with the sudden audio change to the engine noise as well as the sudden loss of acceleration, I'd expect him to take a quick look at EICAS to see what the ( ) the engines are doing. Plus, if the PF was in the right seat and his PFD blanked - I'd expect him to look across to see what's on either the standby or the left seat PFC, and perhaps EICAS.

See the quotes in bold. I realise I'm clutching at straws here but if we take the released version of exchange between the pilots at face value:

Then other possibilites must be considered and we should therefore not default to assuming 'a hand was on the fuel cutoff switches'. Especially as neither of the pilots can defend themselves against such allegations.

I would suggest starting with the maintenence engineer/crew who found 'no fault' after the STAB master caution was investigated immediately prior to this tragic flight. It would not be the first time that 'maintenance' caused an incident...

Also, I urge you all to consider how many accidents have been blamed on 'pilot error' (how convenient when billion-dollar companies are at risk) only for further information to come to light that then exonerates the pilots (these stories don't usually make the front page).

Try to stay open-minded folks. The investigation has a very long way to go.

Upthread there was quite some discussion about the preliminary report's use of the word transition in regard to the operation of the CUTOFF switches.

Several posters have quoted the SAIB recommendation to check these switches. I find it interesting that this Bulletin, an official document, uses the same word.

Perhaps the investigation team, who reference that Bulletin In their report, were influenced by it to use the same word to describe its physical action.

Quote:
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.